hep-ph updates on
High Energy Physics - Phenomenology (hep-ph) updates on the e-print archive
  • Transverse momentum dependent distributions with jets. (arXiv:1807.07573v1 [hep-ph])

    Authors: Daniel Gutierrez-Reyes, Ignazio Scimemi, Wouter J. Waalewijn, Lorenzo Zoppi

    We investigate the use of jets to measure transverse momentum dependent distributions (TMDs). The example we use to present our framework is the dijet momentum decorrelation at lepton colliders. Translating this momentum decorrelation into an angle $\theta \ll 1$, we analyze the factorization of the cross section for the cases $\theta \gg R$, $\theta \sim R$ and $\theta \ll R$, where $R$ is the jet radius. Critically, for the Winner-Take-All axis, the jet TMD has the same double-scale renormalization group evolution as TMD fragmentation functions for all radii $R$. TMD fragmentation functions in factorization theorems may then simply be replaced by the jet TMDs we calculate, and all ingredients to perform the resummation to next-to-next-to-leading logarithmic accuracy are available. Our approach also applies to semi-inclusive deep inelastic scattering (SIDIS), where a jet instead of a hadron is measured in the final state, and we find a clean method to probe the intrinsic transverse momentum of quarks and gluons in the proton that is less sensitive to final-state nonperturbative effects.

  • Unrestored Electroweak Symmetry. (arXiv:1807.07578v1 [hep-ph])

    Authors: Patrick Meade, Harikrishnan Ramani

    The commonly assumed cosmological history of our universe is that at early-times and high-temperatures the universe went through an ElectroWeak Phase Transition (EWPT). Assuming an EWPT, and depending on its strength, there are many implications for baryogenesis, gravitational waves, and the evolution of the universe in general. However, it is not true that all spontaneously broken symmetries at zero-temperature are restored at high-temperature. In particular the idea of "inverse symmetry breaking" has long been established in scalar theories with evidence from both perturbative and lattice calculations. In this letter we demonstrate that with a simple extension of the SM it is possible that the ElectroWeak (EW) symmetry was always broken or only temporarily passed through a symmetry restored phase. These novel phase histories have many cosmological and collider implications that we discuss. The model presented here serves as a useful benchmark comparison for future attempts to discern the phase of our universe at $T\gtrsim$ a few GeV.

  • The Ultraviolet Landscape of Two-Higgs Doublet Models. (arXiv:1807.07581v1 [hep-ph])

    Authors: Manuel E. Krauss, Toby Opferkuch, Florian Staub

    We study the predictions of generic ultraviolet completions of two-Higgs doublet models. We assume that at the matching scale between the two-Higgs doublet model and a ultraviolet complete theory -- which can be anywhere between the TeV and the Planck scale -- arbitrary but perturbative values for the quartic couplings are present. We evaluate the couplings down from the matching scale to the weak scale and study the predictions for the scalar mass spectrum. In particular, we show the importance of radiative corrections which are essential for both an accurate Higgs mass calculation as well as determining the stability of the electroweak vacuum. We study the relation between the mass splitting of the heavy Higgs states and the size of the quartic couplings at the matching scale, finding that only a small class of models exhibit a sizeable mass splitting between the heavy scalars at the weak scale. Moreover, we find a clear correlation between the maximal size of the couplings and the considered matching scale.

  • The Apparent (Gravitational) Horizon in Cosmology. (arXiv:1807.07587v1 [gr-qc])

    Authors: Fulvio Melia

    In general relativity, a gravitational horizon (more commonly known as the "apparent horizon") is an imaginary surface beyond which all null geodesics recede from the observer. The Universe has an apparent (gravitational) horizon, but unlike its counterpart in the Schwarzschild and Kerr metrics, it is not static. It may eventually turn into an event horizon---an asymptotically defined membrane that forever separates causally connected events from those that are not---depending on the equation of state of the cosmic fluid. In this paper, we examine how and why an apparent (gravitational) horizon is manifested in the Friedmann-Robertson-Walker metric, and why it is becoming so pivotal to our correct interpretation of the cosmological data. We discuss its observational signature and demonstrate how it alone defines the proper size of our visible Universe. In so doing, we affirm its physical reality and its impact on cosmological models.

  • Hydrodynamic modes in magnetized chiral plasma with vorticity. (arXiv:1807.07608v1 [hep-th])

    Authors: D. O. Rybalka, E. V. Gorbar, I. A. Shovkovy

    By making use of a covariant formulation of the chiral kinetic theory in the relaxation-time approximation, we derive the first-order dissipative hydrodynamics equations for a uniformly rotating chiral plasma in a magnetic field. We identify the global equilibrium state for the corresponding chiral plasma confined to a cylindrical region with realistic boundary conditions. Then, by using linearized hydrodynamic equations, supplemented by the Maxwell equations, we study hydrodynamic modes of the chiral plasma in the regimes of high temperature and high density. We find that nonzero vorticity has profound effects on both the global equilibrium state of the plasma and the spectrum of its hydrodynamic modes. Possible applications of the main results are briefly discussed.

  • Chiral symmetry-breaking schemes and dynamical generation of masses and field mixing. (arXiv:1807.07616v1 [hep-th])

    Authors: Massimo Blasone, Petr Jizba, Nikolaos E. Mavromatos, Luca Smaldone

    In this Letter we study dynamical chiral symmetry breaking of a generic model with global chiral symmetry. By purely algebraic means we analyze the vacuum structure for different symmetry breaking patterns and show explicitly how non trivial vacuum condensates are required for both mass generation and field mixing phenomena. We stress that the generation of mixing implies the presence of off diagonal condensates in flavor space. In addition, with the help of Ward Takahashi identities, we demonstrate the emergence of Nambu Goldstone modes in the physical spectrum.

  • Border and skewness functions from a leading order fit to DVCS data. (arXiv:1807.07620v1 [hep-ph])

    Authors: H. Moutarde, P. Sznajder, J. Wagner

    We propose new parameterizations for the border and skewness functions appearing in the description of 3D nucleon structure in the language of Generalized Parton Distributions (GPDs). These parameterizations are constructed in a way to fulfill the basic properties of GPDs, like their reduction to Parton Density Functions and Elastic Form Factors. They also rely on the power behavior of GPDs in the $x \to 1$ limit and the propounded analyticity property of Mellin moments of GPDs. We evaluate Compton Form Factors (CFFs), the sub-amplitudes of the Deeply Virtual Compton Scattering (DVCS) process, at the leading order and leading twist accuracy. We constrain the restricted number of free parameters of these new parameterizations in a global CFF analysis of almost all existing proton DVCS measurements. The fit is performed within the PARTONS framework, being the modern tool for generic GPD studies. A distinctive feature of this CFF fit is the careful propagation of uncertainties based on the replica method. The fit results genuinely permit nucleon tomography and may give some insight into the distribution of forces acting on partons.

  • Efficient Probabilistic Inference in the Quest for Physics Beyond the Standard Model. (arXiv:1807.07706v1 [cs.LG])

    Authors: Atilim Gunes Baydin, Lukas Heinrich, Wahid Bhimji, Bradley Gram-Hansen, Gilles Louppe, Lei Shao, Prabhat, Kyle Cranmer, Frank Wood

    We present a novel framework that enables efficient probabilistic inference in large-scale scientific models by allowing the execution of existing domain-specific simulators as probabilistic programs, resulting in highly interpretable posterior inference. Our framework is general purpose and scalable, and is based on a cross-platform probabilistic execution protocol through which an inference engine can control simulators in a language-agnostic way. We demonstrate the technique in particle physics, on a scientifically accurate simulation of the tau lepton decay, which is a key ingredient in establishing the properties of the Higgs boson. High-energy physics has a rich set of simulators based on quantum field theory and the interaction of particles in matter. We show how to use probabilistic programming to perform Bayesian inference in these existing simulator codebases directly, in particular conditioning on observable outputs from a simulated particle detector to directly produce an interpretable posterior distribution over decay pathways. Inference efficiency is achieved via inference compilation where a deep recurrent neural network is trained to parameterize proposal distributions and control the stochastic simulator in a sequential importance sampling scheme, at a fraction of the computational cost of Markov chain Monte Carlo sampling.

  • Searching for heavy Higgs bosons in the $t \bar t Z$ and $t b W$ final states. (arXiv:1807.07734v1 [hep-ph])

    Authors: Ulrich Haisch, Giacomo Polesello

    In the context of two-Higgs doublet models, we explore the possibility of searching for heavy Higgs bosons in the $t \bar t Z$ and $t bW$ final states. We develop realistic analyses strategies and in the case of the $t \bar t Z$ channel provide a detailed evaluation of the new-physics reach at the 14 TeV LHC. We find that already with an integrated luminosity of $300 \, {\rm fb}^{-1}$ searches for the $t \bar t Z$ signature can provide statistically significant constraints at low values of $\tan \beta$ for heavy Higgs masses in the range from around $450 \, {\rm GeV}$ to $1150 \, {\rm GeV}$. Future searches for heavy Higgses in the $tbW$ final state are also expected to be able to probe parts of this parameter space, though the precise constraints turn out to depend sensitively on the assumed systematics on the shape of the $t \bar t$ background.

  • Electromagnetic interactions of mesons induced by the axial-vector -- pseudoscalar mixings. (arXiv:1807.07742v1 [hep-ph])

    Authors: A.A. Osipov, M.M. Khalifa

    It is shown that the diagonalization of the axial-vector -- pseudoscalar transitions in the effective meson Lagrangian in presence of electromagnetic interactions leads to a deviation from the vector meson dominance picture which usually arises in the Nambu - Jona-Lasinio model. The essential features of such modification of the theory are studied. Some important examples are considered in detail.

  • Validation of the Simulation of Collision Events at the LHC. (arXiv:1807.07756v1 [physics.hist-ph])

    Authors: Peter Mättig

    The procedures of validating simulation of particle physics events at the LHC are summarized. Because of the strongly fluctuating particle content of LHC events and detector interactions, particle based Monte Carlo methods are an indispensable tool for data analysis. Simulation in particle physics is founded on factorization and thus its global validation can be realized by validating each individual step in the simulation. This can be accomplished by adopting results of previous measurements, in - situ studies and models. Important in particle physics is to quantify how well simulation is validated such that a systematic uncertainty can be assigned to a measurement. The simulation is tested for a wide range of processes and agrees with data within the assigned uncertainties.

  • A simultaneous understanding of jet and hadron suppression. (arXiv:1807.07788v1 [hep-ph])

    Authors: Jorge Casalderrey-Solana, Zachary Hulcher, Guilherme Milhano, Daniel Pablos, Krishna Rajagopal

    In the context of the hybrid strong/weak coupling model for jet quenching, we perform a global fit to hadron and jet data in the most central bins both at RHIC and LHC. The qualitative and quantitative success of the analysis is attributed to the fact that the model correctly captures the fact that wider jets lose, on average, more energy than the narrower ones, to which high energy hadrons belong. We show how one can understand the relative jet and hadron suppression by analyzing the jet fragmentation functions, and also discuss the role of plasma finite resolution effects.

  • Decoherence in neutrino oscillations: neutrino nature and CPT violation. (arXiv:1807.07823v1 [hep-ph])

    Authors: A. Capolupo, S. M. Giampaolo, G. Lambiase

    We study the phenomenon of the decoherence for neutrinos propagating in long baseline experiments. We show that, the presence of an off-diagonal term in the dissipative matrix induces oscillation formulas for Dirac neutrinos different from the ones for Majorana neutrinos. The decoherence leads also to the violation of the $CPT$ symmetry. We use the values of the experimental parameters in order to relate our theoretical proposal with experiments.

  • Ad Lucem: The Photon in the MMHT PDFs. (arXiv:1807.07846v1 [hep-ph])

    Authors: Ricky Nathvani, Lucian Harland-Lang, Robert Thorne, Alan Martin

    We describe the inclusion of the photon as an additional component of the proton's Parton Distribution Functions (PDFs) in the MMHT framework. The input for the photon is adopted from the recent LUXqed determination. We describe the similarities and differences above the input scale with other photon PDF determinations and the contributions to the MMHT photon from both leading twist and higher twist contributions, and their uncertainties. We study the impact of QED effects on the quark and gluon PDFs and the fit quality, and outline our development of an equivalent set of neutron PDFs.

  • Two-mass three-loop effects in deep-inelastic scattering. (arXiv:1807.07855v1 [hep-ph])

    Authors: J. Ablinger, J. Blümlein, A. De Freitas, A. Goedicke, C. Schneider, K. Schönwald

    We report on recent results on the two-mass corrections for massive operator matrix elements at 2- and 3-loop orders in QCD. These corrections form the building blocks of the variable flavor number scheme. Due to the similar values of the charm and bottom quark masses the two-mass corrections form an important contribution.

  • Geometrically Confined Thermal Field Theory: Finite Size Corrections and Phase Transitions. (arXiv:1807.07871v1 [hep-th])

    Authors: Sylvain Mogliacci, Isobel Kolbé, W. A. Horowitz

    Motivated by the recent shocking results from RHIC and LHC that show quark-gluon plasma signatures in small systems, we study a simple model of a massless, noninteracting scalar field confined with Dirichlet boundary conditions. We use this system to investigate the finite size corrections to thermal field theoretically derived quantities compared to the usual Stefan-Boltzmann limit of an ideal gas not confined in any direction. Two equivalent expressions with different numerical convergence properties are found for the free energy in $D$ rectilinear spacetime dimensions with $c\le D-1$ spatial dimensions of finite extent. We find that the First Law of Thermodynamics generalizes such that the pressure depends on direction but that the Third Law is respected. For systems with finite dimension(s) but infinite volumes, such as a field constrained between two parallel plates or a rectangular tube, the relative fluctuations in energy are zero, and hence the canonical and microcanonical ensembles are equivalent. We present precise numerical results for the free energy, total internal energy, pressure, entropy, and heat capacity of our field between parallel plates, in a tube, and in finite volume boxes of various sizes in 4 spacetime dimensions. For temperatures and system sizes relevant for heavy ion phenomenology, we find large deviations from the Stefan-Boltzmann limit for these quantities, especially for the pressure. Further investigation of an isolated system of fields constrained between parallel plates reveals a divergent isoenergetic compressibility at a critical length $L_c\sim1/T$. We have thus discovered a new second order phase transition via a first principles calculation, a transition that is driven by the size of the system.

  • Neutron lifetime puzzle and neutron -- mirror neutron oscillation. (arXiv:1807.07906v1 [hep-ph])

    Authors: Zurab Berezhiani

    The discrepancy between the neutron lifetimes measured in the beam and trap experiments can be explained via the neutron $n$ conversion into mirror neutron $n'$, its dark partner from parallel mirror sector, provided that $n$ and $n'$ have a tiny mass splitting order $10^{-7}$ eV. In large magnetic fields used in beam experiments $n-n'$ transition is resonantly enhanced and can transform of about a per cent fraction of neutrons into mirror neutrons which decay in invisible mode. Thus less protons will be produced and the measured value $\tau_{\rm beam}$ appears larger than $\beta$-decay time $\tau_{\beta} = \tau_{\rm trap}$. Some phenomenological and astrophysical consequences of this scenario are also briefly discussed.

  • NNLO corrections to VBF Higgs boson production. (arXiv:1807.07908v1 [hep-ph])

    Authors: Juan Cruz-Martinez, Nigel Glover, Thomas Gehrmann, Alexander Huss

    This talk expands on recently published results for the factorising next-to-next-to-leading order (NNLO) QCD corrections to Higgs boson production in the vector boson fusion (VBF) channel. The calculation is fully differential in the kinematics of the Higgs boson and the final state jets and is implemented in the NNLOJET framework for computing higher-order QCD corrections. We find the NNLO corrections to be limited in magnitude to about $\pm 5$\% with a weak kinematical dependence in the transverse momenta and rapidity separation of the two tagging jets.

  • Anomaly-free Dark Matter with Harmless Direct Detection Constraints. (arXiv:1807.07921v1 [hep-ph])

    Authors: S. Caron, J. A. Casas, J. Quilis, R. Ruiz de Austri

    Dark matter (DM) interacting with the SM fields via a $Z'-$boson ('$Z'$-portal') remains one of the most attractive WIMP scenarios, both from the theoretical and the phenomenological points of view. In order to avoid the strong constraints from direct detection and dilepton production, it is highly convenient that the $Z'$ has axial coupling to DM and leptophobic couplings to the SM particles, respectively. In this paper we first explore the conditions for an anomaly-free leptophobic $Z'$, which (if flavour-blind) has to coincide with that from gauged baryon-number in the SM sector. Then there are very few possibilities where, besides leptophobia, the coupling to DM is axial; namely four (quite similar) cases if the content of the dark sector is minimal. The resulting scenario is very predictive, and perfectly viable from the present constraints from DM detection, EW observables and LHC data (di-lepton, di-jet and mono-jet production). We analyze all these constraints, obtaining the allowed areas in the parameter space, which generically prefer $m_{Z'}\lesssim 500$ GeV, apart from resonant regions. The best chances to test these viable areas come from future LHC measurements.

  • Sterile Neutrino Dark Matter. (arXiv:1807.07938v1 [hep-ph])

    Authors: A. Boyarsky, M. Drewes, T. Lasserre, S. Mertens, O. Ruchayskiy

    We review sterile neutrinos as possible Dark Matter candidates. After a short summary on the role of neutrinos in cosmology and particle physics, we give a comprehensive overview of the current status of the research on sterile neutrino Dark Matter. First we discuss the motivation and limits obtained through astrophysical observations. Second, we review different mechanisms of how sterile neutrino Dark Matter could have been produced in the early universe. Finally, we outline a selection of future laboratory searches for keV-scale sterile neutrinos, highlighting their experimental challenges and discovery potential.

  • On Bulk Viscosity at Weak and Strong 't Hooft Couplings. (arXiv:1807.07950v1 [hep-th])

    Authors: Alina Czajka, Keshav Dasgupta, Charles Gale, Sangyong Jeon, Aalok Misra, Michael Richard, Karunava Sil

    Bulk viscosity is an important transport coefficient that exists in the hydrodynamical limit only when the underlying theory is non-conformal. One example being thermal QCD with large number of colors. We study bulk viscosity in such a theory at low energies and at weak and strong 't Hooft couplings when the temperature is above the deconfinement temperature. The weak coupling analysis is based on Boltzmann equation from kinetic theory whereas the strong coupling analysis uses non-conformal holographic techniques from string and M-theories. Using these, many properties associated with bulk viscosity may be explicitly derived. This is a shortened companion paper that summarizes some of the results of our longer paper arXiv:1807.04713.

  • Topology in full QCD at high temperature: a multicanonical approach. (arXiv:1807.07954v1 [hep-lat])

    Authors: Claudio Bonati, Massimo D'Elia, Guido Martinelli, Francesco Negro, Francesco Sanfilippo, Antonino Todaro

    We investigate the topological properties of $N_f = 2+1$ QCD with physical quark masses, at temperatures around 500 MeV. With the aim of obtaining a reliable sampling of topological modes in a regime where the fluctuations of the topological charge $Q$ are very rare, we adopt a multicanonical approach, adding a bias potential to the action which enhances the probability of suppressed topological sectors. This method permits to gain up to three orders magnitude in computational power in the explored temperature regime. Results at different lattice spacings and physical spatial volumes reveal no significant finite size effects and the presence, instead, of large finite cut-off effects, with the topological susceptibility which decreases by 3-4 orders of magnitude while moving from $a \simeq 0.06$ fm towards the continuum limit. The continuum extrapolation is in agreeement with previous lattice determinations, obtained by using ansatzes justified by several theoretical arguments. The parameter $b_2$, related to the fourth order coefficient in the Taylor expansion of the free energy density $f(\theta)$, has instead a smooth continuum extrapolation which is in agreement with the dilute instanton gas approximation.

  • The origin of fermion families and the value of the fine structure constant. (arXiv:1307.2201v3 [physics.gen-ph] UPDATED)

    Authors: J. Lemmon

    This paper is concerned with a way of thinking about the standard model that explains the existence of three fermion families and the value of the fine structure constant. The main idea is that the ultraviolet divergences that we encounter in the quantum field theories of the standard model, when interpreted appropriately, have a deep physical significance that leads to new relationships between the physical and bare masses quarks and leptons. This interpretation is based on the assumption of a quantum gravity induced ultraviolet cutoff at the Planck scale and a novel approach to mass renormalization in which the usual perturbation series for the self-mass of a quark or lepton is rearranged and formally summed. Perturbing around the formally summed expression leads to self-consistency equations for the physical quark and lepton masses with multiple solutions that lie outside the reach of conventional perturbation theory. When applied to the standard model at the lowest level of approximation, this approach explains how three generations of charged leptons with a mass spectrum and a value of the fine structure constant in rough agreement with experiment can emerge from a universal bare mass and bare electromagnetic charge. This approach also explains how three generations of physical quark doublets (six flavors) can emerge from a universal bare doublet and bare color charge. Finally, it explains the origin of mixing (and CP violation) and the absence of flavor-changing neutral currents.

  • QCD running in neutrinoless double beta decay: Short-range mechanisms. (arXiv:1511.03945v2 [hep-ph] UPDATED)

    Authors: M. González, M. Hirsch, S.G. Kovalenko

    The decay rate of neutrinoless double beta ($0\nu\beta\beta$) decay contains terms from heavy particle exchange, which lead to dimension-9 (d=9) six fermion operators at low energies. Limits on the coefficients of these operators have been derived previously neglecting the running of the operators between the high-scale, where they are generated, and the energy scale of double beta decay, where they are measured. Here we calculate the leading order QCD corrections to all possible d=9 operators contributing to the $0\nu\beta\beta$ amplitude and use RGE running to calculate 1-loop improved limits. Numerically, QCD running changes limits by factors of the order of or larger than typical uncertainties in nuclear matrix element calculations. For some specific cases, operator mixing in the running changes limits even by up to two orders of magnitude. Our results can be straightforwardly combined with new experimental limits or improved nuclear matrix element calculations to re-derive updated limits on all short-range contributions to $0\nu\beta\beta$ decay.

  • First results from the DEAP-3600 dark matter search with argon at SNOLAB. (arXiv:1707.08042v3 [astro-ph.CO] UPDATED)

    Authors: DEAP-3600 Collaboration: P.-A. Amaudruz, M. Baldwin, M. Batygov, B. Beltran, C. E. Bina, D. Bishop, J. Bonatt, G. Boorman, M. G. Boulay, B. Broerman, T. Bromwich, J. F. Bueno, A. Butcher, B. Cai, S. Chan, M. Chen, R. Chouinard, B. T. Cleveland, D. Cranshaw, K. Dering, J. DiGioseffo, S. Dittmeier, F. A. Duncan, M. Dunford, A. Erlandson, N. Fatemighomi, S. Florian, A. Flower, R. J. Ford, R. Gagnon, P. Giampa, V. V. Golovko, P. Gorel, R. Gornea, E. Grace, K. Graham, D. R. Grant, E. Gulyev, R. Hakobyan, A. Hall, A. L. Hallin, M. Hamstra, P. J. Harvey, C. Hearns, C. J. Jillings, O. Kamaev, A. Kemp, M. Kuźniak, S. Langrock, F. La Zia, B. Lehnert, J. J. Lidgard, C. Lim, T. Lindner, Y. Linn, S. Liu, P. Majewski, R. Mathew, A. B. McDonald, T. McElroy, T. McGinn, J. B. McLaughlin, S. Mead, R. Mehdiyev, et al. (40 additional authors not shown)

    This paper reports the first results of a direct dark matter search with the DEAP-3600 single-phase liquid argon (LAr) detector. The experiment was performed 2 km underground at SNOLAB (Sudbury, Canada) utilizing a large target mass, with the LAr target contained in a spherical acrylic vessel of 3600 kg capacity. The LAr is viewed by an array of PMTs, which would register scintillation light produced by rare nuclear recoil signals induced by dark matter particle scattering. An analysis of 4.44 live days (fiducial exposure of 9.87 tonne-days) of data taken with the nearly full detector during the initial filling phase demonstrates the detector performance and the best electronic recoil rejection using pulse-shape discrimination in argon, with leakage $<1.2\times 10^{-7}$ (90% C.L.) between 16 and 33 keV$_{ee}$. No candidate signal events are observed, which results in the leading limit on WIMP-nucleon spin-independent cross section on argon, $<1.2\times 10^{-44}$ cm$^2$ for a 100 GeV/c$^2$ WIMP mass (90% C.L.).

  • Impact of medium modification of the nucleon weak and electromagnetic form factors on the neutrino mean free path in dense matter. (arXiv:1802.01749v2 [nucl-th] UPDATED)

    Authors: Parada T. P. Hutauruk, Yongseok Oh, K. Tsushima

    Impact of the in-medium modified nucleon weak and electromagnetic form factors on the neutrino mean free path in dense matter is studied by considering both the weak and electromagnetic interactions of neutrinos with the constituents of the matter. A relativistic mean field model and the quark-meson coupling model are respectively adopted for the in-medium effective nucleon mass and nucleon form factors. We find that the cross sections of neutrino scattering in cold nuclear medium decreases when the in-medium modification of the nucleon weak and electromagnetic form factors are taken into account. This reduction results in the enhancement of the neutrino mean free path, in particular at the baryon density of around a few times of the normal nuclear matter density. The enhancement of the neutrino mean free path is estimated to be about 10--40\% compared with the values obtained without the medium modification of the nucleon form factors, and the enhancement is expected to accelerate the cooling of neutron stars.

  • Target-normal single-spin asymmetry in elastic electron-nucleon scattering. (arXiv:1803.04004v2 [hep-ph] UPDATED)

    Authors: Oleksandr Koshchii, Andrei Afanasev

    We estimate the target-normal single-spin asymmetry at nearly forward angles in elastic electron-nucleon scattering. In the leading-order approximation, this asymmetry is proportional to the imaginary part of the two-photon exchange (TPE) amplitude, which can be expressed as an integral over the doubly virtual Compton scattering (VVCS) tensor. We develop a model that parameterizes VVCS tensor for the case of nearly forward scattering angles. Our parameterization ensures a proper normalization of the imaginary part of the TPE amplitude on the well-known forward limit expression, which is given in terms of nucleon structure functions measurable in inelastic electron-nucleon scattering experiments. We discuss applicability limits of our theory and provide target-normal single-spin asymmetry predictions for both elastic electron-proton and electron-neutron scattering.

  • Addressing the B-physics anomalies in a fundamental Composite Higgs Model. (arXiv:1803.10972v3 [hep-ph] UPDATED)

    Authors: David Marzocca

    I present a model addressing coherently the naturalness problem of the electroweak scale and the observed pattern of deviations from the Standard Model in semi-leptonic decays of $B$ mesons. The Higgs and the two scalar leptoquarks responsible for the $B$-physics anomalies, $S_1 = ({\bf \bar 3}, {\bf 1}, 1/3)$ and $S_3 = ({\bf \bar 3}, {\bf 3}, 1/3)$, arise as pseudo Nambu-Goldstone bosons of a new strongly coupled sector at the multi-TeV scale. I focus on an explicit realization of such a dynamics in terms of a new strongly coupled gauge interaction and extra vectorlike fermions charged under it. The model presents a very rich phenomenology, ranging from flavour observables, Higgs and electroweak precision measurements, and direct searches of new states at the LHC.

  • Low-energy limit of the $O(4)$ quark-meson model from the functional renormalization group approach. (arXiv:1804.01787v2 [hep-ph] UPDATED)

    Authors: Jürgen Eser, Florian Divotgey, Mario Mitter, Dirk H. Rischke

    We compute the low-energy limit of the $O(4)$-symmetric quark-meson model as an effective field theory for Quantum Chromodynamics within the Functional Renormalization Group (FRG) approach. In particular, we analyze the renormalization group flow of momentum-dependent pion self-interactions beyond the local potential approximation. The numerical results for these couplings obtained from the FRG are confronted with a recent tree-level study. Additionally, their effect on the wave-function renormalization and the curvature masses is investigated.

  • Primordial Black Holes from Inflation and Quantum Diffusion. (arXiv:1804.07124v2 [astro-ph.CO] UPDATED)

    Authors: Matteo Biagetti, Gabriele Franciolini, Alex Kehagias, Antonio Riotto

    Primordial black holes as dark matter may be generated in single-field models of inflation thanks to the enhancement at small scales of the comoving curvature perturbation. This mechanism requires leaving the slow-roll phase to enter a non-attractor phase during which the inflaton travels across a plateau and its velocity drops down exponentially. We argue that quantum diffusion has a significant impact on the primordial black hole mass fraction making the classical standard prediction not trustable.

  • Differential decay rates of CP-even and CP-odd Higgs bosons to top and bottom quarks at NNLO QCD. (arXiv:1805.06658v2 [hep-ph] UPDATED)

    Authors: Werner Bernreuther, Long Chen, Zong-Guo Si

    We consider the decay of a neutral Higgs boson of arbitrary CP nature to a massive quark antiquark pair at next-to-next-to-leading order in perturbative QCD. Our analysis is made at the differential level using the antenna subtraction framework. We apply our general set-up to the decays of a CP-even and CP-odd heavy Higgs boson to a top-quark top-antiquark pair and to the decay of the 125 GeV Higgs boson to a massive bottom-quark bottom-antiquark pair. In the latter case we calculate, in particular, the two-jet, three-jet, and four-jet decay rates and, for two-jet events, the energy distribution of the leading jet.

  • Reconciling $B$-decay anomalies with neutrino masses, dark matter and constraints from flavour violation. (arXiv:1806.10146v2 [hep-ph] UPDATED)

    Authors: Chandan Hati, Girish Kumar, Jean Orloff, Ana M. Teixeira

    Motivated by an explanation of the $R_{K^{(*)}}$ anomalies, we propose a Standard Model extension via two scalar SU(2)$_L$ triplet leptoquarks and three generations of triplet Majorana fermions. The gauge group is reinforced by a $Z_2$ symmetry, ensuring the stability of the lightest $Z_2$-odd particle, which is a potentially viable dark matter candidate. Neutrino mass generation occurs radiatively (at the three-loop level), and leads to important constraints on the leptoquark couplings to leptons. We consider very generic textures for the flavour structure of the $h_1$ leptoquark Yukawa couplings, identifying classes of textures which succeed in saturating the $R_{K^{(*)}}$ anomalies. We subsequently carry a comprehensive analysis of the model's contributions to numerous high-intensity observables such as meson oscillations and decays, as well as charged lepton flavour violating processes, which put severe constraints on the flavour structure of these leptoquark extensions. Our findings suggest that the most constraining observables are $K^+ \to \pi^+ \nu \bar \nu$ decays, and charged lepton flavour violating $\mu -e$ conversion in nuclei (among others). Nevertheless, for several classes of flavour textures and for wide mass regimes of the new mediators (within collider reach), this Standard Model extension successfully addresses neutrino mass generation, explains the current $R_{K^{(*)}}$ tensions, and offers a viable dark matter candidate.

  • A mixing interpolation method to mimic pasta phases in compact star matter. (arXiv:1807.03258v3 [nucl-th] UPDATED)

    Authors: David Alvarez-Castillo, David Blaschke

    We present a new method to interpolate between two matter phases that allows for a description of mixed phases and can be used, e.g., for mimicking transitions between pasta structures occuring in the crust as well as in the inner core of compact stars. This interpolation method is based on assuming switch functions that are used to define a mixture of subphases while fulfilling constraints of thermodynamic stability. The width of the transition depends on a free parameter, the pressure increment relative to the critical pressure of a Maxwell construction. As an example we present a trigonometric function ansatz for the switch function together with a pressure increment during the transition. We note that the resulting mixed phase equation of state bears similarities with the appearance of substitutional compounds in neutron star crusts and with the sequence of transitions between different pasta phases in the hadron-to-quark matter transition. We apply this method to the case of a hadron-to-quark matter transition and test the robustness of the compact star mass twin phenomenon against the appearance of pasta phases modeled in this way.

  • Measurements of isospin asymmetry and difference of direct $CP$ asymmetries in $B \to X_s \gamma$ decays with a sum-of-exclusive technique. (arXiv:1807.04236v3 [hep-ex] UPDATED)

    Authors: S. Watanuki, A. Ishikawa, A. Abdesselam, I. Adachi, K. Adamczyk, J. K. Ahn, H. Aihara, S. Al Said, K. Arinstein, Y. Arita, D. M. Asner, H. Atmacan, V. Aulchenko, T. Aushev, R. Ayad, T. Aziz, V. Babu, I. Badhrees, S. Bahinipati, A. M. Bakich, Y. Ban, V. Bansal, E. Barberio, M. Barrett, W. Bartel, P. Behera, C. Beleno, K. Belous, M. Berger, F. Bernlochner, D. Besson, V. Bhardwaj, B. Bhuyan, T. Bilka, J. Biswal, T. Bloomfield, A. Bobrov, A. Bondar, G. Bonvicini, A. Bozek, M. Bravcko, N. Braun, F. Breibeck, J. Brodzicka, T. E. Browder, L. Cao, G. Caria, D. Cervenkov, M.-C. Chang, P. Chang, Y. Chao, V. Chekelian, A. Chen, K.-F. Chen, B. G. Cheon, K. Chilikin, R. Chistov, K. Cho, V. Chobanova, S.-K. Choi, Y. Choi, S. Choudhury, D. Cinabro, J. Crnkovic, S. Cunliffe, T. Czank, M. Danilov, N. Dash, et al. (384 additional authors not shown)

    We report measurements of isospin asymmetry $\Delta_{0-}$ and difference of direct $CP$ asymmetries $\Delta A_{CP}$ between charged and neutral $B \to X_s \gamma$ decays. This analysis is based on the data sample containing $772 \times 10^6 B\bar{B}$ pairs that was collected with the Belle detector at the KEKB energy-asymmetric $e^+ e^-$ collider. Using a sum-of-exclusive technique with invariant $X_s$ mass up to 2.8~GeV/$c^2$, we obtain $\Delta_{0-} = \bigl[+1.70 \pm 1.39 {\rm (stat.)} \pm 0.87 {\rm (syst.)} \pm 1.15 {(f_{+-}/f_{00})}\bigr]$\% and $\Delta A_{CP} = \bigl[+1.26 \pm 2.40 {\rm (stat.)} \pm 0.67{\rm (syst.)}\bigr]$\%, where the last uncertainty for $\Delta_{0-}$ is due to the uncertainty on the fraction of $B^+B^-$ to $B^0\bar{B}^0$ production in $\Upsilon(4S)$ decays. The measured value of $\Delta_{0-}$ is consistent with zero, allowing to constrain the resolved photon contributions in the $B \to X_s \gamma$ decay as well as to improve the branching fraction prediction. The result for $\Delta A_{CP}$ is consistent with a prediction of the SM. We also measure the direct $CP$ asymmetries for charged and neutral $B \to X_s \gamma$ decays. All the measurements are the most precise to date.

  • The three- and four-Higgs couplings in the general two-Higgs-doublet model. (arXiv:1807.04244v2 [hep-ph] UPDATED)

    Authors: D. Jurciukonis, L. Lavoura

    We apply the unitarity bounds and the bounded-from-below (BFB) bounds to the most general scalar potential of the two-Higgs-doublet model (2HDM). We do this in the Higgs basis, i.e. in the basis for the scalar doublets where only one doublet has vacuum expectation value. In this way we obtain bounds on the scalar masses and couplings that are valid for all 2HDMs. We compare those bounds to the analogous bounds that we have obtained for other simple extensions of the Standard Model (SM), namely the 2HDM extended by one scalar singlet and the extension of the SM through two scalar singlets.

  • Non-Unitary Evolution in the General Extended EFT of Inflation & Excited Initial States. (arXiv:1807.06511v1 [hep-th] CROSS LISTED)

    Authors: Amjad Ashoorioon

    I study the "general" case that arises in the Extended Effective Field Theory of Inflation (gEEFToI), in which the coefficients of the sixth order polynomial dispersion relation depend on the physical wavelength of the fluctuation mode, hence they are time-dependent. At arbitrarily short wavelengths the unitarity is lost for each mode. Depending on the values of the gEEFToI parameters in the unitary gauge action, two scenarios can arise: in one, the coefficients of the polynomial become singular, flip signs at some physical wavelength and asymptote to a constant value as the wavelength of the mode is stretched to infinity. Starting from the WKB vacuum, the two-point function is essentially singular in the infinite IR limit. In the other case, the coefficients of the dispersion relation evolve monotonically from zero to a constant value in the infinite IR. In order to have a finite power spectrum starting from the vacuum in this case, the mode function has to be an eigensolution of the Confluent Heun (CH) equation, which leads to a very confined parameter space for gEEFToI. Finally, I look at a solution of the CH equation which is regular in the infinite IR limit and yields a finite power spectrum in either scenario. I demonstrate that this solution asymptotes to an excited state in past infinity in both cases. The result is interpreted in the light of the loss of unitarity for very small wavelengths. The outcome of such a non-unitary phase evolution should prepare each mode in the excited initial state that yields a finite two-point function for all the parameter space. This will be constraining of the new physics that UV completes such scenarios.

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