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Nuclear Theory·nucl-th

Wednesday·December 18, 2019

6 papers—3 primary·3 cross-listed

All6Primary3Cross-lists3
  1. 01

    [Submitted on 17 Dec 2019]

    Unified model of nucleon elastic form factors and implications for neutrino-oscillation experiments

    Xilin Zhang🇺🇸 · T. J. Hobbs🇺🇸 · Gerald A. Miller🇺🇸

    Precise knowledge of the nucleon's axial-current form factors is crucial for modeling GeV-scale neutrino-nucleus interactions. Unfortunately, the axial form factor remains insufficiently constrained to meet the precision requirements of upcoming long-baseline neutrino-oscillation experiments. This work studies the nucleon's axial and vector form factors using the light-front approach to build a quark-diquark model of the nucleon with an explicit pion cloud. The light-front wave functions in both the quark and pion-baryon Fock spaces are first calibrated to existing experimental information on the nucleon's electromagnetic form factors, and then used to predict the axial form factor. The resulting squared charge radius of the axial pseudo-vector form factor is predicted to be , where the small error accounts for the model's parametric uncertainty. We use our form factor results to explore the (quasi-)elastic scattering of neutrinos by (nuclei)nucleons, with the result that the the widely-implemented dipole ansatz is an inadequate approximation of the full form factor for modeling both processes. The approximation leads to a over-estimation of the total cross section, depending on the (anti)neutrino energy. We project over-estimations of similar size in the flux-averaged cross sections for the upcoming DUNE long-baseline neutrino-oscillation experiment.

    Comments:
    24 pages, 13 figures, 11 tables; include more discussion on pion-nucleon coupling; to be published in Phys.Rev.D
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    1912.07797 [pdf]
    PRD(2020)·9 citations
  2. 02

    [Submitted on 17 Dec 2019]

    Global Polarization Effect in the Extremely Rapidly Rotating QGP in HIC

    Zuo-Tang Liang🇨🇳 · Michael Annan Lisa🇺🇸 · Xin-Nian Wang🇨🇳

    This is prepared for a featured article in Nuclear Physics News. Recently, the global polarization of \Lambda and \bar{\Lambda} hyperons in heavy-ion collisions (HIC) has been observed by the STAR Collaboration at the Relativistic Heavy Ion Collider in Brookhaven National Laboratory. The discovery confirms the theoretical prediction made more than ten years ago and indicates that the quark gluon plasma (QGP) produced in HIC possesses a vorticity as high as 10^21s^-1, much higher than any other fluid observed in nature. This opens a new window to study properties of QGP and a new direction in high energy heavy ion physics. This featured article is aimed to report the basic idea, current status and outlook.

    Comments:
    4 pages, 11 figures, to appear in Nuclear Physics News
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1912.07822 [pdf]
    Nucl.Phys.News(2020)·22 citations
  3. 03

    [Submitted on 16 Dec 2019]

    A new state of dense matter in neutron stars with nucleon structure

    Vikram Soni🇮🇳

    The existence of stars with a large mass of 2 solar masses means that the equation of state is stiff enough to provide high enough pressure at large central densities. Previous work shows that such a stiff equation of state is possible if the ground state has nucleons as its constituents. We find this to be so in a chiral soliton ( skyrmion ) model for a composite nucleon which has bound state quarks. The strong binding of the quarks in this composite nucleon is plausibly the origin of the nucleon-nucleon hard core. In this model we find a new state of superdense matter at high density which is a 'topological'cubic crystal of overlapping composite nucleons that are solitons with relativistic quark bound states. The quarks are frozen in a filled band of a unique state, which not an eigenstate of spin or isospin but an eigenstate of spin plus isospin, . In this alternative model we find that all neutron stars have no regular `free'quark matter. Neutron stars whose central density crosses a threshold baryon density of approximately, , will become unstable and go through a decompression (sudden) density discontinuity to conventional quark matter. Sequentially, this contraction of the core of the star will soften the equation of state release a large amount of gravitational potential energy which can give rise to a shock wave and matter ejection. Since the merger of two neutron stars gives a compact state whose mass is larger than the allowed maximum mass, this will be followed by a jet and a short gamma ray burst while transiting into a black hole.

    Comments:
    10 pages, 5 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    1912.08096 [pdf]
    1 citation

Affiliations

first authorsco-authorsvia INSPIRE