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Nuclear Theory·nucl-th

Friday·March 5, 2021

4 papers—2 primary·2 cross-listed

All4Primary2Cross-lists2
  1. 01

    Measurement methods of radial flow in relativistic heavy-ion collisions

    Peng Yang🇨🇳 · Lin Li🇨🇳 · Yu Zhou🇺🇸 · Zhiming Li🇨🇳 · Mingmei Xu🇨🇳 · Yeyin Zhao🇨🇳 · Yuanfang Wu🇨🇳

    Radial flow can be directly extracted from the azimuthal distribution of mean transverse rapidity. We apply the event-plane method and the two-particle correlation method to estimate the anisotropic Fourier coefficient of the azimuthal distribution of mean transverse rapidity. Using the event sample generated by a multiphase transport model with string melting, we show that both methods are effective. For the two-particle correlation method to be reliable, the mean number of particles in an azimuthal bin must be above a certain threshold. Using these two methods, anisotropic radial flow can be estimated in a model-independent way in relativistic heavy-ion collisions.

    nucl-thhep-phnucl-exPRC(2021)·1 citation
  2. 02

    Neutron-neutron scattering length from the He reaction

    Matthias Göbel · Thomas Aumann · Carlos A. Bertulani · Tobias Frederico · Hans-Werner Hammer · Daniel R. Phillips

    We propose a novel method to measure the neutron-neutron scattering length using the He reaction in inverse kinematics at high energies. The method is based on the final state interaction (FSI) between the neutrons after the sudden knockout of the particle. We show that the details of the neutron-neutron relative energy distribution allow for a precise extraction of the -wave scattering length. We present the state-of-the-art in regard to the theory of this distribution. The distribution is calculated in two steps. First, we calculate the ground-state wave function of He as a three-body system. For this purpose we use Halo effective field theory (Halo EFT), which also provides uncertainty estimates for the results. We compare our results at this stage to model calculations done with the computer code FaCE. In a second step we determine the effects of the FSI using the t-matrix. We compare these FSI results to approximate FSI approaches based on standard FSI enhancement factors. While the final distribution is sensitive to the scattering length, it depends only weakly on the effective range. Throughout we emphasize the impact of theoretical uncertainties on the neutron-neutron relative energy distribution, and discuss the extent to which those uncertainties limit the extraction of the neutron-neutron scattering length from the reaction He.

    nucl-thnucl-exPRC(2021)·18 citations
  3. 03

    Neutrino Fast Flavor Conversions in Neutron-star Post-Merger Accretion Disks

    Xinyu Li🇨🇦 · Daniel M. Siegel🇨🇦

    A compact accretion disk may be formed in the merger of two neutron stars or of a neutron star and a stellar-mass black hole. Outflows from such accretion disks have been identified as a major site of rapid neutron-capture (r-process) nucleosynthesis and as the source of 'red' kilonova emission following the first observed neutron-star merger GW170817. We present long-term general-relativistic radiation magnetohydrodynamic simulations of a typical post-merger accretion disk at initial accretion rates of over 400ms post-merger. We include neutrino radiation transport that accounts for effects of neutrino fast flavor conversions dynamically. We find ubiquitous flavor oscillations that result in a significantly more neutron-rich outflow, providing lanthanide and 3rd-peak r-process abundances similar to solar abundances. This provides strong evidence that post-merger accretion disks are a major production site of heavy r-process elements. A similar flavor effect may allow for increased lanthanide production in collapsars. The formalism presented here may also be used in simulations of core-collapse supernovae to explore whether fast conversions strengthen or weaken the explosion.

    ↳ astro-ph.HEastro-ph.SRgr-qchep-ph+1PRL(2021)·132 citations
  4. 04

    Nucleon mass radii and distribution: Holographic QCD, Lattice QCD and GlueX data

    Kiminad A. Mamo🇺🇸 · Ismail Zahed🇺🇸

    We briefly review and expand our recent analysis for all three invariant A,B,D gravitational form factors of the nucleon in holographic QCD. They compare well to the gluonic gravitational form factors recently measured using lattice QCD simulations. The holographic A-term is fixed by the tensor (graviton) Regge trajectory, and the D-term by the difference between the tensor (graviton) and scalar (dilaton) Regge trajectories. The B-term is null in the absence of a tensor coupling to a Dirac fermion in bulk. A first measurement of the tensor form factor A-term is already accessible using the current GlueX data, and therefore the tensor gluonic mass radius, pressure and shear inside the proton, thanks to holography. The holographic A-term and D-term can be expressed exactly in terms of harmonic numbers. The tensor mass radius from the holographic threshold is found to be , in agreement with as extracted from the overall numerical lattice data, and empirical GlueX data. The scalar mass radius is found to be slightly larger .

    ↳ hep-phhep-latnucl-exnucl-thPRD(2021)·85 citations

Affiliations

first authorsco-authorsvia INSPIRE