Tue·Jul 17, 2018Tuesday·July 17, 2018

1. 01*

   The Spin Structure of the Nucleon

   A. Deur🇺🇸 · S. J. Brodsky🇺🇸 · G. F. de Teramond🇨🇷

   We review the present understanding of the spin structure of protons and neutrons, the fundamental building blocks of nuclei collectively known as nucleons. The field of nucleon spin provides a critical window for testing Quantum Chromodynamics (QCD), the gauge theory of the strong interactions since it involves fundamental aspects of hadron structure, and it can be probed in detail in experiments, particularly deep inelastic lepton scattering on polarized targets. QCD was initially probed in high energy deep inelastic lepton scattering with unpolarized beams and targets. With time, interest shifted from testing perturbative QCD to illuminating the nucleon structure itself. In fact, the spin degrees of freedom of hadrons provide an essential and detailed verification of both perturbative and nonperturbative QCD dynamics. Nucleon spin was initially thought of coming mostly from the spin of its quark constituents, based on intuition from the parton model. However, the first experiments showed that this expectation was incorrect. It is now clear that nucleon physics is much more complex, involving quark orbital angular momenta as well as gluonic and sea quark contributions. Thus, the nucleon spin structure remains a most active aspect of QCD research, involving important advances such as the developments of generalized parton distributions (GPD) and transverse momentum distributions (TMD). Elastic and inelastic lepton-proton scattering, as well as photoabsorption experiments provide various ways to investigate non-perturbative QCD. Fundamental sum rules -- such as the Bjorken sum rule for polarized photoabsorption on polarized nucleons -- are also in the non-perturbative domain. This realization triggered a vigorous program to link the low energy effective hadronic description of the strong interactions to fundamental quarks and gluon degrees of freedom of...

   hep-phRept.Prog.Phys.(2019)·162 citations
2. 02*

   Numerical calculation of high-order QED contributions to the electron anomalous magnetic moment

   Sergey Volkov🇷🇺

   This paper describes a method of numerical evaluating high-order QED contributions to the electron anomalous magnetic moment. The method is based on subtraction of infrared and ultraviolet divergences in Feynman-parametric space before integration and on nonadaptive Monte Carlo integration that is founded on Hepp sectors. A realization of the method on the graphics accelerator NVidia Tesla K80 is described. A method of removing round-off errors that emerge due to numerical subtraction of divergences without losing calculation speed is presented. The results of applying the method to all 2-loop, 3-loop, 4-loop QED Feynman graphs without lepton loops are presented. A detailed comparison of the 2-loop and 3-loop results with known analytical ones is given in the paper. A comparison of the contributions of 6 gauge invariant 4-loop graph classes with known analytical values is presented. Moreover, the contributions of 78 sets of 4-loop graphs for comparison with the direct subtraction on the mass shell are presented. Also, the contributions of the 5-loop and 6-loop ladder graphs are given as well as a comparison of these results with known analytical ones. The behavior of the generated Monte Carlo samples is described in detail, a method of the error estimation is presented. A detailed information about the graphics processor performance on these computations and about the Monte Carlo convergence is given in the paper.

   hep-phPRD(2018)·20 citations
3. 03*

   The $\rho$ parameter at three loops and elliptic integrals

   J. Blümlein🇩🇪 · A. De Freitas🇩🇪 · M. van Hoeij🇺🇸 · E. Imamoglu🇺🇸 · P. Marquard🇩🇪 · C. Schneider🇦🇹

   We describe the analytic calculation of the master integrals required to compute the two-mass three-loop corrections to the $\rho$ parameter. In particular, we present the calculation of the master integrals for which the corresponding differential equations do not factorize to first order. The homogeneous solutions to these differential equations are obtained in terms of hypergeometric functions at rational argument. These hypergeometric functions can further be mapped to complete elliptic integrals, and the inhomogeneous solutions are expressed in terms of a new class of integrals of combined iterative non-iterative nature.

   hep-phhep-thmath-phmath.MPPoS(2018)·20 citations
4. 04*

   Dark sector portal with vector-like leptons and flavor sequestering

   Christopher D. Carone🇺🇸 · Shikha Chaurasia🇺🇸 · Tangereen V. B. Claringbold🇺🇸

   We consider models with fermionic dark matter that transforms under a non-Abelian dark gauge group. Exotic, vector-like leptons that also transform under the dark gauge group can mix with standard model leptons after spontaneous symmetry breaking and serve as a portal between the dark and visible sectors. We show in an explicit, renormalizable model based on a dark SU(2) gauge group how this can lead to adequate dark matter annihilation to a standard model lepton flavor so that the correct relic density is obtained. We identify a discrete symmetry that allows mass mixing between the vector-like fermions and a single standard model lepton flavor, while preventing mixing between these fields and the remaining standard model leptons. This flavor sequestering avoids unwanted lepton-flavor-violating effects, substantially relaxing constraints on the mass scale of the vector-like states. We discuss aspects of the phenomenology of the model, including direct detection of the dark matter.

   hep-phPRD(2019)·6 citations
5. 05*

   High Energy Physics and Cosmology at the Unification Frontier: Opportunities and Challenges in the coming years

   Pran Nath🇺🇸

   We give here an overview of recent developments in high energy physics and cosmology and their interconnections that relate to unification, and discuss prospects for the future. Thus there are currently three empirical data that point to supersymmetry as an underlying symmetry of particle physics: the unification of gauge couplings within supersymmetry, the fact that nature respects the supersymmetry prediction that the Higgs boson mass lie below 130 GeV, and vacuum stability up to the Planck scale with a Higgs boson mass at $\sim 125$ GeV while the standard model does not do that. Coupled with the fact that supersymmetry solves the big hierarchy problem related to the quadratic divergence to the Higgs boson mass square along with the fact that there is no alternative paradigm that allows us to extrapolate physics from the electroweak scale to the grand unification scale consistent with experiment, supersymmetry remains a compelling framework for new physics beyond the standard model. The large loop correction to the Higgs boson mass in supersymmetry to lift the tree mass to the experimentally observable value, indicates a larger value of the scale of weak scale supersymmetry, making the observation of sparticles more challenging but still within reach at the LHC for the lightest ones. Recent analyses show that a high energy LHC (HE-LHC) operating at 27 TeV running at its optimal luminosity of $2.5\times 10^{35}$ cm${}^{-2}$s${}^{-1}$ can reduce the discovery period by several years relative to HL-LHC and significantly extend the reach in parameter space of models. In the coming years several experiments related to neutrino physics, searches for supersymmetry, on dark matter and dark energy will have direct impact on the unification frontier.

   hep-phgr-qchep-exInt.J.Mod.Phys.A(2018)·6 citations
6. 06*

   Generating lepton masses and mixings with a heavy vector doublet

   A. E. Cárcamo Hernández🇨🇱 · Jonatan Vignatti🇨🇱 · Alfonso Zerwekh🇨🇱

   We construct two viable extensions of the SM with a heavy vector in the fundamental $SU{\left(2\right)}_L$ representation and nine SM singlet scalar fields, consistent with the current SM fermion mass spectrum and fermionic mixing parameters. The small masses for the active neutrinos are generated from radiative seesaw mechanism at one loop level mediated by the neutral components of the heavy vector as well as by the left handed Majorana neutrinos. The proposed models predicts rates for charged lepton flavor violating processes within the reach of the forthcoming experiments.

   hep-phJ.Phys.G(2019)·18 citations
7. 07*

   New Physics Search in the Doubly Weak Decay ${\overline{B}}^0\to K^{+}{\pi }^{-}$

   Faisal Munir Bhutta🇨🇳 · Ying Li🇨🇳 · Cai-Dian Lü🇨🇳 · Yue-Hong Xie🇨🇳

   The doubly weak transition $b\to dd\bar{s}$ is highly suppressed in the standard model, which makes it a potential channel to explore new physics signals. We present a study of the exclusive two body wrong sign weak decay ${\overline{B}}^0\to K^{+}{\pi }^{-}$ belonging to this class within the perturbative QCD approach. We perform a model independent analysis for various effective dimension-6 operators, in which large effects are possible. We further analyze the considered process in example models such as Randall-Sundrum model, including the custodially protected and the bulk-Higgs Randall-Sundrum model. Exploring the experimentally favored parameter spaces of these models leads to a large and significant enhancement of the decay rate, compared to the standard model result, which might be accessible in future experiments. We propose to look for the wrong sign decay ${\overline{B}}^0\to K^{+}{\pi }^{-}$ via flavour-tagged time-dependent analyses, which can be performed at LHCb and Belle-II.

   hep-phCPC(2019)·2 citations
8. 08*

   Reconstructing heavy Higgs boson masses in Type X Two-Higgs Doublet Model with a light pseudoscalar

   Eung Jin Chun🇰🇷 · Siddharth Dwivedi🇮🇳 · Tanmoy Mondal🇮🇳 · Biswarup Mukhopadhyaya🇮🇳 · Santosh Kumar Rai🇮🇳

   We analyze the prospects of reconstructing the mass of a heavy charged Higgs boson %have been analyzed in the context of a Type X two-Higgs doublet model where a light pseudoscalar $A$ in the mass range $40-60$ GeV is phenomenologically allowed, and is in fact favoured if one wants to explain the muon anomalous magnetic moment. The associated production of charged Higgs with the pseudoscalar $A$ and subsequent decay of the charged Higgs into a $W$ and $A$, is found to be our relevant channel. The branching ratio for $H^{+}\to W^{+}A$ with $M_{H^{+}}\sim 200$ GeV, is close to 50\%. The hadronic decay of the $W$ boson, coupled with the leptonic decays of $A$ into a tau and muon pair, help in identifying the charged Higgs. The neutral heavy Higgs, being degenerate with the charged Higgs for most of the allowed parameter space of the model, also contributes to similar final states. Thus both of these particles are reconstructed within a band of about 10 GeV.

   hep-phhep-exPRD(2018)·21 citations
9. 09*

   Diffraction at a time grating in electron-positron pair creation from vacuum

   J. Z. Kamiński🇵🇱 · M. Twardy🇵🇱 · K. Krajewska🇵🇱

   The Sauter-Schwinger process of electron-positron pair creation from vacuum, driven by a sequence of time-dependent electric-field pulses, is studied in the framework of quantum-field theoretical approach. As demonstrated by our numerical results, the probability distributions of produced pairs exhibit intra- and inter-pulse interference structures. We show that such structures can be observed beyond the regime of applicability of the WKB theory, which was the focus of earlier investigations. Going beyond these developments, we perform the analysis of the time-evolution operator for an arbitrary eigenmode of the fermionic field. This shows that a perfect coherent enhancement of the inter-pulse peaks can never be reached. A nearly perfect coherence, on the other hand, is due to nonadiabatic transitions at avoided crossings of the phases defining the unitary time evolution. This analysis allows us to determine the conditions under which the nearly perfect coherence is lost.

   hep-phquant-phPRD(2018)·27 citations
10. 10*

    Multiloop contributions to the on-shell-$\overline{\mathrm{MS}}$ heavy quark mass relation in QCD and the asymptotic structure of the corresponding series: the updated consideration

    A.L. Kataev🇷🇺 · V.S. Molokoedov🇷🇺

    The asymptotic structure of the QCD perturbative relation between the on-shell and $\overline{\mathrm{MS}}$ heavy quark masses is studied. We estimate the five and six-loop contributions to this relation by three different techniques. First, the effective charges motivated approach in two variants is used. Second, the results following from the large-${\beta }_0$ approximation are analyzed. Finally, the consequences of applying the asymptotic renormalon-based formula are investigated. We show that all approaches lead to corrections which are qualitatively consistent in order of magnitude. Their sign-alternating character in powers of the number of massless quarks is demonstrated. We emphasize that there is no contradiction in the behavior of the fine structure of the renormalon-based estimates with other approaches if one use the detailed information about the normalization factor included in the renormalon asymptotic formula. The obtained five- and six-loop estimates indicate that in the case of the $b$-quark the asymptotic character of the studied relation manifests itself above the fourth order of PT, whereas for the $t$-quark it starts to reveal itself after the seventh order. This allows to conclude that like the running masses, the pole masses of the $b$ and especially $t$-quark in principle may be used in the phenomenologically-oriented studies.

    hep-phhep-exEPJC(2020)·23 citations
11. 11*

    Anisotropic hydrodynamic modeling of heavy-ion collisions at LHC and RHIC

    Mubarak Alqahtani🇸🇦 · Dekrayat Almaalol🇺🇸 · Mohammad Nopoush🇺🇸 · Radoslaw Ryblewski🇵🇱 · Michael Strickland🇺🇸

    In this proceedings contribution, we review 3+1d quasiparticle anisotropic hydrodynamics (aHydroQP). Then, we show some recent phenomenological comparisons between the aHydroQP model and some experimental results. We show comparisons between aHydroQP and Pb-Pb 2.76 TeV collisions from the ALICE collaboration and Au-Au 200 GeV collisions from RHIC experiments. We show that the quasiparticle anisotropic hydrodynamics model is able to describe the experimental results for Pb-Pb and Au-Au collisions quite well for many observables such as the spectra, multiplicity, elliptic flow, and HBT radii in many centrality classes.

    hep-phnucl-thNPA(2019)·6 citations
12. 12*

    Diffractive dijet production: breakdown of factorization

    B. Z. Kopeliovich🇨🇱 · R. Pasechnik🇸🇪 · I. K. Potashnikova🇨🇱

    We analyse the origin of dramatic breakdown of diffractive factorisation, observed in single-diffractive (SD) dijet production in hadronic collisions. One of the sources is the application of the results of measurements of the diagonal diffractive DIS to the off-diagonal hadronic diffractive process. The suppression caused by a possibility of inelastic interaction with the spectator partons is calculated at the amplitude level, differently from the usual probabilistic description. It turns out, however, that interaction with the spectator partons not only suppresses the SD cross section, but also gives rise to the main mechanism of SD dijet production, which is another important source of factorization failure. Our parameter-free calculations of SD-to-inclusive cross section ratio, performed in the dipole representation, agrees with the corresponding CDF Tevatron (Run II) data at $\sqrt{s}=1.96$ TeV in the relevant kinematic regions. The energy and hard scale dependences demonstrate a trend, opposite to the factorisation-based expectations, similarly to the effect observed earlier in diffractive Abelian radiation.

    hep-phPRD(2018)·7 citations
13. 13*

    In search of a UV completion of the Standard Model - 378.000 models that don't work

    Daniele Barducci🇮🇹 · Marco Fabbrichesi🇮🇹 · Carlos M. Nieto🇮🇹 · Roberto Percacci🇮🇹 · Vedran Skrinjar🇮🇹

    Asymptotically safe extensions of the Standard Model have been searched for by adding vector-like fermions charged under the Standard Model gauge group and having Yukawa-like interactions with new scalar fields. Here we study the corresponding renormalization group beta functions to next and next-to-next to leading order in the perturbative expansion, varying the number of extra fermions and the representations they carry. We test the fixed points of the beta functions against various criteria of perturbativity to single out those that are potentially viable. We show that all the candidate ultraviolet fixed points are unphysical for these models: either they are unstable under radiative corrections, or they cannot be matched to the Standard Model at low energies.

    hep-phhep-thJHEP(2018)·27 citations
14. 14*

    Bound states and QCD

    Paul Hoyer🇫🇮

    The similarities of hadrons and atoms motivate a study of the principles of QED bound states and of their applicability to QCD. The power series in $\alpha$ and $\log \alpha$ of the binding energy is reflected in the Fock expansion of the bound state in temporal gauge ($A^0=0$). Gauss' constraint on physical states fixes the gauge for time independent transformations and determines the instantaneous interaction within each Fock state. Positronium atoms generate a classical (dipole) electric field, whereas there can be no color octet gluon field for color singlet hadrons. Hence the gluon field generated by each color component of a hadron need not vanish at spatial infinity. Gauss' constraint has a homogeneous solution with a single parameter $\Lambda$ that is compatible with Poincaré invariance. The corresponding potential is linear for $q\bar{q}$ and $gg$ Fock states, and confining also for other states ($q\bar{q}g,qqq$). This approach is consistent with the quarkonium phenomenology based on the Cornell potential at lowest order. The relativistic meson and glueball eigenstates of the QCD Hamiltonian with the $O({\alpha }_s^0)$ linear potential are determined. The states lie on linear Regge trajectories and their daughters. There are also massless bound states which allow to include a $J^{PC}=0^{++}$ condensate in the perturbative vacuum, thus breaking chiral symmetry spontaneously.

    hep-ph5 citations
15. 15*

    Chiral Magnetic Effect in Isobaric Collisions from Anomalous-Viscous Fluid Dynamics (AVFD)

    Shuzhe Shi🇺🇸 · Hui Zhang🇨🇳 · Defu Hou🇨🇳 · Jinfeng Liao🇺🇸

    The isobaric collision experiment at RHIC provides the unique opportunity to detect the possible signal of Chiral Magnetic Effect (CME) in heavy ion collisions. The idea is to contrast the correlation observables of the two colliding systems that supposedly have identical flow-driven background contributions while quite different CME signal contributions due to the 10% variation in their nuclear charge and thus magnetic field strength. With the recently developed quantitative simulation tool for computing CME signal, the Anomalous-Viscous Fluid Dynamics (AVFD), we demonstrate that a joint (multiplicity + elliptic-flow) event selection is crucial for this purpose. We further propose to use the absolute difference between RuRu and ZrZr events (after using identical event selection) for detecting CME signal and make predictions for the correlation observables.

    hep-phnucl-exnucl-thNPA(2019)·11 citations
16. 16*

    Unified framework for heavy flavor and quarkonium production in high multiplicity p+p and p+A collisions at RHIC and LHC

    Yan-Qing Ma🇨🇳 · Prithwish Tribedy🇺🇸 · Raju Venugopalan🇺🇸 · Kazuhiro Watanabe🇺🇸

    We discuss the production of $D$-mesons and $J/\psi$ in high multiplicity proton-proton and proton-nucleus collisions within the Color-Glass-Condensate (CGC) framework. We demonstrate that the modification of the LHC data on $D$ and $J/\psi$ yields in high multiplicity events relative to minimum bias events arise from a significant enhancement of the gluon saturation scales of the corresponding rare parton configurations in the colliding protons and nuclei. For a given event multiplicity, we predict these relative yields to be energy independent from $\sqrt{s}=200$ GeV at RHIC to the highest LHC energies.

    hep-phhep-exnucl-exnucl-thNPA(2019)·3 citations
17. 17*

    A new solution of the fermionic mass hierarchy of the standard model

    Gauhar Abbas🇮🇳

    We present a new mechanism for solving the fermionic masses and mixing hierarchies of the standard model through a minimal symmetry ${\mathcal{Z}}_2\times {\mathcal{Z}}_5$. The mechanism is also capable of explaining the neutrino masses and mixing parameters. The phenomenological bounds arising from kaon mixing are also derived on the parameter space of the model.

    hep-phInt.J.Mod.Phys.A(2021)·21 citations
18. 18*

    Exclusive production of $B_c$ mesons in $e^{+}{e}^{-}$ colliders

    Yan-Bing Wei🇨🇳 · Run-Hui Li🇨🇳 · Dan Luo🇨🇳 · Cai-Dian Lü🇨🇳 · Yue-Long Shen🇨🇳

    Within the framework of the perturbative QCD approach, we calculate the time-like $B_c{B}_c(B_c^{\ast })$ form factors $F(Q^2)$ and $A_2(Q^2)$. We include relativistic corrections and QCD corrections, either of which can give about $20\%$ correction to the leading-order contribution, but there are cancellation effects between them. We calculate the cross sections of the $e^{+}{e}^{-}\to B_c^{-}{B}_c^{+}(B_c^{\ast +})$ processes. The cross sections are enhanced at the $Z$ pole to be ${\sigma }^{PP}(Q=m_Z)\sim 1.3\times 10^{-5}\text{pb}$ and ${\sigma }^{PV}(Q=m_Z)\sim 2.5\times 10^{-5}\text{pb}$, which are still too small to be detected by proposed $e^{+}{e}^{-}$ colliders such as the Circular Electron Positron Collider.

    hep-phCPC(2018)·4 citations
19. 19*

    Investigating the sterile neutrino parameters with QLC in 3 + 1 scenario

    Gazal Sharma🇮🇳 · B. C. Chauhan🇮🇳

    In the scenario with four generation quarks and leptons and using a 3 + 1 neutrino model having one sterile and the three standard active neutrinos with a $4\times 4$ unitary transformation matrix, $U_{PMN{S}_4}$, we perform a model-based analysis using the latest global data and determine bounds on the sterile neutrino parameters i.e. the neutrino mixing angles. Motivated by our previous results, where, in a quark-lepton complementarity (QLC) model we predicted the values of ${\theta }_{13}^{PMNS}=(9_{-2}^{+1}{)}^{\circ }$ and ${\theta }_{23}^{PMNS}=(40.60_{-0.3}^{+0.1}{)}^{\circ }$. In the QLC model the non-trivial correlation between $CK{M}_4$ and $PMN{S}_4$ mixing matrix is given by the correlation matrix $V_{c_4}$. Monte Carlo simulations are performed to estimate the texture of $V_{c4}$ followed by the calculation of $PMN{S}_4$ using the equation, $U_{PMN{S}_4}=(U_{CK{M}_4}.{\psi }_4{)}^{-1}.V_{c_4}$, where ${\psi }_4$ is a diagonal phase matrix. The sterile neutrino mixing angles, ${\theta }_{14}^{PMNS}$, ${\theta }_{24}^{PMNS}$ and ${\theta }_{34}^{PMNS}$ are assumed to be freely varying between $(0-\pi /4)$ and obtained results which are consistent with the data available from various experiments, like No$\nu$A, MINOS, SuperK, Ice Cube-DeepCore. In further investigation, we analytically obtain approximately similar ranges for various neutrino mixing parameters $\mid U_{\mu 4}{\mid }^2$ and $\mid U_{\tau 4}{\mid }^2$.

    hep-phAdv.High Energy Phys.(2019)·2 citations
20. 20*

    The double-soft integral for an arbitrary angle between hard radiators

    Fabrizio Caola🇬🇧 · Maximilian Delto🇩🇪 · Hjalte Frellesvig🇩🇪 · Kirill Melnikov🇩🇪

    We consider the double-soft limit of a generic QCD process involving massless partons and integrate analytically the double-soft eikonal functions over the phase-space of soft partons (gluons or quarks) allowing for an arbitrary relative angle between the three-momenta of two hard massless radiators. This result provides one of the missing ingredients for a fully analytic formulation of the nested soft-collinear subtraction scheme recently proposed by some of us.

    hep-phEPJC(2018)·45 citations
21. 21*

    Charm decays

    Stefan de Boer🇩🇪

    The importance of charm decays in the context of flavor is motivated. A theory overview on recent developments in leptonic and semileptonic decays, hadronic two-body decays, and rare decays is presented. Standard Model (SM) predictions as well as tests of the SM are pointed out, {\it e.g.}~how to discover direct CP violation in charm decays and how to search for physics beyond the SM. Differences between rare charm and beauty decays are discussed.

    hep-phPoS(2018)·2 citations
22. 22*

    Correlated gluonic hot spots meet symmetric cumulants data at LHC energies

    Javier L. Albacete🇪🇸 · Harri Niemi🇩🇪 · Hannah Petersen🇩🇪 · Alba Soto-Ontoso🇪🇸

    We present a systematic study on the influence of spatial correlations between the proton constituents, in our case gluonic hot spots, their size and their number on the symmetric cumulant SC(2,3), at the eccentricity level, within a Monte Carlo Glauber framework [1]. When modeling the proton as composed by 3 gluonic hot spots, the most common assumption in the literature, we find that the inclusion of spatial correlations is indispensable to reproduce the negative sign of SC(2,3) in the highest centrality bins as dictated by data. Further, the subtle interplay between the different scales of the problem is discussed. To conclude, the possibility of feeding a 2+1D viscous hydrodynamic simulation with our entropy profiles is exposed.

    hep-phhep-exnucl-thNPA(2019)·2 citations
23. 23*

    Testing coalescence and statistical-thermal production scenarios for (anti-)(hyper-)nuclei and exotic QCD objects at energies available at the CERN Large Hadron Collider

    Francesca Bellini🇨🇭 · Alexander Philipp Kalweit🇨🇭

    We present a detailed comparison of coalescence and thermal-statistical models for the production of (anti-)(hyper-)nuclei in high-energy collisions. For the first time, such a study is carried out as a function of the size of the object relative to the size of the particle emitting source. Our study reveals large differences between the two scenarios for the production of objects with extended wave-functions. While both models give similar predictions and show similar agreement with experimental data for (anti-)deuterons and (anti-)3He nuclei, they largely differ in their description of (anti-)hyper-triton production. We propose to address experimentally the comparison of the production models by measuring the coalescence parameter systematically for different (anti-)(hyper-)nuclei in different collision systems and differentially in multiplicity. Such measurements are feasible with the current and upgraded Large Hadron Collider experiments. Our findings highlight the unique potential of ultra-relativistic heavy-ion collisions as a laboratory to clarify the internal structure of exotic QCD objects and can serve as a basis for more refined calculations in the future.

    hep-phnucl-exnucl-thPRC(2019)·114 citations
24. 24*

    One-loop amplitudes for k_T-dependent factorization

    Andreas van Hameren🇵🇱

    I report on progress in the calculation of one-loop amplitudes with a space-like gluon. Amplitudes with space-like partons are relevant for factorization procedure s that require initial-state partons with non-vanishing transverse momentum components.

    hep-phPoS(2018)·1 citation
25. 25*

    Massive three loop form factors in the planar limit

    Jakob Ablinger🇦🇹 · Johannes Bluemlein🇩🇪 · Peter Marquard🇩🇪 · Narayan Rana🇩🇪 · Carsten Schneider🇦🇹

    We present the color planar and complete light quark QCD contributions to the three loop heavy quark form factors in the case of vector, axial-vector, scalar and pseudo-scalar currents. We evaluate the master integrals applying a new method based on differential equations for general bases, which is applicable for any first order factorizing systems. The analytic results are expressed in terms of harmonic polylogarithms and real-valued cyclotomic harmonic polylogarithms.

    hep-phPoS(2018)·0 citations
26. 26*

    Electromagnetic and Axial Current Form Factors and Spectroscopy of Three-Flavor Holographic Baryons

    Ori C. Druks🇺🇸 · Pang H.C. Lau🇺🇸 · Ismail Zahed🇺🇸

    We present an analysis of the three-flavor holographic model of QCD associated to a $D4/D8$ brane configuration, with symmetry breaking induced by a worldsheet instanton associated to a closed loop connecting $D4-D8-D6-\overline{D8}$. We calculate the electromagnetic and axial couplings of all octet and decuplet baryons, as well as several negative parity excitations, with and without symmetry breaking effects, and demonstrate qualitative and quantitative agreement with many available experimental measurements, with marked improvement over the analogous two-flavor models.

    hep-phhep-thPRD(2019)·4 citations
27. 27*

    $R_{K^{(\ast )}}$ with leptoquarks and the origin of Yukawa couplings

    Ivo de Medeiros Varzielas🇵🇹 · Stephen F. King🇬🇧

    We construct a model where the Yukawa couplings of the Standard Model (SM) fermions arise from the breaking of a $Z_2$ symmetry and through mixing with a fourth family of vector-like fermions. By adding a scalar leptoquark, which is an electroweak triplet and odd under the $Z_2$ symmetry, we obtain an explanation for $R_{K^{(\ast )}}$ that is linked to the origin of the Yukawa couplings. The coupling of SM fermions to the leptoquark is mediated by the fourth family fermions, and is predicted to be related to CKM entries and mass ratios of SM fermions.

    hep-phJHEP(2018)·34 citations
28. 28*

    CGC/saturation approach: secondary Reggeons and $\rho =Re/Im$ dependence on energy

    E. Gotsman (Tel Aviv U.)🇮🇱 · E. Levin (Tel Aviv U./UTFSM)🇮🇱 · I. Potashnikova (UTFSM)🇨🇱

    In this letter we demonstrate that a model which is based on the CGC/saturation approach, is able to describe soft interaction collisions for the wide range of $W=\sqrt{s}=30GeV÷13TeV$ including the new TOTEM data at 13 TeV. We have incorporated the secondary Reggeons in our approach which enables us to describe the complete set of the soft data, including the energy behaviour of $\rho$ the ratio of the real to imaginary parts of the elastic scattering amplitude. We argue that it is premature to claim that an odderon contribution is necessary, but estimate its possible strength as $1mb$ to the real part of the amplitude at W = 13 \,TeV. We show that the odderon contribution depends on the value of energy leading to $\mathrm{ReA}\text{Lb}\mathrm{s},\mathrm{t}=0\text{Rb}$= 8 mb at W=21.2 \,GeV. Bearing this in mind we do not believe that $\rho$ at high energies is the appropriate observable for detecting the odderon contribution. The successful description of the soft data in the wide range of energy strengthens our claim that the CGC/saturation approach is the only viable candidate for an effective theory for high energy QCD.

    hep-phPLB(2018)·24 citations
29. 29*

    Comment on arXiv:1408.0288v2 [hep-ph] and Phys. Rev. D 90, 085017 (2014), "A new evaluation of the antiproton production cross section for cosmic ray studies", Mattia di Mauro et al

    R.H. Bernstein🇺🇸

    The referred-to paper on antiproton production contains two errors: an error in the value reported for one of the fit parameters and an error in units. I give the errors and the corrected values when possible.

    hep-phastro-ph.HEhep-ex1 citation
30. 30*

    Drifting Photons on Optical Paths: Mirrors, Sub-mm Resolution in 4 Dimensions, and Transverse/Longitudinal Phase Space: Exploiting Time Resolution

    Henry J. Frisch🇺🇸

    I discuss the status of MCP-based photo-detector amplification sections and Cherenkov light sources for precise timing measurements of charged particles and gamma rays. Sub-psec resolution is predicted for the large pulses such as those produced by a charged particle or electromagnetic shower traversing a photo-detector entrance window. Measuring events with sub-mm resolution in each of the 4 dimensions expands the optical phase space from 4 dimensions, allowing emittance transformations that can minimize expensive instrumented photo-sensitive area.

    ↳ physics.ins-detastro-ph.IMhep-exhep-ph+1PoS(2019)·3 citations
31. 31*

    Microscopic collectivity: The ridge and strangeness enhancement from string-string interactions

    Christian Bierlich🇸🇪

    We present the microscopic model for collective effects, built on string-string interactions (string shoving and rope hadronization), recently implemented in the PYTHIA 8 and DIPSY event generators. Rope hadronization is shown to give a good description of strangeness enhancement across pp, pA and AA collisions systems, while string shoving qualitatively describes the ridge observed in pp collisions.

    ↳ nucl-thhep-phNPA(2019)·27 citations
32. 32*

    A Bi-Directional Big Bang / Crunch Universe within a Two-State-Vector Quantum Mechanics?

    Fritz W. Bopp🇩🇪

    A two boundary quantum mechanics incorporating a big bang / big crunch universe is carefully considered. After a short motivation of the concept we address the central question how a proposed a-causal quantum universe can be consistent with what is known about macroscopia and how it might find experimental support.

    ↳ quant-phhep-phphysics.hist-phFound.Phys.(2019)·4 citations
33. 33*

    New measures of longitudinal decorrelation of harmonic flow

    Piotr Bozek🇵🇱 · Wojciech Broniowski🇵🇱

    Harmonic flow in relativistic heavy-ion collisions is observed in a broad range of rapidities, and the flow at different rapidities is correlated. However, fluctuations lead to a small decorrelation of the harmonic flow magnitudes and flow angles at different rapidities. Using a hydrodynamic model with Glauber Monte Carlo initial conditions we show that the flow angle decorrelation strongly depends on the flow magnitude in the event. We propose observables to measure this effect in experiment.

    ↳ nucl-thhep-phnucl-exNPA(2019)·1 citation
34. 34*

    IP-Glasma Phenomenology Beyond 2D

    Scott McDonald🇨🇦 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦

    We present a novel formulation of the IP-Glasma initial state model in 3+1D in which the 2+1D boost invariant IP-Glasma is generalized through JIMWLK rapidity evolution of the pre-collision Wilson lines \cite{Schenke:2016ksl}. In order to consistently accommodate a non-boost-invariant system, the initial conditions are generalized to 3+1D. By breaking boost invariance, the 3+1D model no longer trivially satisfies Gauss' law at the initial time, and we now enforce it locally. We compare the time evolution of the chromo-electric and chromo-magnetic fields as well as the transverse and longitudinal pressures in the 3+1D case with the boost invariant result.

    ↳ nucl-thhep-phnucl-exNPA(2019)·16 citations
35. 35*

    Hydrodynamic Fluctuations in Relativistic Heavy-Ion Collisions

    Mayank Singh🇨🇦 · Chun Shen🇺🇸 · Scott McDonald🇨🇦 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦

    We present a novel approach to the treatment of thermal fluctuations in the (3+1)-D viscous hydrodynamic simulation MUSIC. The phenomenological impact of thermal fluctuations on hadronic observables is investigated using the IP-Glasma + hydrodynamics + hadronic cascade hybrid approach. The anisotropic flow observed in heavy-ion collision experiments is mostly attributed to the hydrodynamic response to the event-by-event collision geometry and to the sub-nucleon quantum fluctuations. However, hydrodynamic fluctuations are present during the dynamical evolution of the Quark Gluon Plasma (QGP) and are quantified by the fluctuation-dissipation theorem. They can leave their imprint on final-state observables. By analyzing the thermal noise mode-by-mode, we provide a consistent scheme of treating these fluctuations as the source terms for hydrodynamic fields. These source terms are then evolved together with hydrodynamic equations of motion. Such a treatment captures the non-perturbative nature of the evolution for these thermal fluctuations.

    ↳ nucl-thhep-phnucl-exNPA(2019)·59 citations
36. 36*

    Identification of Long-lived Charged Particles using Time-Of-Flight Systems at the Upgraded LHC detectors

    O. Cerri🇺🇸 · S. Xie🇺🇸 · Cristian Peña🇺🇸 · Maria Spiropulu🇺🇸

    We study the impact of picosecond precision timing detection systems on the LHC experiments' long-lived particle search program during the HL-LHC era. We develop algorithms that allow us to reconstruct the mass of such charged particles and perform particle identification using the time-of-flight measurement. We investigate the reach for benchmark scenarios as a function of the timing resolution, and find sensitivity improvement of up to a factor of ten, depending on the new heavy particle mass.

    ↳ hep-exhep-phphysics.ins-detJHEP(2019)·22 citations
37. 37*

    No Net Charge Separation in Hot QCD in a Magnetic Field

    E. J. Ferrer🇺🇸 · V de la Incera🇺🇸

    We study the realization of axion electrodynamics in QCD in the presence of a background magnetic field at temperatures high enough for the occurrence of topological charge transitions that are reflected in the presence of a $\theta$-vacuum term in the action. We show that in this system, the Maxwell equations contain two equal and opposite electric currents that are proportional to the time derivative of the axion field $\theta$. One of these currents comes directly from the Abelian chiral anomaly term in the action and can be interpreted as a polarization current due to the magnetoelectricity of the system with CP-broken symmetry. The other current is obtained from the regular tadpole diagrams and can be understood as produced by the medium chiral imbalance and the single spin projection of the quarks in the lowest Landau level. Since the two currents cancel out, the net electric charge separation along the magnetic field, a phenomenon known as the Chiral Magnetic Effect, does not take place in hight-T QCD at least in equilibrium, in sharp contrast with many claims in the literature. We discuss the similarities and differences with Weyl semimetals in a magnetic field.

    ↳ hep-thcond-mat.str-elhep-phPRD(2018)·1 citation
38. 38*

    Lattice computation of the electromagnetic contributions to kaon and pion masses

    S. Basak🇮🇳 · A. Bazavov🇺🇸 · C. Bernard🇺🇸 · C. DeTar🇺🇸 · E. Freeland🇺🇸 · Steven Gottlieb🇺🇸 · U.M. Heller🇺🇸 · J. Laiho🇺🇸 · L. Levkova🇺🇸 · J. Osborn🇺🇸 · R.L. Sugar🇺🇸 · A. Torok🇺🇸 and 3 other authors

    We present a lattice calculation of the electromagnetic (EM) effects on the masses of light pseudoscalar mesons. The simulations employ 2+1 dynamical flavors of asqtad QCD quarks, and quenched photons. Lattice spacings vary from $\approx 0.12$ fm to $\approx 0.045$ fm. We compute the quantity $ϵ$, which parameterizes the corrections to Dashen's theorem for the $K^{+}$-$K^0$ EM mass splitting, as well as ${ϵ}_{K^0}$, which parameterizes the EM contribution to the mass of the $K^0$ itself. An extension of the nonperturbative EM renormalization scheme introduced by the BMW group is used in separating EM effects from isospin-violating quark mass effects. We correct for leading finite-volume effects in our realization of lattice electrodynamics in chiral perturbation theory, and remaining finite-volume errors are relatively small. While electroquenched effects are under control for $ϵ$, they are estimated only qualitatively for ${ϵ}_{K^0}$, and constitute one of the largest sources of uncertainty for that quantity. We find $ϵ=0.78(1{)}_{\mathrm{stat}}({}_{-11}^{+8}{)}_{\mathrm{syst}}$ and ${ϵ}_{K^0}=0.035(3{)}_{\mathrm{stat}}(20{)}_{\mathrm{syst}}$. We then use these results on 2+1+1 flavor pure QCD HISQ ensembles and find $m_u/m_d=0.4529(48{)}_{\mathrm{stat}}({}_{-67}^{+150}{)}_{\mathrm{syst}}$.

    ↳ hep-lathep-phPRD(2019)·57 citations
39. 39*

    Confronting hydrodynamic predictions with Xe-Xe data

    Giuliano Giacalone🇫🇷 · Jacquelyn Noronha-Hostler🇺🇸 · Matthew Luzum🇧🇷 · Jean-Yves Ollitrault🇫🇷

    Comparing collision systems of different size, at near the same collision energy, offers us the opportunity to probe the scaling behavior and therefore the nature of the system itself. Recently, we made predictions for Xe-Xe collisions at 5.44 TeV using viscous hydrodynamic simulations, noting that the scaling from the larger Pb-Pb system is rather generic, and arguing that robust predictions can be made that do not depend on details of the model. Here we confront our predictions with measurements that were subsequently made in a short Xe-Xe run at the LHC by the ALICE, ATLAS, and CMS collaborations. We find that the predictions are largely confirmed. Of particular interest is a strong indication of a non-spherical shape for the ${}^{129}$Xe nucleus.

    ↳ nucl-thhep-phNPA(2019)·8 citations
40. 40*

    Initial conditions for nuclear collisions: theory overview

    Aleksas Mazeliauskas🇩🇪

    We overview the current status and recent developments on initial conditions in ultra-relativistic nucleus-nucleus collisions. Specifically, we look at the progress in understanding the role of sub-nucleonic fluctuations in large and small collision systems. Next, we review the current ideas of going beyond boost invariant initial conditions and introducing physically motivated rapidity fluctuations at RHIC and LHC energies. Finally, we discuss the time evolution of initial stages and the matching between different descriptions of the QGP.

    ↳ nucl-thhep-phNPA(2019)·6 citations
41. 41*

    Constraints on neutrino speed, weak equivalence principle violation, Lorentz invariance violation, and dual lensing from the first high-energy astrophysical neutrino source TXS 0506+056

    Ranjan Laha🇩🇪

    We derive stringent constraints on neutrino speed, weak equivalence principle violation, Lorentz invariance violation, and dual lensing from the first high-energy astrophysical neutrino source: TXS 0506+056. Observation of neutrino (IceCube-170922A) and photons in a similar time frame and from the same direction is used to derive these limits. We describe ways in which these constraints can be further improved by orders of magnitude.

    ↳ astro-ph.HEastro-ph.COhep-exhep-ph+1PRD(2019)·38 citations
42. 42*

    Hadronic observables in p+p and d+Au collisions at RHIC using CGC+PYTHIA

    Björn Schenke🇺🇸 · Sören Schlichting🇺🇸 · Prithwish Tribedy🇺🇸 · Raju Venugopalan🇺🇸

    The IP-Glasma model of CGC combined with the Lund model of PYTHIA provides a very successful description of hadron production from gluon dominated non-equilibrium matter in various small collision systems. This new CGC+PYTHIA framework, naturally reproduces several characteristic features of the hadronic observables such as the mass ordering of $v_2(p_T)$ and $⟨p_T⟩$, often ascribed to collectivity driven by hydrodynamics at the LHC. In this contribution we extend our work to provide a systematic comparison of particle spectra and multiplicity distributions in p+p and d+Au collisions at the RHIC.

    ↳ nucl-thhep-phnucl-exNPA(2019)·3 citations
43. 43*

    Chiral phase transition of (2+1)-flavor QCD

    H.-T. Ding🇨🇳 · P. Hegde🇮🇳 · F. Karsch🇩🇪 · A. Lahiri🇩🇪 · S.-T. Li🇨🇳 · S. Mukherjee🇺🇸 · P. Petreczky🇺🇸

    We present here results on the determination of the critical temperature in the chiral limit for (2+1)-flavor QCD. We propose two novel estimators of the chiral critical temperature where quark mass dependence is strongly suppressed compared to the conventional estimator using pseudo-critical temperatures. We have used the HISQ/tree action for the numerical simulation with lattices with three different temporal extent $N_{\tau }=$6, 8, 12 and varied the aspect ratio over the range $4\le N_{\sigma }/N_{\tau }\le 8$. To approach the chiral limit, the light quark mass has been decreased keeping the strange quark mass fixed at its physical value. Our simulations correspond to the range of pion masses, 55 MeV $\le m_{\pi }\le$ 160 MeV.

    ↳ hep-lathep-phNPA(2019)·32 citations
44. 44*

    Applications of deep learning to relativistic hydrodynamics

    Hengfeng Huang🇨🇳 · Bowen Xiao🇨🇳 · Huixin Xiong🇨🇳 · Zeming Wu🇨🇳 · Yadong Mu🇨🇳 · Huichao Song (Peking U)🇨🇳

    In this proceeding, we will briefly review our recent progress on implementing deep learning to relativistic hydrodynamics. We will demonstrate that a successfully designed and trained deep neural network, called {\tt stacked U-net}, can capture the main features of the non-linear evolution of hydrodynamics, which could also rapidly predict the final profiles for various testing initial conditions.

    ↳ nucl-thcond-mat.dis-nnhep-exhep-ph+1NPA(2019)·5 citations
45. 45*

    A novel way to search for light dark matter in lepton beam-dump experiments

    L. Marsicano🇮🇹 · M. Battaglieri🇮🇹 · M. Bondì🇮🇹 · C. D. R. Carvajal🇨🇴 · A. Celentano🇮🇹 · M. De Napoli🇮🇹 · R. De Vita🇮🇹 · E. Nardi🇮🇹 · M. Raggi🇮🇹 · P. Valente🇮🇹

    A novel mechanism to produce and detect Light Dark Matter in experiments making use of GeV electrons (and positrons) impinging on a thick target (beam-dump) is proposed. The positron-rich environment produced by the electromagnetic shower allows to produce an $A^{\prime }$ via non-resonant ($e^{+}+e^{-}\to \gamma +A^{\prime }$) and resonant ($e^{+}+e^{-}\to A^{\prime }$) annihilation on atomic electrons. The latter mechanism, for some selected kinematics, results in a larger sensitivity with respect to limits derived by the commonly used $A^{\prime }-strahlung$. This idea, applied to Beam Dump Experiments and {\it active} Beam Dump Experiments pushes down the current limits by an order of magnitude.

    ↳ hep-exhep-phPRL(2018)·85 citations
46. 46*

    A Solution to the 1+1D Gauged Chiral Fermion Problem

    Juven Wang🇺🇸 · Xiao-Gang Wen🇺🇸

    We show that the 3450 U(1) chiral fermion theory can appear as the low energy effective field theory of a 1+1D local lattice model, with an on-site U(1) symmetry and finite-range interactions. The on-site U(1) symmetry means that the U(1) symmetry can be gauged (gaugeable for both background probe and dynamical fields), which leads to a non-perturbative definition of chiral gauge theory --- a chiral fermion theory coupled to U(1) gauge theory. Our construction can be generalized to regularize any U(1)-anomaly-free 1+1D gauged chiral fermion theory with a zero chiral central charge (thus no gravitational anomaly) by a lattice, thanks to the recently proven "Poincaré dual" equivalence between the U(1) 't Hooft anomaly free condition and the U(1) symmetric interaction gapping rule, via a bosonization-fermionization technique.

    ↳ hep-latcond-mat.str-elhep-phhep-thPRD·70 citations
47. 47*

    Conformal Symmetry and Feynman Integrals

    Simone Zoia🇩🇪

    Singularities hidden in the collinear region around an external massless leg may lead to conformal symmetry breaking in otherwise conformally invariant finite loop momentum integrals. For an $\ell$-loop integral, this mechanism leads to a set of linear $2$nd-order differential equations with a non-homogeneous part. The latter, due to the contact nature of the anomaly in momentum space, is determined by $(\ell -1)$-loop information. Solving such differential equations in general is an open problem. In the case of 5-particle amplitudes up to two loops, the function space is known, and we can thus follow a bootstrap approach to write down the solution. As a first application of this method, we bootstrap the 6D penta-box integral.

    ↳ hep-thhep-phPoS(2018)·5 citations
48. 48*

    Lattice-based QCD equation of state at finite baryon density: Cluster Expansion Model

    V. Vovchenko🇩🇪 · J. Steinheimer🇩🇪 · O. Philipsen🇩🇪 · A. Pasztor🇩🇪 · Z. Fodor🇩🇪 · S.D. Katz🇭🇺 · H. Stoecker🇩🇪

    The QCD equation of state at finite baryon density is studied in the framework of a Cluster Expansion Model (CEM), which is based on the fugacity expansion of the net baryon density. The CEM uses the two leading Fourier coefficients, obtained from lattice simulations at imaginary ${\mu }_B$, as the only model input and permits a closed analytic form. Excellent description of the available lattice data at both ${\mu }_B=0$ and at imaginary ${\mu }_B$ is obtained. We also demonstrate how the Fourier coefficients can be reconstructed from baryon number susceptibilities.

    ↳ hep-lathep-phnucl-thNPA(2019)·21 citations
49. 49*

    Exact solutions of the bound Dirac and Klein Gordon equations in non co propagating electromagnetic plane waves

    A. Hartin🇬🇧

    A new class of exact solutions of the bound Dirac and bound Klein Gordon equations in non co propagating plane waves is found. The solutions are based on the physical principle of maintaining local gauge invariance in the Furry picture Lagrangian when N external fields can undergo independent gauge transformations. The solutions can be expressed in terms of the Hamilton Jacobi action and a gauge invariant effective particle momentum in the ensemble of external fields. Rotations of the effective particle momentum, which preserve local gauge invariance, are introduced into the action using matrix calculus. The set of such rotations provides the class of new solutions constituting a family of Volkov like solutions for one external field. When applied to two or more non co propagating external fields, the rotational symmetry provides counter terms which decouple the fields. The bound state equations of motion become solvable for any number of non co propagating external fields. Through angular spectral decomposition, which represents electromagnetic fields of any form as a spatial Fourier series of non co propagating plane waves, the new solutions described here can be applied to strong field physics problems in any external electromagnetic field.

    ↳ physics.opticshep-phhep-th0 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.