hep-ph updates on
High Energy Physics - Phenomenology (hep-ph) updates on the e-print archive
  • Direct detection of primordial black hole dark matter. (arXiv:1906.06348v1 [hep-ph])

    Authors: Benjamin V. Lehmann, Christian Johnson, Stefano Profumo, Thomas Schwemberger

    If dark matter is composed of primordial black holes, such black holes can span an enormous range of masses. A variety of observational constraints exist on massive black holes, and black holes with masses below $10^{15}\,\mathrm{g}$ are often assumed to have completely evaporated by the present day. But if the evaporation process halts at the Planck scale, it would leave behind a stable relic, and such objects could constitute the entirety of dark matter. Neutral Planck-scale relics are effectively invisible to both astrophysical and direct detection searches. However, we argue that such relics may typically carry electric charge, making them visible to terrestrial detectors. We evaluate constraints and detection prospects in detail, and show that if not already ruled out by monopole searches, this scenario can be largely explored within the next decade using existing or planned experimental equipment. A single detection would have enormous implications for cosmology, black hole physics, and quantum gravity.

  • Oscillons and Dark Matter. (arXiv:1906.06352v1 [hep-ph])

    Authors: Jan Olle, Oriol Pujolas, Fabrizio Rompineve

    Oscillons are bound states sustained by self-interactions that appear in rather generic scalar models. They can be extremely long-lived and in the context of cosmology they have a built-in formation mechanism - parametric resonance instability. These features suggest that oscillons can affect the standard picture of scalar ultra-light dark matter (ULDM) models. We explore this idea along two directions. First, we investigate numerically oscillon lifetimes and their dependence on the shape of the potential. We find that scalar potentials that occur in well motivated axion-like models can lead to oscillons that live up to $10^8$ cycles or more. Second, we discuss the observational constraints on the ULDM models once the presence of oscillons is taken into account. For a wide range of axion masses, oscillons decay around or after matter-radiation equality and can thus act as early seeds for structure formation. We also discuss the possibility that oscillons survive up to today. In this case they can most easily play the role of dark matter.

  • Model Independent analysis of MeV scale dark matter: II. Implications from $e^-e^+$ colliders and Direct Detection. (arXiv:1906.06364v1 [hep-ph])

    Authors: Debajyoti Choudhury, Divya Sachdeva

    Dark matter particles with masses in the sub-GeV range have escaped severe constraints from direct detection experiments such as LUX, PANDAX-II and XENON100 as the corresponding recoil energies are, largely, lower than the detector thresholds. In a companion paper, we demonstrated, in a model independent approach, that a significantly large fraction of the parameter space escapes the cosmological and astrophysical constraints. We show here, though, that the remaining parameter space lends itself to the possibility of discovery at both direct detection experiments (such as CRESST-II) as well as in a low-energy collider such as Belle-II.

  • Interpretable deep learning for nuclear deformation in heavy ion collisions. (arXiv:1906.06429v1 [nucl-th])

    Authors: Long-Gang Pang, Kai Zhou, Xin-Nian Wang

    The structure of heavy nuclei is difficult to disentangle in high-energy heavy-ion collisions. The deep convolution neural network (DCNN) might be helpful in mapping the complex final states of heavy-ion collisions to the nuclear structure in the initial state. Using DCNN for supervised regression, we successfully extracted the magnitude of the nuclear deformation from event-by-event correlation between the momentum anisotropy or elliptic flow ($v_2$) and total number of charged hadrons ($dN_{\rm ch}/d\eta$) within a Monte Carlo model. Furthermore, a degeneracy is found in the correlation between collisions of prolate-prolate and oblate-oblate nuclei. Using the Regression Attention Mask algorithm which is designed to interpret what has been learned by DCNN, we discovered that the correlation in total-overlapped collisions is sensitive to only large nuclear deformation, while the correlation in semi-overlapped collisions is discriminative for all magnitudes of nuclear deformation. The method developed in this study can pave a way for exploration of other aspects of nuclear structure in heavy-ion collisions.

  • Constraining the $3-3-1$ model with heavy neutral leptons using $(g-2)_{\mu}$ and dark matter observables. (arXiv:1906.06444v1 [hep-ph])

    Authors: C. E. Alvarez-Salazar, O. L. G. Peres

    We find constraints on the highest scale of symmetry breaking of a model with gauge symmetry $SU(3)_C \otimes SU(3)_L \otimes U(1)_X$ with heavy neutral leptons in the fermion triplets, calculating the anomalous magnetic moment of the muon and using results of the relic abundance of dark matter and experiments searching for its direct detection.

    In order to do this, we have calculated the one-loop contribution of new particles in the model to $(g-2)_{\mu}$, finding a favoured region for the scale at which $SU(3)_L$ is broken, and we have found lower bounds for this scale making a comparison of the predictions for the detection of a fermion dark matter candidate in the model in terms of simplified dark matter models, identifying the dominant portal for its interactions with standard model particles, and using constraints for the relic abundance and spin-independent scattering cross section of the fermion candidate with protons.

  • Small $x$ phenomenology on gluon evolution through BFKL equation in light of a constraint in multi-Regge kinematics. (arXiv:1906.06468v1 [hep-ph])

    Authors: P. Phukan, M. Lalune, J. K. Sarma

    We investigate the impact of so called kinematic constraint on gluon evolution at small $x$. Implanting the constraint on the real emission term of gluon ladder diagram, we obtain an integro-differential form of BFKL equation. Later we solve the equation analytically using the method of characteristics. We sketch the Bjorken x and transverse momentum $k_t^2$ dependence of our solution of unintegrated gluon distributions $f(x,k_t^2)$ in kinematic constraint supplemented BFKL equation and contrasted the same with original BFKL equation. Then we extract the collinear gluon density $xg(x,Q^2)$ from unintegrated gluon distributions $f(x,k_t^2)$ and compared our theoretical prediction with that of global data fits viz. NNPDF3.1sx and CT14. Finally we assess the sensitivity of $f(x,k_t^2)$ towards BFKL intercept $\lambda$ for three canonical choices of $\lambda$ viz. o.4, 0.5 and 0.6.

  • Contributions of Jets in Net Charge Fluctuations from the Beam Energy Scan at RHIC and LHC. (arXiv:1906.06482v1 [hep-ph])

    Authors: Bushra Ali, Shaista Khan, Shakeel Ahmad

    Dynamical net charge fluctuations have been studied in ultra-relativistic heavy-ion collisions from the beam energy scan at RHIC and LHC energies by carrying out the hadronic model simulation. Monte Carlo model, HIJING is used to generate events in two different modes, HIJING-default with jet quenching switched off and jet/minijet production switched off. A popular variable, $\nu_{[+-,dyn]}$ is used to study the net charge fluctuations in different centrality bins and the findings are compared with the available experimental values reported earlier. Although the broad features of net charge fluctuations are reproduced by the HIJING, yet the model predicts the larger magnitude of fluctuations as compared to the one observed in experiments. The role of jets/minijets production in reducing the net charge fluctuations is, however distinctly visible from the analysis of the two types of HIJING events. Furthermore, $dN_{ch}/d\eta$ and $1/N$ scaling is partially exhibited which is due to the fact that in HIJING, nucleus-nucleus collisions are treated as multiple independent nucleon-nucleon collisions.

  • $R$-symmetric NMSSM from Unification. (arXiv:1906.06486v1 [hep-ph])

    Authors: Sibo Zheng

    We study the NMSSM with the knowledge about unification. While this model is a simple and effective extension to avoid the dilemmas the MSSM confronts in the infrared energy region, it is challenging to seclude the singlet $N$ in the renormalization group trajectory from unification scale to weak scale. We propose for the first time identifying the singlet as the goldstino supermultiplet of supersymmetry breaking. Following this proposal, we derive the constraints from naturalness, show simple examples of general O' Raifeartaigh models, and discuss distinctive features in the R-symmetric NMSSM with $N$ as the goldstino supermultiplet.

  • Heavy hadron molecules in effective field theory: the emergence of exotic nuclear landscapes. (arXiv:1906.06491v1 [hep-ph])

    Authors: Manuel Pavon Valderrama

    Heavy hadron molecules were first theorized from a crude analogy with the deuteron and the nuclear forces binding it, a conjecture which was proven to be on the right track after the discovery of the $X(3872)$. However, this analogy with nuclear physics has not been seriously exploited beyond a few calculations in the two- and three-body sectors, leaving a great number of possible theoretical consequences unexplored. Here we show that nuclear and heavy hadron effective field theories are formally identical: using a suitable notation, there is no formal difference between these two effective field theories. For this, instead of using the standard heavy superfield notation, we have written the heavy hadron interactions directly in terms of the light quark degrees of freedom. We give a few examples of how to exploit this analogy, e.g. the calculation of the two-pion exchange diagrams. Yet the most relevant application of the present idea is the conjecture of exotic nuclear landscapes, i.e. the possibility of few heavy hadron bound states with characteristics similar to those of the standard nuclei.

  • Top-quark pair production at the LHC: Fully differential QCD predictions at NNLO. (arXiv:1906.06535v1 [hep-ph])

    Authors: Stefano Catani, Simone Devoto, Massimiliano Grazzini, Stefan Kallweit, Javier Mazzitelli

    We report on a new fully differential calculation of the next-to-next-to-leading-order (NNLO) QCD radiative corrections to the production of top-quark pairs at hadron colliders. The calculation is performed by using the $q_T$ subtraction formalism to handle and cancel infrared singularities in real and virtual contributions. The computation is implemented in the Matrix framework, thereby allowing us to efficiently compute arbitrary infrared-safe observables for stable top quarks. We present NNLO predictions for several single- and double-differential kinematical distributions in $pp$ collisions at the centre-of-mass energy $\sqrt{s}=13$ TeV, and we compare them with recent LHC data by the CMS collaboration.

  • A machine learning study to identify spinodal clumping in high energy nuclear collisions. (arXiv:1906.06562v1 [nucl-th])

    Authors: Jan Steinheimer, LongGang Pang, Kai Zhou, Volker Koch, Jørgen Randrup, Horst Stoecker

    The coordinate and momentum space configurations of the net baryon number in heavy ion collisions that undergo spinodal decomposition, due to a first-order phase transition, are investigated using state-of-the-art machine-learning methods. Coordinate space clumping, which appears in the spinodal decomposition, leaves strong characteristic imprints on the spatial net density distribution in nearly every event. On the other hand, the corresponding momentum distributions do not show clear event-by-event features. However, a small subset of events can be systematically differentiated even if only the momentum space information is available. In such scenarios, observables like the baryon number cumulants signal a spinodal non-equilibrium phase transition. Indeed the third-order cumulant, the skewness, does exhibit a peak at the beam energy ($\mathrm{E}_{\mathrm{lab}}= 3-4$ A GeV), where the transient hot and dense system created in the heavy ion collision reaches the first-order phase transition.

  • Improved description of the HERA data with a new simple PDF parametrization. (arXiv:1906.06573v1 [hep-ph])

    Authors: Francesco Giuli

    A new parametrization for the parton distribution functions with a higher flexibility in the small-$x$ region is presented. It has been implemented in the xFitter open-source PDF fitting tool, and compared to the default xFitter parametrization, used for the determination of the HERAPDF set. It has been found that the combined inclusive HERA I+II data can be described using NNLO theory with a significantly higher quality than HERAPDF2.0: the $\chi^2$ is reduced by more than 60 units, having used only four more parameters. Our result highlights a significant parametrization bias in the default xFitter parametrization at small $x$, which would lead to even more dramatic effects when used for higher energy colliders, where the small-$x$ region is more relevant. We also find that the inclusion of small-$x$ resummation leads to a further reduction by approximately 30 extra units in $\chi^2$. In this contribution, we review the results of the recent paper "A new simple PDF parametrization: improved description of the HERA data" (arXiv:1902.11125).

  • Detecting new signals under background mismodelling. (arXiv:1906.06615v1 [])

    Authors: Sara Algeri

    Searches for new astrophysical phenomena often involve several sources of non-random uncertainties which can lead to highly misleading results. Among these, model-uncertainty arising from background mismodelling can dramatically compromise the sensitivity of the experiment under study. Specifically, overestimating the background distribution in the signal region increases the chances of missing new physics. Conversely, underestimating the background outside the signal region leads to an artificially enhanced sensitivity and a higher likelihood of claiming false discoveries. The aim of this work is to provide a unified statistical strategy to perform modelling, estimation, inference, and signal characterization under background mismodelling. The method proposed allows to incorporate the (partial) scientific knowledge available on the background distribution and provides a data-updated version of it in a purely nonparametric fashion without requiring the specification of prior distributions. Applications in the context of dark matter searches and radio surveys show how the tools presented in this article can be used to incorporate non-stochastic uncertainty due to instrumental noise and to overcome violations of classical distributional assumptions in stacking experiments.

  • The decays $\tau\rightarrow (K, K(1460))\nu_{\tau}$ and the value of the weak decay coefficients ${F}_{K}$ and ${{F}_{{K}^{'}}}$ in the extended NJL model. (arXiv:1906.06680v1 [hep-ph])

    Authors: M. K. Volkov, K. Nurlan, A . A. Pivovarov

    In the extended NJL model, the decay widths of $\tau\rightarrow (K, K(1460))\nu_{\tau}$, $(K, K(1460))\rightarrow {\mu}\nu_{\mu}$ are calculated. The contributions from intermediate axial-vector mesons ${K}_{1}(1270)$, ${K}_{1}(1400)$ and the first radially excited state ${K}_{1}(1650)$ are taken into account. Estimates for the weak decay coefficients ${F}_{K}$ and ${{F}_{{K}^{'}}}$ are given. Predictions are made for the width of $\tau\rightarrow K(1460)\nu_{\tau}$ decay and ${{F}_{{K}^{'}}}$ constant.

  • Dynamically Generated Inflation from Non-Riemannian Volume Forms. (arXiv:1906.06691v1 [gr-qc])

    Authors: David Benisty, Eduardo Guendelman, Emil Nissimov, Svetlana Pacheva

    We propose a simple modified gravity model {\em without} any initial matter fields in terms of several alternative non-Rie\-mann\-ian spacetime volume elements within the metric (second order) formalism. We show how the non-Rie\-mann\-ian volume-elements, when passing to the physical Einstein frame, create a canonical scalar field and produce dynamically a non-trivial inflationary-type potential for the latter with a large flat region and a stable low-lying minimum. We study the evolution of the cosmological solutions from the point of view of theory of dynamical systems. The theory predicts the spectral index $n_s \approx 0.96$ and the tensor-to-scalar ratio $r \approx 0.002$ for 60 $e$-folds, which is in accordance with the observational data. In the future Euclid and SPHEREx missions or the BICEP3 experiment are expected to provide experimental evidence to test those predictions.

  • Sudakov suppression of the Balitsky-Kovchegov kernel. (arXiv:1906.06825v1 [hep-ph])

    Authors: Du-xin Zheng, Jian Zhou

    To sum high energy leading logarithms in a consistent way, one has to impose the strong ordering in both projectile rapidity and dense target rapidity simultaneously, which results in a kinematically improved Balitsky-Kovchegov(BK) equation. We find that beyond this strong ordering region, the important sub-leading double logarithms arise at high order due to the incomplete cancellation between real corrections and virtual corrections in a t-channel calculation. Based on this observation, we further argue that these double logarithms are the Sudakov type ones, and thus can be resummed into an exponential leading to a Sudakov suppressed BK equation.

  • Presupernova neutrino signals as potential probes of neutrino mass hierarchy. (arXiv:1906.06839v1 [astro-ph.HE])

    Authors: Gang Guo, Yong-Zhong Qian, Alexander Heger

    We assess the potential of using presupernova neutrino signals at the Jiangmen Underground Neutrino Observatory (JUNO) to probe the yet-unknown neutrino mass hierarchy. Using models for stars of 12, 15, 20, and 25 solar masses, we find that if the electron antineutrino signals from such a star can be predicted precisely and the star is within ~440-880 pc, the number of events of electron antineutrino captures on protons detected within one day of its explosion allows to determine the hierarchy at the > ~95% confidence level. For determination at this level using such signals from Betelgeuse, which is at a distance of ~222 pc, the uncertainty in the predicted number of signals needs to be < ~14-30%. In view of more realistic uncertainties, we discuss and advocate a model-independent determination using both electron neutrino and antineutrino signals from Betelgeuse. This method is feasible if the cosmogenic background for neutrino-electron scattering events can be reduced by a factor of ~2.5-10 from the current estimate. Such reduction might be achieved by using coincidence of the background events, the exploration of which for JUNO is highly desirable.

  • The cos$\phi_R$ asymmetry of dihadron production in double longitudinally polarized SIDIS. (arXiv:1906.06845v1 [hep-ph])

    Authors: Wei Yang, Hui Li, Zhun Lu

    We present a study on the double longitudinal-spin asymmetry of dihadron production in semi-inclusive deep inelastic scattering, in which the transverse momentum of the final-state hadron pairs is integrated out.In particular, we investigate the origin of the $\cos\phi_R$ azimuthal asymmetry for which we take into account the coupling of the helicity distribution $g_1$ and the twist-3 dihadron fragmentation function $\widetilde{D}^{\sphericalangle}$. We calculate the $s$-wave and $p$-wave interference term $\widetilde{D}^{\sphericalangle}_{ot}$ in a spectator model. We estimate the $\cos\phi_R$ asymmetry at the kinematics of COMPASS which is collecting data on dihadron prouduction in polarized deep inelastic scattering. The prediction of the same asymmetry at JLab 12GeV and a future EIC are also presented. Our study indicates that measuring the $\cos\phi_R$ asymmetry in SIDIS may be a ideal way to probe the dihadron fragmentation function $\widetilde{D}^{\sphericalangle}$.

  • The Role of Future Lepton Colliders for Fermionic Z-portal Dark Matter. (arXiv:1906.06864v1 [hep-ph])

    Authors: Dilip Kumar Ghosh, Taisuke Katayose, Shigeki Matsumoto, Ipsita Saha, Satoshi Shirai, Tomohiko Tanabe

    The fermionic Z-portal dark matter model suffers from severe constraints from direct detection experiments. However, a narrow parameter space around the Z-funnel region is beyond the reach due to the resonance annihilation. In this paper, we provide an intriguing collider prospect for probing the Z-funnel dark matter mass range at the future lepton colliders including the beam polarization feature. We have done a comprehensive analysis for mono-photon signal at the colliders for such a dark matter. A realistic estimation for the 90% C.L. constraints with the systematic beam uncertainties has also been provided.

  • Inflation, Proton Decay, and Higgs-Portal Dark Matter in $SO(10) \times U(1)_\psi$. (arXiv:1906.06869v1 [hep-ph])

    Authors: Nobuchika Okada, Digesh Raut, Qaisar Shafi

    We propose a simple non-supersymmetric grand unified theory (GUT) based on the gauge group $SO(10) \times U(1)_\psi$. The model includes 3 generations of fermions in ${\bf 16}$ ($+1$), ${\bf 10}$ ($-2$) and ${\bf 1}$ ($+4$) representations. The ${\bf 16}$-plets contain Standard Model (SM) fermions plus right-handed neutrinos, and the ${\bf 10}$-plet and the singlet fermions are introduced to make the model anomaly-free. Gauge coupling unification at $M_{GUT} \simeq 5 \times 10^{15}-10^{16}$ GeV is achieved by including an intermediate Pati-Salam breaking at $M_{I} \simeq 10^{12}-10^{11}$ GeV, which is a natural scale for the seesaw mechanism. For $M_{I} \simeq 10^{12}-10^{11}$, proton decay will be tested by the Hyper-Kamiokande experiment. The extra fermions acquire their masses from $U(1)_\psi$ symmetry breaking, and a $U(1)_\psi$ Higgs field drives a successful inflection-point inflation with a low Hubble parameter during inflation, $H_{inf} \ll M_{I}$. Hence, cosmologically dangerous monopoles produced from $SO(10)$ and PS breakings are diluted away. The reheating temperature after inflation can be high enough for successful leptogenesis. With the Higgs field contents of our model, a ${\bf Z}_2$ symmetry remains unbroken after GUT symmetry breaking, and the lightest mass eigenstate among linear combinations of the ${\bf 10}$-plet and the singlet fermions serves as a Higgs-portal dark matter (DM). We identify the parameter regions to reproduce the observed DM relic density while satisfying the current constraint from the direct DM detection experiments. The present allowed region will be fully covered by the future direct detection experiments such as LUX-ZEPLIN DM experiment. In the presence of the extra fermions, the SM Higgs potential is stabilized up to $M_{I}$.

  • Study of Lepton Universality at Belle. (arXiv:1906.06871v1 [hep-ex])

    Authors: Markus Tobias Prim

    The Belle Collaboration presented three recent Belle analyses: The search for $B\rightarrow l\nu\gamma$ ($l = e, \mu$) with improved hadronic tagging, the search for $B\rightarrow \mu \nu_\mu$ with inclusive tagging and the test of lepton universality in $B\rightarrow K^*ll$ ($l = e, \mu$) decays.

  • Lorentz Invariance Violation effects on UHECR propagation: a geometrized approach. (arXiv:1906.06948v1 [hep-ph])

    Authors: M.D.C. Torri, S. Bertini, M. Giammarchi, L. Miramonti

    We explore the possibility to geometrize the interaction of massive fermions with the quantum structure of space-time, trying to create a theoretical background, in order to explain what some recent experimental results seem to implicate on the propagation of Ultra High Energy Cosmic Rays (UHECR). We will investigate part of the phenomenological implications of this approach on the predicted effect of the UHECR suppression, in fact recent evidences seem to involve the modification of the GZK cut-off phenomenon. The search for an effective theory, which can explain this physical effect, is based on Lorentz Invariance Violation (LIV), which is introduced via Modified Dispersion Relations (MDRs). Furthermore we illustrate that this perspective implies a more general geometry of space-time than the usual Riemannian one, indicating, for example, the opportunity to resort to Finsler theory.

  • The Higgs width in the SMEFT. (arXiv:1906.06949v1 [hep-ph])

    Authors: Ilaria Brivio, Tyler Corbett, Michael Trott

    We calculate the total and partial inclusive Higgs widths at leading order in the Standard Model Effective Field Theory (SMEFT). We report results incorporating SMEFT corrections for two and four body Higgs decays through vector currents in this limit. The narrow width approximation is avoided and all phase space integrals are directly evaluated. We explain why the narrow width approximation fails more significantly in the SMEFT compared to the SM, despite the narrowness of the observed $\rm SU(2) \times U(1)$ bosons in both theories. Our results are presented in a manner that allows various input parameter schemes to be used, and they allow the inclusive branching ratios and decay widths of the Higgs to be numerically determined without a Monte Carlo generation of phase space for each Wilson coefficient value chosen.

  • Double D-meson production in proton-proton and proton-lead collisions at the LHC. (arXiv:1906.06971v1 [hep-ph])

    Authors: Ilkka Helenius, Hannu Paukkunen

    We consider the simultaneous production of two heavy-flavoured hadrons - particularly D mesons - at the LHC. We base our calculations on collinearly factorized QCD at next-to-leading order, using the contemporary parton distribution functions and D-meson fragmentation functions. The contributions of double-parton scatterings are included in the approximation of independent partonic interactions. Our framework benchmarks well with the available proton-proton data from the LHCb collaboration giving us confidence to make predictions for proton-lead collisions. Our results indicate that the double D-meson production in proton-lead collisions should be measurable at the LHCb kinematics with the already collected Run-II data, and should provide evidence for double-parton scattering at perturbative scales with a nuclear target.

  • Resonant Decay of Gravitational Waves into Dark Energy. (arXiv:1906.07015v1 [gr-qc])

    Authors: Paolo Creminelli, Giovanni Tambalo, Filippo Vernizzi, Vicharit Yingcharoenrat

    We study the decay of gravitational waves into dark energy fluctuations $\pi$, taking into account the large occupation numbers. We describe dark energy using the effective field theory approach, in the context of generalized scalar-tensor theories. When the $ m_3^3 \delta K\delta g^{00}$ (cubic Horndeski) and $\tilde m_4^2$ (beyond Horndeski) operators are present, the gravitational wave acts as a classical background for $\pi$ and modifies its dynamics. In particular, $\pi$ fluctuations are described by a Mathieu equation and feature instability bands that grow exponentially. Focusing on the regime of small gravitational-wave amplitude, corresponding to narrow resonance, we calculate analytically the produced $\pi$, its energy and the change of the gravitational-wave signal. The resonance is affected by $\pi$ self-interactions in a way that we cannot describe analytically. This effect is very relevant for the operator $m_3^3$ and it probably kills the instability. In the case of the $\tilde m_4^2$ operator self-interactions can be neglected, at least in some regimes. The modification of the gravitational-wave signal is observable for $10^{-20} \lesssim \alpha_{\rm H} \lesssim 10^{-17}$ with a LIGO/Virgo-like interferometer and for $10^{-16} \lesssim \alpha_{\rm H} \lesssim 10^{-10}$ with a LISA-like one. These values are well below the bound from the perturbative decay of the graviton, $\alpha_{\rm H} \lesssim 10^{-10}$.

  • Azimuthal asymmetries in unpolarized SIDIS and Drell-Yan processes: a case study towards TMD factorization at subleading twist. (arXiv:1906.07037v1 [hep-ph])

    Authors: Alessandro Bacchetta, Giuseppe Bozzi, Miguel G. Echevarria, Cristian Pisano, Alexey Prokudin, Marco Radici

    We consider the azimuthal distribution of the final observed hadron in semi-inclusive deep-inelastic scattering and the lepton pair in the Drell-Yan process. In particular, we focus on the $\cos \phi$ modulation of the unpolarized cross section and on its dependence upon transverse momentum. At low transverse momentum, for these observables we propose a factorized expression based on tree-level approach and conjecture that the same formula is valid in transverse-momentum dependent (TMD) factorization when written in terms of subtracted TMD parton distributions. Our formula correctly matches with the collinear factorization results at high transverse momentum, solves a long-standing problem and is a necessary step towards the extension of the TMD factorization theorems up to the subleading twist.

  • Weak production of strange $\Xi$ baryons off the nucleon. (arXiv:1906.07049v1 [hep-ph])

    Authors: M. Rafi Alam, I. Ruiz Simo

    The charged current Cabibbo-supressed associated $K \Xi$ production off the nucleon induced by anti-neutrinos is studied at low and intermediate energies. The non-resonant terms are obtained using a microscopical model based on the SU(3) chiral Lagrangian. The basic parameters of the model are $f_\pi$, the pion decay constant, Cabibbo's angle, the proton and neutron magnetic moments and the axial vector coupling constants for the baryons octet, D and F, that are obtained from the analysis of the semileptonic decays of neutron and hyperons. In addition, we also consider $\Sigma^\ast(1385)$ resonance, which can decay in $K \Xi$ final state when this channel is open. The studied mechanism is the prime source of $\Xi$ production at anti-neutrino energies around $2$ GeV and the calculated cross sections at these energies can be measured at the current and future neutrino experiments.

  • Probing New Physics with $\bar B \to \rho(770) \, \ell^- \bar \nu_\ell$ and $\bar B \to a_1(1260) \, \ell^- \bar \nu_\ell$. (arXiv:1906.07068v1 [hep-ph])

    Authors: P. Colangelo, F. De Fazio, F. Loparco

    The $B$ meson semileptonic modes to $\rho(770)$ and $a_1 (1260)$ are useful to pin down possible non Standard Model effects. The 4d differential $\bar B \to \rho(\pi \pi) \ell^- \bar \nu_\ell$ and $ \bar B \to a_1 (\rho \pi) \ell^- \bar \nu_\ell$ decay distributions are computed in SM and in extensions involving new Lepton Flavour Universality violating semileptonic $b \to u$ operators. The Large Energy limit for the light meson is also considered for both modes. The new effective couplings are constrained using the available data, and several observables in $\bar B \to \rho(\pi\pi) \ell^- \bar \nu_\ell$ in which NP effects can be better identified are selected, using the angular coefficient functions. The complementary role of $\bar B \to \rho(\pi \pi) \ell^- \bar \nu_\ell$ and $\bar B \to a_1 (\rho \pi) \ell^- \bar \nu_\ell$ is discussed.

  • AMS-02 antiprotons are consistent with a secondary astrophysical origin. (arXiv:1906.07119v1 [astro-ph.HE])

    Authors: Mathieu Boudaud, Yoann Génolini, Laurent Derome, Julien Lavalle, David Maurin, Pierre Salati, Pasquale D. Serpico

    The AMS-02 experiment has ushered cosmic-ray physics into precision era. In a companion paper, we designed an improved method to calibrate propagation models on B/C data. Here we provide a robust prediction of the $\bar{p}$ flux, accounting for several sources of uncertainties and their correlations. Combined with a correlation matrix for the $\bar{p}$ data, we show that the latter are consistent with a secondary origin. This Letter presents key elements relevant to dark matter search in this channel, notably by pointing out the inherent difficulties in achieving predictions at the percent-level precision.

  • Non-Gaussian Formation of Primordial Black Holes: Effects on the Threshold. (arXiv:1906.07135v1 [astro-ph.CO])

    Authors: Alex Kehagias, Ilia Musco, Antonio Riotto

    Primordial black holes could have been formed in the early universe from sufficiently large cosmological perturbations re-entering the horizon when the Universe is still radiation dominated. These originate from the spectrum of curvature perturbations generated during inflation at small-scales. Because of the non-linear relation between the curvature perturbation $\zeta$ and the overdensity $\delta\rho$, the formation of the primordial black holes is affected by intrinsic non-Gaussianity even though the curvature perturbation is Gaussian. We investigate the impact of this non-Gaussianity on the critical threshold $\delta_c$ which measures the excess of mass of the perturbation, finding a relative change with respect to the value obtained using a linear relation between $\zeta$ and $\delta\rho$, of a few percent. This shows that the value of the critical threshold is rather robust against non-linearities. This allows a computation of the abundance of primordial black holes which is more precise than using the critical amplitude of the peak, since the latter is more sensitive to the local feature of the shape of the perturbation. The same holds also when cosmologically interesting values of local primordial non-Gaussianity are added to the curvature perturbation.

  • Reggeized model for $\gamma p \to \rho^- \Delta^{++}(1232)$ photoproduction. (arXiv:1612.02071v2 [hep-ph] UPDATED)

    Authors: Byung-Geel Yu, Kook-Jin Kong

    A model for the reaction $\gamma p\to\rho^-\Delta^{++}$ is presented with the $t$-channel $\pi+\rho$ exchanges reggeized to describe the reaction up to high energies. Gauge invariance of $\rho$ exchange is discussed in connection with the convergence of the reaction cross section at high energy. The roles of electromagnetic (EM) multipole moments of $\Delta^{++}$ baryon and of $\rho^-$ meson are analyzed in total and differential cross sections and spin density matrix elements. Photon polarization asymmetry $\Sigma$ is predicted for a measurement of electromagnetic moments of $\rho^-$ and of $\Delta^{++}$.

  • $\Sigma_{b}\to\Sigma_c^*$ weak decays in the light-front quark model with two schemes to deal with the polarization of diquark. (arXiv:1711.02518v4 [hep-ph] UPDATED)

    Authors: Hong-Wei Ke Ning Hao, Xue-Qian Li

    Thanks to the remarkable achievements of LHC, a large database on baryons has been accumulated, so it is believed that the time for precisely studying baryons especially heavy baryons, has come. By analyzing the data, the quark-diquark structure which has been under intensive discussions, can be tested. In this work the decay widths of weak transitions $\Sigma_b\to \Sigma^*_c+X$ are calculated in terms of the light front quark model (LFQM). To carry out the calculations, the quark-diquark picture is employed where an axial-vector diquark composed of two light quarks serves as a spectator in the concerned processes. The first step of this work is to construct the vertex functions for $\Sigma^{(*)}_c$ and $\Sigma_b$, then the relevant form factors are derived. It is shown that under the heavy quark limit the Isgur-Wise functions for the transition are re-deduced. Indeed, how to properly depict the polarization ($\epsilon_{\mu}$) of the diquark is slightly tricky. In this work, we apply two schemes to explicitly determine the momentum-dependence of the diquark. The corresponding numerical results are presented which will be testified by the future experiments.

  • Solving the fermionic mass hierarchy of the standard model. (arXiv:1712.08052v3 [hep-ph] UPDATED)

    Authors: Gauhar Abbas

    We show that a simultaneous explanation for fermionic mass hierarchy among and within the fermionic families, quark-mixing, can be obtained in an extension of the standard model, with real singlet scalar fields, which is UV completed by vector-like fermions and a strongly interacting sector.

  • Catalytic effects of monopoles in QCD. (arXiv:1807.04808v2 [hep-lat] UPDATED)

    Authors: Masayasu Hasegawa

    We want to find indications that magnetic monopoles in quantum chromodynamics (QCD) exist; therefore, we introduce a monopole and anti-monopole pair in the QCD vacuum of the quenched SU(3) by applying the monopole creation operator on the vacuum. We investigate the catalytic effects of monopoles on chiral symmetry breaking using the Dirac operator of the overlap fermions that preserves the chiral symmetry in the lattice gauge theory. First, we confirm that the eigenstate of the monopole creation operator becomes the coherent state and that the monopole creation operator makes monopoles and anti-monopoles in the QCD vacuum. We have found the catalytic effects of monopoles on observables by varying the values of the magnetic charges of the additional monopole and anti-monopole as follows: (i) The decay constants of the pseudoscalar increase. (ii) The values of the chiral condensate, defined as a negative number, decrease. (iii) The light quarks and the pseudoscalar mesons become heavy. The catalytic effects of monopoles on the partial decay width and the lifetime of the charged pion are estimated using the numerical results of the pion decay constant and the pion mass. (iv) The decay width of the charged pion becomes wider than the experimental result, and the lifetime of the charged pion becomes shorter than the experimental result. These are the catalytic effects of monopoles in QCD, which we find in this research.

  • Microlensing of X-ray Pulsars: a Method to Detect Primordial Black Hole Dark Matter. (arXiv:1812.01427v2 [astro-ph.HE] UPDATED)

    Authors: Yang Bai, Nicholas Orlofsky

    Primordial black holes (PBHs) with a mass from $10^{-16}$ to $10^{-11}\,M_\odot$ may comprise 100% of dark matter. Due to a combination of wave and finite source size effects, the traditional microlensing of stars does not probe this mass range. In this paper, we point out that X-ray pulsars with higher photon energies and smaller source sizes are good candidate sources for microlensing for this mass window. Among the existing X-ray pulsars, the Small Magellanic Cloud (SMC) X-1 source is found to be the best candidate because of its apparent brightness and long distance from Earth. We have analyzed the existing observation data of SMC X-1 by the RXTE telescope (around 10 days) and found that PBH as 100% of dark matter is close to but not yet excluded. Future longer observation of this source by X-ray telescopes with larger effective areas such as AstroSat, Athena, Lynx, and eXTP can potentially close the last mass window where PBHs can make up all of dark matter.

  • Systematic construction of basis invariants in the 2HDM. (arXiv:1812.02614v2 [hep-ph] UPDATED)

    Authors: Andreas Trautner

    A new systematic method for the explicit construction of (basis-)invariants is introduced and employed to construct the full ring of basis invariants of the Two-Higgs-Doublet-Model (2HDM) scalar sector. Co- and invariant quantities are obtained by the use of hermitian projection operators. These projection operators are constructed from Young tableaux via birdtrack diagrams and they are used in two steps. First, to extract basis-covariant quantities, and second, to combine the covariants in order to obtain the actual basis invariants. The Hilbert series and Plethystic logarithm are used to find the number and structure of the complete set of generating invariants as well as their interrelations (syzygies). Having full control over the complete ring of (CP-even and CP-odd) basis invariants, we give a new and simple proof of the necessary and sufficient conditions for explicit CP conservation in the 2HDM, confirming earlier results by Gunion and Haber. The method generalizes to other models, with the only foreseeable limitation being computing power.

  • Discovery reach for wino and higgsino dark matter with a disappearing track signature at a 100 TeV $pp$ collider. (arXiv:1901.02987v2 [hep-ph] UPDATED)

    Authors: Masahiko Saito, Ryu Sawada, Koji Terashi, Shoji Asai

    Within the theory of supersymmetry, the lightest neutralino is a dark matter candidate and is often assumed to be the lightest supersymmetric particle (LSP) as well. If the neutral wino or higgsino is dark matter, the upper limit of the LSP mass is determined by the observed relic density of dark matter. If the LSP is a nearly-pure neutral state of the wino or higgsino, the lightest chargino state is expected to have a significant lifetime due to a tiny mass difference between the LSP and the chargino. This article presents discovery potential of the 100 TeV future circular hadron collider (FCC) for the wino and higgsino dark matter using a disappearing-track signature. The search strategy to extend the discovery reach to the thermal limits of wino/higgsino dark matter is discussed with detailed studies on the background rate and the reference design of the FCC-hadron detector under possible running scenarios of the FCC-hadron machine. A proposal of modifying the detector layout and several ideas to improve the sensitivity further are also discussed.

  • Probing the photonic content of the proton using photon-induced dilepton production in $p+\textrm{Pb}$ collisions at the LHC. (arXiv:1901.06305v2 [hep-ph] UPDATED)

    Authors: Mateusz Dyndal, Alexander Glazov, Marta Luszczak, Renat Sadykov

    We propose a new experimental method to probe the photon parton distribution function inside the proton (photon PDF) at LHC energies. The method is based on the measurement of dilepton production from the $\gamma p\rightarrow\ell^+\ell^-+X$ reaction in proton--lead collisions. These experimental conditions guarantee a clean environment, both in terms of reconstruction of the final state and in terms of possible background. We firstly calculate the cross sections for this process with collinear photon PDFs, where we identify optimal choice of the scale, in analogy to deep inelastic scattering kinematics. We then perform calculations including the transverse-momentum dependence of the probed photon. Finally we estimate rates of the process for the existing LHC data samples.

  • Baryogenesis from B Meson Oscillations. (arXiv:1901.08141v2 [hep-ph] UPDATED)

    Authors: Ann E. Nelson, Huangyu Xiao

    We show how CP violating B meson oscillations in conjunction with baryon number violating decays can generate the cosmological asymmetry between matter and anti-matter, and explore the parameter space of a simple, self-contained model, which can be tested via exotic B meson decays, and via the charge asymmetry in semi-leptonic decays of neutral B mesons.

  • Anomaly matching in QCD thermal phase transition. (arXiv:1901.08188v2 [hep-th] UPDATED)

    Authors: Kazuya Yonekura

    We study an 't Hooft anomaly of massless QCD at finite temperature. With the imaginary baryon chemical potential at the Roberge-Weiss point, there is a $\mathbb{Z}_2$ symmetry which can be used to define confinement. We show the existence of a mixed anomaly between the $\mathbb{Z}_2$ symmetry and the chiral symmetry, which gives a strong relation between confinement and chiral symmetry breaking. The anomaly is a parity anomaly in the QCD Lagrangian reduced to three dimensions. It is reproduced in the chiral Lagrangian by a topological term related to Skyrmion charge, matching the anomaly before and after QCD phase transition. The effect of the imaginary chemical potential is suppresssed in the large $N$ expansion, and we discuss implications of the 't~Hooft anomaly matching for the nature of QCD phase transition with and without the imaginary chemical potential. Arguments based on universality alone are disfavored, and a first order phase transition may be the simplest possibility if the large $N$ expansion is qualitatively good.

  • U(1)' coupling constant at low energies from heterotic orbifolds. (arXiv:1901.10102v2 [hep-ph] UPDATED)

    Authors: Yessenia Olguin-Trejo, Omar Perez-Figueroa, Ricardo Perez-Martinez, Saul Ramos-Sanchez

    Additional Abelian gauge interactions are generic to string compactifications. In heterotic string models, gauge coupling unification of such forces and other gauge interactions is natural due to their common origin. In this letter we study systematically the 1-loop running of the coupling constants in effective vacua emerging from Z8 heterotic orbifold compactifications that provide the matter spectrum of the MSSM plus some vectorlike exotics, restricting to vacua that yield a non-anomalous U(1)' symmetry, gauge coupling unification and the observed values of known gauge couplings. We determine the low-energy value of the U(1)' coupling constant for different scales of supersymmetry breakdown. We find that the U(1)' coupling constant is quite restricted in string models to lie in the range 0.46-0.7 for low-scale supersymmetry or 0.44-0.6 in other cases. We argue that the phenomenology of these string vacua should be further explored to solve some extant issues, such as the stability of the Higgs vacuum.

  • Spectrum of the $uudc \bar c$ hidden charm pentaquark with an SU(4) flavor-spin hyperfine interaction. (arXiv:1902.07101v3 [hep-ph] UPDATED)

    Authors: Fl. Stancu

    We study a few of the lowest states of the pentaquark $uudc\overline{c}$, of positive and negative parity, in a constituent quark model with an SU(4) flavour-spin hyperfine interaction. The pentaquark positive parity is the antiquark parity times that of the four-quark subsystem. For positive parity we introduce space wave functions of appropriate permutation symmetry with one unit of orbital angular momentum in the internal motion. We show that the lowest positive parity states $1/2^+, 3/2^+$ are located below the $1/2^-$ state with all quarks in the ground state. We compare our results with the LHCb three narrow pentaquark structures reported in 2019.

  • Mesons with Beauty and Charm: New Horizons in Spectroscopy. (arXiv:1902.09735v2 [hep-ph] UPDATED)

    Authors: Estia J. Eichten, Chris Quigg

    The $B_c ^+$ family of $(c\bar{b})$ mesons with beauty and charm is of special interest among heavy quarkonium systems. The $B_c ^+$ mesons are intermediate between $(c\bar{c})$ and $(b\bar{b})$ states both in mass and size, so many features of the $(c\bar{b})$ spectrum can be inferred from what we know of the charmonium and bottomonium systems. The unequal quark masses mean that the dynamics may be richer than a simple interpolation would imply, in part because the charmed quark moves faster in $B_c$ than in the $J/\psi$. Close examination of the $B_c ^+$ spectrum can test our understanding of the interactions between heavy quarks and antiquarks and may reveal where approximations break down. ...

  • The quenched SU(2) scalar-gluon vertex in minimal Landau gauge. (arXiv:1902.10568v2 [hep-lat] UPDATED)

    Authors: Axel Maas

    The question of whether confining effects are visible in correlation functions is a long-standing one. Complementing investigations on the propagators of fundamental and adjoint scalar matter particles here the quenched scalar-gluon vertex is investigated. For this purpose a multitude of lattice setups in two, three, and four dimensions is analyzed in quenched SU(2) lattice gauge theory. Though both cases are quantitatively different, neither a qualitative difference nor any singularities are observed.

  • On the Origin of Two-Loop Neutrino Mass from SU(5) Grand Unification. (arXiv:1902.11254v2 [hep-ph] UPDATED)

    Authors: Shaikh Saad

    In this work we propose a renormalizable model based on the $SU(5)$ gauge group where neutrino mass originates at the two-loop level without extending the fermionic content of the Standard Model (SM). Unlike the conventional $SU(5)$ models, in this proposed scenario, neutrino mass is intertwined with the charged fermion masses. In addition to correctly reproducing the SM charged fermion masses and mixings, neutrino mass is generated at the quantum level, hence naturally explains the smallness of neutrino masses. In this set-up, we provide examples of gauge coupling unification that simultaneously satisfy the proton decay constraints. This model has the potential to be tested experimentally by measuring the proton decay in the future experiments. Scalar leptoquarks that are naturally contained within this framework can accommodate the recent B-physics anomalies.

  • Application of the path optimization method to the sign problem in an effective model of QCD with a repulsive vector-type interaction. (arXiv:1903.03679v2 [hep-lat] UPDATED)

    Authors: Kouji Kashiwa, Yuto Mori, Akira Ohnishi

    The path optimization method is applied to a QCD effective model with the Polyakov loop and the repulsive vector-type interaction at finite temperature and density to circumvent the model sign problem. We show how the path optimization method can increase the average phase factor and control the model sign problem. This is the first study which correctly treats the repulsive vector-type interaction in the QCD effective model with the Polyakov-loop via the Markov-chain Monte-Carlo approach. It is shown that the complexification of the temporal component of the gluon field and also the vector-type auxiliary field are necessary to evade the model sign problem within the standard path-integral formulation.

  • Neutrino Topology Reconstruction at DUNE and Applications to Searches for Dark Matter Annihilation in the Sun. (arXiv:1903.04175v2 [astro-ph.HE] UPDATED)

    Authors: Carsten Rott, DongYoung Jeong, Jason Kumar, David Yaylali

    We consider a new technique for neutrino energy and topology reconstruction at DUNE. In particular, we show that when the direction of the incoming neutrino is known, one can use the measured directions of the outgoing leptonic and hadronic particles to reconstruct poorly-measured quantities, such as the hadronic cascade energy. We show that this alternative technique yields an energy resolution which is comparable to current reconstruction methods which sum measured energies. As a proof of concept we apply this new reconstruction method to a search for dark matter annihilation in the Sun. We show that the use of directional information from both the leptonic and hadronic interaction products allows one to effectively reject backgrounds and isolate the signal, giving competitive sensitivities.

  • Theta dependence of the vacuum energy density in chiral effective Lagrangian models at finite temperature, above $T_c$. (arXiv:1903.10307v2 [hep-ph] UPDATED)

    Authors: Enrico Meggiolaro

    In this work, extending a previous study at zero temperature ($T=0$), we perform a systematic study of the modifications to the QCD vacuum energy density $\epsilon_{vac}$ in the finite-temperature case, above the chiral transition at $T_c$, caused by a nonzero value of the parameter $\theta$, using two different effective Lagrangian models which implement the $U(1)$ axial anomaly of the fundamental theory and which are both well defined also above $T_c$. In particular, we derive (and critically compare) the expressions for the topological susceptibility $\chi$ and for the second cumulant $c_4$ starting from the $\theta$ dependence of $\epsilon_{vac}(\theta)$ in the two models.

  • Off-shell single-top-quark production in the Standard Model Effective Field Theory. (arXiv:1903.11023v2 [hep-ph] UPDATED)

    Authors: Tobias Neumann, Zack Sullivan

    We present a fully differential and spin-dependent $t$-channel single-top-quark calculation at next-to-leading order (NLO) in QCD including off-shell effects by using the complex mass scheme in the Standard Model (SM) and in the Standard Model Effective Field Theory (SMEFT). We include all relevant SMEFT operators at $1/\Lambda^2$ that contribute at NLO in QCD for a fully consistent comparison to the SM at NLO. In addition, we include chirality flipping operators that do not interfere with the SM amplitude and contribute only at $1/\Lambda^4$ with a massless $b$-quark. Such higher order effects are usually captured by considering anomalous right-handed $Wtb$ and left-handed $Wtb$ tensor couplings. Despite their formal suppression in the SMEFT, they describe an important class of models for new physics. Our calculation and analysis framework is publicly available in MCFM.

  • Emergence of a complete heavy-quark spin symmetry multiplet: seven molecular pentaquarks in light of the latest LHCb analysis. (arXiv:1903.11560v3 [hep-ph] UPDATED)

    Authors: Ming-Zhu Liu, Ya-Wen Pan, Fang-Zheng Peng, Mario Sanchez Sanchez, Li-Sheng Geng, Atsushi Hosaka, Manuel Pavon Valderrama

    A recent analysis by the LHCb collaboration suggests the existence of three narrow pentaquark-like states --- the $P_c(4312)$,$P_c(4440)$ and $P_c(4457)$ --- instead of just one in the previous analysis (the $P_c(4450)$). The closeness of the $P_c(4312)$ to the $\bar{D} \Sigma_c$ threshold and the $P_c(4440)$/$P_c(4457)$ to the $\bar{D}^* \Sigma_c$ one suggests a molecular interpretation of these resonances. We show that these three pentaquark-like resonances can be naturally accommodated in a contact-range effective field theory description that incorporates heavy-quark spin symmetry. This description leads to the prediction of all the seven possible S-wave heavy antimeson-baryon molecules (that is, there should be four additional molecular pentaquarks in addition to the $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$), providing the first example of a heavy-quark spin symmetry molecular multiplet that is complete. If this is confirmed, it will not only give us an impressive example of the application of heavy-quark symmetries and effective field theories in hadron physics: it will also uncover a clear and powerful ordering principle for the molecular spectrum, reminiscent of the SU(3)-flavor multiplets to which the light hadron spectrum conforms.

  • Strong decays of double-charmed pseudoscalar and scalar $cc\overline{u}\overline{d}$ tetraquarks. (arXiv:1903.11975v3 [hep-ph] UPDATED)

    Authors: S. S. Agaev, K. Azizi, H. Sundu

    The strong decays of the pseudoscalar and scalar double-charmed tetraquarks $ T_{cc;\overline{u}\overline{d}}^{+}$ and $\widetilde{T}_{cc;\overline{u} \overline{d}}^{+}$ are investigated in the framework of the QCD sum rule method. The mass and coupling of these exotic four-quark mesons are calculated in the framework of the QCD two-point sum rule approach by taking into account vacuum condensates of the quark, gluon, and mixed local operators up to dimension 10. Our results for masses $m_{T}=(4130~\pm 170)~ \mathrm{MeV} $ and $m_{\widetilde{T}}=(3845~\pm 175)~\mathrm{MeV}$ demonstrate that these tetraquarks are strong-interaction unstable resonances and decay to conventional mesons through the channels $T_{cc; \overline{u}\overline{d}}^{+} \to D^{+}D^{\ast }(2007)^{0},~D^{0}D^{\ast }(2010)^{+}$ and $\widetilde{T}_{cc;\overline{u}\overline{d}}^{+}\to D^{+}D^{0}$. Key quantities necessary to compute the partial width of these decay modes, i.e., the strong couplings of two $D$ mesons and a corresponding tetraquark $g_i,~i=1,2$, and $G$ are extracted from the QCD three-point sum rules. The full width $\Gamma _{T}=(129.9\pm 23.5)~\mathrm{ MeV}$ demonstrates that the tetraquark $T_{cc;\overline{u}\overline{d}}^{+}$ is a broad resonance, whereas the scalar exotic meson with $\Gamma _{ \widetilde{T}}=(12.4\pm 3.1)~\mathrm{MeV}$ can be classified as a relatively narrow state.

  • Revisiting $\Lambda_{b}\to\Lambda_{c}$ and $\Sigma_{b}\to\Sigma_{c}$ weak decays in the light-front quark model. (arXiv:1904.05705v2 [hep-ph] UPDATED)

    Authors: Hong-Wei Ke, Ning Hao, Xue-Qian Li

    In this work, we study $\Lambda_{b}\to\Lambda_{c}$ and $\Sigma_{b}\to\Sigma_{c}$ weak decays in the light-front quark model. As is well known, the key point for such calculations is properly evaluating the hadronic transition matrix elements which are dominated by the non-perturbative QCD effect. In our calculation, we employ the light-front quark model and rather than the traditional diquark picture, we account the two spectator light quarks as individual ones. Namely during the transition, they retain their color indices, momenta and spin polarizations unchanged. Definitely, the subsystem composed of the two light quarks is still in a color-anti-triplet and possesses a definite spin, but we do not priori assume the two light quarks to be in a bound system-diquark. Our purpose is probing the diquark picture, via comparing the results with the available data, we test the validity and applicability of the diquark structure which turns a three-body problem into a two-body one, so greatly simplifies the calculation. It is indicated that the two approaches (diquark and a subsystem within which the two light quarks are free) lead to similar numerical results even though the model parameters in the two schemes might deviate slightly. Thus, the diquark approach seems sufficiently reasonable.

  • Effective gauge theories of superfluidity with topological order. (arXiv:1904.08570v2 [hep-th] UPDATED)

    Authors: Yuji Hirono, Yuya Tanizaki

    We discuss the low-energy dynamics of superfluidity with topological order in $(3+1)$ spacetime dimensions. We generalize a topological $BF$ theory by introducing a non-square $K$ matrix, and this generalized $BF$ theory can describe massless Nambu-Goldstone bosons and anyonic statistics between vortices and quasiparticles. We discuss the general structure of discrete and continuous higher-form symmetries in this theory, which can be used to classify quantum phases. We describe how to identify the appearance of topological order in such systems and discuss its relation to a mixed 't Hooft anomaly between discrete higher-form symmetries. We apply this framework to the color-flavor locked phase of dense QCD, which shows anyonic particle-vortex statistics while no topological order appears. An explicit example of superfluidity with topological order is discussed.

  • B-meson charged current anomalies: the post-Moriond status. (arXiv:1904.10432v3 [hep-ph] UPDATED)

    Authors: Debjyoti Bardhan, Diptimoy Ghosh

    In this note, we discuss the impact of the recent Belle result on the various theoretical explanations of the $R_D$ and $R_{D^*}$ anomalies. The pure tensor explanation, which was strongly disfavoured by the measurements of $F_L^{D^*}$ and high-$p_T$ $p \, p \to \tau \, \nu$ searches before Moriond, is now completely allowed because of reduction of the experimental world-average. Moreover, the pure right-chiral vector solution (involving right-chiral neutrinos) has now moved into the $2\sigma$ allowed range of the LHC $p \, p \to \tau \, \nu$ searches. We also critically re-examine the bound on $\mathcal{B}(B_c^- \to \tau^- \bar{\nu}_\tau)$ from LEP data and show that the bound is considerably weaker than the number $10\%$ often used in the recent literature.

  • Bouncing Universe from Nothing. (arXiv:1904.12312v3 [gr-qc] UPDATED)

    Authors: Hiroki Matsui, Fuminobu Takahashi, Takahiro Terada

    We find a class of solutions for a homogeneous and isotropic universe in which the initially expanding universe stops expanding, experiences contraction, and then expands again (the "bounce"), in the framework of Einstein gravity with a real scalar field without violating the null energy condition nor encountering any singularities. Two essential ingredients for the bouncing universe are the positive spatial curvature and the scalar potential which becomes flatter at large field values. Depending on the initial condition, either the positive curvature or the negative potential stops the cosmic expansion and begins the contraction phase. The flat potential plays a crucial role in triggering the bounce. After the bounce, the flat potential naturally allows the universe to enter the slow-roll inflation regime, thereby making the bouncing universe compatible with observations. If the e-folding of the subsequent inflation is just enough, a positive spatial curvature may be found in the future observations. Our scenario nicely fits with the creation of the universe from nothing, which leads to the homogeneous and isotropic universe with positive curvature. As a variant of the mechanism, we also find solutions representing a cyclic universe.

  • Novel ideas in nonleptonic decays of double heavy baryons. (arXiv:1905.06219v2 [hep-ph] UPDATED)

    Authors: Thomas Gutsche, Mikhail A. Ivanov, Jürgen G. Körner, Valery E. Lyubovitskij

    The recent discovery of double charm baryon states by the LHCb Collaborarion and their high precision mass determination calls for a comprehensive analysis of the nonleptonic decays of double and single heavy baryons. Nonleptonic baryon decays play an important role in particle phenomenology since they allow to study the interplay of long and short distance dynamics of the Standard Model (SM). Further, they allow one to search for New Physics effects beyond the SM. We review recent progress in experimental and theoretical studies of the nonleptonic decays of heavy baryons with a focus on double charm baryon states and their decays. In particular, we discuss new ideas proposed by the present authors to calculate the $W$-exchange matrix elements of the nonleptonic decays of double heavy baryons. An important ingredient in our approach is the compositeness condition of Salam and Weinberg, and an effective implementation of infrared confinement both of which allow one to describe the nonperturbative structure of baryons composed of light and heavy quarks. Further we discuss an ab initio calculational method for the treatment of the so-called $W$-exchange diagrams generated by $W^{\pm}$ boson exchange between quarks. We found that the $W^{\pm}$-exchange contributions are not suppressed in comparison with the tree-level (factrorizing) diagrams and must be taken into account in the evaluation of matrix elements. Moreover, there are decay processes such as the doubly Cabibbo-suppressed decay $\Xi_c^+ \to p \phi$ recently observed by the LHCb Collaboration which is contributed to only by one single $W$-exchange diagram.

  • Incomplete equilibration in high-multiplicity pp and pPb events at LHC. (arXiv:1905.06532v2 [hep-ph] UPDATED)

    Authors: Nachiketa Sarkar, Paramita Deb, Premomoy Ghosh

    Multiple Reflection Expansion (MRE) formalism has been introduced to the hadron resonance gas model to study the finite-size effect on the chemical freeze-out of equilibrated hadron gas, likely to be produced in high-multiplicity events of pp, pA and AA collisions at LHC and RHIC. The degree of equilibration at the freeze-out for different colliding systems has been compared, in terms of thermodynamic variables, by contrasting ideal equilibrium conditions provided by first-principle LQCD calculations. In contrast to AA collisions, the freeze-out condition in the high-multiplicity pp and pA events remain away from the ideal thermodynamic limit, indicating incomplete equilibration. Quantitative comparison in terms of Knudsen number confirms the finding.

  • Charged Higgs bosons in the NMSSM under current LHC constraints. (arXiv:1905.09412v2 [hep-ph] UPDATED)

    Authors: Zhaoxia Heng, Lin Guo, Pengqiang Sun, Wei Wei

    Charged Higgs boson is a crucial prediction of new physics beyond the SM. In this work, we perform a comprehensive scan over the parameter space of NMSSM considering various experimental constraints including the direct search limits from the 13 TeV LHC, and consider the scenario that the next-to-lightest CP-even Higgs boson is SM-like. We find that the masses of charged Higgs bosons can be as light as 350 GeV, the lightest CP-even Higgs boson $h_1$ is predominantly singlet and can be as light as 48 GeV, and the lightest CP-odd Higgs boson $a_1$ is also singlet-dominated and can be as light as 82 GeV. The charged Higgs bosons mainly decay to $t\bar{b}$ or $\bar{t} b$, but the branching ratio of the exotic decays $H^\pm\to W^\pm h_1$ and $H^\pm\to W^\pm a_1$ can maximally reach to 20\% and 11\%, respectively, which can be used to distinguish the NMSSM from MSSM. Such a heavy charged Higgs boson is unaccessible at the 13 TeV LHC with a luminosity of 36.1 $\rm fb^{-1}$ and its detection needs higher energy and/or higher luminosity.

  • Canonical interpretation of $Y(10750)$ and $\Upsilon(10860)$ in the $\Upsilon$ family. (arXiv:1905.10344v2 [hep-ph] UPDATED)

    Authors: Qi Li, Ming-Sheng Liu, Qi-Fang Lü, Long-Cheng Gui, Xian-Hui Zhong

    Inspired by the new resonance $Y(10750)$, we calculate the masses and two-body OZI-allowed strong decays of the higher vector bottomonium sates within both screened and linear potential models. We discuss the possibilities of $\Upsilon(10860)$ and $Y(10750)$ as mixed states via the $S-D$ mixing. Our results suggest that $Y(10750)$ and $\Upsilon(10860)$ might be explained as mixed states between $5S$- and $4D$-wave vector $b\bar{b}$ states. The $Y(10750)$ and $\Upsilon(10860)$ resonances may correspond to the mixed states dominated by the $4D$- and $5S$-wave components, respectively. The mass and the strong decay behaviors of the $\Upsilon(11020)$ resonance are consistent with the assignment of the $\Upsilon(6S)$ state in the potential models.

  • Impact of Non-perturbative QCD on CP Violation in Many-Body Final States of Flavor Transitions. (arXiv:1905.10871v3 [hep-ph] UPDATED)

    Authors: I. I. Bigi

    The title of my talk pointed out central statements: the impact of non-perturbative QCD on {\bf CP} asymmetries in many-body FS in charm \& beauty hadrons. For practical reasons one measures first {\bf CP} violation in two-body final states of heavy flavor hadrons. However, those are small parts of charm hadrons and tiny ones for beauty hadrons; therefore one has to probe {\bf CP} asymmetries in three- \& four-body final states. Thus the transitions to the many-body FS basically give information about the underlying dynamics. The impact of non-perturbative QCD on {\bf CP} asymmetries in many-body FS shows that -- in principle; it is a true challenge even in a semi-quantitative way. One needs correlations with other transitions. That is my strategy; however, I have to discuss the tactics on the same level like using consistent parameterization of the CKM matrix. Our community has entered a novel era: direct {\bf CP} violation has been found in $D^0 \to h^+h^-$ decays \cite{CHARM}. Finally I give short comments about the possible impact of New Dynamics on direct {\bf CP} violation in $K_L \to 2 \pi$ and probe {\bf CP} asymmetry in $J/\psi \to \bar \Lambda \Lambda$ transitions.

  • Is the $Y(2175)$ a Strangeonium Hybrid Meson?. (arXiv:1905.12779v2 [hep-ph] UPDATED)

    Authors: J. Ho, R. Berg, T. G. Steele, W. Chen, D. Harnett

    QCD Gaussian sum-rules are used to explore the vector ($J^{PC}=1^{--}$) strangeonium hybrid interpretation of the $Y(2175)$. Using a two-resonance model consisting of the $Y(2175)$ and an additional resonance, we find that the relative resonance strength of the $Y(2175)$ in the Gaussian sum-rules is less than 5\% that of a heavier 2.9 GeV state. This small relative strength presents a challenge to a dominantly-hybrid interpretation of the $Y(2175)$.

  • Limits on the Charged Higgs Parameters in the Two Higgs Doublet Model using CMS $\sqrt{s}=13$ TeV Results. (arXiv:1906.02520v2 [hep-ph] UPDATED)

    Authors: Prasenjit Sanyal

    Latest CMS results on the upper limits on $\sigma_{H^\pm}$BR($H^\pm \rightarrow \tau^\pm\nu)$ and $\sigma_{H^\pm}$BR($H^+ \rightarrow t\bar{b}$) for $\sqrt{s}=13$ TeV at an integrated luminosity of 35.9 fb$^{-1}$ are used to impose constraints on the charged Higgs $H^\pm$ parameters within the Two Higgs Doublet Model (2HDM). The 2HDM is the simplest extension of Standard Model (SM) under the same gauge symmetry to contain charged Higgs and is relatively less constrained compared to Minimal Supersymmetric Standard Model (MSSM). The latest results lead to much more stringent constraints on charged Higgs parameter space in comparison to the earlier 8 TeV results. The CMS collaboration also studied the exotic bosonic decay $H^\pm \rightarrow W^\pm A$ and $A \rightarrow \mu^+ \mu^-$ for the first time and put upper limits on the BR($t\rightarrow H^+ b$) for light charged Higgs. These constraints lead to exclusion of parameter space which are not excluded by the $\tau \nu$ channel. For comparison the exclusion regions from flavour physics constraints are also discussed.

  • Thermal Field Theory of the Tsallis statistics. (arXiv:1906.02893v2 [hep-ph] UPDATED)

    Authors: Mahfuzur Rahaman, Trambak Bhattacharyya, Jan-e Alam

    Classical and quantum Tsallis distributions have been widely used in many branches of natural and social sciences. But, the quantum field theory of the Tsallis distributions is relatively a less explored arena. In this article we derive the expression for the thermal two-point functions for the Tsallis statistics with the help of the corresponding statistical mechanical formulations. We show that the quantum Tsallis distributions used in the literature appear in the thermal part of the propagator much in the same way the Boltzmann-Gibbs distributions appear in the conventional thermal field theory. As an application of our findings, thermal mass of the real scalar bosons subjected to phi^4 interaction has been calculated in the Tsallis statistics.

  • m_c and m_b from M_B_c and new estimate of f_B_c. (arXiv:1906.03614v2 [hep-ph] UPDATED)

    Authors: Stephan Narison (CNRS-Montpellier)

    We extract (for the first time) the correlated values of the running masses m_c and m_b from M_Bc using QCD Laplace sum rules (LSR) within stability criteria where pertubative (PT) expressions at N2LO and non-perturbative (NP) gluon condensates at LO are included. We deduce : m_c(m_c) = 1275(11) MeV and m_b(m_b) = 4216(10) MeV. Combined with our recent estimates from charmonium, bottomium and D, B sum rules, we deduce the new QCD Spectral Sum Rules (QSSR) global average m_c(m_c) = 1266(5) MeV and m_b(m_b) = 4199(6) MeV. As a result, we present an improved prediction of f_B_c =431(7)MeV.

  • Chromopolarizabilities of bottomonia from the $\Upsilon(2S,3S,4S) \to \Upsilon(1S,2S)\pi\pi$ transitions. (arXiv:1906.05766v2 [hep-ph] UPDATED)

    Authors: Yun-Hua Chen, Feng-Kun Guo

    The dipion transitions $\Upsilon(2S,3S,4S) \to \Upsilon(1S,2S)\pi\pi$ are systemaically studied by considering the mechanisms of the hadronization of soft gluons, exchanging the bottomoniumlike $Z_b$ states, and the bottom-meson loops. The strong pion-pion final-state interaction, especially including the channel coupling to $K\bar{K}$ in the $S$-wave, is taken into account in a model-independent way using the dispersion theory. Through fitting to the available experimental data, we extract values of the transition chromopolarizabilities $|\alpha_{\Upsilon(mS)\Upsilon(nS)}|$, which measure the chromoelectric couplings of the bottomonia with soft gluons. It is found that the $Z_b$ exchange has a large impact on the extracted chromopolarizablity values. The obtained $|\alpha_{\Upsilon(2S)\Upsilon(1S)}|$ considering the $Z_b$ exchange is $(2.9\pm 2.0)\times 10^{-2}~\text{GeV}^{-3}$, about one order of magnitude smaller than the one without considering the $Z_b$ exchange effect. This indicates that the interactions of bottomonia with light hadrons through exchanging soft gluons are very weak, and the $u$-channel exchange of the $Z_b$ states should be much more important for the $\Upsilon\pi$ scattering than the $t$-channel soft-gluon exchange.

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