Mon·Mar 30, 2020Monday·March 30, 2020

1. 01*

   Deuteron EDM induced by CP violating couplings of pseudoscalar mesons

   Alexey S. Zhevlakov🇷🇺 · Valery E. Lyubovitskij🇩🇪

   We analyze contributions to the electric dipole (EDM) and Schiff (SFM) moments of deuteron induced by the CP-violating three-pseudoscalar meson couplings using phenomenological Lagrangian approach involving nucleons and pseudoscalar mesons $P=\pi ,K,\eta ,{\eta }^{\prime }$. Deuteron is considered as a proton-neutron bound state and its properties are defined by one- and two-body forces. One-body forces correspond to a picture there proton and neutron are quasi free constituents of deuteron and their contribution to the deuteron EDM (dEDM) is simply the sum of proton and neutron EDMs. Two-body forces in deuteron are induced by one-meson exchange between nucleons. They produce a contribution to the dEDM, which is estimated using corresponding potential approach. From numerical analysis of nucleon and deuteron EDMs we derive stringent limits on CP-violating hadronic couplings and $\bar{\theta }$ parameter. We showed that proposed measurements of proton and deuteron EDMs at level of $\sim 10^{-29}$ by the Store Ring EDM and JEDI Collaborations will provide more stringent upper limits on the CP violating parameters.

   hep-phPRD(2020)·13 citations
2. 02*

   Study of ${\bar{B}}_s\to K^{(\ast )}{\ell }^{+}{\ell }^{-}$ decays in the PQCD factorization approach with the lattice QCD input

   Su-Ping Jin🇨🇳 · Xue-Qing Hu🇨🇳 · Zhen-Jun Xiao🇨🇳

   In this paper, we studied systematically the semileptonic decays ${\bar{B}}_s\to K^{(\ast )}{\ell }^{+}{\ell }^{-}$ with $l^{-}=(e^{-},{\mu }^{-},{\tau }^{-})$ by using the perturbative QCD (PQCD) and the "PQCD+Lattice" factorization approach, respectively. We first evaluated all relevant form factors $F_i(q^2)$ in the low $q^2$ region using the PQCD approach, and we also take the available Lattice QCD results at the end point $q_{max}^2$ as additional inputs to improve the extrapolation of the form factors to the high $q^2$ region. We calculated the branching ratios and other twelve kinds of physical observables. From our studies, we find the following points: (a) for ${\bar{B}}_s\to K{l}^{+}{l}^{-}$ decays, the PQCD and "PQCD+Lattice" predictions for branching ratios (BRs) $\mathcal{B}({\bar{B}}_s\to K{l}^{+}{l}^{-})$, the ratios of the BRs $R_K^{e\mu }$ and $R_K^{\mu \tau }$, and the longitudinal polarization asymmetry of the leptons $P_L$ agree well within errors; (b) the PQCD and "PQCD+Lattice" predictions for the CP averaged branching ratio $\mathcal{B}({\bar{B}}_s\to K^{\ast }{\mu }^{+}{\mu }^{-})$ are $(3.17_{-0.78}^{+0.95})\times 10^{-8}$ and $(2.48_{-0.50}^{+0.56})\times 10^{-8}$ respectively, which agree well with the LHCb measured value $(2.9\pm 1.1)\times 10^{-8}$ and the light-cone sum rule (LCSR) prediction; (c) for the ratios $R_{K^{\ast }}^{e\mu }$ and $R_{K^{\ast }}^{\mu \tau }$, the PQCD and "PQCD+Lattice" predictions agree well with each other and have a small error less than $10\%$; (d) for the direct CP asymmetries ${\mathcal{A}}_{CP}$ of all considered decay modes, they are always very small as expected: less than $5\%$ in magnitude; and (e) for the angular observables $P_{1,2,3}$ and $P_{4,5,6,8}^{\prime }$ , our theoretical predictions for each kind of lepton are consistent within errors. We believe that above predictions could be tested by future LHCb and Belle-II experiments.

   hep-phhep-exhep-latPRD(2020)·12 citations
3. 03*

   Light Meson Parton Distribution Functions from Basis Light-Front Quantization and QCD Evolution

   Jiangshan Lan🇨🇳 · Chandan Mondal🇨🇳 · Shaoyang Jia🇺🇸 · Xingbo Zhao🇨🇳 · James P. Vary🇺🇸

   We investigate the parton distribution functions (PDFs) of the pion and kaon from the eigenstates of a light-front effective Hamiltonian in the constituent quark-antiquark representation suitable for low-momentum scale applications. By taking these scales as the only free parameters, the valence quark distribution functions of the pion, after QCD evolving, are consistent with the E615 experiment at Fermilab. In addition, the ratio of the up quark distribution in the kaon to that in the pion also agrees with the NA3 experimental result at CERN.

   hep-phnucl-thHadron 2019, 581-585·4 citations
4. 04*

   Cross sections for 2-to-1 meson-meson scattering

   Wan-Xia Li🇨🇳 · Xiao-Ming Xu🇨🇳 · H. J. Weber🇺🇸

   We study the processes $K\bar{K}\to \varphi$, $\pi D\to D^{\ast }$, $\pi \bar{D}\to {\bar{D}}^{\ast }$, and the production of $\psi (3770)$, $\psi (4040)$, $\psi (4160)$, and $\psi (4415)$ mesons in collisions of charmed mesons or charmed strange mesons. The process of 2-to-1 meson-meson scattering involves a quark and an antiquark from the two initial mesons annihilating into a gluon and subsequently the gluon being absorbed by the spectator quark or antiquark. Transition amplitudes for the scattering process derive from the transition potential in conjunction with mesonic quark-antiquark wave functions and the relative-motion wave function of the two initial mesons. We derive these transition amplitudes in the partial wave expansion of the relative-motion wave function of the two initial mesons so that parity and total-angular-momentum conservation are maintained. We calculate flavor and spin matrix elements in accordance with the transition potential and unpolarized cross sections for the reactions using the transition amplitudes. Cross sections for the production of $\psi (4040)$, $\psi (4160)$, and $\psi (4415)$ relate to nodes in their radial wave functions. We suggest the production of $\psi (4040)$, $\psi (4160)$, and $\psi (4415)$ as probes of hadronic matter that results from the quark-gluon plasma created in ultrarelativistic heavy-ion collisions.

   hep-phnucl-thEPJC(2021)·5 citations
5. 05*

   Investigation of rare semileptonic $B_c$ decays into $(D_{(}s,d{)}^{(}(\ast ))){\mu }^{+}{\mu }^{-}$ decays with non-universal $Z^{\prime }$ effect

   P. Maji🇮🇳 · S. Mahata🇮🇳 · P. Nayek🇮🇳 · S. Biswas🇮🇳 · S. Sahoo🇮🇳

   In this paper, we analyze different decay observables of semileptonic $B_c$ decays into $(D_{(}s,d{)}^{(}(\ast ))){\mu }^{+}{\mu }^{-}$ such as branching ratio, forward-backward asymmetry, polarization fraction and lepton polarization asymmetry in the non-universal Z' model. We have also studied the dependence of branching fraction to the new model parameters. Here, we have found that the values of different decay parameters increase in the Z' model, which provides a possible way out for the search of new physics as well as the unknown phenomena of charm B meson.

   hep-phCPC(2020)·6 citations
6. 06*

   Measuring the trilinear Higgs boson self--coupling at the 100 TeV hadron collider via multivariate analysis

   Jubin Park🇰🇷 · Jung Chang🇰🇷 · Kingman Cheung🇹🇼 · Jae Sik Lee🇰🇷

   We perform a multivariate analysis of Higgs-pair production via the decay channel $HH\to b\bar{b}\gamma \gamma$ at the future 100 TeV $pp$ collider to determine the trilinear Higgs self--coupling (THSC) ${\lambda }_{3H}$, which takes the value of 1 in the standard model. We consider all known background processes. For the signal we adopt the most recent event generator of {\tt POWHEG-BOX-V2} to exploit the NLO distributions for Toolkit for Multivariate Data Analysis (TMVA). Through the technique of Boosted Decision Tree (BDT) analysis trained for ${\lambda }_{3H}=1$, compared to the the conventional cut-and-count approach, the signal-to-background ratio improves tremendously from about $1/10$ to $1$ and the significance can reach up to $20.5$ with a luminosity of 3 ab${}^{-1}$ without including systematic uncertainties. In addition, by implementing a likelihood fitting of the signal-plus-background $M_{\gamma \gamma bb}$ distribution with optimized bin sizes, it is possible to determine the THSC with the precision of 7.5\% at 68\% CL even at the early stage of 100 TeV hadron collider with 3 ab${}^{-1}$.

   hep-phPRD(2020)·12 citations
7. 07*

   Improving $t\bar{t}$ reconstruction in the dilepton channel at future lepton colliders

   P. Martín-Ramiro🇪🇸 · J. M. Moreno🇪🇸

   A future lepton collider, such as the proposed CLIC or ILC, would allow to study top quark properties with unprecedented precision. In this paper, we present a method to reconstruct the $t\bar{t}$ decay in the dilepton channel at future $e^{+}{e}^{-}$ colliders. We derive a simple, closed analytical expression for the neutrino four-momenta as a function of the $W$ boson mass and develop a maximization procedure to find the optimal solution for the reconstruction of the full $t\bar{t}$ event. We show that our method is able to reconstruct neutrino four-momenta with an error of less than $2\%$ in $60\%$ of the times. Finally, we test the performance of this reconstruction method in the calculation of the helicity fractions of the $W$ boson. A precise measurement of these observables could be used to probe new physics effects in the $Wtb$ vertex. We find that, from a large $t\bar{t}$ sample, our reconstruction method allows to calculate these observables with an accuracy better than $1\%$.

   hep-phhep-ex1 citation
8. 08*

   Dark-matter spontaneous freeze out

   Hervé Partouche🇫🇷

   We consider the possibility that thermalized dark-matter particles acquire their mass thanks to the spontaneous breaking of a symmetry below some critical temperature. We describe the regime where a freeze out mechanism takes place shortly after the onset of the phase transition, while the dark-matter mass has not yet reached its final constant value. For such a "spontaneous freeze out" to yield the correct relic density, the present-time cross section of annihilation of the dark matter into Standard-Model states has to be one or two orders of magnitude larger than in the case of a constant dark-matter mass.

   hep-phastro-ph.HEhep-th0 citations
9. 09*

   What pp SUSY limits mean for future e${}^{+}$e${}^{-}$ colliders

   Mikael Berggren (1) ((1) DESY, Hamburg, Germany)🇩🇪

   It is well-known that e${}^{+}$e${}^{-}$ colliders have the power to with certainty exclude or discover any SUSY model that predicts a Next to lightest SUSY particle (an NLSP) that has a mass up to slightly below the half the centre-of-mass energy of the collider. Here, we present an estimation of the power of present and future hadron colliders to extend the reach of searches for SUSY, with particular emphasis whether it can be claimed that either discovery or exclusion is {\it guaranteed} in a region of LSP and NLSP masses - no set of values of the other SUSY could change the conclusion. A scan over SUSY parameter space was done, only requiring that the NLSP was a bosino - the hardest case - with mass not larger than a few TeV. The mass-spectrum, cross-sections and decay branching ratios found in this region were confronted with projections of sensitivity at future hadron colliders. In our conclusions we weigh in the maturity of the analysis the projections are based upon. The conclusion is that although future hadron colliders have a large discovery-reach, i.e. potential to discover {\it some} SUSY model, hardly any models with low-to-medium LSP-NLSP mass-differences can be excluded with certainty. The models that are expected to be excluded/discovered are, on one hand, those with mass-differences larger than those allowed by models with GUT-scale $M_1$-$M_2$ unification, and on the other hand, a tiny region where the mass-difference is so small that the NLSP decays in the tracking volume of the detectors. Excluding the latter possibility does not, however, allow to exclude the possibility of a Wino or Higgsino LSP: at any value of the LSP mass, we could identify models where the NLSP lifetime would be too short for a signal to be seen.

   hep-phhep-ex17 citations
10. 10*

    Disentangling different structures in heavy-light four-quark states

    Paul C. Wallbott🇩🇪 · Gernot Eichmann🇵🇹 · Christian S. Fischer🇩🇪

    Models proposed to explain recently discovered heavy-light four-quark states already assume certain internal structures, i.e. the (anti)quark constituents are grouped into diquark/antidiquark clusters, heavy-meson/light-meson clusters (hadrocharmonium) or heavy-light meson molecules. We propose and use an approach to four-quark states based on Dyson-Schwinger and Bethe-Salpeter equations that has the potential to discriminate between these models. We study the masses of heavy-light $cq\bar{q}\bar{c}$ and $cc\bar{q}\bar{q}$ four-quark states with $q=u,d,s$ and quantum numbers $I(J^{PC})=0(1^{++}),1(1^{+-}),0(0^{++})$ and $1(0^{+}),0(1^{+}),1(1^{+})$. We identify the dominant components of the ground states with these quantum numbers and suggest candidates for corresponding experimental states. Most notably, we find strong heavy-light meson-meson and negligible diquark-antidiquark components in all $cq\bar{q}\bar{c}$ states, whereas for $cc\bar{q}\bar{q}$ states diquarks are present. A potential caveat in the $I=0$ channels is the necessary but costly inclusion of $c\bar{c}$ components which is relegated to future work.

    hep-phhep-latPRD(2020)·20 citations
11. 11*

    Charm Physics Confronts High-$p_T$ Lepton Tails

    Javier Fuentes-Martin🇨🇭 · Admir Greljo🇨🇭 · Jorge Martin Camalich🇪🇸 · Jose David Ruiz-Alvarez🇨🇴

    We present a systematic survey of possible short-distance new-physics effects in (semi)leptonic charged- and neutral-current charmed meson decays. Using the Standard Model Effective Field Theory (SMEFT) to analyze the most relevant experimental data at low and high energies, we demonstrate a striking complementarity between charm decays and high invariant mass lepton tails at the LHC. Interestingly enough, high-$p_T$ Drell-Yan data offer competitive constraints on most new physics scenarios. Furthermore, the full set of correlated constraints from $K$, $\pi$ and $\tau$ decays imposed by $SU(2{)}_L$ gauge invariance is considered. The bounds from $D_{(s)}$ decays, high-$p_T$ lepton tails and $SU(2{)}_L$ relations chart the space of the SMEFT affecting semi(leptonic) charm flavor transitions.

    hep-phhep-exJHEP(2020)·111 citations
12. 12*

    Parton-shower effects in Higgs production via Vector-Boson Fusion

    Barbara Jäger🇩🇪 · Alexander Karlberg🇬🇧 · Simon Plätzer🇦🇹 · Johannes Scheller🇩🇪 · Marco Zaro🇮🇹

    We present a systematic investigation of parton-shower and matching perturbative uncertainties for Higgs-boson production via vector-boson fusion. To this end we employ different generators at next-to-leading order QCD accuracy matched with shower Monte Carlo programs, PYTHIA8, and HERWIG7, and a next-to-next-to-leading order QCD calculation. We thoroughly analyse the intrinsic sources of uncertainty within each generator, and then compare predictions among the different tools using the respective recommended setups. Within typical vector-boson fusion cuts, the resulting uncertainties on observables that are accurate to next-to-leading order are at the 10% level for rates and even smaller for shapes. For observables sensitive to extra radiation effects uncertainties of about 20% are found. We furthermore show how a specific recoil scheme is needed when PYTHIA8 is employed, in order not to encounter unphysical enhancements for these observables. We conclude that for vector-boson fusion processes an assessment of the uncertainties associated with simulation at next-to-leading order matched to parton showers based only on the variation of renormalisation, factorisation and shower scales systematically underestimates their true size.

    hep-phEPJC(2020)·62 citations
13. 13*

    Matching scalar leptoquarks to the SMEFT at one loop

    Valerio Gherardi🇮🇹 · David Marzocca🇮🇹 · Elena Venturini🇩🇪

    In this paper we present the complete one-loop matching conditions, up to dimension-six operators of the Standard Model effective field theory, resulting by integrating out the two scalar leptoquarks $S_1$ and $S_3$. This allows a phenomenological study of low-energy constraints on this model at one-loop accuracy, which will be the focus of a subsequent work. Furthermore, it provides a rich comparison for functional and computational methods for one-loop matching, that are being developed. As a corollary result, we derive a complete set of dimension-six operators independent under integration by parts, but not under equations of motions, called Green's basis, as well as the complete reduction formulae from this set to the Warsaw basis.

    hep-phhep-thJHEP(2020)·135 citations
14. 14*

    Quark and pion condensates at finite isospin density in chiral perturbation theory

    Prabal Adhikari🇺🇸 · Jens O. Andersen🇳🇴

    In this paper, we consider two-flavor QCD at zero temperature and finite isospin chemical potential (${\mu }_I$) using a model-independent analysis within chiral perturbation theory at next-to-leading order. We calculate the effective potential, the chiral condensate and the pion condensate in the pion-condensed phase at both zero and nonzero pionic source. We compare our finite pionic source results for the chiral condensate and the pion condensate with recent (2+1)-flavor lattice QCD results and find that they are in excellent agreement.

    hep-phhep-latnucl-thEPJC(2020)·20 citations
15. 15*

    Investigations of electroweak symmetry breaking mechanism for Higgs boson decays into four fermions

    T.V. Obikhod🇺🇦 · I.A. Petrenko🇺🇦

    Models with extended Higgs boson sectors are of prime importance for investigating the mechanism of electroweak symmetry breaking for Higgs decays into four fermions and for Higgs-production in association with a vector bosons. In the framework of the Two-Higgs-Doublet Model using two scenarios obtained from the experimental measurements we presented next-to-leading-order results on the four-fermion decays of light CP-even Higgs boson, $h\to 4f$. With the help of Monte Carlo program Prophecy 4f 3.0, we calculated the values $\Gamma ={\Gamma }_{EW}/\left({\Gamma }_{EW}+{\Gamma }_{SM}\right)$ and $\Gamma ={\Gamma }_{EW+QCD}/\left({\Gamma }_{EW+QCD}+{\Gamma }_{SM}\right)$ for Higgs boson decay channels $H\to {\nu }_{\mu }\overline{\mu }e\overline{{\nu }_e}$, $\mu \overline{\mu }e\overline{e}$, $e\overline{e}e\overline{e}$. We didn't find significant difference when accounting QCD corrections to EW processes in the decay modes of Higgs boson. Using computer programs Pythia 8.2 and FeynHiggs we calculated the following values: $\sigma (VBH)BR(H\to ZZ)$ and $\sigma (VBF)BR(H\to WW)$ for VBF production processes, $\sigma (ggH)BR(H\to WW)$ and $\sigma (ggH)BR(H\to ZZ)$ for gluon fusion production process at 13 and 14 TeV and found good agreement with experimental data.

    hep-phProb.Atomic Sci.Technol.(2020)·0 citations
16. 16*

    Ratios of the hadronic contributions to the lepton $g-2$ from Lattice QCD+QED simulations

    D. Giusti🇩🇪 · S. Simula🇮🇹

    The ratios among the leading-order (LO) hadronic vacuum polarization (HVP) contributions to the anomalous magnetic moments of electron, muon and tau-lepton, $a_{\ell =e,\mu \tau }^{HVP,LO}$, are computed using lattice QCD+QED simulations. The results include the effects at order $O({\alpha }_{em}^2)$ as well as the electromagnetic and strong isospin-breaking corrections at orders $O({\alpha }_{em}^3)$ and $O({\alpha }_{em}^2(m_u-m_d))$, respectively, where $(m_u-m_d)$ is the $u$- and $d$-quark mass difference. We employ the gauge configurations generated by the Extended Twisted Mass Collaboration with $N_f=2+1+1$ dynamical quarks at three values of the lattice spacing ($a\simeq 0.062,0.082,0.089$ fm) with pion masses in the range 210 - 450 MeV. We show that in the case of the electron-muon ratio the hadronic uncertainties in the numerator and in the denominator largely cancel out, while in the cases of the electron-tau and muon-tau ratios such a cancellation does not occur. For the electron-muon ratio we get $R_{e/\mu }\equiv (m_{\mu }/m_e{)}^2(a_e^{HVP,LO}/a_{\mu }^{HVP,LO})=1.1456(83)$ with an uncertainty of $\simeq 0.7\%$. Our result, which represents an accurate Standard Model (SM) prediction, agrees very well with the estimate obtained using the results of dispersive analyses of the experimental $e^{+}{e}^{-}\to$ hadrons data. Instead, it differs by $\simeq 2.7$ standard deviations from the value expected from present electron and muon (g - 2) experiments after subtraction of the current estimates of the QED, electro-weak, hadronic light-by-light and higher-order HVP contributions, namely $R_{e/\mu }=0.575(213)$. An improvement of the precision of both the experiment and the QED contribution to the electron (g - 2) by a factor of $\simeq 2$ could be sufficient to reach a tension with our SM value of the ratio $R_{e/\mu }$ at a significance level of $\simeq 5$ standard deviations.

    ↳ hep-lathep-exhep-phphysics.atom-phPRD(2020)·15 citations
17. 17*

    Charged multi-hadron systems in lattice QCD+QED

    S. R. Beane🇺🇸 · W. Detmold🇺🇸 · R. Horsley🇬🇧 · M. Illa🇪🇸 · M. Jafry🇺🇸 · D. J. Murphy🇺🇸 · Y. Nakamura🇯🇵 · H. Perlt🇩🇪 · P. E. L. Rakow🇬🇧 · G. Schierholz🇩🇪 · P. E. Shanahan🇺🇸 · H. Stüben🇩🇪 and 4 other authors

    Systems with the quantum numbers of up to twelve charged and neutral pseudoscalar mesons, as well as one-, two-, and three-nucleon systems, are studied using dynamical lattice quantum chromodynamics and quantum electrodynamics (QCD+QED) calculations and effective field theory. QED effects on hadronic interactions are determined by comparing systems of charged and neutral hadrons after tuning the quark masses to remove strong isospin breaking effects. A non-relativistic effective field theory, which perturbatively includes finite-volume Coulomb effects, is analyzed for systems of multiple charged hadrons and found to accurately reproduce the lattice QCD+QED results. QED effects on charged multi-hadron systems beyond Coulomb photon exchange are determined by comparing the two- and three-body interaction parameters extracted from the lattice QCD+QED results for charged and neutral multi-hadron systems.

    ↳ hep-lathep-phnucl-thPRD(2021)·88 citations
18. 18*

    Planck scale from broken local conformal invariance in Weyl geometry

    Ichiro Oda🇯🇵

    We show that in a quadratic gravity based on Weyl's conformal geometry, the Planck mass scale can be generated from quantum effects of the gravitational field and the Weyl gauge field via the Coleman-Weinberg mechanism where a local scale symmetry is broken. At the same time, the Weyl gauge field acquires a mass less than the Planck mass by absorbing the scalar graviton. The shape of the effective potential is almost flat owing to a gravitational character and high symmetries, so our model would provide for an attractive model for the inflationary universe. We also present a toy model showing spontaneous symmetry breakdown of a global scale symmetry by moving from the Jordan frame to the Einstein one, and point out its problems.

    ↳ hep-thgr-qchep-phPoS(2020)·6 citations
19. 19*

    Second-order effective energy-momentum tensor of gravitational scalar perturbations with perfect fluid

    Inyong Cho🇰🇷 · Jinn-Ouk Gong🇰🇷 · Seung Hun Oh🇰🇷

    We investigate the second-order gravitational scalar perturbations for a barotropic fluid. We derive the effective energy-momentum tensor described by the quadratic terms of the gravitational and the matter perturbations. We show that the second-order effective energy-momentum tensor is gauge dependent. We impose three gauge conditions (longitudinal, spatially-flat, and comoving gauges) for dust and radiation. The resulting energy-momentum tensor is described only by a gauge invariant variable, but the functional form depends on the gauge choice. In the matter-dominated epoch with dust-like fluid background, the second-order effective energy density and pressure of the perturbations evolve as 1/a^2 in all three gauge choices, like the curvature density of the Universe, but they do not provide the correct equation of state. The value of this parameter depends also on the gauge choice. In the radiation-dominated epoch, the perturbations in the short-wave limit behave in the same way as the radiation-like fluid in the longitudinal and the spatially-flat gauges. However, they behave in a different way in the comoving gauge. As a whole, we conclude that the second-order effective energy-momentum tensor of the scalar perturbation is strictly gauge dependent.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2020)·9 citations
20. 20*

    Anomalous chiral transports and spin polarization in heavy-ion collisions

    Yu-Chen Liu🇨🇳 · Xu-Guang Huang🇨🇳

    Relativistic heavy-ion collisions create hot quark-gluon plasma as well as very strong electromagnetic (EM) and fluid vortical fields. The strong EM field and vorticity can induce intriguing macroscopic quantum phenomena such as chiral magnetic, chiral separation, chiral electric separation, and chiral vortical effects as well as the spin polarization of hadrons. These phenomena provide us with experimentally feasible means to study the nontrivial topological sector of quantum chromodynamics, the possible parity violation of strong interaction at high temperature, and the subatomic spintronics of quark-gluon plasma. These studies, both in theory and in experiments, are strongly connected with other subfields of physics such as condensed matter physics, astrophysics, and cold atomic physics, and thus form an emerging interdisciplinary research area. We give an introduction to the aforementioned phenomena induced by the EM field and vorticity and an overview of the current status of their experimental research in heavy-ion collisions. We also briefly discuss spin hydrodynamics as well as chiral and spin kinetic theories.

    ↳ nucl-thhep-phnucl-exNucl.Sci.Tech.(2020)·120 citations
21. 21*

    String Backgrounds in String Geometry

    Masaki Honda🇯🇵 · Matsuo Sato🇯🇵

    String geometry theory is a candidate of the non-perturbative formulation of string theory. In order to determine the string vacuum, we need to clarify how string backgrounds are described in string geometry theory. In this paper, we show that the string backgrounds are embedded in configurations of the fields of a string geometry model. Especially, we show that the configurations satisfy the equations of motion of the string geometry model if and only if the embedded string backgrounds satisfy their equations of motion. This means that classical dynamics of the string backgrounds are described as a part of classical dynamics in string geometry theory. Furthermore, we define an energy of the configurations in the string geometry model because they do not depend on the string geometry time. A string background can be determined by minimizing the energy.

    ↳ hep-thgr-qchep-phInt.J.Mod.Phys.A(2020)·14 citations
22. 22*

    Nonperturbative Effects on Radiative Energy Loss of Heavy Quarks

    Shuai Y.F. Liu🇨🇳 · Ralf Rapp🇺🇸

    The radiative energy loss of fast partons traveling through the quark-gluon plasma (QGP) is commonly studied within perturbative QCD (pQCD). Nonperturbative (NP) effects, which are expected to become important near the critical temperature, have been much less investigated. Here, we utilize a recently developed $T$-matrix approach to incorporate NP effects for gluon emission off heavy quarks propagating through the QGP. We set up four cases that contain, starting from a Born diagram calculation with color-Coulomb interaction, an increasing level of NP components, by subsequently including (remnants of) confining interactions, resummation in the heavy-light scattering amplitude, and off-shell spectral functions for both heavy and light partons. For each case we compute the power spectra of the emitted gluons, heavy-quark transport coefficients (drag and transverse-momentum broadening, $\hat{q}$), and the path-length dependent energy loss within a "QGP brick" at fixed temperature. Investigating the differences in these quantities between the four cases illustrates how NP mechanisms affect gluon radiation processes. While the baseline perturbative processes experience a strong suppression of soft radiation due to thermal masses of the emitted gluons, confining interactions, ladder resummations and broad spectral functions (re-)generate a large enhancement toward low momenta and low temperatures. For example, for a 10 GeV charm quark at 200 MeV temperature, they enhance the transport coefficients by up to a factor of 10, while the results smoothly converge to perturbative results at sufficiently hard scales.

    ↳ nucl-thhep-phnucl-exJHEP(2020)·23 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.