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Nuclear Theory·nucl-th

Monday·March 16, 2020

12 papers—6 primary·6 cross-listed

All12Primary6Cross-lists6
  1. 07

    Collins-Soper Kernel for TMD Evolution from Lattice QCD

    Phiala Shanahan🇺🇸 · Michael Wagman🇺🇸 · Yong Zhao🇺🇸

    The Collins-Soper kernel relates transverse momentum-dependent parton distribution functions (TMDPDFs) at different energy scales. For small parton transverse momentum , this kernel is non-perturbative and can only be determined with controlled uncertainties through experiment or first-principles calculations. This work presents the first exploratory determination of the Collins-Soper kernel using the lattice formulation of Quantum Chromodynamics. In a quenched calculation, the kernel is determined at scales in the range 250 MeV GeV, and an analysis of the remaining systematic uncertainties is undertaken.

    ↳ hep-lathep-phnucl-thPRD(2020)·137 citations
  2. 08

    Meson-baryon scattering in resummed baryon chiral perturbation theory using time-ordered perturbation theory

    X.-L. Ren🇩🇪 · E. Epelbaum🇩🇪 · J. Gegelia🇩🇪 · Ulf-G. Meißner🇩🇪

    Integral equations for meson-baryon scattering amplitudes are obtained by utilizing time-ordered perturbation theory for a manifestly Lorentz-invariant formulation of baryon chiral perturbation theory. Effective potentials are defined as sums of two-particle irreducible contributions of time-ordered diagrams and the scattering amplitudes are obtained as solutions of integral equations. Ultraviolet renormalizability is achieved by solving integral equations for the leading order amplitude and including higher order corrections perturbatively. As an application of the developed formalism, pion-nucleon scattering is considered.

    ↳ hep-phnucl-thEPJC(2020)·8 citations
  3. 09

    Momentum Anisotropy of Leptons from Two Photon Processes in Heavy Ion Collisions

    Bo-Wen Xiao🇨🇳 · Feng Yuan🇺🇸 · Jian Zhou🇨🇳

    We investigate the azimuthal angular correlation between the lepton transverse momentum and the impact parameter in non-central heavy-ion collisions, where the leptons are produced through two-photon scattering. Among the Fourier harmonic coefficients, a significant asymmetry is found for the typical kinematics at RHIC and LHC with a mild dependence on the , whereas is power suppressed by the lepton mass over . This unique prediction, if confirmed from the experiments, shall provide crucial information on the production mechanism for the dilepton in two-photon processes.

    ↳ hep-phhep-exnucl-exnucl-thPRL(2020)·37 citations
  4. 10

    Charge radius of the short-lived Ni and correlation with the dipole polarizability

    S. Kaufmann🇩🇪 · J. Simonis🇩🇪 · S. Bacca🇩🇪 · J. Billowes🇬🇧 · M. L. Bissell🇬🇧 · K. Blaum🇩🇪 · B. Cheal🇬🇧 · R. F. Garcia Ruiz🇬🇧 · W. Gins🇧🇪 · C. Gorges🇩🇪 · G. Hagen🇺🇸 · H. Heylen🇩🇪 and 17 other authors

    We present the first laser spectroscopic measurement of the neutron-rich nucleus Ni at the \mbox{} subshell closure and extract its nuclear charge radius. Since this is the only short-lived isotope for which the dipole polarizability has been measured, the combination of these observables provides a benchmark for nuclear structure theory. We compare them to novel coupled-cluster calculations based on different chiral two- and three-nucleon interactions, for which a strong correlation between the charge radius and dipole polarizability is observed, similar to the stable nucleus Ca. Three-particle--three-hole correlations in coupled-cluster theory substantially improve the description of the experimental data, which allows to constrain the neutron radius and neutron skin of Ni.

    ↳ nucl-exnucl-thPRL(2020)·48 citations
  5. 11

    Spallation of r-Process Nuclei Ejected from a Neutron Star Merger

    Xilu Wang · Brian D. Fields · Matthew Mumpower · Trevor Sprouse · Rebecca Surman · Nicole Vassh

    Neutron star mergers (NSMs) are rapid neutron capture (r-process) nucleosynthesis sites, which eject materials at high velocities, from 0.1c to as high as 0.6c. Thus the r-process nuclei ejected from a NSM event are sufficiently energetic to initiate spallation reactions with the interstellar medium (ISM) particles. With a thick-target model for the propagation of high-speed heavy nuclei in the ISM, we find that spallation reactions may shift the r-process abundance patterns towards solar data, particularly around the low-mass edges of the r-process peaks where neighboring nuclei have very different abundances. The spallation effects depend both on the astrophysical conditions of the r-process nuclei and nuclear physics inputs for the nucleosynthesis calculations and the propagation process. This work extends that of [Wang et al.(2019)] by focusing on the influence of nuclear physics variations on spallation effects.

    ↳ astro-ph.HEnucl-thJ.Phys.Conf.Ser.(2020)·0 citations
  6. 12

    Semiclassical Approximation meets Keldysh-Schwinger diagrammatic technique: Scalar

    A.A. Radovskaya🇷🇺 · A.G. Semenov🇷🇺

    We study the evolution of the non-equilibrium quantum fields from a highly excited initial state in two approaches: the standard Keldysh-Schwinger diagram technique and the semiclassical expansion. We demonstrate explicitly that these two approaches coincide if the coupling constant and the Plank constant are small simultaneously. Also, we discuss loop diagrams of the perturbative approach, which are summed up by the leading order term of the semiclassical expansion. As an example, we consider shear viscosity for the scalar field theory at the leading semiclassical order. We introduce the new technique that unifies both semiclassical and diagrammatic approaches and open the possibility to perform the resummation of the semiclassical contributions.

    ↳ hep-phcond-mat.stat-mechhep-thnucl-thEPJC(2021)·23 citations

Affiliations

first authorsco-authorsvia INSPIRE