hep-ph updates on
High Energy Physics - Phenomenology (hep-ph) updates on the e-print archive
  • Probing Muonic Forces and Dark Matter at Kaon Factories. (arXiv:1902.07715v1 [hep-ph])

    Authors: Gordan Krnjaic, Gustavo Marques-Tavares, Diego Redigolo, Kohsaku Tobioka

    Rare kaon decays are excellent probes of light, new weakly-coupled particles. If such particles $X$ couple preferentially to muons, they can be produced in $K\to \mu \nu X$ decays. In this letter we evaluate the future sensitivity for this process at NA62 assuming $X$ decays either invisibly or to di-muons. Our main physics target is the parameter space that resolves the $(g-2)_\mu$ anomaly, where $X$ is a gauged $L_\mu-L_\tau$ vector or a muon-philic scalar. The same parameter space can also accommodate dark matter freeze out or reduce the tension between cosmological and local measurements of $H_0$ if the new force decays to dark matter or neutrinos, respectively. We show that for invisible $X$ decays, a dedicated single muon trigger analysis at NA62 could probe much of the remaining $(g-2)_\mu$ favored parameter space. Alternatively, if $X$ decays to muons, NA62 can perform a di-muon resonance search in $K\to 3 \mu \nu$ events and greatly improve existing coverage for this process. Independently of its sensitivity to new particles, we find that NA62 is also sensitive to the Standard Model predicted rate for $K \to 3\mu \nu$, which has never been measured.

  • Higgs Parity, Strong CP, and Dark Matter. (arXiv:1902.07726v1 [hep-ph])

    Authors: David Dunsky, Lawrence J. Hall, Keisuke Harigaya

    An exact spacetime parity replicates the $SU(2) \times U(1)$ electroweak interaction, the Higgs boson $H$, and the matter of the Standard Model. This "Higgs Parity" and the mirror electroweak symmetry are spontaneously broken at scale $v' = \left\langle{H'} \right\rangle \gg \left\langle{H}\right\rangle$, yielding the Standard Model below $v'$ with a quartic coupling that essentially vanishes at $v'$: $\lambda_{SM}(v') \sim 10^{-3}$. The strong CP problem is solved as Higgs parity forces the masses of mirror quarks and ordinary quarks to have opposite phases. Dark matter is composed of mirror electrons, $e'$, stabilized by unbroken mirror electromagnetism. These interact with Standard Model particles via kinetic mixing between the photon and the mirror photon, which arises at four-loop level and is a firm prediction of the theory. Physics below $v'$, including the mass and interaction of $e'$ dark matter, is described by $\textit{one fewer parameter}$ than in the Standard Model. The allowed range of $m_{e'}$ is determined by uncertainties in $(\alpha_s, m_t, m_h)$, so that future precision measurements of these will be correlated with the direct detection rate of $e'$ dark matter, which, together with the neutron electric dipole moment, will probe the entire parameter space.

  • Superasymptotic and Hyperasymptotic approximation to the Operator Product Expansion. (arXiv:1902.07736v1 [hep-th])

    Authors: Cesar Ayala, Xabier Lobregat, Antonio Pineda

    Given an observable and its operator product expansion (OPE), we present expressions that carefully disentangle truncated sums of the perturbative series in powers of $\alpha$ from the non-perturbative (NP) corrections. This splitting is done with NP power accuracy. Analytic control of the splitting is achieved and the organization of the different terms is done along an super/hyper-asymptotic expansion. As a test we apply the methods to the static potential in the large $\beta_0$. We see the superasymptotic and hyperasymptotic structure of the observable in full glory.

  • Cosmological Magnetic Field and Dark Energy as two sides of the same coin. (arXiv:1902.07737v1 [hep-ph])

    Authors: Ariel R. Zhitnitsky

    It has been recently argued \cite{Barvinsky:2017lfl} that the de Sitter phase in cosmology might be naturally generated as a result of dynamics of the topologically nontrivial sectors in a strongly coupled QCD-like gauge theory in expanding universe. It is known that the de Sitter phase is realized in the history of our Universe twice: the first occurrence is coined as the inflation, while the second time (which is occurring now) is dubbed as the dark energy (DE). The crucial element of the proposal \cite{Barvinsky:2017lfl} is the presence of a nontrivial gauge holonomy which is the source of the vacuum energy leading to the de Sitter behaviour. It has been also argued that the anomalous coupling of the system with the Standard Model (SM) particles leads to the reheating epoch in case of the {\it inflationary} phase. A similar anomalous coupling of the system with the Maxwell $E\&M$ field during the {\it DE epoch} generates the cosmological magnetic field. The intensity of the field is estimated on the level of $10^{-10}$G while the corresponding correlation length reaches the scale of the visible Universe.

  • Probing the Neutrino Mass Ordering with Atmospheric Neutrinos from Three Years of IceCube DeepCore Data. (arXiv:1902.07771v1 [hep-ex])

    Authors: M. G. Aartsen, M. Ackermann, J. Adams, J. A. Aguilar, M. Ahlers, M. Ahrens, C. Alispach, K. Andeen, T. Anderson, I. Ansseau, G. Anton, C. Argüelles, J. Auffenberg, S. Axani, P. Backes, H. Bagherpour, X. Bai, A. Barbano, S. W. Barwick, V. Baum, R. Bay, J. J. Beatty, K.-H. Becker, J. Becker Tjus, S. BenZvi, D. Berley, E. Bernardini, E. Bernardini, D. Z. Besson, G. Binder, D. Bindig, E. Blaufuss, S. Blot, C. Bohm, M. Börner, S. Böser, O. Botner, E. Bourbeau, J. Bourbeau, F. Bradascio, J. Braun, H.-P. Bretz, S. Bron, J. Brostean-Kaiser, A. Burgman, R. S. Busse, T. Carver, C. Chen, E. Cheung, D. Chirkin, K. Clark, L. Classen, G. H. Collin, J. M. Conrad, P. Coppin, P. Correa, D. F. Cowen, R. Cross, P. Dave, J. P. A. M. de André, C. De Clercq, J. J. DeLaunay, H. Dembinski, K. Deoskar, et al. (272 additional authors not shown)

    The Neutrino Mass Ordering (NMO) remains one of the outstanding questions in the field of neutrino physics. One strategy to measure the NMO is to observe matter effects in the oscillation pattern of atmospheric neutrinos above $\sim 1\,\mathrm{GeV}$, as proposed for several next-generation neutrino experiments. Moreover, the existing IceCube DeepCore detector can already explore this type of measurement. We present results of a first search for the signature of the NMO with three years of DeepCore data based on two independent analyses. These analyses include a full treatment of systematic uncertainties and a statistically-rigorous method to determine the significance for the NMO from a fit to the data. For the more sensitive analysis, we observe a preference for Normal Ordering with a $p$-value of $p_\mathrm{IO} = 15.3\%$ and $\mathrm{CL}_\mathrm{s}=53.3\%$ for the Inverted Ordering hypothesis, while the experimental results from both analyses are consistent within their uncertainties. Since the result is independent of the value of $\delta_\mathrm{CP}$ and obtained from energies $E_\nu \gtrsim 5\,\mathrm{GeV}$, it is complementary to recent results from long-baseline experiments. These analyses set the groundwork for the future of this measurement with more capable detectors, such as the IceCube Upgrade and the proposed PINGU detector.

  • LIGO/Virgo Black Holes from a First Order QCD Phase Transition. (arXiv:1902.07805v1 [hep-ph])

    Authors: Hooman Davoudiasl

    We propose that $O(10 M_{\rm Sun})$ black holes observed by LIGO/Virgo originate from a first order QCD phase transition at a temperature $T_* \lesssim 100$ MeV. This is implemented by keeping the Higgs vacuum expectation value and hence quark masses at zero down to $T\sim T_*$, making QCD confinement a first order electroweak phase transition. This electro-strong transition could have interesting ramifications for particle cosmology, as electroweak sphalerons stay active till $T \gtrsim T_*$. We realize our scenario through hidden gauge dynamics and a scalar which could potentially be viable dark matter.

  • Palatini formulation of pure $R^2$ gravity yields Einstein gravity with no massless scalar. (arXiv:1902.07876v1 [hep-th])

    Authors: Ariel Edery, Yu Nakayama

    Pure $R^2$ gravity has been shown to be equivalent to Einstein gravity with non-zero cosmological constant and a massless scalar field. We show that the Palatini formulation of pure $R^2$ gravity is equivalent to Einstein gravity with non-zero cosmological constant as before but with no massless scalar field. This is an important new development because the massless scalar field is not readily identifiable with any known particle in nature or unknown particles like cold dark matter which are expected to be massive. We then include a non-minimally coupled Higgs field as well as fermions to discuss how the rest of the standard model fields fit into this paradigm.

  • Single-spin asymmetry in dihadron production in SIDIS off the longitudinally polarized nucleon target. (arXiv:1902.07889v1 [hep-ph])

    Authors: Wei Yang, Xiaoyu Wang, Yongliang Yang, Zhun Lu

    We study the single longitudinal-spin asymmetry of dihadron production in semi-inclusive deep inelastic scattering process. We consider the collinear picture in which the transverse momentum of the final-state hadron pair is integrated out, such that the $\sin \phi_R$ azimuthal asymmetry arises from the coupling $h_L\, H_{1}^{\sphericalangle}$ as well as the coupling $g_1 \,\widetilde{G}^{\sphericalangle}$. We calculate the unknown twist-3 dihadron fragmentation function $\widetilde{G}^{\sphericalangle}$ using a spectator model which is successful in describing the dihadron production in the unpolarized process. Using the spectator model results for the quark distributions and dihadron fragmentation functions, we estimate the $\sin \phi_R$ asymmetry of dihadron production in SIDIS at the kinematics of COMPASS and compare it with the COMPASS preliminary data. In addition, the prediction on the $\sin \phi_R$ asymmetry at the typical kinematics of the future Electron Ion Collider is also presented. In order to test the reliability of the spectator model estimate, we compare the model result for the distribution $h_L$ with the Wandzura-Wilczek approximation for that distribution, and compare $H_{1}^{\sphericalangle}$ with the existing parametrization. Although the asymmetry is dominated by the $h_L H_{1}^{\sphericalangle}$ term, we find that the contribution from the $g_1\, \widetilde{G}^{\sphericalangle}$ term should also be taken into account in certain kinematical region.

  • Charged neutron stars and observational tests of a dark force weaker than gravity. (arXiv:1902.07914v1 [hep-ph])

    Authors: Marco Fabbrichesi, Alfredo Urbano

    We discuss the possibility of exploring an unbroken U(1) gauge interaction in the dark sector by means of gravitational waves. Dark sector states charged under the dark force can give a macroscopic charge to astronomical bodies. Yet the requirement of having gravitationally bounded stars limits this charge to negligible values if the force has a sizeable strength. Gravitational tests are only possible if the dark force is weaker than gravity. By solving the Einstein-Maxwell field equations, we study in detail an explicit model for dark charge generation and separation in a neutron star. Charged states originate from the decay of neutrons inside the star into three dark fermions; we show that in this model the equation of state is consistent with limits on neutron star masses and tidal deformability. We find that while the dark force can be observed in binary mergers (making them an optimal observational test even though with limited precision), it is Debye screened in binary pulsars (for which more precise data exist). The emitted radiation in the inspiral phase of a binary system is modified and the dark force tested at the level of the uncertainty of the experimental detection. The test covers a region where current limits on deviations from Newton inverse-squared law come from geophysical and laser-ranging observations.

  • Violation of Wiedemann-Franz Law for a Hot Hadronic Matter created at NICA, FAIR and RHIC Energies using Non-extensive Statistics. (arXiv:1902.07922v1 [hep-ph])

    Authors: Rutuparna Rath, Sushanta Tripathy, Bhaswar Chatterjee, Raghunath Sahoo, Swatantra K. Tiwari, Abhishek Nath

    We present here the computation of electrical and thermal conductivity by solving the Boltzmann transport equation in relaxation time approximation. We use the $q$-generalized Boltzmann distribution function to incorporate the effects of non-extensivity. The behaviour of these quantities with changing temperature and baryochemical potential has been studied as the system slowly moves towards thermodynamic equilibrium. We have estimated the Lorenz number at NICA, FAIR and the top RHIC energies and studied as a function of temperature, baryochemical potential and the non-extensive parameter, $q$. We have observed that Wiedemann-Franz law is violated for a non-extensive hadronic phase.

  • Thermal radiation and inclusive production in the CGC/saturation approach at high energies. (arXiv:1902.07923v1 [hep-ph])

    Authors: E. Gotsman (Tel Aviv U.), E. Levin (Tel Aviv U./UTFSM)

    In this paper, we discuss the inclusive production of hadrons in the framework of CGC/saturation approach. We argue, that the gluon jet inclusive production stems from the vicinity of the saturation momentum, even for small values of the transverse momenta $p_T$. Since in this region, theoretically, we know the scattering amplitude, we claim that we can provide reliable estimates for this process. We demonstrate, that in a widely accepted model for confinement, to describe the experimental data, we require a thermal radiation term. In this model the parton (quark or gluon) with the transverse momenta of the order of $Q_s$ decays into hadrons with the given fragmentation functions. However, we show that other approaches for the confinement could describe the data, without a need for the thermal emission

  • Low $x$ physics as an infinite twist (G)TMD framework: unravelling the origins of saturation. (arXiv:1902.07930v1 [hep-ph])

    Authors: Tolga Altinoluk, Renaud Boussarie

    We show how the formulations of low $x$ physics involving Wilson line operators can be fully rewritten into an infinite twist TMD or GTMD framework, respectively for inclusive and exclusive observables. This leads to a perfect match between low $x$ physics and moderate $x$ formulations of QCD in terms of GTMDs, TMDs, GPDs or PDFs. We derive the BFKL limit as a kinematic limit and argue that beyond the Wandzura-Wilczek approximation, 3-body and 4-body unintegrated PDFs should be taken into account even in this regime. Finally, we analyze how saturation should be understood as three distinct effects: saturation through non-linearities in the evolution equations at small $x$, saturation through multiple interactions with slow gluons as TMD gauge links, and saturation as the enhancement of genuine twist corrections.

  • On Future High-Energy Colliders. (arXiv:1902.07964v1 [physics.hist-ph])

    Authors: Gian Francesco Giudice

    I outline some of the physics reasons to pursue a future programme in high-energy colliders.

  • Two-loop splitting in double parton distributions. (arXiv:1902.08019v1 [hep-ph])

    Authors: Markus Diehl, Jonathan R. Gaunt, Peter Ploessl, Andreas Schafer

    Double parton distributions (DPDs) receive a short-distance contribution from a single parton splitting to yield the two observed partons. We investigate this mechanism at next-to-leading order (NLO) in perturbation theory. Technically, we compute the two-loop matching of both the position and momentum space DPDs onto ordinary PDFs. This also yields the 1 -> 2 splitting functions appearing in the evolution of momentum-space DPDs at NLO. We give results for the unpolarised, colour-singlet DPDs in all partonic channels. These quantities are required for calculations of double parton scattering at full NLO. We discuss various kinematic limits of our results, and we verify that the 1 -> 2 splitting functions are consistent with the number and momentum sum rules for DPDs.

  • Clifford-based spectral action and renormalization group analysis of the gauge couplings. (arXiv:1902.08090v1 [hep-ph])

    Authors: Ufuk Aydemir

    The Spectral Action Principle in the noncommutative geometry framework provides simultaneous derivation of the actions of the Standard Model and General Relativity by reconciling them in a geometric setting, and hence offers an explanation for their common origin. However, one of the requirements in the minimal formalism, unification of the gauge coupling constants, is not satisfied, since the basic construction does not introduce anything new that can change the renormalization group running of the Standard Model, in which unification is known not to be realized; this is indeed one of the reasons why extensions to the minimal formalism have been constructed. On the other hand, it has been recently argued that incorporating structure of the Clifford algebra into the finite part of the spectral triple, which is the main object that encodes the complete information of a noncommutative space, gives rise to five additional scalar fields in the basic framework, three of which have the same quantum numbers. In this paper, we address the question whether these scalars can help to achieve unification of the gauge couplings in this modified minimal formalism. Adopting the most general approach, we perform a six-parameter renormalization group analysis at the one-loop level, allowing the mass values of these five scalars to float from the electroweak scale to putative unification scale, i.e. emergence scale of the spectral action. We show that out of twenty possible configurations of mass hierarchy of these additional scalars, there does not exist even a single case that can lead to unification. In consequence, the spectral action formalism requires a model construction scheme beyond the (modified) minimal framework.

  • Boosted Top quark polarization. (arXiv:1902.08096v1 [hep-ph])

    Authors: Rohini Godbole, Monoranjan Guchait, Charanjit K. Khosa, Jayita Lahiri, Seema Sharma, Aravind H. Vijay

    In top quark production, the polarization of top quarks, decided by the chiral structure of couplings, is likely to be modified in the presence of any new physics contribution to the production. Hence the same is a good discriminator for those new physics models wherein the couplings have a chiral structure different than that in the Standard Model (SM). In this note we construct probes of the polarization of a top quark decaying hadronically, using easily accessible kinematic variables such as the energy fraction or angular correlations of the decay products. Tagging the boosted top quark using the usual jet sub structure technique we study robustness of these observables for a benchmark process, $W^{\prime} \to tb$. We demonstrate that the energy fraction of b-jet in the laboratory frame and a new angular variable, constructed by us in the top rest frame, are both very powerful tools to discriminate between the left and right polarized top quarks. Based on the polarization sensitive angular variables, we construct asymmetries which reflect the polarization. We study the efficiency of these variables for two new physics processes where which give rise to boosted top quarks: (i) decay of the top squark in the context of supersymmetry searches, and (ii) decays of the Kaluza-Klein(KK) graviton and KK gluon, in Randall Sundrum(RS) model. Remarkably, it is found that the asymmetry can vary over a wide range about +20\% to -20\%. The dependence of asymmetry on top quark couplings of the new particles present in these models beyond the SM (BSM) is also investigated in detail.

  • A single TeV-scale scalar leptoquark in $\mathbf{SO(10)}$ grand unification and $\mathbf{B}$-decay anomalies. (arXiv:1902.08108v1 [hep-ph])

    Authors: Ufuk Aydemir, Tanumoy Mandal, Subhadip Mitra

    One of the explanations proposed for the recent rare $B$-decay anomalies is the existence of a scalar leptoquark. We investigate a grand unification scenario where a single, charge -1/3 scalar leptoquark ($S_1$) is present as the only new physics candidate at the TeV-scale. This leptoquark along with the Standard Model (SM) Higgs doublet originates from the 10-dimensional real scalar multiplet in $\mathrm{SO}(10)$ grand unification framework. An $S_1$ residing in the same representation as the SM Higgs motivates the idea that its mass is close to the electroweak scale as the peculiar mass splittings within this multiplet do not occur. Therefore, possible detection of a TeV-scale $S_1$ leptoquark, unaccompanied by any other new particles, could be interpreted in favour of $\mathrm{SO}(10)$ grand unification. We explicitly show how the gauge coupling unification is achieved with only one intermediate symmetry breaking scale at which the Pati-Salam gauge group, obtained from the $\mathrm{SO}(10)$ breaking at the unification scale, is broken into the SM group. We investigate the phenomenological implications of our scenario and show that an $S_1$ with a specific Yukawa texture can still be a viable candidate to explain the $R_{D^{(*)}}$ anomalies. In order to obtain the allowed parameter space of our scenario, we consider the relevant flavour data including $R_{D^{(*)}}$ and $R_K^{\nu\nu}$ measurements, $Z\to\tau\tau$ decay and the latest $\tau\tau$ resonance search data at the LHC. We find that the LHC data strongly constrain the $S_1$ parameter space. We also find that there exist parts of parameter space where a single $S_1$ can still explain the $R_{D^{(*)}}$ anomalies without being in conflict with any of these constraints.

  • Exclusive vector meson production in heavy ion collisions. (arXiv:1902.08136v1 [hep-ph])

    Authors: V.A.Khoze, A.D.Martin, M.G.Ryskin

    We discuss the salient features of exclusive vector meson production in heavy ion collisions at LHC energies. Special attention is paid to the space-time picture of the process. We account for both coherent and incoherent contributions. The explicit quantitative predictions are given for the $\rho$-meson differential cross section in lead-lead collisions in different kinematical configurations relevant for the LHCb and ALICE experiments.

  • Effective-field theory analysis of the $\tau^{-}\rightarrow (K \pi)^{-}\nu_{\tau}$ decays. (arXiv:1902.08143v1 [hep-ph])

    Authors: Javier Rendón, Pablo Roig, Genaro Toledo Sánchez

    We analyze the $\tau^-\to(K\pi)^-\nu_\tau$ decays within an effective field theory description of heavy new physics (NP) modifying the SM left-handed weak charged current and include refined SM input (with controlled uncertainties) for the participant meson form factors exploiting chiral symmetry, dispersion relations and data. We include the leading dimension six operators and work at linear order in the effective couplings. Within this setting we:

    i) confirm that it is impossible to understand the BaBar anomaly in the CP asymmetry measurement (we find an upper bound for the NP contribution slightly larger than in Phys. Rev. Lett. 120 (2018) no.14, 141803, but still irrelevant compared to the experimental uncertainty by four orders of magnitude approximately);

    ii) first show that the anomalous bump present in the published Belle data for the $K_S\pi^-$ invariant mass distribution close to threshold cannot be due to heavy NP;

    iii) first bind the heavy NP effective couplings using $\tau^-\to(K\pi)^-\nu_\tau$ decays and show that they are competitive with those found in hyperon semileptonic decays (but clearly not with those obtained in Kaon (semi)leptonic decays).

    We also compare the SM predictions with the possible deviations caused by NP in a couple of Dalitz plot distributions, in the forward-backward asymmetry and in the di-meson invariant mass distribution and discuss the most interesting measurements to be performed at Belle-II using these decays data.

  • The strong running coupling from the gauge sector of Domain Wall lattice QCD with physical quark masses. (arXiv:1902.08148v1 [hep-ph])

    Authors: S. Zafeiropoulos, Ph. Boucaud, F. De Soto, J. Rodríguez-Quintero, J. Segovia

    We report on the first computation of the strong running coupling at the physical point (physical pion mass) from the ghost-gluon vertex, computed from lattice simulations with three flavors of Domain Wall fermions. We find $\alpha_{\overline{\rm MS}}(m_Z^2)=0.1172(11)$, in remarkably good agreement with the world-wide average. Our computational bridge to this value is the Taylor-scheme strong coupling, which has been revealed of great interest by itself because it can be directly related to the quark-gluon interaction kernel in continuum approaches to the QCD bound-state problem.

  • BFKL Pomeron and the survival factor. (arXiv:1902.08151v1 [hep-ph])

    Authors: V.A.Khoze, A.D.Martin, M.G.Ryskin

    We consider the absorptive corrections and the rapidity gap survival factor which are necessary to provide the unitarization of the BFKL Pomeron. In particular we discuss the role of the enhanced screening diagrams.

  • High precision determination of $\alpha_s$ from a global fit of jet rates. (arXiv:1902.08158v1 [hep-ph])

    Authors: Andrii Verbytskyi, Andrea Banfi, Adam Kardos, Pier Francesco Monni, Stefan Kluth, Gábor Somogyi, Zoltán Szőr, Zoltán Trócsányi, Zoltán Tulipánt, Giulia Zanderighi

    We present state-of-the-art extractions of the strong coupling based on N$^3$LO+NNLL accurate predictions for the two-jet rate in the Durham clustering algorithm at $e^+e^-$ collisions, as well as a simultaneous fit of the two- and three-jet rates taking into account correlations between the two observables. The fits are performed on a large range of data sets collected at LEP and PETRA colliders, with energies spanning from $35$ GeV to $207$ GeV. Owing to the high accuracy of the predictions used, the perturbative uncertainty is considerably smaller than that due to hadronization. Our best determination at the $Z$ mass is $\alpha_s(M_Z) = 0.11881 \pm 0.00063(exp.) \pm 0.00101(hadr.) \pm 0.00045(ren.) \pm 0.00034(res.)$, which is in agreement with the latest world average and has a comparable total uncertainty.

  • Scattering amplitudes versus potentials in nuclear effective field theory: is there a potential compromise?. (arXiv:1902.08172v1 [nucl-th])

    Authors: Manuel Pavon Valderrama

    In effective field theory physical quantities, in particular observables, are expressed as a power series in terms of a small expansion parameter. For non-perturbative systems, for instance nuclear physics, this requires the non-perturbative treatment of at least a part of the interaction (or the potential, if we are dealing with a non-relativistic system). This is not entirely trivial and as a consequence different interpretations on how to treat these systems have appeared. A practical approach is to expand the effective potential, where this potential is later fully iterated in the Schr\"odinger equation for obtaining amplitudes and observables. The expectation is that this will lead to observables that will have an implicit power counting expansion. Here we explicitly check whether the amplitudes are actually following the same power counting as the potential. It happens that reality does not necessarily conform to expectations and the amplitudes will often violate the power counting with which the potential has been expanded. A more formal approach is to formulate the expansion directly in terms of amplitudes and observables, which is the original aim of the effective field theory idea. Yet this second approach is technically complicated. We explore here the possibility of constructing potentials that when fully iterated will make sure that amplitudes indeed are expansible in terms of a small expansion parameter.

  • Instability of exotic compact objects and its implications for gravitational-wave echoes. (arXiv:1902.08180v1 [gr-qc])

    Authors: Baoyi Chen, Yanbei Chen, Yiqiu Ma, Ka-Lok R. Lo, Ling Sun

    Exotic compact objects (ECOs) have recently become an exciting research subject, since they are speculated to have a special response to the incident gravitational waves (GWs) that leads to GW echoes. We show that energy carried by GWs can easily cause the event horizon to form out of a static ECO --- leaving no echo signals towards spatial infinity. To show this, we use the ingoing Vaidya spacetime and take into account the back reaction due to incoming GWs. Demanding that an ECO does not collapse into a black hole puts an upper bound on the compactness of the ECO, at the cost of less distinct echo signals for smaller compactness. The trade-off between echoes' detectability and distinguishability leads to a fine tuning of ECO parameters for LIGO to find distinct echoes. We also show that an extremely compact ECO that can survive the gravitational collapse and give rise to GW echoes might have to expand its surface in a non-causal way.

  • When Primordial Black Holes from Sound Speed Resonance Meet a Stochastic Background of Gravitational Waves. (arXiv:1902.08187v1 [astro-ph.CO])

    Authors: Yi-Fu Cai, Chao Chen, Xi Tong, Dong-Gang Wang, Sheng-Feng Yan

    As potential candidates of dark matter, primordial black holes (PBHs) are within the core scopes of various astronomical observations. In light of the explosive development of gravitational wave (GW) and radio astronomy, we thoroughly analyze a stochastic background of cosmological GWs, induced by over large primordial density perturbations, with several spikes that was inspired by the sound speed resonance effect and can predict a particular pattern on the mass spectrum of PBHs. With a specific mechanicsm for PBHs formation, we for the first time perform the study of such induced GWs that originate from both the inflationary era and the radiation-dominated phase. We report that, besides the traditional process of generating GWs during the radiation-dominated phase, the contribution of the induced GWs in the sub-Hubble regime during inflation can become significant at critical frequency band because of a narrow resonance effect. All contributions sum together to yield a specific profile of the energy spectrum of GWs that can be of observable interest in forthcoming astronomical experiments. Our study shed light on the possible joint probe of PBHs via various observational windows of multi-messenger astronomy, including the search for electromagnetic effects with astronomical telescopes and the stochastic background of relic GWs with GW instruments.

  • Electromagnetic instability and Schwinger effect in the Witten-Sakai-Sugimoto model with D0-D4 background. (arXiv:1612.07087v3 [hep-th] UPDATED)

    Authors: Wenhe Cai, Kang-le Li, Si-wen Li

    Using the Witten-Sakai-Sugimoto model in the D0-D4 background, we holographically compute the vacuum decay rate of the Schwinger effect in this model. Our calculation contains the influence of the D0-brane density which could be identified as the $\theta$ angle or chiral potential in QCD. Under the strong electromagnetic fields, the instability appears due to the creation of quark-antiquark pairs and the associated decay rate can be obtained by evaluating the imaginary part of the effective Euler-Heisenberg action which is identified as the action of the probe brane with a constant electromagnetic field. In the bubble D0-D4 configuration, we find the decay rate decreases when the $\theta$ angle increases since the vacuum becomes heavier in the present of the glue condensate in this system. And the decay rate matches to the result in the black D0-D4 configuration at zero temperature limit according to our calculations. In this sense, the Hawking-Page transition of this model could be consistently interpreted as the confined/deconfined phase transition. Additionally there is another instability from the D0-brane itself in this system and we suggest that this instability reflects to the vacuum decay triggered by the $\theta$ angle as it is known in the $\theta$-dependent QCD.

  • Probing underlying event in Z-boson events using event shape observables. (arXiv:1801.05218v2 [hep-ph] UPDATED)

    Authors: Deepak Kar, Dimbiniaina Soanasolo Rafanoharana

    Experimental measurements of observables sensitive to the underlying event (UE) in $Z$-boson events have been performed by both ATLAS and CMS experiments at the LHC. However, in the busy LHC environment, these observables receive substantial contribution from jets originating from initial state radiation (ISR). We probe if using event shape observables in conjunction with the UE observables can help us to disentangle the effect of the UE from jets originating in ISR.

  • From homogeneous matter to finite nuclei: Role of the effective mass. (arXiv:1805.11321v2 [nucl-th] UPDATED)

    Authors: Hana Gil, Panagiota Papakonstantinou, Chang Ho Hyun, Yongseok Oh

    Recent astronomical observations, nuclear-reaction experiments, and microscopic calculations have placed new constraints on the nuclear equation of state (EoS) and revealed that most nuclear structure models fail to satisfy those constraints upon extrapolation to infinite matter. A reverse procedure for imposing EoS constraints on nuclear structure has been elusive. Here we present for the first time a method to generate a microscopic energy density functional (EDF) for nuclei from a given immutable EoS. The method takes advantage of a natural Ansatz for homogeneous nuclear matter, the Kohn-Sham framework, and the Skyrme formalism. We apply it to the realistic nuclear EoS of Akmal-Pandharipande-Ravenhall and describe successfully closed-(sub)shell nuclei. In the process, we provide predictions for the neutron skin thickness of nuclei based directly on the given EoS. Crucially, bulk and static nuclear properties are found practically independent of the assumed effective mass value - a unique result in bridging EDF of finite and homogeneous systems in general.

  • A Systematic Expansion of Running Couplings and Masses. (arXiv:1806.02534v4 [hep-th] UPDATED)

    Authors: F.A. Chishtie, D.G.C. McKeon, T.N. Sherry

    As an alternative to directly integrating their defining equations to find the running coupling $a(\mu)$ and the running mass $m(\mu)$, we expand these quantities in powers of $\ln\left(\frac{\mu}{\mu^\prime}\right)$ and their boundary values $a(\mu^\prime)$ and $m(\mu^\prime)$. Renormalization group summation is used to partially sum these logarithms. We consider this approach using both the $\overline{MS}$ and 't Hooft renormalization schemes. We also show how the couplings and masses in any two mass independent renormalization schemes are related.

  • Energetics of High-Energy Cosmic Radiations. (arXiv:1806.04194v2 [astro-ph.HE] UPDATED)

    Authors: Kohta Murase, Masataka Fukugita

    The luminosity densities of high-energy cosmic radiations are studied to find connections among the various components, including high-energy neutrinos measured with IceCube and gamma rays with the Fermi satellite. Matching the cosmic-ray energy generation rate density in a GeV-TeV range estimated for Milky Way with the ultrahigh-energy component requires a power-law index of the spectrum, $s_{\rm cr}\approx2.1-2.2$, somewhat harder than $s_{\rm cr}\approx2.3-2.4$ for the local index derived from the AMS-02 experiment. The soft GeV-TeV cosmic-ray spectrum extrapolated to higher energies can be compatible with PeV cosmic rays inferred from neutrino measurements, but overshoots the CR luminosity density to explain GeV-TeV gamma rays. The extrapolation from ultrahigh energies with a hard spectrum, on the other hand, can be consistent with both neutrinos and gamma-rays. These point towards either reacceleration of galactic cosmic rays or the presence of extragalactic sources with a hard spectrum. We discuss possible cosmic-ray sources that can be added.

  • Extension of the electrodynamics in the presence of the axion and dark photon. (arXiv:1806.09972v3 [hep-ph] UPDATED)

    Authors: Fa Peng Huang, Hye-Sung Lee

    We present the extended electrodynamics in the presence of the axion and dark photon. We derive the extended versions of Maxwell's equations and dark Maxwell's equations (for both massive and massless dark photons) as well as the wave equations. We discuss the implications of this extended electrodynamics including the enhanced effects in the particle conversions under the external magnetic or dark magnetic field. We also discuss the recently reported anomaly in the redshifted 21cm spectrum using the extended electrodynamics.

  • Primordial Black Holes from the QCD axion. (arXiv:1807.01707v2 [hep-ph] UPDATED)

    Authors: Francesc Ferrer, Eduard Masso, Giuliano Panico, Oriol Pujolas, Fabrizio Rompineve

    We propose a mechanism to generate Primordial Black Holes (PBHs) which is independent of cosmological inflation and occurs slightly below the QCD phase transition. Our setup relies on the collapse of long-lived string-domain wall networks and is naturally realized in QCD axion models with domain wall number $N_{DW}>1$ and Peccei-Quinn symmetry broken after inflation. In our framework, dark matter is mostly composed of axions in the meV mass range along with a small fraction, $\Omega_{\text{PBH}} \gtrsim 10^{-6} \Omega_{\text{CDM}} $ of heavy $M \sim 10^4-10^7 M_\odot$ PBHs. The latter could play a role in alleviating some of the shortcomings of the $\Lambda$CDM model on sub-galactic scales. The scenario has distinct signatures in ongoing axion searches as well as gravitational wave observatories.

  • Charged hadron fragmentation functions from collider data. (arXiv:1807.03310v3 [hep-ph] UPDATED)

    Authors: The NNPDF Collaboration: Valerio Bertone, Nathan P. Hartland, Emanuele R. Nocera, Juan Rojo, Luca Rottoli

    We present NNFF1.1h, a new determination of unidentified charged-hadron fragmentation functions (FFs) and their uncertainties. Experimental measurements of transverse-momentum distributions for charged-hadron production in proton-(anti)proton collisions at the Tevatron and at the LHC are used to constrain a set of FFs originally determined from electron-positron annihilation data. Our analysis is performed at next-to-leading order in perturbative quantum chromodynamics. We find that the hadron-collider data is consistent with the electron-positron data and that it significantly constrains the gluon FF. We verify the reliability of our results upon our choice of the kinematic cut in the hadron transverse momentum applied to the hadron-collider data and their consistency with NNFF1.0, our previous determination of the FFs of charged pions, kaons, and protons/antiprotons.

  • A new mechanism to enhance primordial tensor fluctuations in single field inflation. (arXiv:1808.10475v2 [gr-qc] UPDATED)

    Authors: Maria Mylova, Ogan Özsoy, Susha Parameswaran, Gianmassimo Tasinato, Ivonne Zavala

    We discuss a new mechanism to enhance the spectrum of primordial tensor fluctuations in single field inflationary scenarios. The enhancement relies on a transitory non-attractor inflationary phase, which amplifies the would-be decaying tensor mode, and gives rise to a growth of tensor fluctuations at superhorizon scales. We show that the enhancement produced during this phase can be neatly treated via a tensor duality between an attractor and non-attractor phase, which we introduce. We illustrate the mechanism and duality in a kinetically driven scenario of inflation, with non-minimal couplings between the scalar and the metric.

  • Charmed Baryon Decay to a Strange Baryon Plus a Pion Using QCD Sum Rules. (arXiv:1809.00199v5 [hep-ph] UPDATED)

    Authors: Leonard S. Kisslinger, Bijit Singha

    This is an extension of the prediction of strange baryon decays to the decays of charmed baryons using QCD Sum Rules. Using QCD Sum Rules we estimate the decay $\Lambda^+_c (udc) \rightarrow \Lambda^o_s(uds)+ \pi^+$. Although some weak decays of the $\Lambda^+_c$ have been measured, since it is difficult to measure $\Lambda^+_c \rightarrow \Lambda^o_s+ \pi^+$ our estimates should be useful for future experiments

  • 2HDECAY - A program for the Calculation of Electroweak One-Loop Corrections to Higgs Decays in the Two-Higgs-Doublet Model Including State-of-the-Art QCD Corrections. (arXiv:1810.00768v2 [hep-ph] UPDATED)

    Authors: Marcel Krause, Margarete Muhlleitner, Michael Spira

    We present the program package 2HDECAY for the calculation of the partial decay widths and branching ratios of the Higgs bosons of a general CP-conserving 2-Higgs doublet model (2HDM). The tool includes the full electroweak one-loop corrections to all two-body on-shell Higgs decays in the 2HDM that are not loop-induced. It combines them with the state-of-the-art QCD corrections that are already implemented in the program HDECAY. For the renormalization of the electroweak sector an on-shell scheme is implemented for most of the renormalization parameters. Exceptions are the soft-$\mathbb{Z}_2$-breaking squared mass scale $m_{12}^2$, where an $\overline{\text{MS}}$ condition is applied, as well as the 2HDM mixing angles $\alpha$ and $\beta$, for which several distinct renormalization schemes are implemented. The tool 2HDECAY can be used for phenomenological analyses of the branching ratios of Higgs decays in the 2HDM. Furthermore, the separate output of the electroweak contributions to the tree-level partial decay widths for several different renormalization schemes allows for an efficient analysis of the impact of the electroweak corrections and the remaining theoretical error due to missing higher-order corrections. The latest version of the program package 2HDECAY can be downloaded from the URL .

  • Baryogenesis and Dark Matter from $B$ Mesons. (arXiv:1810.00880v3 [hep-ph] UPDATED)

    Authors: Gilly Elor, Miguel Escudero, Ann E. Nelson

    We present a new mechanism of Baryogenesis and dark matter production in which both the dark matter relic abundance and the baryon asymmetry arise from neutral $B$ meson oscillations and subsequent decays. This set-up is testable at hadron colliders and $B$-factories. In the early Universe, decays of a long lived particle produce $B$ mesons and anti-mesons out of thermal equilibrium. These mesons/anti-mesons then undergo CP violating oscillations before quickly decaying into visible and dark sector particles. Dark matter will be charged under Baryon number so that the visible sector baryon asymmetry is produced without violating the total baryon number of the Universe. The produced baryon asymmetry will be directly related to the leptonic charge asymmetry in neutral $B$ decays; an experimental observable. Dark matter is stabilized by an unbroken discrete symmetry, and proton decay is simply evaded by kinematics. We will illustrate this mechanism with a model that is unconstrained by di-nucleon decay, does not require a high reheat temperature, and would have unique experimental signals -- a positive leptonic asymmetry in $B$ meson decays, a new decay of $B$ mesons into a baryon and missing energy, and a new decay of $b$-flavored baryons into mesons and missing energy. These three observables are testable at current and upcoming collider experiments, allowing for a distinct probe of this mechanism.

  • Classical behaviour of Q-balls in the Wick-Cutkosky model. (arXiv:1810.03558v2 [hep-th] UPDATED)

    Authors: A.G. Panin, M.N. Smolyakov

    In this paper, we continue discussing Q-balls in the Wick--Cutkosky model. Despite Q-balls in this model are composed of two scalar fields, they turn out to be very useful and illustrative for examining various important properties of Q-balls. In particular, in the present paper we study in detail (analytically and numerically) the problem of classical stability of Q-balls, including the nonlinear evolution of classically unstable Q-balls, as well as the behaviour of Q-balls in external fields in the non-relativistic limit.

  • Testing Lorentz invariance and CPT symmetry using gamma-ray burst neutrinos. (arXiv:1810.03571v2 [hep-ph] UPDATED)

    Authors: Xinyi Zhang, Bo-Qiang Ma

    A recent work [Y. Huang and B.-Q. Ma, Commun. Phys. {\bf 1}, 62 (2018)] associated all four PeV neutrinos observed by IceCube to gamma-ray bursts (GRBs), and revealed a regularity which indicates a Lorentz violation scale $E_{\rm LV}=(6.5\pm0.4)\times10^{17}$ GeV with opposite sign factors $s=\pm 1$ between neutrinos and antineutrinos. The association of "time delay" and "time advance" events with neutrinos and antineutrinos (or vice versa) is only a hypothesis since the IceCube detector cannot tell the chirality of the neutrinos, and further experimental tests are needed to verify this hypothesis. We derive the values of the CPT-odd Lorentz violating parameters in the standard-model extension (SME) framework, and perform a threshold analysis on the electron-positron pair emission of the superluminal neutrinos (or antineutrinos). We find that different neutrino/antineutrino propagation properties, suggested by Y. Huang and B.-Q. Ma, can be described in the SME framework with both Lorentz invariance and CPT symmetry violation, but with a threshold energy constraint. A viable way on testing the CPT symmetry violation between neutrinos and antineutrinos is suggested.

  • An asymptotically safe guide to quantum gravity and matter. (arXiv:1810.07615v2 [hep-th] UPDATED)

    Authors: Astrid Eichhorn

    Asymptotic safety generalizes asymptotic freedom and could contribute to understanding physics beyond the Standard Model. It is a candidate scenario to provide an ultraviolet extension for the effective quantum field theory of gravity through an interacting fixed point of the Renormalization Group. Recently, asymptotic safety has been established in specific gauge-Yukawa models in four dimensions in perturbation theory, providing a starting point for asymptotically safe model building. Moreover, an asymptotically safe fixed point might even be induced in the Standard Model under the impact of quantum fluctuations of gravity in the vicinity of the Planck scale. This review contains an overview of the key concepts of asymptotic safety, its application to matter and gravity models, exploring potential phenomenological implications and highlighting open questions.

  • Particle decay from statistical thermal model in high energy nucleus-nucleus collision. (arXiv:1810.09101v3 [hep-ph] UPDATED)

    Authors: Ning Yu, Xiaofeng Luo

    In high energy nucleus-nucleus collisions, it is difficult to measure the contributions of resonance strong decay and weak decay to the final measured hadrons as well as the corresponding effects on some physical observables. To provide a reference from statistical thermal model, we performed a systematic analysis for the energy dependence of particle yield and yield ratios in Au + Au collisions. We found that the primary fraction of final hadrons decreases with increasing collision energy and somehow saturates around $\sqrt{s_\textrm{NN}}$ = 10 GeV, indicating a limiting temperature in hadronic interactions. The fraction of strong or weak decay for final hadrons show a different energy dependence behavior comparing to the primarily produced hadrons. These energy dependences of various particle yield and yield ratios from strong or weak decay can provide us with baselines for many hadronic observables in high energy nucleus-nucleus collisions.

  • Light and heavy flavor dijet production and dijet mass modification in heavy ion collisions. (arXiv:1810.10007v2 [hep-ph] UPDATED)

    Authors: Zhong-Bo Kang, Jared Reiten, Ivan Vitev, Boram Yoon

    Back-to-back light and heavy flavor dijet measurements are promising experimental channels to accurately study the physics of jet production and propagation in a dense QCD medium. They can provide new insights into the path length, color charge, and mass dependence of quark and gluon energy loss in the quark-gluon plasma produced in reactions of ultra-relativistic nuclei. To this end, we perform a comprehensive study of both light and heavy flavor dijet production in heavy ion collisions. We propose the modification of dijet invariant mass distributions in such reactions as a novel observable that shows enhanced sensitivity to the QGP transport properties and heavy quark mass effects on in-medium parton showers. This is achieved through the addition of the jet quenching effects on the individual jets as opposed to their subtraction. The latter drives the subtle effects on more conventional observables, such as the dijet momentum imbalance shifts, which we also calculate here. Results are presented in Pb+Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV for comparison to data at the Large Hadron Collider and in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV to guide the future sPHENIX program at the Relativistic Heavy Ion Collider.

  • Gluequark Dark Matter. (arXiv:1811.06975v2 [hep-ph] UPDATED)

    Authors: Roberto Contino, Andrea Mitridate, Alessandro Podo, Michele Redi

    We introduce the gluequark Dark Matter candidate, an accidentally stable bound state made of adjoint fermions and gluons from a new confining gauge force. Such scenario displays an unusual cosmological history where perturbative freeze-out is followed by a non-perturbative re-annihilation period with possible entropy injection. When the gluequark has electroweak quantum numbers, the critical density is obtained for masses as large as PeV. Independently of its mass, the size of the gluequark is determined by the confinement scale of the theory, leading at low energies to annihilation rates and elastic cross sections which are large for particle physics standards and potentially observable in indirect detection experiments.

  • Impact of final state interactions on neutrino-nucleon pion production cross sections extracted from neutrino-deuteron reaction data. (arXiv:1812.00144v2 [hep-ph] UPDATED)

    Authors: S.X. Nakamura (Univ. Science and Technology of China, Univ. Cruzeiro do Sul), H. Kamano (RCNP), T. Sato (RCNP, J-PARC)

    The current and near-future neutrino oscillation experiments require significantly improved neutrino-nucleus reaction models. Neutrino-nucleon pion production data play a crucial role to validate corresponding elementary amplitudes that go into such neutrino-nucleus models. Thus the currently available data extracted from charged-current neutrino-deuteron reaction data ($\nu_\mu d\to \mu^-\pi NN$) must be corrected for nuclear effects such as the Fermi motion and final state interactions (FSI). We study $\nu_\mu d\to \mu^-\pi NN$ with a theoretical model including the impulse mechanism supplemented by FSI from $NN$ and $\pi N$ rescatterings. An analysis of the spectator momentum distributions reveals that the FSI effects significantly reduce the spectra over the quasi-free peak region, and leads to a useful recipe to extract information of elementary $\nu_\mu N\to \mu^-\pi N$ processes using $\nu_\mu d\to \mu^-\pi NN$ data, with the important FSI corrections taken into account. We provide $\nu_\mu N\to \mu^-\pi N$ total cross sections by correcting the deuterium bubble chamber data for the FSI and Fermi motion. The results will bring a significant improvement on neutrino-nucleus reaction models for the near-future neutrino-oscillation experiments.

  • Revisiting constraints on 3+1 active-sterile neutrino mixing using IceCube data. (arXiv:1812.00831v3 [hep-ph] UPDATED)

    Authors: Luis Salvador Miranda, Soebur Razzaque

    Recent IceCube search results for sterile neutrino increased tension between the combined appearance and disappearance experiments. On the other hand, MiniBooNE latest data confirms at $4.9\sigma$ CL the short-baseline oscillation anomaly. We analyze published IceCube data based on two different active-sterile mixing schemes using one additional sterile neutrino flavor. We present exclusion regions in the parameter ranges $0.01 \le \sin^2 \theta_{24} \le 0.1$ and $0.1~{\rm eV}^2 \le \Delta m^2_{42} \le 10~{\rm eV}^2$ for the mass-mixing and flavor-mixing schemes. Under the more conservative mass-mixing scheme, $3\sigma$ CL allowed regions for the appearance experiment and MiniBooNE latest result are excluded at $\gtrsim 3\sigma$ CL. In case of less-restrictive flavor-mixing scheme, results from the appearance experiments are excluded at $\gtrsim 2\sigma$ CL. We also find that including prompt component of the atmospheric neutrino flux relaxes constraints on sterile mixing for $\Delta m^2_{42} \gtrsim 1~{\rm eV}^2$.

  • High-Energy Expansion of Two-Loop Massive Four-Point Diagrams. (arXiv:1812.04373v3 [hep-ph] UPDATED)

    Authors: Go Mishima

    We apply the method of regions to the massive two-loop integrals appearing in the Higgs pair production cross section at the next-to-leading order, in the high energy limit. For the non-planar integrals, a subtle problem arises because of the indefinite sign of the second Symanzik polynomial. We solve this problem by performing an analytic continuation of the Mandelstam variables such that the second Symanzik polynomial has a definite sign. Furthermore, we formulate the procedure of applying the method of regions systematically. As a by-product of the analytic continuation of the Mandelstam variables, we obtain crossing relations between integrals in a simple and systematic way. In our formulation, a concept of "template integral" is introduced, which represents and controls the contribution of each region. All of the template integrals needed in the computation of the Higgs pair production at the next-to-leading order are given explicitly. We also develop techniques to solve Mellin-Barnes integrals, and show them in detail. Although most of the calculation is shown for the concrete example of the Higgs pair production process, the application to other similar processes is straightforward, and we anticipate that our method can be useful also for other cases.

  • Gravity-Mediated SUSY Breaking, R Symmetry and Hyperbolic Kaehler Geometry. (arXiv:1812.10284v2 [hep-ph] UPDATED)

    Authors: C. Pallis

    A novel realization of the gravity-mediated SUSY breaking is presented taking into account a continuous global R symmetry. Consistently with it, we employ a linear superpotential for the hidden sector superfield and a Kaehler potential parameterizing the SU(1,1)/U(1) Kaehler manifold with constant curvature -1/2. The classical vacuum energy vanishes without unnatural fine tuning and non-vanishing soft SUSY-breaking parameters, of the order of the gravitino mass, arise. A solution to the mu problem of MSSM may be also achieved by conveniently applying the Giudice-Masiero mechanism. The potentially troublesome R axion may acquire acceptably large mass by explicitly breaking the R symmetry in the Kaehler potential through a quartic term which does not affect, though, the achievements above.

  • Double copy structure of CFT correlators. (arXiv:1812.11129v2 [hep-th] UPDATED)

    Authors: Joseph A. Farrow, Arthur E. Lipstein, Paul McFadden

    We consider the momentum-space 3-point correlators of currents, stress tensors and marginal scalar operators in general odd-dimensional conformal field theories. We show that the flat space limit of these correlators is spanned by gauge and gravitational scattering amplitudes in one higher dimension which are related by a double copy. Moreover, we recast three-dimensional CFT correlators in terms of tree-level Feynman diagrams without energy conservation, suggesting double copy structure beyond the flat space limit.

  • Gauge-Independent Approach to Resonant Dark Matter Annihilation. (arXiv:1812.11944v2 [hep-ph] UPDATED)

    Authors: Mateusz Duch, Bohdan Grzadkowski, Apostolos Pilaftsis

    In spontaneously broken gauge theories, transition amplitudes describing dark-matter (DM) annihilation processes through a resonance may become highly inaccurate close to a production threshold, if a Breit-Wigner (BW) ansatz with a constant width is used. To partially overcome this problem, the BW propagator needs to be modified by including a momentum dependent decay width. However, such an approach to resonant transition amplitudes generically suffers from gauge artefacts that may also give rise to a bad or ambiguous high-energy behaviour for such amplitudes. We address the two problems of gauge dependence and high-energy unitarity within a gauge-independent framework of resummation implemented by the so-called Pinch Technique. We study DM annihilation via scalar resonances in a gauged U(1)$_X$ complex-scalar extension of the Standard Model that features a massive stable gauge field which can play the role of the DM. We find that the predictions for the DM abundance may vary significantly from previous studies based on the naive BW ansatz and propose an alternative simple approximation which leads to the correct DM phenomenology. In particular, our results do not depend on the gauge-fixing parameter and are consistent with considerations from high-energy unitarity.

  • Dual MeV Gamma-Ray and Dark Matter Observatory - GRAMS Project. (arXiv:1901.03430v2 [astro-ph.HE] UPDATED)

    Authors: Tsuguo Aramaki, Per Hansson Adrian, Georgia Karagiorgi, Hirokazu Odaka

    GRAMS (Gamma-Ray and AntiMatter Survey) is a novel project that can simultaneously target both astrophysical observations with MeV gamma rays and an indirect dark matter search with antimatter. The GRAMS instrument is designed with a cost-effective, large-scale LArTPC (Liquid Argon Time Projection Chamber) detector surrounded by plastic scintillators. The astrophysical observations at MeV energies have not yet been well-explored (the so-called "MeV-gap") and GRAMS can improve the sensitivity by more than an order of magnitude compared to previous experiments. While primarily focusing on MeV gamma-ray observations, GRAMS is also optimized for cosmic ray antimatter surveys to indirectly search for dark matter. In particular, low-energy antideuterons will provide an essentially background-free dark matter signature. GRAMS will be a next generation experiment beyond the current GAPS (General AntiParticle Spectrometer) project for antimatter survey.

  • Testing for observability of Higgs effective couplings in triphoton production at FCC-hh. (arXiv:1901.04784v2 [hep-ph] UPDATED)

    Authors: H. Denizli, K. Y. Oyulmaz, A. Senol

    We investigate the potential of the $pp\to \gamma\gamma\gamma +X$ process to probe CP-conserving and CP-violating dimension-six operators of Higgs-gauge boson interactions in a model-independent Standard Model effective field theory framework at the center of mass energy of 100 TeV which is designed for Future Circular hadron-hadron Collider. Signal events in the existence of anomalous Higgs boson couplings at $H\gamma\gamma$ and $HZ\gamma$ vertices and the relevant SM background events are generated in MadGraph, then passed through Pythia 8 for parton showering and Delphes to include detector effects. After detailed examination of kinematic variables, we use invariant mass distribution of two leading photons with optimized kinematic cuts to obtain constraints on the Wilson coefficients of dimension-six operators. We report that limits at 95\% confidence level on $\bar{c}_{\gamma}$ and $\tilde{c}_{\gamma}$ couplings with an integrated luminosity of 10 ab$^{-1}$ are [-0.0041; 0.0019] and [-0.0027; 0.0027], respectively.

  • Threshold effects in heavy quarkonium spectroscopy. (arXiv:1902.02835v2 [hep-ph] UPDATED)

    Authors: J. Ferretti

    In this contribution, we discuss the possible importance of continuum-coupling (or threshold) effects in heavy quarkonium spectroscopy. Our calculations are carried out in a coupled-channel model, where meson-meson higher Fock (or molecular-type) components are introduced in $Q \bar Q$ bare meson wave functions by means of a pair-creation mechanism. After providing a quick resume of the main characteristics of the coupled-channel model, we briefly discuss its application to the calculation of the masses of heavy quarkonium-like $\chi_{\rm c}(2P)$ and $\chi_{\rm b}(3P)$ states with threshold corrections. We show that the introduction of pair-creation effects in the Quark Model (QM) formalism makes it possible to explain the deviations of $\chi_{\rm c}(2P)$ states' masses from the experimental data, without affecting the good QM description of the properties of $\chi_{\rm b}(3P)$ states.

  • The Radial Acceleration Relation (RAR): the crucial cases of Dwarf Discs and of Low Surface Brightness galaxies. (arXiv:1810.08472v2 [astro-ph.GA] CROSS LISTED)

    Authors: Chiara Di Paolo, Paolo Salucci, Jean Philippe Fontaine

    McGaugh et al. (2016) have found, in a large sample of disc systems, a tight nonlinear relationship between the total radial accelerations $g$ and their components $g_b$ arisen from the distribution of the baryonic matter [McGaugh_2016]. Here, we investigate the existence of such relation in Dwarf Disc Spirals and Low Surface Brightness galaxies on the basis of [Karukes_2017] and [DiPaolo_2018]. We have accurate mass profiles for 36 Dwarf Disc Spirals and 72 LSB galaxies. These galaxies have accelerations that cover the McGaugh range but also reach out to one order of magnitude below the smallest accelerations present in McGaugh et al. (2016) and span different Hubble Types. We found, in our samples, that the $g$ vs $g_b$ relation has a very different profile and also other intrinsic novel properties, among those, the dependence on a second variable: the galactic radius, normalised to the optical radius $R_{opt}$, at which the two accelerations are measured. We show that the new far than trivial $g$ vs $(g_b, r/R_{opt})$ relationship is nothing else than a direct consequence of the complex, but coordinated mass distributions of the baryons and the dark matter (DM) in disc systems. Our analysis shows that the McGaugh et al. (2016) relation is a limiting case of a new universal relation that can be very well framed in the standard "DM halo in the Newtonian Gravity" paradigm.

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