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Nuclear Theory·nucl-th

Thursday·April 26, 2018

7 papers—3 primary·4 cross-listed

All7Primary3Cross-lists4
  1. 01

    Photons from thermalizing matter in heavy ion collisions

    Vladimir Khachatryan🇺🇸 · Bjoern Schenke🇺🇸 · Mickey Chiu🇺🇸 · Axel Drees🇺🇸 · Thomas K. Hemmick🇺🇸 · Norbert Novitzky🇺🇸

    We investigate the production of direct photons in heavy ion collisions within the modified bottom-up thermalization scenario, which we show to be related to the thermalizing Glasma framework. The dynamics of the parton system up to thermalization/equilibration can be described by two momentum scales, by means of which we express the photon invariant yield excluding the prompt pQCD contribution. We derive an analytic formula, which provides an estimate of photon production from thermalizing matter for a wide range of collision systems and energies. We compare the yield with that measured in the PHENIX Au+Au run04 and the combined run07+run10 data sets at root-s = 200GeV. We also make theory-data comparisons for Pb+Pb at 2760 GeV and d+Au at 200 GeV collision energies. Finally, we make predictions for the direct photon invariant yield from collisions of U+U, Cu+Au, He+Au at 200 GeV and Pb+Pb at 5020 GeV.

    nucl-thNPA(2018)·13 citations
  3. 03

    Exploring the applicability of dissipative fluid dynamics to small systems by comparison to the Boltzmann equation

    K. Gallmeister🇩🇪 · H. Niemi🇩🇪 · C. Greiner🇩🇪 · D. H. Rischke🇩🇪

    [Background] Experimental data from heavy-ion experiments at RHIC-BNL and LHC-CERN are quantitatively described using relativistic fluid dynamics. Even p+A and p+p collisions show signs of collective behavior describable in the same manner. Nevertheless, small system sizes and large gradients strain the limits of applicability of fluid-dynamical methods. [Purpose] The range of applicability of fluid dynamics for the description of the collective behavior, and in particular of the elliptic flow, of small systems needs to be explored. [Method] Results of relativistic fluid-dynamical simulations are compared with solutions of the Boltzmann equation in a longitudinally boost-invariant picture. As initial condition, several different transverse energy-density profiles for equilibrated matter are investigated. [Results] While there is overall a fair agreement of energy- and particle-density profiles, components of the shear-stress tensor are more sensitive to details of the implementation. The highest sensitivity is exhibited by quantities influenced by properties of the medium at freeze-out. [Conclusions] For some quantities, like the shear-stress tensor, agreement between fluid dynamics and transport theory extends into regions of Knudsen numbers and inverse Reynolds numbers where relativistic fluid dynamics is believed to fail.

    nucl-thhep-phPRC(2018)·22 citations
  4. 04

    Kinetic theory for classical and quantum many-body chaos

    Sašo Grozdanov🇺🇸 · Koenraad Schalm🇳🇱 · Vincenzo Scopelliti🇳🇱

    For perturbative scalar field theories, the late-time-limit of the out-of-time-ordered correlation function that measures (quantum) chaos is shown to be equal to a Boltzmann-type kinetic equation that measures the total gross (instead of net) particle exchange between phase space cells, weighted by a function of energy. This derivation gives a concrete form to numerous attempts to derive chaotic many-body dynamics from ad hoc kinetic equations. A period of exponential growth in the total gross exchange determines the Lyapunov exponent of the chaotic system. Physically, the exponential growth is a front propagating into an unstable state in phase space. As in conventional Boltzmann transport, which follows from the dynamics of the net particle number density exchange, the kernel of this kinetic integral equation is also set by the 2-to-2 scattering rate. This provides a mathematically precise statement of the known fact that in dilute weakly coupled gases transport and scrambling (or ergodicity) are controlled by the same physics.

    ↳ hep-thcond-mat.stat-mechhep-phnlin.CD+1PRE(2019)·42 citations
  5. 05

    Hidden-strange molecular states and the bound state via a QCD van der Waals force

    Jun He🇨🇳 · Hongxia Huang🇨🇳 · Dian-Yong Chen🇨🇳 · Xinmei Zhu🇨🇳

    In this work, we study the hidden-strange molecular states composed of a baryon and a vector meson in a coupled-channel interaction. With the help of the effective Lagrangians which coupling constants are determined by the SU(3) symmetry, the interaction is constructed and inserted into the quasipotential Bethe-Salpeter equation to search for poles in the complex plane, which correspond to molecular states. Two poles are found with a spin parity near the and the thresholds, which can be related to the and the , respectively. No pole near the threshold can be found if direct interaction between a nucleon and meson is neglected according to the OZI rule. After introducing the QCD van der Waals force between a nucleon and meson, a narrow state can be produced near the threshold. Inclusion of the QCD van der Waals force changes the line shape of the invariant mass spectrum in the channel leading to a worse agreement with the present low-precision data. Future experiments at BelleII, JLab, and other facilities will be very helpful to clarify the existence of these possible hidden-strange molecular states.

    ↳ hep-phnucl-exnucl-thPRD(2018)·15 citations
  6. 06

    Sensitivity of Neutrino-Nucleus Interaction Measurements to 2p2h Excitations

    Stephen Dolan🇫🇷 · Ulrich Mosel🇩🇪 · Kai Gallmeister🇩🇪 · Luke Pickering🇺🇸 · Sara Bolognesi🇫🇷

    We calculate the charged-current cross sections obtained at the T2K off-axis near detector for -induced events without pions and any number of protons in the final state using transport theory as encoded in the GiBUU model. In a comparison with recent T2K data the strength of the 2p2h multinucleon correlations is determined. Linking this to the isospin (T) of the initial nuclear state, it is found that T=0 leads to a significantly better fit of the recent cross sections obtained by T2K, thus achieving consistency of the 2p2h multi-nucleon correlation contributions between electron-nucleus and neutrino-nucleus reactions.

    ↳ hep-exhep-phnucl-exnucl-thPRC(2018)·36 citations
  7. 07

    Drag force on heavy diquarks and gauge/string duality

    Oleg Andreev🇷🇺

    We use gauge/string duality to model a doubly heavy diquark in a color antitriplet moving in a thermal plasma at temperatures near the critical. With the assumption that there is no relative motion between the constituents, we calculate the drag force on the diquark. At high enough speed we find that diquark string configurations develop a cusp. In addition, we estimate the spatial string tension at non-zero baryon chemical potential, and also briefly discuss an extension to a triply heavy triquark in a color triplet.

    ↳ hep-phhep-lathep-thnucl-thPRD(2018)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE