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Nuclear Theory·nucl-th

Monday·January 13, 2020

8 papers—3 primary·5 cross-listed

All8Primary3Cross-lists5
  1. 04

    Real-time dynamics of axion particle production due to spontaneous decay of a coherent axion field

    Xu-Guang Huang🇨🇳 · Dmitri E. Kharzeev🇺🇸 · Hidetoshi Taya🇨🇳

    We show that the coherent axion field spontaneously decays by emitting axion particles via quantum tunneling if axion potential has more than one minimum. By employing the -expansion and mean field approximation, we develop a formalism to trace the real-time dynamics of the axion particle production including its backreaction to the coherent axion field. We also present numerical results for the time evolution of various physical quantities including the strength of the coherent axion field, phase-space density of produced axion particles, energy density, and pressure. Phenomenological implications of our results are also discussed.

    ↳ hep-phastro-ph.HEgr-qchep-th+1PRD(2020)·5 citations
  2. 05

    Fluctuation dynamics in a relativistic fluid with a critical point

    Xin An🇺🇸 · Gokce Basar🇺🇸 · Mikhail Stephanov🇺🇸 · Ho-Ung Yee🇺🇸

    To describe dynamics of bulk and fluctuations near the QCD critical point we develop general relativistic fluctuation formalism for a fluid carrying baryon charge. Feedback of fluctuations modifies hydrodynamic coefficients including bulk viscosity and conductivity and introduces nonlocal and non-instantaneous terms in constitutive equations. We perform necessary ultraviolet (short-distance) renormalization to obtain cutoff independent deterministic equations suitable for numerical implementation. We use the equations to calculate the universal non-analytic small-frequency dependence of transport coefficients due to fluctuations (long-time tails). Focusing on the critical mode we show how this general formalism matches existing Hydro+ description of fluctuations near the QCD critical point and nontrivially extends it inside and outside of the critical region.

    ↳ hep-thcond-mat.stat-mechhep-phnucl-thPRC(2020)·70 citations
  3. 06

    Differential comparison of identified-hadron spectra from high-energy A-B nuclear collisions based on a two-component model of hadron production

    Thomas A. Trainor🇺🇸

    Identified-hadron (PID) spectra from 2.76 TeV Pb-Pb and - collisions are analyzed via a two-component (soft + hard) model (TCM) of hadron production in high-energy nuclear collisions. The PID TCM is adapted with minor changes from a recent analysis of PID hadron spectra from 5 TeV -Pb collisions. Results from LHC data are compared with a PID TCM for 200 GeV Au-Au pion and proton spectra. 2.76 TeV proton spectra exhibit strong inefficiencies above 1 GeV/c estimated by comparing the - spectrum with the corresponding TCM. After inefficiency correction Pb-Pb proton spectra are very similar to Au-Au proton spectra. PID A-A spectra are generally inconsistent with radial flow. Jet-related Pb-Pb and Au-Au spectrum hard components exhibit strong suppression at higher in more-central collisions corresponding to results from spectrum ratio but also, for pions and kaons, exhibit dramatic enhancements below GeV/c that are concealed by . In contrast, enhancements of proton hard components appear only above 1 GeV/c suggesting that the baryon/meson "puzzle" is a jet phenomenon. Modification of spectrum hard components in more-central A-A collisions is consistent with increased gluon splitting during jet formation but with approximate conservation of leading-parton energy within a jet via the lower- enhancements.

    ↳ hep-phnucl-th5 citations
  4. 07

    Testing the origin of the "" with the reaction

    Wei-Hong Liang🇨🇳 · E. Oset🇨🇳

    We study the reactions with and , in the region of invariant masses of MeV. The strong coupling of the resonance to makes the mechanism based on exchange very efficient to produce this resonance observed in the invariant mass distribution. In addition, in all the reactions one observes an associated peak at MeV which comes from the decay mode of the when the is placed off shell at higher invariant masses. We claim this to be the reason for the peak of the distribution seen in the experiments which has been associated to the "" resonance.

    ↳ hep-phhep-exnucl-thEPJC(2020)·4 citations
  5. 08

    The rate of photon production in the quark-gluon plasma from lattice QCD

    Marco Cè🇩🇪 · Tim Harris🇮🇹 · Harvey B. Meyer🇩🇪 · Aman Steinberg🇩🇪 · Arianna Toniato🇩🇪

    We calculate the thermal rate of real-photon production in the quark-gluon plasma at a temperature of MeV using lattice QCD. The calculation is based on the difference between the spatially transverse and longitudinal parts of the polarization tensor, which has the advantage of falling off rapidly at large frequencies. We obtain this linear combination in the time-momentum representation from lattice QCD with two flavors of quarks in the continuum limit with a precision of about two parts per mille. Applying a theoretically motivated fit ansatz for the associated spectral function, we obtain values for the photon rate that are in line with QCD weak-coupling calculations; for photon momenta , our non-perturbative results constrain the rate to be no larger than twice the weak-coupling prediction. We also provide a physics interpretation of the electromagnetic spectral functions valid for all frequencies and momenta.

    ↳ hep-lathep-phnucl-thPRD(2020)·23 citations

Affiliations

first authorsco-authorsvia INSPIRE