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Nuclear Theory·nucl-th

Monday·April 30, 2018

6 papers—3 primary·3 cross-listed

All6Primary3Cross-lists3
  1. 04

    [Submitted on 26 Apr 2018] (cross-list from hep-ph)

    Searching for the QCD critical point via the rapidity dependence of cumulants

    Jasmine Brewer🇺🇸 · Swagato Mukherjee🇺🇸 · Krishna Rajagopal🇺🇸 · Yi Yin🇺🇸

    The search for a possible critical point in the QCD phase diagram is ongoing in heavy ion collision experiments at RHIC which scan the phase diagram by scanning the beam energy; a coming upgrade will increase the luminosity and extend the rapidity acceptance of the STAR detector. In fireballs produced in RHIC collisions, the baryon density depends on rapidity. By employing Ising universality together with a phenomenologically motivated freezeout prescription, we show that the resulting rapidity dependence of cumulant observables sensitive to critical fluctuations is distinctive. The dependence of the kurtosis (of the event-by-event distribution of the number of protons) on rapidity near mid-rapidity will change qualitatively if a critical point is passed in the scan. Hence, measuring the rapidity dependence of cumulant observables can enhance the prospect of discovering a critical point, in particular if it lies between two energies in the beam energy scan.

    Comments:
    6 pages, 2 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1804.10215 [pdf]
    PRC(2018)·56 citations
  2. 05

    [Submitted on 26 Apr 2018] (cross-list from cond-mat.quant-gas)

    Polarized fermions in one dimension: density and polarization from complex Langevin calculations, perturbation theory, and the virial expansion

    Andrew C. Loheac🇺🇸 · Jens Braun🇩🇪 · Joaquín E. Drut🇺🇸

    We calculate the finite-temperature density and polarization equations of state of one-dimensional fermions with a zero-range interaction, considering both attractive and repulsive regimes. In the path-integral formulation of the grand-canonical ensemble, a finite chemical potential asymmetry makes these systems intractable for standard Monte Carlo approaches due to the sign problem. Although the latter can be removed in one spatial dimension, we consider the one-dimensional situation in the present work to provide an efficient test for studies of the higher-dimensional counterparts. To overcome the sign problem, we use the complex Langevin approach, which we compare here with other approaches: imaginary-polarization studies, third-order perturbation theory, and the third-order virial expansion. We find very good qualitative and quantitative agreement across all methods in the regimes studied, which supports their validity.

    Comments:
    9 pages, 6 figures
    Subjects:
    Quantum Gases (cond-mat.quant-gas); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
    arXiv:
    1804.10257 [pdf]
    PRD(2018)·17 citations
  3. 06

    [Submitted on 26 Apr 2018] (cross-list from hep-ex)

    A model of antineutron annihilation in experimental searches for neutron-antineutron transformations

    Elena S. Golubeva🇷🇺 · Joshua L. Barrow🇺🇸 · Charles G. Ladd🇺🇸

    Searches for baryon number violation, including searches for proton decay and neutron-antineutron transformation, are expected to play an important role in the evolution of our understanding of beyond Standard Model physics. The neutron-antineutron transformation is a key prediction of certain popular theories of baryogenesis, and the experiments such as the Deep Underground Neutrino Experiment and the European Spallation Source plan to search for this process with bound- and free-neutron systems. Accurate simulation of this process in Monte Carlo will be important for the proper reconstruction and separation of these rare events from background. This article presents developments towards accurate simulation of the annihilation process for use in a cold, free neutron beam for neutron-antineutron searches from antineutron-carbon annihilation, as carbon-12 is the target of choice for the European Spallation Source's NNBar Collaboration. Initial efforts are also made in this paper to perform analogous studies for intra-nuclear transformation searches in argon-40 nuclei, although this latter work will be properly addressed in our next publication.

    Comments:
    24 pages, 13 figures, 5 tables, 54 references, European Spallation Source NNbar Collaboration signal simulation article
    Subjects:
    High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
    arXiv:
    1804.10270 [pdf]
    PRD(2019)·37 citations

Affiliations

first authorsco-authorsvia INSPIRE