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Nuclear Theory·nucl-th

Thursday·April 9, 2015

3 papers—1 primary·2 cross-listed

All3Primary1Cross-lists2
  1. 01

    The nuclear symmetry energy and other isovector observables from the point of view of nuclear structure

    G. Colo' · X. Roca-Maza (University of Milano and INFN, Milano, Italy) · N. Paar (University of Zagreb, Croatia)

    In this contribution, we review some works related with the extraction of the symmetry energy parameters from isovector nuclear excitations, like the giant resonances. Then, we move to the general issue of how to assess whether correlations between a parameter of the nuclear equation of state and a nuclear observable are robust or not. To this aim, we introduce the covariance analysis and we discuss some counter-intuitive, yet enlightening, results from it.

    nucl-thActa Phys.Polon.B(2015)·3 citations
  2. 02

    Dilepton and photon production in the presence of a nontrivial Polyakov loop

    Yoshimasa Hidaka🇯🇵 · Shu Lin🇺🇸 · Robert D. Pisarski🇺🇸 · Daisuke Satow🇮🇹

    We calculate the production of dileptons and photons in the presence of a nontrivial Polyakov loop in QCD. This is applicable to the semi-Quark Gluon Plasma (QGP), at temperatures above but near the critical temperature for deconfinement. The Polyakov loop is small in the semi-QGP, and near unity in the perturbative QGP. Working to leading order in the coupling constant of QCD, we find that there is a mild enhancement, ~ 20%, for dilepton production in the semi-QGP over that in the perturbative QGP. In contrast, we find that photon production is strongly suppressed in the semi-QGP, by about an order of magnitude, relative to the perturbative QGP. In the perturbative QGP photon production contains contributions from 2->2 scattering and collinear emission with the Landau- Pomeranchuk-Migdal (LPM) effect. In the semi-QGP we show that the two contributions are modified differently. The rate for 2->2 scattering is suppressed by a factor which depends upon the Polyakov loop. In contrast, in an SU(N) gauge theory the collinear rate is suppressed by 1/N, so that the LPM effect vanishes at infinite N. To leading order in the semi-QGP at large N, we compute the rate from 2->2 scattering to the leading logarithmic order and the collinear rate to leading order.

    ↳ hep-phnucl-thJHEP(2015)·52 citations
  3. 03

    Constraining scalar dark matter with Big Bang nucleosynthesis and atomic spectroscopy

    Y. V. Stadnik🇦🇺 · V. V. Flambaum🇦🇺

    Scalar dark matter can interact with Standard Model (SM) particles, altering the fundamental constants of Nature in the process. Changes in the fundamental constants during and prior to Big Bang nucleosynthesis (BBN) produce changes in the primordial abundances of the light elements. By comparing the measured and calculated (within the SM) primordial abundance of He, which is predominantly determined by the ratio of the neutron-proton mass difference to freeze-out temperature at the time of weak interaction freeze-out prior to BBN, we are able to derive stringent constraints on the mass of a scalar dark matter particle together with its interactions with the photon, light quarks and massive vector bosons via quadratic couplings in , as well as its interactions with massive vector bosons via linear couplings in . We also derive a stringent constraint on the quadratic interaction of with the photon from recent atomic dysprosium spectroscopy measurements.

    ↳ astro-ph.COhep-phhep-thnucl-th+111 citations

Affiliations

first authorsco-authorsvia INSPIRE