Mon·Jul 23, 2018Monday·July 23, 2018

1. 01*

   Border and skewness functions from a leading order fit to DVCS data

   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.

   hep-phEPJC(2018)·72 citations
2. 02*

   Searching for heavy Higgs bosons in the $t\bar{t}Z$ and $tbW$ final states

   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 $tbW$ 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 $300{\mathrm{fb}}^{-1}$ 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 $450\mathrm{GeV}$ to $1150\mathrm{GeV}$. 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.

   hep-phhep-exJHEP(2018)·38 citations
3. 03*

   Electromagnetic interactions of mesons induced by the axial-vector -- pseudoscalar mixings

   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.

   hep-phPRD(2018)·6 citations
4. 04*

   A simultaneous understanding of jet and hadron suppression

   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.

   hep-phNPA(2019)·0 citations
5. 05*

   Decoherence in neutrino oscillations, neutrino nature and CPT violation

   A. Capolupo🇮🇹 · S. M. Giampaolo🇭🇷 · G. Lambiase🇮🇹

   We analyze many aspects of the phenomenon of the decoherence for neutrinos propagating in long baseline experiments. We show that, in the presence of an off-diagonal term in the dissipative matrix, the Majorana neutrino can violate the CP T symmetry, which, on the contrary, is preserved for Dirac neutrinos. We show that oscillation formulas for Majorana neutrinos depend on the choice of the mixing matrix U. Indeed, different choices of U lead to different oscillation formulas. Moreover, we study the possibility to reveal the differences between Dirac and Majorana neutrinos in the oscillations. We use the present values of the experimental parameters in order to relate our theoretical proposal with experiments.

   hep-phPLB(2019)·60 citations
6. 06*

   Ad Lucem: The Photon in the MMHT PDFs

   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.

   hep-phPoS(2018)·5 citations
7. 07*

   Two-mass three-loop effects in deep-inelastic scattering

   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.

   hep-phPoS(2018)·2 citations
8. 08*

   Neutron lifetime puzzle and neutron -- mirror neutron oscillation

   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 $n^{\prime }$, its dark partner from parallel mirror sector, provided that $n$ and $n^{\prime }$ have a tiny mass splitting order $10^{-7}$ eV. In large magnetic fields used in beam experiments $n-n^{\prime }$ 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 ${\tau }_{\mathrm{beam}}$ appears larger than $\beta$-decay time ${\tau }_{\beta }={\tau }_{\mathrm{trap}}$. Some phenomenological and astrophysical consequences of this scenario are also briefly discussed.

   hep-phEPJC(2019)·129 citations
9. 09*

   NNLO corrections to VBF Higgs boson production

   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.

   hep-phPoS(2018)·4 citations
10. 10*

    Anomaly-free Dark Matter with Harmless Direct Detection Constraints

    S. Caron🇳🇱 · J. A. Casas🇪🇸 · J. Quilis🇪🇸 · R. Ruiz de Austri🇪🇸

    Dark matter (DM) interacting with the SM fields via a $Z^{\prime }-$boson ('$Z^{\prime }$-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 $Z^{\prime }$ 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 $Z^{\prime }$, 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 $m_{Z^{\prime }}\lesssim 500$ GeV, apart from resonant regions. The best chances to test these viable areas come from future LHC measurements.

    hep-phJHEP(2018)·19 citations
11. 11*

    Sterile Neutrino Dark Matter

    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.

    hep-phastro-ph.COhep-exPPNP(2019)·650 citations
12. 12*

    Broadening Dark Matter Searches at the LHC: Mono-X versus Darkonium Channels

    Anirudh Krovi🇺🇸 · Ian Low🇺🇸 · Yue Zhang🇺🇸

    Current searches for dark matter at the LHC focus on mono-X signatures: the production of dark matter in association with a Standard Model (SM) particle. The simplest benchmark introduces a massive spin-1 mediator, the $Z^{\prime }$ boson, between the dark matter $\chi$ and the SM. Limits derived from mono-X channels are most effective when the mediator can decay into two on-shell dark matter particles: $M_{Z^{\prime }}\gtrsim 2M_{\chi }$. We broaden the experimental reach into the complementary region, where the $Z^{\prime }$ mediator is much lighter than the dark matter. In this scenario the $Z^{\prime }$ mediates an effective long-range force between the dark matter, thereby facilitating the formation of darkonium bound states, as is common in many dark sector models. The darkonium becomes active when $M_{\chi }>M_{Z^{\prime }}/{\alpha }_{\mathrm{eff}}$, where ${\alpha }_{\mathrm{eff}}$ is the effective fine-structure constant in the dark sector. Moreover, the darkonium could decay back into SM quarks, without producing missing transverse momentum in the detector. Considering multijet final states, we reinterpret existing searches to constrain the simple $Z^{\prime }$ benchmark beyond the region probed by mono-X searches. Assuming a baryonic $Z^{\prime }$ mediator and a Dirac dark matter, direct detection bounds can be loosened by giving a small Majorana mass to the dark matter. We also consider the interplay between mono-X and darkonium channels at future high energy colliders, which is at the frontier of probing the model parameter space.

    hep-phhep-exJHEP(2018)·22 citations
13. 13*

    Multiquark States in the Thomas-Fermi Quark Model and on the Lattice

    Walter Wilcox🇺🇸 · Suman Baral🇺🇸

    We describe work being done at Baylor University investigating the possibility of new states of mesonic matter containing two or more quark-antiquark pairs. To put things in context, we begin by describing the lattice approach to hadronic physics. We point out there is a need for a quark model which can give an overall view of the quark interaction landscape. A new application of the Thomas-Fermi (TF) statistical quark model is described, similar to a previous application to baryons. The main usefulness of this model will be to detect systematic energy trends in the composition of the various particles. It could be a key to identifying {\it families} of bound states, rather than individual cases. Numerical results based upon a set of parameters derived from a phenomenological model of tetraquarks are given.

    hep-phhep-latInt.J.Mod.Phys.A(2019)·7 citations
14. 14*

    The Apparent (Gravitational) Horizon in Cosmology

    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.

    ↳ gr-qcastro-ph.COhep-phAm.J.Phys.(2018)·38 citations
15. 15*

    Shape Is Destiny II: Configurational Information Approach to Instantons and False Vacuum Decay in D-dimensional Spacetime

    Marcelo Gleiser🇺🇸 · Damian R. Sowinski🇺🇸

    We extend the use of Configurational Information Measures (CIMSs) to instantons and vacuum decay in arbitrary spatial dimensions. We find that both the complexity and the information content in the shape of instanton solutions have distinct regions of behavior in parameter space, discriminating between qualitative thin and thick wall profiles. For Euclidean spaces of dimension $D$, we show that for $D>6$ instantons undergo a qualitative change of behavior from their lower- dimensional counterparts, indicating that $D=6$ is a critical dimension. We also find a scaling law relating the different CIMs to the rate of vacuum decay, thus connecting the stability of the vacuum to the informational complexity stored in the shape of the related critical bounce.

    ↳ hep-thhep-phnlin.PSPRD(2018)·33 citations
16. 16*

    Hydrodynamic modes in a magnetized chiral plasma with vorticity

    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 charged chiral plasma with background electromagnetic fields. We identify the global equilibrium state for a rotating 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 magnetized rotating chiral plasma in the regimes of high temperature and high density. We find that, in both regimes, dynamical electromagnetism has profound effects on the spectrum of propagating modes. In particular, there are only the sound and Alfvén waves in the regime of high temperature, and the plasmons and helicons at high density. We also show that the chiral magnetic wave is universally overdamped because of high electrical conductivity in plasma that causes an efficient screening of charge fluctuations. The physics implications of the main results are briefly discussed.

    ↳ hep-thhep-phnucl-thPRD(2019)·26 citations
17. 17*

    Dynamical generation of field mixing via flavor vacuum condensate

    Massimo Blasone🇮🇹 · Petr Jizba🇨🇿 · Nikolaos E. Mavromatos🇬🇧 · Luca Smaldone🇮🇹

    In this paper we study dynamical chiral symmetry breaking of a generic quantum field theoretical model with global chiral flavor symmetry. By purely algebraic means we analyze the vacuum structure for different symmetry breaking schemes and show explicitly how the ensuing non-trivial flavor vacuum condensate characterizes the phenomenon of field mixing. In addition, with the help of Ward-Takahashi identities we demonstrate the emergence of a correct number of Nambu-Goldstone modes in the physical spectrum.

    ↳ hep-thhep-phmath-phmath.MPPRD(2019)·28 citations
18. 18*

    Efficient Probabilistic Inference in the Quest for Physics Beyond the Standard Model

    Atılım Güneş Baydin🇬🇧 · Lukas Heinrich🇺🇸 · Wahid Bhimji🇺🇸 · Lei Shao🇺🇸 · Saeid Naderiparizi · Andreas Munk · Jialin Liu · Bradley Gram-Hansen🇬🇧 · Gilles Louppe🇧🇪 · Lawrence Meadows🇺🇸 · Philip Torr · Victor Lee and 3 other authors

    We present a novel probabilistic programming framework that couples directly to existing large-scale simulators through a cross-platform probabilistic execution protocol, which allows general-purpose inference engines to record and control random number draws within simulators in a language-agnostic way. The execution of existing simulators as probabilistic programs enables highly interpretable posterior inference in the structured model defined by the simulator code base. 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. 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 a Markov chain Monte Carlo baseline.

    ↳ cs.LGhep-phphysics.data-anstat.MLIn Advances in Neural Information Process…·8 citations
19. 19*

    Validation of the Simulation of Collision Events at the LHC

    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.

    ↳ physics.hist-phhep-ph1 citation
20. 20*

    On Bulk Viscosity at Weak and Strong 't Hooft Couplings

    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.

    ↳ hep-thcond-mat.str-elhep-phnucl-thMod.Phys.Lett.A(2020)·8 citations
21. 21*

    Topology in full QCD at high temperature: a multicanonical approach

    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 of 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 with smaller uncertainties but obtained based on ansatzes justified by several theoretical assumptions. 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 (DIGA); moreover, a direct measurement of the relative weights of the different topological sectors gives an even stronger support to the validity of DIGA.

    ↳ hep-lathep-phhep-thJHEP(2018)·96 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.