Fri·Mar 1, 2019Friday·March 1, 2019

1. 01*

   Tachyonic $\delta$-Tsallis entropy of a thermal tachyonic BIon

   Aroonkumar Beesham🇿🇦 · Alireza Sepehri🇿🇦

   When a brane and an anti-brane come close to each other, the tachyonic potential between them increases and a tachyon wormhole is formed. This configuration, which consists of two branes and a tachyonic wormhole, is called a thermal tachyonic BIon. By considering the thermodynamic behaviour of this system, one finds that its entropy has the same form as that of the Tsallis one. By decreasing the separation between the branes, the tachyonic potential increases, and the entropy grows.

   hep-phgr-qc0 citations
2. 02*

   Phenomenology of diffractive DIS in the framework of fracture functions and determination of diffractive parton distribution functions

   Hamzeh Khanpour🇮🇷

   The goal of this study is to determine a set of diffractive parton distribution function (diffractive PDFs) from a QCD analysis of all available and up-to-date diffractive deep inelastic scattering (diffractive DIS) data sets from HERA $ep$ collider, including the most recent H1 and ZUES combined inclusive diffractive cross section measurements. This extraction of diffractive PDFs, referred to as {\tt HK19-DPDF}, is performed at next-to-leading (NLO) and next-to-next-to-leading (NNLO) in perturbative QCD. This new determination of diffractive PDFs is based on the fracture functions methodology, a QCD framework designed to provide a statistically sound representation of diffractive DIS processes. Heavy quark contributions to the diffractive DIS are considered within the framework of the FONLL general mass variable flavor number scheme (GM-VFNS) and the "Hessian approach" is used to determine the uncertainties of diffractive PDFs. We discuss the novel aspects of the approach used in the present analysis, namely an optimized and flexible parametrization of the diffractive PDFs as well as a strategy based on the fully factorization theorem for diffractive hard processes. We then present the diffractive PDFs, and discuss the fit quality and the stability upon variations of the kinematic cuts and the fitted data sets. We find that the systematic inclusion of higher-order QCD corrections could improves the description of the data. We compare the extracted sets of diffractive PDFs based on the fracture functions approach to other recent sets of diffractive PDFs, finding in general very good agreements.

   hep-phhep-exPRD(2019)·22 citations
3. 03*

   Establishing the Dark Matter Relic Density in an Era of Particle Decays

   Carlos Maldonado🇨🇱 · James Unwin🇺🇸

   If the early universe is dominated by an energy density which evolves other than radiation-like the normal Hubble-temperature relation $H\propto T^2$ is broken and dark matter relic density calculations in this era can be significantly different. We first highlight that for a population of states $\varphi$ sourcing an initial expansion rate of the form $H\propto T^{2+n/2}$ for $n\ge -4$, during the period of appreciable $\varphi$ decays the evolution transitions to $H\propto T^4$. The decays of $\varphi$ imply a source of entropy production in the thermal bath which alters the Boltzmann equations and impacts the dark matter relic abundance. We show that the form of the initial expansion rate leaves a lasting imprint on relic densities established while $H\propto T^4$ since the value of the exponent $n$ changes the temperature evolution of the thermal bath. In particular, a dark matter relic density set via freeze-in or non-thermal production is highly sensitive to the temperature dependance of the initial expansion rate. This work generalises earlier studies which assumed initial expansion rates due to matter or kination domination.

   hep-phastro-ph.COJCAP(2019)·37 citations
4. 04*

   Revisiting the SUSY mu problem and its solutions in the LHC era

   Kyu Jung Bae🇰🇷 · Howard Baer🇺🇸 · Vernon Barger🇺🇸 · Dibyashree Sengupta🇺🇸

   The supersymmetry preserving mu parameter in SUSY theories is naively expected to be of order the Planck scale while phenomenology requires it to be of order the weak scale. This is the famous SUSY mu problem. Its solution involves two steps: 1. first forbid mu, perhaps via some symmetry, and then 2. re-generate it of order the scale of soft SUSY breaking terms. However, present LHC limits suggest the soft breaking scale m_{soft} lies in the multi-TeV regime whilst naturalness requires mu~ m_{W,Z,h}~ 100 GeV so that a Little Hierarchy (LH) appears with mu << m_{soft}. We review twenty previously devised solutions to the SUSY mu problem and re-evaluate them in light of whether they are apt to support the LH. We organize the twenty solutions according to: 1. solutions from supergravity/superstring constructions, 2. extended MSSM solutions, 3. solutions from an extra local U(1)' and 4. solutions involving Peccei-Quinn (PQ) symmetry and axions. Early solutions would invoke a global Peccei-Quinn symmetry to forbid the mu term while relating the mu solution to solving the strong CP problem via the axion. We discuss the gravity-safety issue pertaining to global symmetries and the movement instead toward local gauge symmetries or R-symmetries, either continuous or discrete. At present, discrete R-symmetries of order M (Z_M^R) which emerge as remnants of Lorentz symmetry of compact dimensions seem favored. Even so, a wide variety of regenerative mechanisms are possible, some of which relate to other issues such as the strong CP problem or the generation of neutrino masses. We also discuss the issue of experimental verification or falsifiability of various solutions to the mu problem. Almost all solutions seem able to accommodate the LH.

   hep-phPRD(2019)·78 citations
5. 05*

   Nature of the $Y(4260)$: A light-quark perspective

   Yun-Hua Chen🇨🇳 · Ling-Yun Dai🇨🇳 · Feng-Kun Guo🇨🇳 · Bastian Kubis🇩🇪

   The $Y(4260)$ has been one of the most puzzling pieces among the so-called $XYZ$ states. In this paper, we try to gain insights into the structure of the $Y(4260)$ from the light-quark perspective. We study the dipion invariant mass spectrum of the $e^{+}{e}^{-}\to Y(4260)\to J/\psi {\pi }^{+}{\pi }^{-}$ process and the ratio of the cross sections $\sigma (e^{+}{e}^{-}\to J/\psi K^{+}{K}^{-})/\sigma (e^{+}{e}^{-}\to J/\psi {\pi }^{+}{\pi }^{-})$. In particular, we consider the effects of different light-quark SU(3) eigenstates inside the $Y(4260)$. The strong pion-pion final-state interactions as well as the $K\bar{K}$ coupled channel in the $S$-wave are taken into account in a model-independent way using dispersion theory. We find that the SU(3) octet state plays a significant role in these transitions, implying that the $Y(4260)$ contains a large light-quark component. Our findings suggest that the $Y(4260)$ is neither a hybrid nor a conventional charmonium state, and they are consistent with the $Y(4260)$ having a sizeable $\bar{D}{D}_1$ component which, however, is not completely dominant.

   hep-phhep-exnucl-thPRD(2019)·44 citations
6. 06*

   Spontaneous Twin Symmetry Breaking

   Tae Hyun Jung🇰🇷

   We consider a twin Higgs scenario where the $Z_2$ twin symmetry is broken spontaneously, not explicitly. This scenario provides an interesting interpretation of the Higgs metastability in the standard model; the $SU(4)$ breaking scale $f$ is determined by the scale where the Higgs self quartic coupling flips its sign. However, for the misalignment of nonzero vacuum expectation values of the twin Higgs fields, parameter tuning of $\mathcal{O}(m_h^2/f^2)$ is required like explicit twin symmetry breaking scenarios. For the minimal model with the exact twin symmetry, $f$ is $\mathcal{O}$($10^{10}$ GeV), so the model is very unnatural. We point out that the tuning can be significantly reduced ($f\gtrsim 2.7$ TeV) if there are twin vector-like leptons with large Yukawa coupling to twin Higgs fields.

   hep-phPRD(2019)·17 citations
7. 07*

   Computing one-loop corrections to effective vertices with two scales in the EFT for Multi-Regge processes in QCD

   Maxim Nefedov🇷🇺

   The computation of one-loop corrections to Reggeon-Particle-Particle effective vertices with two scales of virtuality is considered in the framework of gauge-invariant effective field theory for Multi-Regge processes in QCD. Rapidity divergences arising in loop integrals are regulated by "tilted Wilson lines" prescription. General analysis of rapidity divergences at one loop is given and necessary scalar integrals with one and two scales of virtuality are computed. Two examples of effective vertices at one loop are considered: the effective vertex of interaction of (space-like) virtual photon with one Reggeized and one Yang-Mills quark and the effective vertex of Reggeized gluon to Yang-Mills gluon transition with an insertion of the operator $\mathrm{tr}\left[G_{\mu \nu }{G}^{\mu \nu }\right]$ carrying the (space-like) off-shell momentum. All terms $\sim r^{\pm ϵ}$ in the rapidity-regulator variable $r$ cancel between diagrams and only $\log r$-divergence is left. It is checked on several examples, that obtained results indeed allow one to reproduce Regge limit of one-loop QCD scattering amplitudes.

   hep-phNPB(2019)·60 citations
8. 08*

   Loop-induced direct detection signatures from CP-violating scalar mediators

   Fatih Ertas🇩🇪 · Felix Kahlhoefer🇩🇪

   We investigate direct detection signatures of dark matter particles interacting with quarks via a light spin-0 mediator with general CP phases. Since tree-level scattering may be strongly suppressed in the non-relativistic limit, loop contributions play an important role and can lead to observable signals in near-future experiments. We study the phenomenology of different mediator masses and CP phases with an emphasis on scenarios with maximal CP violation and Higgs portal models. Intriguingly, the sum of the rates obtained at tree- and loop-level can give a characteristic recoil spectrum not obtainable from a single type of interaction. We furthermore develop a novel method for decomposing the two-loop contribution to effective interactions between dark matter and gluons into two separate one-loop diagrams, which in our case substantially simplifies the calculation of the important top-quark contribution.

   hep-phJHEP(2019)·55 citations
9. 09*

   Technicolor models with coupled systems of Schwinger-Dyson equations

   A. Doff🇧🇷 · A. A. Natale🇧🇷

   When Technicolor (TC), QCD, Extended Technicolor (ETC) and other interactions become coupled through their different Schwinger-Dyson equations, the solution of these equations are modified in comparison with the ones of the isolated equations. The change in the self-energies is similar to the one obtained in the presence of four-fermion interactions, but without their \textsl{ad hoc} inclusion in the theory. In this case TC and QCD self-energies decrease logarithmically with the momenta, what allow us to build models where ETC boson masses can be pushed to very high energies, and their effects will barely appear at present energies. Here we present a detailed discussion of this class of TC models. We first review the Schwinger-Dyson TC and QCD coupled equations, explaining the origin of the asymptotic self-energies. We develop the basic ideas of how viable TC models may be built along this line, where ordinary lepton masses appear naturally lighter than quark masses. One specific unified TC model associated with a necessary horizontal (or family) symmetry is described. The values of scalar and pseudo-Goldstone boson masses in this class of models are also discussed, as well as the value of the trilinear scalar coupling, and the consistency of the models with the experimental constraints.

   hep-phhep-lathep-thPRD(2019)·10 citations
10. 10*

    Supersymmetric QCD with $N_f<N$ revisited

    Renata Jora🇷🇴

    We introduce in supersymmetric QCD with $N_f<N$ additional meson singlet degrees of freedom made of $2N_f-2$ supermultiplets. We construct an alternative superpotential with $N_f^2$ constraints and show its consistency. Based on this superpotential we prove that for $\frac{N}{2}<N_f<N$ the supersymmetry is unbroken whereas for $N_f\le \frac{N}{2}$ is dynamically broken.

    hep-phhep-th1 citation
11. 11*

    Witten index and dynamical supersymmetry breaking of a gauge theory

    Renata Jora🇷🇴

    We estimate the Witten index for a supersymmetric gauge theory with or without massless matter. For pure supersymmetric Yang Mills our result reproduces the results in the literature. For the known theories with dynamical symmetry breaking the Witten index is determined to be exactly zero. Our calculation sheds light on the possibility of dynamical supersymmetry breaking for those theories considered up to now unsolvable.

    hep-phhep-th0 citations
12. 12*

    A new simple PDF parametrization: improved description of the HERA data

    Marco Bonvini🇮🇹 · Francesco Giuli🇮🇹

    We introduce a new parametrization for the parton distribution functions (PDFs) designed to be flexible in the small-x region. We implement it in the xFitter open-source PDF fitting tool, and compare it to the default xFitter parametrization, widely used for many PDF studies, and notably for the HERAPDF determination. We find that we can describe the combined inclusive HERA I+II data using NNLO theory with a significantly higher quality than HERAPDF2.0: the ${\chi }^2$ is reduced by more than 60 units, having used only four more parameters. Our result highlights a significant parametrization bias in the default xFitter parametrization at small x, which would lead to even more dramatic effects when used for higher energy colliders, where the small-x region is more relevant. We also find that the inclusion of small-x resummation, that was shown in previous studies to lead to similar improvements in the fit quality, further reduces the ${\chi }^2$ by approximately 30 extra units.

    hep-phhep-exEur.Phys.J.Plus(2019)·58 citations
13. 13*

    Heavy resonances at energy-frontier hadron colliders

    Clement Helsens🇨🇭 · David Jamin🇨🇭 · Michelangelo L. Mangano🇨🇭 · Thomas G. Rizzo🇺🇸 · Michele Selvaggi🇨🇭

    This paper explores the physics reach of the proton-proton Future Circular Collider (FCC-hh) and of the High-Energy LHC (HE-LHC) for searches of new particles produced in the $s$-channel and decaying to two high-energy leptons, jets (non-tops), tops or W/Z bosons. We discuss the expected discovery potential and exclusion limits for benchmark models predicting new massive particles that result in resonant structures in the invariant mass spectrum. We also present a detailed study of the HE-LHC potential to discriminate among different models, for a $Z^{\prime }$ that could be discovered by the end of High-Luminosity LHC (HL-LHC).

    hep-phhep-exEPJC(2019)·56 citations
14. 14*

    Novel Method for Precisely Measuring the $X(3872)$ Mass

    Feng-Kun Guo🇨🇳

    The $X(3872)$ is the first and the most interesting one amongst the abundant $XYZ$ states. Its mass coincides exactly with the $D^0{\bar{D}}^{\ast 0}$ threshold with an uncertainty of 180 keV. Precise knowledge of its mass is crucial to understand the $X(3872)$. However, whether it is above or below the $D^0{\bar{D}}^{\ast 0}$ threshold is still unknown. We propose a completely new method to measure the $X(3872)$ mass precisely by measuring the $X(3872)\gamma$ line shape between 4010 and 4020 MeV, which is strongly sensitive to the $X(3872)$ mass relative to the $D^0{\bar{D}}^{\ast 0}$ threshold due to a triangle singularity. This method can be applied to experiments which produce copious $D^{\ast 0}{\bar{D}}^{\ast 0}$ pairs, such as electron-positron, proton-antiproton and other experiments, and may lead to much more precise knowledge about the $X(3872)$ mass.

    hep-phhep-exnucl-exnucl-thPRL(2019)·77 citations
15. 15*

    On the Origin of Two-Loop Neutrino Mass from SU(5) Grand Unification

    Shaikh Saad🇺🇸

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

    hep-phPRD(2019)·30 citations
16. 16*

    Jet Substructure Measurements of Interference in Non-Interfering SMEFT Effects

    Rafael Aoude🇩🇪 · William Shepherd🇩🇪

    The tails of diboson production at the LHC are sensitive to the interference between Standard Model and higher dimension operators parameterizing the effects of heavy new physics. However, helicity selection rules for the diboson scattering amplitudes set an obstruction to the naïve interference contributions of dimension six operators, causing the total diboson rate correction's leading contribution to cancel. In this case, carefully measuring the azimuthal decay angles "resurrects" the interference, recouping sensitivity to the "non-interfering" operators. We explore these signatures in detail, and find that the EFT uncertainties associated with higher-dimensional operators are uniquely well-suppressed by the construction of an asymmetry variable which is only generated by these non-interfering operators, relegating the effects of higher-dimensional, interfering operators to the same status as statistical errors in this observable. We perform a complete analysis of this azimuthal interference pattern in hadronic decays of W bosons using jet substructure techniques to tag the bosons and measure their azimuthal decay angles. This technique provides a valuable cross-check to purely-leptonic measurements of interference resurrection in diboson production.

    hep-phJHEP(2019)·11 citations
17. 17*

    Dreaming Awake: Disentangling the Underlying Physics in Case of a SUSY-like Discovery at the LHC

    Konstantin T. Matchev🇺🇸 · Filip Moortgat🇨🇭 · Luc Pape🇨🇭

    The purpose of this review is to investigate what kind of physics can be extracted at the LHC, assuming a discovery is made in events with missing transverse momentum, as generically expected in supersymmetry (SUSY) with R-parity conservation. To set the scene, we first discuss the collider phenomenology of the six possible electroweakino benchmark scenarios, as they provide valuable insight into what one might be facing at the LHC. We review the existing methods for mass reconstruction from measured kinematic endpoints in the distributions of suitable variables, e.g., the invariant masses of various sets of visible decay products, as well as the $M_{T2}$ and the $M_2$ types of variables. We propose to extend the application of these methods to the various topologies of fully hadronic final states, possibly with hadronically reconstructed massive bosons (W, Z or h). We test the idea with a simplified simulation of events in the main electroweakino benchmark scenarios. We find that the fully hadronic events allow the complete determination of the relevant mass spectrum. For comparison, we also review the potential of the standard kinematic endpoint methods for final states involving leptons from the decays of (on-shell or off-shell) sleptons. We find that with 300 $f{b}^{-1}$, the statistics for the leptonic events is very marginal and they look less promising than the fully hadronic channels. This corresponds to a complete reversal of the usual paradigm, where leptonic events comprised the gold-plated SUSY channels. Finally, we put together all available information and summarize what level of understanding of the underlying physics can be achieved. We show that, as a by-product of the mass reconstruction, it is also possible to determine the production cross sections and decay branching ratios, which in turn enable us to pinpoint the underlying model.

    hep-phhep-exJ.Phys.G(2019)·8 citations
18. 18*

    Particle Physics at Ultrahigh Energies

    Glennys R. Farrar🇺🇸

    We explore particle physics beyond accelerator energies, motivated by questions exposed in astroparticle physics observations: 1) Are there reasonable modifications to the standard extrapolations of LHC-tuned hadronic interaction models, so that ultrahigh energy cosmic ray (UHECR) showers are well-described with a purely protonic primary composition rather than requiring a tuned, energy-dependent composition mixture as needed in conventional models? 2) What modifications to standard models can solve the deficiency in the predicted ground signal found in hybrid UHECR observations? We find that a pure proton composition provides an excellent fit to shower observations, if the QCD inelastic cross section increases more rapidly above $E_{\mathrm{cm}}\approx 60$ TeV than in conventional models, and speculate as to possible reasons this may happen; the "muon deficiency" can be cured by relatively minor modifications to particle ratios in unexplored kinematic regimes below and above LHC energies.

    hep-phastro-ph.HE14 citations
19. 19*

    Neutrino spin oscillations in external fields in curved spacetime

    Maxim Dvornikov (IZMIRAN)🇷🇺

    We study spin oscillations of massive Dirac neutrinos in background matter, electromagnetic and gravitational fields. First, using the Dirac equation for a neutrino interacting with the external fields in curved spacetime, we rederive the quasiclassical equation for the neutrino spin evolution, which was proposed previously basing on principles of the general covariance. Then, we apply this result for the description of neutrino spin oscillations in nonmoving and unpolarized matter under the influence of a constant transverse magnetic field and a gravitational wave. We derive the effective Schrödinger equation for neutrino oscillations in these external fields and solve it numerically. Choosing realistic parameters of external fields, we show that the parametric resonance can take place in spin oscillations of low energy neutrinos. Some astrophysical applications are briefly discussed.

    hep-phastro-ph.HEgr-qcPRD(2019)·32 citations
20. 20*

    Optimized predictions for $W\to B_c+\gamma$ by combining light-cone and NRQCD approaches

    Feng Feng🇨🇳 · Yu Jia🇨🇳 · Wen-Long Sang🇨🇳

    The rare process of $W$ radiative decay into the $B_c$ meson can serve as an interesting play ground for testing two influential perturbative QCD approaches: non-relativistic quantum chromodynamics (NRQCD) and ligh-cone (LC) factorization. Since the $B_c$ meson is a genuine heavy quarkonium which is composed of two different species of heavy quarks, it is natural to employ NRQCD factorization to tackle this exclusive quarkonium production process; on the other hand, since the mass of the $W$ boson is much greater than that of the $B_c$, the collinear factorization is also a viable approach. To fully disentangle the contributions from several distinct scales $M_W$, $m_Q$, $m_{Q}v$ ($v$ represents the typical velocity of the $c/\bar{b}$ quarks inside $B_c$), and ${\Lambda }_{\mathrm{QCD}}$, we carry out a joint analysis that combines both light-cone and NRQCD factorization approaches, and compute the order-${\alpha }_s$ correction to $W\to B_c+\gamma$. With the aid of the celebrated Efremov-Radyushkin-Brodsky-Lepage (ERBL) evolution equation, we resum the leading collinear logarithms ${\alpha }_s\ln \frac{M_W}{m_Q}$ to all orders in ${\alpha }_s$. We also explore some phenomenological implications of our predictions.

    hep-phhep-ex6 citations
21. 21*

    Neutrino Portals to Dark Matter

    M. Blennow🇪🇸 · E. Fernandez-Martinez🇪🇸 · A. Olivares-Del Campo🇬🇧 · S. Pascoli🇬🇧 · S. Rosauro-Alcaraz🇪🇸 · A. V. Titov🇬🇧

    We explore the possibility that dark matter interactions with Standard Model particles are dominated by interactions with neutrinos. We examine whether it is possible to construct such a scenario in a gauge invariant manner. We first study the coupling of dark matter to the full lepton doublet and confirm that this generally leads to the dark matter phenomenology being dominated by interactions with charged leptons. We then explore two different implementations of the neutrino portal in which neutrinos mix with a Standard Model singlet fermion that interacts directly with dark matter through either a scalar or vector mediator. In the latter cases we find that the neutrino interactions can dominate the dark matter phenomenology. Present neutrino detectors can probe dark matter annihilations into neutrinos and already set the strongest constraints on these realisations. Future experiments such as Hyper-Kamiokande, MEMPHYS, DUNE, or DARWIN could allow to probe dark matter-neutrino cross sections down to the value required to obtain the correct thermal relic abundance.

    hep-phEPJC(2019)·170 citations
22. 22*

    Boosting the dark matter signal with Coulomb resonances

    Rakhi Mahbubani🇨🇭 · Kin Mimouni🇨🇭

    We show that the presence of nearby Coulombic resonances at finite energy could lead to the enhancement of the dark matter annihilation cross section at specific non-zero velocities correlated with the mass splitting between the dark matter pair and that of the resonance. If one of these resonant velocities approximately matches the velocity of dark matter in our local neighbourhood, we would see this enhancement in existing indirect-detection measurements, such as the measurements of the continuum photon spectrum made by HESS and Fermi-LAT. We explore this effect in the context of pure Higgsino and Wino dark matter with a variable splitting between charged and neutral components, controlled by the Wilson coefficient of a higher-dimension operator. For electroweak WIMPs a relevant and appreciable enhancement from Coulomb resonances requires tuning the charged-neutral splitting to be of order the Coulomb binding energies. This leads to strong exclusions of Higgsino dark matter with charged-neutral splittings in the narrow ranges (2, 2.5) and (8.5, 10.5) MeV. In contrast, by decreasing the charged-neutral splitting for the thermal Wino, we can move the Yukawa resonance away from the thermal relic mass, decreasing the indirect-detection signal to a level that is compatible with HESS measurements in the window (25, 35) MeV.

    hep-phastro-ph.HEJCAP(2019)·3 citations
23. 23*

    Flavor neutrino states for pedestrians

    Massimo Blasone🇮🇹 · Luca Smaldone🇮🇹 · Giuseppe Vitiello🇮🇹

    In this paper we discuss the ontology of flavor states of oscillating neutrinos. While an heuristic approach to this subject, experimentally successful in the high energy regime, is generally adopted, a logically consistent definition of flavor states describing neutrinos produced and detected in weak processes is still desirable and essential from a theoretical perspective. Here we briefly review basic facts and present some arguments which suggest that the definition of flavor states as eigenstates of flavor charges is the most reasonable one.

    hep-phJ.Phys.Conf.Ser.(2019)·16 citations
24. 24*

    Electromagnetic Scattering in Degenerate and Partially Degenerate Nuclear Matter

    Stephan Stetina🇦🇹

    I calculate the rate of electromagnetic scattering in degenerate and partially degenerate plasmas composed of electrons, muons, protons, and neutrons. Correlations with strong interactions, induced by the polarizability of electromagnetically and strongly charged protons, are taken into account. At subnuclear densities induced interactions are shown to cause a drastic increase of the longitudinal scattering rate. The results obtained are particularly relevant for the electron contribution to transport in the outer core of neutron stars, and represent a first step towards a realistic calculation of transport phenomena in neutron star mergers.

    ↳ nucl-thastro-ph.SRhep-ph1 citation
25. 25*

    Optimizing Laser Pulses for Narrowband Inverse Compton Sources in the High-Intensity Regime

    Daniel Seipt🇩🇪 · Vasily Yu. Kharin🇩🇪 · Sergey G. Rykovanov🇩🇪

    Scattering of ultraintense short laser pulses off relativistic electrons allows one to generate a large number of X- or $\gamma$-ray photons with the expense of the spectral width---temporal pulsing of the laser inevitable leads to considerable spectral broadening. In this Letter, we describe a simple method to generate optimized laser pulses that compensate the nonlinear spectrum broadening, and can be thought of as a superposition of two oppositely linearly chirped pulses delayed with respect to each other. We develop a simple analytical model that allow us to predict the optimal parameters of such a two-pulse---the delay, amount of chirp and relative phase---for generation of a narrowband {\gamma}-ray spectrum. Our predictions are confirmed by numerical optimization and simulations including 3D effects.

    ↳ physics.plasm-phhep-phphysics.acc-phphysics.atom-phPRL(2019)·17 citations
26. 26*

    Dressed Quark Tensor Vertex and Nucleon Tensor Charge

    Langtian Liu🇨🇳 · Lei Chang🇨🇳 · Yu-xin Liu🇨🇳

    We construct the quark-antiquark scattering kernels of Bethe-Salpeter equation from the quark self-energy directly under two specific forms of quark-gluon vertices. The quark dressed tensor vertex is then calculated within this consistent framework and rainbow-ladder(RL) approximation. After employing a simplified nucleon model, the nucleon tensor charge can be defined with the tensor vertex. We then compute the tensor charge with the bare tensor vertex and the dressed vertices obtained in this framework and in RL approximation. The obtained results are consistent with the lattice QCD calculations. We also find that typically the gluon dressing effects suppress the nucleon tensor charge compared to the bare tensor vertex, by about $23\%$ for RL approximation, and turn to be about $13\%$ in this framework.

    ↳ nucl-thhep-phPRD(2019)·11 citations
27. 27*

    Inhomogeneous phases in the 1+1 dimensional Gross-Neveu model at finite number of fermion flavors

    Laurin Pannullo🇩🇪 · Julian Lenz🇩🇪 · Marc Wagner🇩🇪 · Björn Wellegehausen🇩🇪 · Andreas Wipf🇩🇪

    We study the phase diagram of the 1+1 dimensional Gross-Neveu model at finite number of fermion flavors using lattice field theory. Numerical results are presented, which indicate the existence of an inhomogeneous phase, where the chiral condensate is a spatially oscillating function.

    ↳ hep-lathep-phhep-thActa Phys.Polon.Supp.(2020)·19 citations
28. 28*

    Quantum coherence of relic gravitons and Hanbury Brown-Twiss interferometry

    Massimo Giovannini🇨🇭

    The coherence of the relic gravitons is investigated within a quantum mechanical perspective. After introducing the notion and the properties of the generalized Glauber correlators valid in the tensor case, the degrees of first- and second-order coherence are evaluated both inside and beyond the effective horizon. The inclusive approach (encompassing the polarizations of the gravitons) is contrasted with the exclusive approximation where the total intensity is calculated either from a single polarization or even from a single mode of the field. While the relic gravitons reentering the effective horizon after the end of a quasi-de Sitter stage of expansion are first-order coherent, the Hanbury Brown-Twiss correlations always exhibit a super-Poissonian statistics with different quantitative features that depend on the properties of their initial states and on the average over the tensor polarizations.

    ↳ hep-thastro-ph.COgr-qchep-phPRD(2019)·14 citations
29. 29*

    Determination of the quark-gluon string parameters from the data on pp, pA and AA collisions at wide energy range using Bayesian Gaussian Process Optimization

    Vladimir Kovalenko (Saint Petersburg State University)🇷🇺

    Bayesian Gaussian Process Optimization can be considered as a method of the determination of the model parameters, based on the experimental data. In the range of soft QCD physics, the processes of hadron and nuclear interactions require using phenomenological models containing many parameters. In order to minimize the computation time, the model predictions can be parameterized using Gaussian Process regression, and then provide the input to the Bayesian Optimization. In this paper, the Bayesian Gaussian Process Optimization has been applied to the Monte Carlo model with string fusion. The parameters of the model are determined using experimental data on multiplicity and cross section of pp, pA and AA collisions at wide energy range. The results provide important constraints on the transverse radius of the quark-gluon string ($r_{str}$) and the mean multiplicity per rapidity from one string (${\mu }_0$).

    ↳ physics.data-anhep-phnucl-thPoS(2019)·1 citation
30. 30*

    Five-Loop Static Contribution to the Gravitational Interaction Potential of Two Point Masses

    J. Blümlein🇩🇪 · A. Maier🇩🇪 · P. Marquard🇩🇪

    We compute the static contribution to the gravitational interaction potential of two point masses in the velocity-independent five-loop (and 5th post-Newtonian) approximation to the harmonic coordinates effective action in a direct calculation. The computation is performed using effective field methods based on Feynman diagrams in momentum-space in $d=3-2\epsilon$ space dimensions. We also reproduce the previous results including the 4th post-Newtonian order.

    ↳ gr-qchep-phhep-thPLB(2020)·122 citations
31. 31*

    Quantum Corrected Black Holes from String T-Duality

    Piero Nicolini🇩🇪 · Euro Spallucci🇮🇹 · Michael F. Wondrak🇩🇪

    In this paper we present some stringy corrections to black hole spacetimes emerging from string T-duality. As a first step, we derive the static Newtonian potential by exploiting the relation between the T-duality and the path integral duality. We show that the intrinsic non-perturbative nature of stringy corrections introduce an ultraviolet cutoff known as zero-point length in the path integral duality literature. As a result, the static potential is found to be regular. We use this result to derive a consistent black hole metric for the spherically symmetric, electrically neutral case. It turns out that the new spacetime is regular and is formally equivalent to the Bardeen metric, apart from a different ultraviolet regulator. On the thermodynamics side, the Hawking temperature admits a maximum before a cooling down phase towards a thermodynamically stable end of the black hole evaporation process. The findings support the idea of universality of quantum black holes.

    ↳ gr-qchep-phhep-thPLB(2019)·134 citations
32. 32*

    Cosmic tau neutrino detection via Cherenkov signals from air showers from Earth-emerging taus

    Mary Hall Reno🇺🇸 · John F. Krizmanic🇺🇸 · Tonia M. Venters🇺🇸

    We perform a new, detailed calculation of the flux and energy spectrum of Earth-emerging $\tau$-leptons generated from the interactions of tau neutrinos and antineutrinos in the Earth. A layered model of the Earth is used to describe the variable density profile of the Earth. Different assumptions regarding the neutrino charged- and neutral-current cross sections as well as the $\tau$-lepton energy loss models are used to quantify the systematic uncertainty from these on the results. A baseline simulation is then used to generate the optical Cherenkov signal from upward-moving extensive air showers generated by the $\tau$-lepton decay in the atmosphere, applicable to a range of space-based instruments. We use this simulation to determine the neutrino sensitivity for $E_{\nu }>$ 10 PeV for a space-based experiment with performance similar to that for the Probe of Extreme MultiMessenger Astrophysics (POEMMA) mission currently under study.

    ↳ astro-ph.HEhep-phPRD(2019)·53 citations
33. 33*

    A Quadrillion Standard Models from F-theory

    Mirjam Cvetic🇺🇸 · James Halverson🇺🇸 · Ling Lin🇺🇸 · Muyang Liu🇺🇸 · Jiahua Tian🇺🇸

    We present an explicit construction of $\mathcal{O}(10^{15})$ globally consistent string compactifications that realize the exact chiral spectrum of the Standard Model of particle physics with gauge coupling unification in the context of F-theory. Utilizing the power of algebraic geometry, all global consistency conditions can be reduced to a single criterion on the base of the underlying elliptically fibered Calabi--Yau fourfolds. For toric bases, this criterion only depends on an associated polytope and is satisfied for at least $\mathcal{O}(10^{15})$ bases, each of which defines a distinct compactification.

    ↳ hep-thhep-phmath.AGPRL(2019)·66 citations
34. 34*

    Neutrino Quantum Kinetics in Compact Objects

    Sherwood A. Richers🇺🇸 · Gail C. McLaughlin🇺🇸 · James P. Kneller🇺🇸 · Alexey Vlasenko🇺🇸

    Neutrinos play a critical role of transporting energy and changing the lepton density within core-collapse supernovae and neutron star mergers. The quantum kinetic equations (QKEs) combine the effects of neutrino-matter interactions treated in classical Boltzmann transport with the neutrino flavor-changing effects treated in neutrino oscillation calculations. We present a method for extending existing neutrino interaction rates to full QKE source terms for use in numerical calculations. We demonstrate the effects of absorption and emission by nucleons and nuclei, electron scattering, electron-positron pair annihilation, nucleon-nucleon bremsstrahlung, neutrino-neutrino scattering. For the first time, we include all these collision terms self-consistently in a simulation of the full isotropic QKEs in conditions relevant to core-collapse supernovae and neutron star mergers. For our choice of parameters, the long-term evolution of the neutrino distribution function proceeds similarly with and without the oscillation term, though with measurable differences. We demonstrate that electron scattering, nucleon-nucleon bremsstrahlung processes, and four-neutrino processes dominate flavor decoherence in the protoneutron star (PNS), absorption dominates near the shock, and all of the considered processes except elastic nucleon scattering are relevant in the decoupling region. Finally, we propose an effective decoherence opacity that at most energies predicts decoherence rates to within a factor of 10 in our model PNS and within 20% outside of the PNS.

    ↳ astro-ph.HEhep-phnucl-thPRD(2019)·95 citations
35. 35*

    Non-Abelian Proca-Dirac-Higgs theory: particle-like solutions and their energy spectrum

    Vladimir Dzhunushaliev🇰🇿 · Vladimir Folomeev🇰🇿 · Arislan Makhmudov🇿🇦

    We study a system consisting of a non-Abelian SU(2) Proca field interacting with nonlinear scalar (Higgs) and spinor fields. For such a system, it is shown that particle-like solutions with finite energy do exist. It is demonstrated that the solutions depend on three free parameters of the system, including the central value of the scalar field ${\xi }_0$. For some fixed values of ${\xi }_0$, we find energy spectra of the solutions. It is shown that for each of the cases under consideration there is a minimum value of the energy $\Delta =\Delta ({\xi }_0)$ (the mass gap $\Delta ({\xi }_0)$ for a fixed value of ${\xi }_0$). The behavior of the function $\Delta ({\xi }_0)$ is studied for some range of ${\xi }_0$.

    ↳ hep-thhep-phPRD(2019)·13 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.