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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
  4. 04

    [Submitted on 17 Dec 2019] (cross-list from nucl-ex)

    Shell evolution of isotones towards Ca: First spectroscopy of Ti

    M. L. Cortés🇯🇵 · W. Rodriguez🇨🇴 · P. Doornenbal🇯🇵 · A. Obertelli🇫🇷 · J. D. Holt🇨🇦 · S. M. Lenzi🇮🇹 · J. Menéndez🇯🇵 · F. Nowacki🇫🇷 · K. Ogata🇯🇵 · A. Poves🇪🇸 · T. R. Rodríguez🇪🇸 · A. Schwenk🇩🇪 and 72 other authors

    Excited states in the isotone Ti were populated via the VTi reaction at 200~MeV/u at the Radioactive Isotope Beam Factory and studied using -ray spectroscopy. The energies of the and transitions, observed here for the first time, indicate a deformed Ti ground state. These energies are increased compared to the neighboring Cr and Fe isotones, suggesting a small decrease of quadrupole collectivity. The present measurement is well reproduced by large-scale shell-model calculations based on effective interactions, while ab initio and beyond mean-field calculations do not yet reproduce our findings. The shell-model calculations for Ti show a dominant configuration with four neutrons excited across the gap. Likewise, they indicate that the island of inversion extends down to , disfavoring a possible doubly magic character of the elusive Ca.

    Subjects:
    Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1912.07887 [pdf]
    PLB(2020)·48 citations
  5. 05

    [Submitted on 17 Dec 2019] (cross-list from hep-ph)

    An Effective Theory of Quarkonia in QCD Matter

    Yiannis Makris🇮🇹 · Ivan Vitev🇺🇸

    The problem of quarkonium production in heavy ion collisions presents a set of unique theoretical challenges -- from the relevant production mechanism of and to the relative significance of distinct cold and hot nuclear matter effects in the observed attenuation of quarkonia. Inthese proceedings we summarize recent work on the generalization of non-relativistic Quantum Chromodynamics (NRQCD) to include off-shell gluon (Glauber/Coulomb) interactions in strongly interacting matter. This new effective theory provides for the first time a universal microscopic description of the in-medium interaction of heavy quarkonia, consistently applicable to a range of phases such as cold nuclear matter, dense hadron gas, and quark-gluon plasma. It is an important step forward in understanding the common trends in proton-nucleus and nucleus-nucleus data on quarkonium suppression. We derive explicitly the leading and sub-leading interaction terms in the Lagrangian and show the connection of the leading result to existing phenomenology.

    Comments:
    Proceedings of Quark Matter 2019, 4 pages, 2 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1912.08008 [pdf]
    NPA(2021)·6 citations
  6. 06

    [Submitted on 17 Dec 2019] (cross-list from hep-ph)

    Probing the Sivers function with an unpolarized target: GTMD distributions and the Odderons

    Renaud Boussarie🇺🇸 · Yoshitaka Hatta🇺🇸 · Lech Szymanowski🇵🇱 · Samuel Wallon🇫🇷

    It is commonly believed that the Sivers function has uniquely to do with processes involving a transversely polarized nucleon. In this paper we show that it is not necessarily the case. We demonstrate that exclusive pion production in polarized electron-proton scattering in the forward region is a direct probe of the gluon Sivers function due to its connection to the QCD Odderon.

    Comments:
    6 pages, 1 figure
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1912.08182 [pdf]
    PRL(2020)·48 citations

Affiliations

first authorsco-authorsvia INSPIRE