Tue·Apr 9, 2019Tuesday·April 9, 2019

1. 01*

   Simplified dark matter models with loop effects in direct detection and the constraints from indirect detection and collider search

   Tong Li🇨🇳 · Peiwen Wu🇰🇷

   We reexamine the simplified dark matter (DM) models with fermionic DM particle and spin-0 mediator. The DM-nucleon scattering cross sections of these models are low-momentum suppressed at tree-level, but receive sizable loop-induced spin-independent contribution. We perform one-loop calculation for scalar-type and twist-2 DM-quark operators and complete two-loop calculation for scalar-type DM-gluon operator. By analyzing the loop-level contribution from new operators, we find that future direct detection experiments can be sensitive to a fraction of parameter space. The indirect detection and collider search also provide complementary constraints on these models.

   hep-phCPC(2019)·14 citations
2. 02*

   QCD analysis of non-singlet structure functions at NNLO accuracy, based on the Laplace transform

   Maral Salajegheh🇮🇷 · S. Mohammad Moosavi Nejad🇮🇷 · Abolfazl Mirjalili🇮🇷 · S. Atashbar Tehrani🇮🇷

   In this work, using the Laplace transformation technique we present our results for non-singlet quark distributions as well as nucleon structure function $F_2(x,Q^2)$ in unpolarized case at next-to-next-to-leading order (NNLO) QCD accuracy. We shall particularly compare our results for the sets of valence-quark parton distribution functions with the contemporary collaborations like CT14, CT18, MMHT14, MKAM16 and NNPDF. To construct the nucleon structure function we employ the expansion of Jacobi polynomials which is a suitable transform to convert the results of non-singlet structure function from the Laplace $s$-space to Bjorken $x$-space. We shall also consider the contributions of target mass correction as well as the higher twist effects at large-$x$ region for the proton and deuteron structure functions. Our results for the unpolarized quark distribution functions and nucleon structure functions are in good agreement with recent theoretical models and available experimental data.

   hep-phEur.Phys.J.Plus(2020)·5 citations
3. 03*

   Transverse Force Tomography

   Fatma P. Aslan🇺🇸 · Matthias Burkardt🇺🇸 · Marc Schlegel🇺🇸

   While twist-2 GPDs allow for a determination of the distribution of partons on the transverse plane, twist-3 GPDs contain quark-gluon correlations that provide information about the average transverse color Lorentz force acting on quarks. We demonstrate how twist-3 GPDs can be used to provide transverse position information about that force.

   hep-phPRD(2019)·27 citations
4. 04*

   Precise prediction for the W boson mass in the MRSSM

   Philip Diessner🇩🇪 · Georg Weiglein🇩🇪

   The mass of the W boson, $M_W$, plays a central role for high-precision tests of the electroweak theory. Confronting precise theoretical predictions with the accurately measured experimental value provides a high sensitivity to quantum effects of the theory entering via loop contributions. The currently most accurate prediction for the W boson mass in the Minimal R-symmetric Supersymmetric Standard Model (MRSSM) is presented. Employing the on-shell scheme, it combines all numerically relevant contributions that are known in the Standard Model (SM) in a consistent way with all MRSSM one-loop corrections. Special care is taken in the treatment of the triplet scalar vacuum expectation value $v_T$ that enters the prediction for $M_W$ already at lowest order. In the numerical analysis the decoupling properties of the supersymmetric loop contributions and the comparison with the MSSM are investigated. Potentially large numerical effects of the MRSSM-specific $\Lambda$ superpotential couplings are highlighted. The comparison with existing results in the literature is discussed.

   hep-phJHEP(2019)·21 citations
5. 05*

   Raman stimulated neutrino pair emission

   H. Hara🇯🇵 · M. Yoshimura🇯🇵

   A new scheme using macroscopic coherence is proposed from a theoretical point to experimentally determine the neutrino mass matrix, in particular the absolute value of neutrino masses, and the mass type, Majorana or Dirac. The proposed process is a collective, coherent Raman scattering followed by neutrino-pair emission from an excited state $|e⟩$ of a long lifetime to a lower energy state $|g⟩$; ${\gamma }_0+|e⟩\to \gamma +{\sum }_{ij}{\nu }_i\overline{{\nu }_j}+|g⟩$ with ${\nu }_i\overline{{\nu }_j}$ consisting of six massive neutrino-pairs. Calculated angular distribution has six $(ij)$ thresholds of massive neutrino-pair emission which show up as steps at different angles in the distribution. Angular locations of thresholds and event rates of the angular distribution make it possible to experimentally determine the smallest neutrino mass to the level of less than 1 meV (accordingly all three masses using neutrino oscillation data) , the mass ordering pattern , normal or inverted, and to distinguish whether neutrinos are of Majorana or Dirac type. Event rates of neutrino-pair emission, when the mechanism of macroscopic coherence amplification works, may become large enough for realistic experiments by carefully selecting certain types of target atoms or ions doped in crystals. The problem to be overcome is macro-coherently amplified quantum electrodynamic background of the process, ${\gamma }_0+|e⟩\to \gamma +{\gamma }_2+{\gamma }_3+|g⟩$, when two extra photons, ${\gamma }_2,{\gamma }_3$, escape detection. We illustrate our idea using neutral Xe and trivalent Ho ion doped in dielectric crystals.

   hep-phcond-mat.otherhep-exphysics.atom-phEPJC(2019)·7 citations
6. 06*

   Accidental scale-invariant Majorana dark matter in leptoquark-Higgs portals

   Ahmad Mohamadnejad🇮🇷

   We study a classically accidental scale-invariant extension of the Standard Model (SM) containing three additional fields, a vector leptoquark ($V_{\mu }$), a real scalar ($\varphi$), and a neutral Majorana fermion ($\chi$) as a dark matter (DM) candidate. The scalar $\varphi$ (scalon) and Majorana fermion $\chi$ are both singlets under the SM gauge group, while $V_{\mu }$ has (\textbf{3}, \textbf{1}, 2/3) quantum numbers under the $SU(3{)}_c\times SU(2{)}_L\times U(1{)}_Y$. The Majorana DM couples to the SM sector via both Higgs and leptoquark portals. We perform a scan over the independent parameters to determine the viable parameter space consistent with the Planck data for DM relic density, and with the PandaX-II and LUX direct detection limits for the spin-independent (SI) and spin-dependent (SD) DM-nucleon cross section. The model generally evades indirect detection constraints while being consistent with collider data.

   hep-phNPB(2019)·20 citations
7. 07*

   Dynamical supersymmetry for strange quark and $ud$ antidiquark in hadron mass spectrum

   Taiju Amano (1,2)🇯🇵 · Daisuke Jido (2,1) ((1) Tokyo Metropolitan University, (2) Tokyo Institute of Technology)🇯🇵

   Speculating that the $ud$ diquark with spin 0 has a similar mass to the constituent $s$ quark, we introduce a symmetry between the $s$ quark and the $\overline{ud}$ diquark. Constructing an algebra for this symmetry, we regard a triplet of the $s$ quarks with spin up and down and the $\overline{ud}$ diquark with spin 0 as a fundamental representation of this algebra. We further build higher representations constructed by direct products of the fundamental representations. We propose assignments of hadrons to the multiples of this algebra. We find in particular that $\{D_s,D_s^{\ast },{\Lambda }_c\}$, $\{{\eta }_s,\varphi ,\Lambda ,f_0(1370)\}$ and $\{{\Omega }_c,T_{sc}\}$ form a triplet, a nonet and a quintet, respectively, where $T_{sc}$ is a genuine tetraquark meson composed of $\overline{ud}sc$. We also find a mass relation between them by introducing the symmetry breaking due to the mass difference between the $s$ quark and the $\overline{ud}$ diquark. The masses of possible tetraquarks $\overline{ud}sc$ and $\overline{ud}sb$ are estimated from the symmetry breaking and the masses of ${\Omega }_c$ and ${\Omega }_b$ to be 2.942 GeV and 6.261 GeV, respectively.

   hep-phnucl-thPTEP(2019)·3 citations
8. 08*

   Two-flavor chiral perturbation theory at nonzero isospin: Pion condensation at zero temperature

   Prabal Adhikari🇺🇸 · Jens O. Andersen🇳🇴 · Patrick Kneschke🇳🇴

   In this paper, we calculate the equation of state of two-flavor finite isospin chiral perturbation theory at next-to-leading order in the pion-condensed phase at zero temperature. We show that the transition from the vacuum phase to a Bose-condensed phase is of second order. While the tree-level result has been known for some time, surprisingly quantum effects have not yet been incorporated into the equation of state. We find that the corrections to the quantities we compute, namely the isospin density, pressure, and equation of state, increase with increasing isospin chemical potential. We compare our results to recent lattice simulations of 2+1 flavor QCD with physical quark masses. The agreement with the lattice results is generally good and improves somewhat as we go from leading order to next-to-leading order in $\chi$PT.

   hep-phEPJC(2019)·47 citations
9. 09*

   A modular $A_4$ symmetric model of dark matter and neutrino

   Takaaki Nomura🇰🇷 · Hiroshi Okada🇰🇷

   We propose a model based on modular $A_4$ symmetry containing a dark matter candidate, realizing radiatively induced neutrino mass at one-loop level. One finds that stability of dark matter candidate can be assured by nonzero value of modular weight and heavy neutral fermion mass hierarchies, which include dark matter under the $A_4$ triplet, are uniquely determined; $M_X\ll M_2<M_3$. Therefore we clearly identify single dark matter field which can discriminate from the other models with $A_4$ modular symmetry. Then we discuss several phenomenological aspects and show predictions on the lepton sector.Especially, we find $0.56\lesssim {\sin }^2{\theta }_{23}\lesssim 0.624$, which could have an advantage of this narrow region and be also discriminated from the other modular $A_4$ models.

   hep-phPLB(2019)·127 citations
10. 10*

    Alignment limit in three Higgs-doublet models

    Dipankar Das🇸🇪 · Ipsita Saha🇯🇵

    The LHC Higgs data is showing a gradual inclination towards the SM result and realization of an SM-like limit becomes essential for BSM scenarios to survive. Considering the accuracy that can be achieved in future colliders, BSMs that acquire the alignment limit with an SM-like Higgs boson coupling can surpass others in the long run. Using a convenient parametrization, we demonstrate that the alignment limit for CP-conserving 3HDMs takes on the same analytic structure as that in the case of 2HDMs. Using the example of a $Z_3$-symmetric 3HDM, we illustrate how such alignment conditions can be efficiently implemented for numerical analysis in a realistic scenario.

    hep-phPRD(2019)·42 citations
11. 11*

    Exclusion of heavy, broad resonances from precise measurements of WZ and VH final states at the LHC

    You-Ying Li🇹🇼 · Rosy Nicolaidou🇫🇷 · Stathes Paganis🇹🇼

    A novel search for heavy vector resonances in the $H\to b\bar{b}$ and $Z\to b\bar{b}$ final states in association with a leptonically decaying $V$ ($Z$ or $W$) and $W$-only respectively, is proposed. It is argued that excesses with respect to the Standard Model prediction should be observed in all final states (0, 1 or 2 leptons), with the 1-lepton final state being the strongest. Since the relative strengths of these excesses depend on branching ratios and efficiencies, this is a clear signal for the presence of heavy resonances or their low mass tails. A general vector-triplet model is used to explore the discovery potential as a function of the resonance mass and width. Recent Higgs to $b\bar{b}$ observation data reported by the experiments ATLAS and CMS are used to test the model. Current limits are extended to resonance widths over mass as large as 9%.

    hep-phEPJC(2019)·9 citations
12. 12*

    Lepton-flavor-violating semileptonic $\tau$ decay and $K\to \pi \nu \bar{\nu }$

    Xiao-Gang He🇹🇼 · Jusak Tandean🇹🇼 · German Valencia🇦🇺

    We consider lepton-flavor violation in strangeness changing ($|\Delta S|=1$) semileptonic $\tau$-lepton decays arising from new physics encoded in a standard model effective Lagrangian. Its invariance under the standard model gauge group entails the relevance of other processes which can serve as complementary probes of the new physics operators. We show in particular that for some of them the bounds implied by current data on the rare kaon decays involving a neutrino pair, $K\to \pi \nu \bar{\nu }$, are stronger than the existing limits from direct searches for lepton-flavor-violating semileptonic $\tau$ decays. We discuss additional processes affected by the same operators and find that certain leptonic charged-meson decays also provide stricter constraints on a few more of them. Upcoming results of ongoing experiments such as Belle II and NA62 will further test the new physics parameter space.

    hep-phhep-exPLB(2019)·11 citations
13. 13*

    Extracting analytical one-loop amplitudes from numerical evaluations

    Giuseppe De Laurentis🇬🇧 · Daniel Maître🇬🇧

    In this article we present a method to generate analytic expressions for the integral coefficients of loop amplitudes using numerical evaluations only. We use high-precision arithmetic to explore the singularity structure of the coefficients and decompose them into parts of manageable complexity. To illustrate the usability of our method we provide analytical expressions for all helicity configurations of the colour-ordered six-point gluon amplitudes at one loop with a gluon in the loop.

    hep-phJHEP(2019)·50 citations
14. 14*

    Vector SIMP dark matter with approximate custodial symmetry

    Soo-Min Choi🇰🇷 · Hyun Min Lee🇰🇷 · Yann Mambrini🇫🇷 · Mathias Pierre🇪🇸

    We consider a novel scenario for Vector Strongly Interacting Massive Particle (VSIMP) dark matter with local $SU(2{)}_X\times U(1{)}_{Z^{\prime }}$ symmetry in the dark sector. Similarly to the Standard Model, after the dark symmetry is broken spontaneously by the VEVs of dark Higgs fields, the approximate custodial symmetry determines comparable but split masses for $SU(2{)}_X$ gauge bosons. In this model, we show that $U(1{)}_{Z^{\prime }}$-charged gauge boson of $SU(2{)}_X$ ($X_{\pm }$) becomes a natural candidate for SIMP dark matter, annihilating through $3\to 2$ or forbidden $2\to 2$ annihilations due to gauge self-interactions. On the other hand, the $U(1{)}_{Z^{\prime }}$-neutral gauge boson of $SU(2{)}_X$ achieves the kinetic equilibrium of dark matter through a gauge kinetic mixing between $U(1{)}_{Z^{\prime }}$ and Standard Model. We present the parameter space for the correct relic density in our model and discuss in detail the current constraints and projections from colliders and direct detection experiments.

    hep-phJHEP(2019)·45 citations
15. 15*

    Quark and gluon condensates in QCD reevaluated

    Renata Jora🇷🇴

    We compute the quark and gluon condensates in $QCD$ with $N$ colors and $N_f$ flavors based on the renormalization group equations and on the knowledge of a single scale ${\Lambda }_{QCD}$. For $N=3$ and $N_f=3$ our findings are in the good range for $0.2\le {\Lambda }_{QCD}\le 0.36$ and in excellent agreement with the results in the literature from sum rules for a value ${\Lambda }_{QCD}=0.28$.

    hep-phActa Phys.Polon.B(2020)·2 citations
16. 16*

    Quark masses, CKM angles and Lepton Flavour Universality violation

    Riccardo Barbieri🇮🇹 · Robert Ziegler🇨🇭

    A properly defined and suitably broken $U(2)$ flavour symmetry leads to successful quantitative relations between quark mass ratios and CKM angles. At the same time the intrinsic distinction introduced by $U(2)$ between the third and the first two families of quarks and leptons may support anomalies in charged and neutral current semi-leptonic $B$-decays of the kind tentatively observed in current flavour experiments. We show how this is possible by the exchange of the $(3,1{)}_{2/3}$ vector leptoquark in two $U(2)$-models with significantly different values of Lepton Flavour Universality violation, observable in foreseen experiments.

    hep-phJHEP(2019)·19 citations
17. 17*

    Neutrino-Dark Matter Portals

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

    The nature of dark matter is one of the open problems of the Standard Model of particle physics. Despite the great experimental efforts, we have not yet found a positive signal of its interactions with ordinary matter. One possible explanation would be that the dark matter particle is primarily coupled to another elusive particle, neutrinos. In this work we study this possibility with several realisations.

    hep-ph0 citations
18. 18*

    Uncovering latent jet substructure

    Barry M. Dillon🇸🇮 · Darius A. Faroughy🇸🇮 · Jernej F. Kamenik🇸🇮

    We apply techniques from Bayesian generative statistical modeling to uncover hidden features in jet substructure observables that discriminate between different a priori unknown underlying short distance physical processes in multi-jet events. In particular, we use a mixed membership model known as Latent Dirichlet Allocation to build a data-driven unsupervised top-quark tagger and $t\bar{t}$ event classifier. We compare our proposal to existing traditional and machine learning approaches to top jet tagging. Finally, employing a toy vector-scalar boson model as a benchmark, we demonstrate the potential for discovering New Physics signatures in multi-jet events in a model independent and unsupervised way.

    hep-phhep-exPRD(2019)·89 citations
19. 19*

    An Emergent Higgs Alignment

    Karim Benakli🇫🇷 · Yifan Chen🇫🇷 · Gaëtan Lafforgue-Marmet🇫🇷

    We explain how an $SU(2{)}_R$ R-symmetry allows alignment of the vacuum expectation value and the mass eigenstates in the Higgs bosons squared-mass matrix. More important, we discuss how our parametrization of the breaking of this global symmetry allows to quantitatively apprehend the diverse sources of misalignment, which are kept, by supersymmetry, small.

    hep-phPoS(2019)·2 citations
20. 20*

    Generalized Parton Distributions from charged current meson production

    Marat Siddikov🇨🇱 · Ivan Schmidt🇨🇱

    In this paper we prove that the simultaneous study of both $\rho$- and $\pi$-meson production by charged currents in Bjorken kinematics allows for a very clean extraction of the leading twist Generalized Parton Distributions of the target, with inherent control of the contribution of higher-twist corrections. Also, it might provide target-independent constraints on the distribution amplitudes of the produced mesons. We expect that such processes might be studied either in neutrino-induced or in electron-induced processes. According to our numerical estimates, the cross-sections of these processes are within the reach of JLab and EIC experiments.

    hep-phhep-exPRD(2019)·15 citations
21. 21*

    Dark Sector Equilibration During Nucleosynthesis

    Asher Berlin🇺🇸 · Nikita Blinov🇺🇸 · Shirley Weishi Li🇺🇸

    Light, weakly-coupled dark sectors may be naturally decoupled in the early universe and enter equilibrium with the Standard Model bath during the epoch of primordial nucleosynthesis. The equilibration and eventual decoupling of dark sector states modifies the expansion rate of the universe, which alters the predicted abundances of the light elements. This effect can be encompassed in a time-varying contribution to $N_{\mathrm{eff}}$, the effective number of neutrino species, such that $N_{\mathrm{eff}}$ during nucleosynthesis differs from its measured value at the time of recombination. We investigate the impact of such variations on the light element abundances with model-independent templates for the time-dependence of $N_{\mathrm{eff}}$ as well as in specific models where a dark sector equilibrates with neutrinos or photons. We find that significant modifications of the expansion rate are consistent with the measured abundances of light nuclei, provided that they occur during specific periods of nucleosynthesis. In constraining concrete models, the relative importance of the cosmic microwave background and primordial nucleosynthesis is highly model-dependent.

    hep-phastro-ph.COPRD(2019)·60 citations
22. 22*

    Where are the Next Higgs Bosons?

    Christopher T. Hill🇺🇸 · Pedro A. N. Machado🇺🇸 · Anders E. Thomsen🇩🇰 · Jessica Turner🇺🇸

    Simple symmetry arguments applied to the third generation lead to a prediction: there exist new sequential Higgs doublets with masses of order $\lesssim 5$ TeV, with approximately universal Higgs-Yukawa coupling constants, $g\sim 1$. This is calibrated by the known Higgs boson mass, the top quark Higgs-Yukawa coupling, and the $b$-quark mass. A new massive weak-isodoublet, $H_b$, coupled to the $b$-quark with $g\sim 1$ is predicted, and may be accessible to the LHC at $13$ TeV, and definitively at the energy upgraded LHC of $26$ TeV. The extension to leptons generates a new $H_{\tau }$ and a possible $H_{{\nu }_{\tau }}$ doublet. The accessibility of the latter depends upon whether the mass of the $\tau$-neutrino is Dirac or Majorana.

    hep-phhep-exPRD(2019)·17 citations
23. 23*

    Transverse momentum dependent distributions in $e^{+}{e}^{-}$ and semi-inclusive deep-inelastic scattering using jets

    Daniel Gutierrez-Reyes🇪🇸 · Ignazio Scimemi🇪🇸 · Wouter J. Waalewijn🇳🇱 · Lorenzo Zoppi🇳🇱

    The extraction of transverse momentum dependent distributions (TMDs) in semi-inclusive deep inelastic scattering (SIDIS) is complicated by the presence of both initial- and final-state nonperturbative physics. We recently proposed measuring jets (instead of hadrons) as a solution, showing that for the Winner-Take-All jet axis the same factorization formulae valid for hadrons applied to jets of arbitrary size. This amounts to simply replacing TMD fragmentation functions by our TMD jet functions. In this paper we present the calculation of these jet functions at one loop. We obtain phenomenological results for $e^{+}{e}^{-}\to$ dijet (Belle II, LEP) and SIDIS (HERA, EIC) with a jet, building on the arTeMiDe code. Surprisingly, we find that the limit of large jet radius describes the full $R$ results extremely well, and we extract the two-loop jet function in this limit using Event2, allowing us to achieve N${}^3$LL accuracy. We demonstrate the perturbative convergence of our predictions and explore the kinematic dependence of the cross section. Finally, we investigate the sensitivity to nonperturbative physics, demonstrating that jets are a promising probe of proton structure.

    hep-phnucl-thJHEP(2019)·83 citations
24. 24*

    The LPM effect in sequential bremsstrahlung: from large-N QCD to N=3 via the SU(N) analog of Wigner 6-j symbols

    Peter Arnold🇺🇸

    Consider a high-energy parton showering as it traverses a QCD medium such as a quark-gluon plasma. Interference effects between successive splittings in the shower are potentially very important but have so far been calculated (even in idealized theoretical situations) only in soft emission or large-$N_{\mathrm{c}}$ limits, where $N_{\mathrm{c}}$ is the number of quark colors. In this paper, we show how one may remove the assumption of large $N_{\mathrm{c}}$ and so begin investigation of $N_{\mathrm{c}}=3$ without soft-emission approximations. Treating finite $N_{\mathrm{c}}$ requires (i) classifying different ways that four gluons can form a color singlet and (ii) calculating medium-induced transitions between those singlets, for which we find application of results for the generalization of Wigner 6-$j$ symbols from angular momentum to SU($N_{\mathrm{c}}$). Throughout, we make use of the multiple scattering ($\hat{q}$) approximation for high-energy partons crossing quark-gluon plasmas, and we find that this approximation is self-consistent only if the transverse-momentum diffusion parameter $\hat{q}$ for different color representations satisfies Casimir scaling (even for strongly-coupled, and not just weakly-coupled, quark-gluon plasmas). We also find that results for $N_{\mathrm{c}}=3$ depend, mathematically, on being able to calculate the propagator for a coupled non-relativistic quantum harmonic oscillator problem in which the spring constants are operators acting on a 5-dimensional Hilbert space of internal color states. Those spring constants are represented by constant $5\times 5$ matrices, which we explicitly construct. We are unaware of any closed form solution for this type of harmonic oscillator problem, and we discuss prospects for using numerical evaluation.

    hep-phnucl-thPRD(2019)·14 citations
25. 25*

    Simulations of the Glasma in 3+1D

    David Müller🇦🇹

    The Glasma is a gluonic state of matter which can be created in collisions of relativistic heavy ions and is a precursor to the quark-gluon plasma. The existence of this state is a prediction of the color glass condensate (CGC) effective theory. In many applications of the CGC framework, the boost invariant approximation is employed. It assumes that the longitudinal extent of the nuclei can be approximated as infinitesimally thin. Consequently, the Glasma produced from such a collision is boost invariant and can be effectively described in 2+1D. Therefore, observables of the boost invariant Glasma are by construction independent of rapidity. The main goal of this thesis is to develop a numerical method for the non-boost-invariant setting where nuclei are assumed to be thin, but of finite longitudinal extent. This is in conflict with a number of simplifications that are used in the boost invariant case. In particular, one has to describe the collisions in 3+1D in the laboratory or center-of-mass frame. The change of frame forces the explicit inclusion of the color charges of nuclei. The new method is tested using an extension of the McLerran-Venugopalan model which includes a parameter for longitudinal thickness. It reproduces the boost invariant setting as a limiting case. Studying the pressure components of the Glasma, one finds the pressure anisotropy remains large. The energy density of the Glasma depends on rapidity due to the explicit breaking of boost invariance. The width of the observed rapidity profiles is controlled by the collision energy and can be shown to roughly agree with experimental data. Finally, a new numerical scheme for real-time lattice gauge theory is developed which provides higher numerical stability than the previous method. This new scheme is shown to be gauge-covariant and conserves the Gauss constraint even for large time steps.

    hep-phhep-latnucl-th13 citations
26. 26*

    QED Phenomena in an Ultrastrong Magnetic Field. II. Electron-Positron Scattering, $e^{\pm }$-Ion Scattering, and Relativistic Bremsstrahlung

    Alexander Kostenko (University of Toronto)🇨🇦 · Christopher Thompson (CITA)🇨🇦

    This paper continues the approach of Kostenko \& Thompson to calculating quantum electrodynamic processes in the ultrastrong magnetic field near some neutron stars, such as magnetars or merging binary neutron stars. Here we consider electron-positron scattering, the Coulomb scattering of electrons and positrons off ions, and relativistic $e^{\pm }$-ion bremsstrahlung. The evaluation of differential and total cross sections simplifies considerably when the magnetic field lies in the range $10^3{B}_{\mathrm{Q}}\gg B\gg B_{\mathrm{Q}}$, where $B_{\mathrm{Q}}\equiv m^2/e=4.4\times 10^{13}$ G. Then, relativistic motion of $e^{\pm }$ is possible even when restricted to the lowest Landau state. Accurate results for differential and total cross sections are obtained by truncating the sum over intermediate-state Landau levels and otherwise disregarding terms inversely proportional to the magnetic field, which are complicated enough to have inhibited previous attempts to calculate magnetic electron-positron scattering and relativistic bremsstrahlung. A quantitative account is made of the effects of Debye screening.

    ↳ astro-ph.HEhep-phApJ(2019)·11 citations
27. 27*

    The effect of strong electric field on the evolution of charmonium in quark gluon plasma

    Wu Biaogang🇨🇳 · Chen Baoyi🇨🇳 · Zhao Xingbo🇨🇳

    In ultra-relativistic heavy-ion collisions, the strong electric field can be produced by the colliding nuclei. The magnitude of the electric field $E$ is on the order of $eE\sim m_{\pi }^2$ at the early stage of the collision. In quark gluon plasma (QGP), such a strong electric field can have a significant impact on the evolution of charmonia. We employ the time-dependent Schrödinger equation to study the evolution of charmonium states in the strong electric field generated by the moving charges. The electric field can result in transitions between charmonium states with different angular momenta. In order to see this effect, we make comparisons between the yields of $J/\psi$, ${\psi }^{\prime }$ and ${\chi }_c$ with and without the electric field. The results show that in the early stage of the collision the electric field induces significant dissociation of $J/\psi$. In the meantime, ${\chi }_c$ is generated via the transition from $J/\psi$ by the electric field.

    ↳ nucl-thhep-phNucl.Phys.Rev.(2019)·2 citations
28. 28*

    Vacuum energy in the effective field theory of general relativity

    J. Gegelia🇩🇪 · Ulf-G. Meißner🇩🇪

    In the framework of an effective field theory of general relativity a model of scalar and vector bosons interacting with the metric field is considered. It is shown in the framework of a two-loop order calculation that for the cosmological constant term which is fixed by the condition of vanishing vacuum energy the graviton remains massless and there exists a self-consistent effective field theory of general relativity coupled to matter fields defined on a flat Minkowski background. This result is obtained under the assumption that the energy-momentum tensor of the gravitational field is given by the pseudotensor of Landau-Lifshitz's classic textbook. Implications for the cosmological constant problem are also briefly discussed.

    ↳ hep-thgr-qchep-phPRD(2019)·7 citations
29. 29*

    Probing galactic cosmic ray distribution with TeV gamma-ray sky

    M. Cataldo🇮🇹 · G. Pagliaroli🇮🇹 · V. Vecchiotti🇮🇹 · F.L. Villante🇮🇹

    The distribution of cosmic rays in the Galaxy at energies above few TeVs is still uncertain and this affects the expectations for the diffuse gamma flux produced by hadronic interactions of cosmic rays with the interstellar gas. We show that the TeV gamma-ray sky can provide interesting constraints. Namely, we compare the flux from the galactic plane measured by Argo-YBJ, HESS, HAWC and Milagro with the expected flux due to diffuse emission and point-like and extended sources observed by HESS showing that experimental data can already discriminate among different hyphoteses for cosmic ray distribution. The constraints can be strengthened if the contribution of sources not resolved by HESS is taken into account.

    ↳ astro-ph.HEhep-phJCAP(2019)·35 citations
30. 30*

    The $b_1$ resonance in coupled $\pi \omega$, $\pi \varphi$ scattering from lattice QCD

    Antoni J. Woss🇬🇧 · Christopher E. Thomas🇬🇧 · Jozef J. Dudek🇺🇸 · Robert G. Edwards🇺🇸 · David J. Wilson🇮🇪

    We present the first lattice QCD calculation of coupled $\pi \omega$ and $\pi \varphi$ scattering, incorporating coupled $S$ and $D$-wave $\pi \omega$ in $J^P=1^{+}$. Finite-volume spectra in three volumes are determined via a variational analysis of matrices of two-point correlation functions, computed using large bases of operators resembling single-meson, two-meson and three-meson structures, with the light-quark mass corresponding to a pion mass of $m_{\pi }\approx 391$ MeV. Utilizing the relationship between the discrete spectrum of finite-volume energies and infinite-volume scattering amplitudes, we find a narrow axial-vector resonance ($J^{PC}=1^{+-}$), the analogue of the $b_1$ meson, with mass $m_R\approx 1380$ MeV and width ${\Gamma }_R\approx 91$ MeV. The resonance is found to couple dominantly to $S$-wave $\pi \omega$, with a much-suppressed coupling to $D$-wave $\pi \omega$, and a negligible coupling to $\pi \varphi$ consistent with the `OZI rule'. No resonant behavior is observed in $\pi \varphi$, indicating the absence of a putative low-mass $Z_s$ analogue of the $Z_c$ claimed in $\pi J/\psi$. In order to minimally present the contents of a unitary three-channel scattering matrix, we introduce an $n$-channel generalization of the traditional two-channel Stapp parameterization.

    ↳ hep-lathep-phPRD(2019)·82 citations
31. 31*

    A Lattice Story of Proton Spin

    Yi-Bo Yang🇨🇳

    In this contribution, I summarized the recent Lattice QCD consensuses on the quark helicity, plus the investigations on the gluon helicity and orbital angular momenta. The preliminary non-perturbative normalized and renormalized Ji quark and gluon angular momentum results are also reported and compared with the previous 1-loop perturbative renormalized results.

    ↳ hep-lathep-phnucl-thPoS(2019)·7 citations
32. 32*

    Lattice QCD investigation of a doubly-bottom $\bar{b}\bar{b}ud$ tetraquark with quantum numbers $I(J^P)=0(1^{+})$

    Luka Leskovec🇺🇸 · Stefan Meinel🇺🇸 · Martin Pflaumer🇩🇪 · Marc Wagner🇩🇪

    We use lattice QCD to investigate the spectrum of the $\bar{b}\bar{b}ud$ four-quark system with quantum numbers $I(J^P)=0(1^{+})$. We use five different gauge-link ensembles with $2+1$ flavors of domain-wall fermions, including one at the physical pion mass, and treat the heavy $\bar{b}$ quark within the framework of lattice nonrelativistic QCD. Our work improves upon previous similar computations by considering in addition to local four-quark interpolators also nonlocal two-meson interpolators and by performing a Lüscher analysis to extrapolate our results to infinite volume. We obtain a binding energy of $(-128\pm 24\pm 10)\text{MeV}$, corresponding to the mass $(10476\pm 24\pm 10)\text{MeV}$, which confirms the existence of a $\bar{b}\bar{b}ud$ tetraquark that is stable with respect to the strong and electromagnetic interactions.

    ↳ hep-lathep-phPRD(2019)·160 citations
33. 33*

    Hidden Cores of Active Galactic Nuclei as the Origin of Medium-Energy Neutrinos: Critical Tests with the MeV Gamma-Ray Connection

    Kohta Murase (PSU)🇺🇸 · Shigeo S. Kimura (Tohoku U.)🇺🇸 · Peter Meszaros (PSU)🇺🇸

    Mysteries about the origin of high-energy cosmic neutrinos have deepened by the recent IceCube measurement of a large diffuse flux in the 10-100 TeV range. Based on the standard disk-corona picture of active galactic nuclei (AGN), we present a phenomenological model enabling us to systematically calculate the spectral sequence of multimessenger emission from the AGN coronae. We show that protons in the coronal plasma can be stochastically accelerated up to PeV energies by plasma turbulence, and find that the model explains the large diffuse flux of medium-energy neutrinos if the cosmic rays carry only a few percent of the thermal energy. We find that the Bethe-Heitler process plays a crucial role in connecting these neutrinos and cascaded MeV gamma rays, and point out that the gamma-ray flux can even be enhanced by the reacceleration of secondary pairs. Critical tests of the model are given by its prediction that a significant fraction of the MeV gamma-ray background correlates with about 10 TeV neutrinos, and nearby Seyfert galaxies including NGC 1068 are promising targets for IceCube, KM3Net, IceCube-Gen2, and future MeV gamma-ray telescopes.

    ↳ astro-ph.HEastro-ph.COastro-ph.GAhep-phPRL(2020)·271 citations
34. 34*

    Statistics of Inflating Regions in Eternal Inflation

    Mudit Jain🇺🇸 · Mark P. Hertzberg🇺🇸

    We compute the distribution of sizes of inflating and non-inflating regions in an eternally inflating Universe. As a first illustrative problem, we study a simple scenario of an eternally inflating Universe in the presence of a massless scalar field $\phi$ whose field values lie within some finite domain $\phi \in (-{\phi }_{cr},{\phi }_{cr})$, with $\pm {\phi }_{cr}$ marking the onset of thermalization/crunching. We compute many important quantities, including the fractal dimension, distribution of field values among inflating regions, and the number of inflating and non-inflating Hubble regions. With the aid of simulations in 1 spatial dimension, we show this eternally inflating Universe reaches a steady state in which average sizes of inflating regions grow only as a power law in the field's crunch value $\sim {\phi }_{cr}^2$ (extension to higher dimensions is $\sim {\phi }^{2/D}$), contrary to a naive expectation of an exponential dependence. Furthermore, the distribution in sizes exhibits an exponential fall off for large distances (with an initial power law for inflating regions). We leave other interesting cases of more realistic potentials and time varying Hubble parameter for future work, with a possible application to the SM Higgs in the early Universe.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2019)·14 citations
35. 35*

    Cooling Theory Faced with Old Warm Neutron Stars: Role of Non-Equilibrium Processes with Proton and Neutron Gaps

    Keisuke Yanagi🇯🇵 · Natsumi Nagata🇯🇵 · Koichi Hamaguchi🇯🇵

    Recent observations have found several candidates for old warm neutron stars whose surface temperatures are above the prediction of the standard neutron star cooling scenario, and thus require some heating mechanism. Motivated by these observations, we study the non-equilibrium beta process in the minimal cooling scenario of neutron stars, which inevitably occurs in pulsars. This out-of-equilibrium process yields the late time heating in the core of a neutron star, called the rotochemical heating, and significantly changes the time evolution of the neutron star surface temperature. To perform a realistic analysis of this heating effect, we include the singlet proton and triplet neutron pairing gaps simultaneously in the calculation of the rate and emissivity of this process, where the dependence of these pairing gaps on the nucleon density is also taken into account. We then compare the predicted surface temperature of neutron stars with the latest observational data. We show the simultaneous inclusion of both proton and neutron gaps is advantageous for the explanation of the old warm neutron stars since it enhances the heating effect. It is then found that the observed surface temperatures of the old warm millisecond pulsars, J2124-3358 and J0437-4715, are explained for various choices of nucleon gap models. The same setup is compatible with the observed temperatures of ordinary pulsars including old warm ones, J0108-1431 and B0950+08, by choosing the initial rotational period of each neutron star accordingly. In particular, the upper limit on the surface temperature of J2144-3933 can be satisfied if its initial period is $\gtrsim 10\mathrm{ms}$.

    ↳ astro-ph.HEastro-ph.SRhep-phMNRAS(2020)·36 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.