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Nuclear Theory·nucl-th

Monday·April 20, 2015

16 papers—6 primary·10 cross-listed

All16Primary6Cross-lists10
  1. 01

    Completing the picture of the Roper resonance

    Jorge Segovia🇪🇸 · Bruno El-Bennich🇧🇷 · Eduardo Rojas🇧🇷 · Ian C. Cloet🇺🇸 · Craig D. Roberts🇺🇸 · Shu-Sheng Xu🇨🇳 · Hong-Shi Zong🇨🇳

    We employ a continuum approach to the three valence-quark bound-state problem in relativistic quantum field theory to predict a range of properties of the proton's radial excitation and thereby unify them with those of numerous other hadrons. Our analysis indicates that the nucleon's first radial excitation is the Roper resonance. It consists of a core of three dressed-quarks, which expresses its valence-quark content and whose charge radius is 80% larger than the proton analogue. That core is complemented by a meson cloud, which reduces the observed Roper mass by roughly 20%. The meson cloud materially affects long-wavelength characteristics of the Roper electroproduction amplitudes but the quark core is revealed to probes with .

    nucl-thhep-lathep-phnucl-exPRL(2015)·144 citations
  2. 02

    Influence of statistics on the measured moments of conserved quantities in relativistic heavy ion collisions

    Lizhu Chen🇨🇳 · Zhiming Li🇨🇳 · Xia Zhong🇨🇳 · Yuncun He🇨🇳 · Yuanfang Wu🇨🇳

    We study statistics dependence of the probability distributions and the means of measured moments of conserved quantities, respectively. The required statistics of all interested moments and their products are estimated based on a simple simulation. We also explain why the measured moments are underestimated when the statistics are insufficient.With the statistics at RHIC/BES, the second and third order moments can be reliably obtained based on the method of Centrality bin width correction (CBWC), which can not be applied for the fourth order moments at low energy. With planning statistics at RHIC/BES II, and improved CBWC method, in a finer centrality bin scale should be measurable. This will help us to understand the current observation of energy and centrality dependence of high-order moments.

    nucl-thnucl-exJ.Phys.G(2015)·6 citations
  3. 03

    Theoretical neutron-capture cross sections for r-process nucleosynthesis in the Ca region

    T. Rauscher · W. Böhmer · K.-L. Kratz · W. Balogh · H. Oberhummer

    We calculate neutron capture cross sections for r-process nucleosynthesis in the Ca region, namely for the isotopes S, Ar, Ti, Cr, and Fe. While previously only cross sections resulting from the compound nucleus reaction mechanism (Hauser-Feshbach) have been considered, we recalculate not only that contribution to the cross section but also include direct capture on even-even nuclei. The level schemes, which are of utmost importance in the direct capture calculations, are taken from quasi-particle states obtained with a folded-Yukawa potential and Lipkin-Nogami pairing. Most recent deformation values derived from experimental data on -decay half lives are used where available. Due to the consideration of direct capture, the capture rates are enhanced and the "turning points" in the r-process path are shifted to slightly higher mass numbers. We also discuss the sensitivity of the direct capture cross sections on the assumed deformation.

    nucl-th0 citations
  4. 04

    Quartet excitations and cluster spectra in light nuclei

    J. Cseh · G. Riczu

    The relation of quarteting and clustering in atomic nuclei is discussed based on symmetry-considerations. This connection enables us to predict a complete high-energy cluster spectrum from the description of the low-energy quartet part. As an example the Si nucleus is considered, including its well-established ground-state region, the recently proposed superdeformed band, and the high-lying molecular resonances.

    nucl-thPLB(2016)·21 citations
  5. 05

    Unified treatment of sub-saturation stellar matter at zero and finite temperature

    F. Gulminelli🇫🇷 · Ad. R. Raduta🇷🇴

    The standard variational derivation of stellar matter structure in the Wigner-Seitz approximation is generalized to the finite temperature situation where a wide distribution of different nuclear species can coexist in the same density and proton fraction condition, possibly out of -equilibrium. The same theoretical formalism is shown to describe on one side the single-nucleus approximation (SNA), currently used in most core collapse supernova simulations, and on the other side the nuclear statistical equilibrium (NSE) approach, routinely employed in r- and p-process explosive nucleosynthesis problems. In particular we show that in-medium effects have to be accounted for in NSE to have a theoretical consistency between the zero and finite temperature modeling. The bulk part of these in-medium effects is analytically calculated and shown to be different from a van der Waals excluded volume term. This unified formalism allows controlling quantitatively the deviations from the SNA in the different thermodynamic conditions, as well as having a NSE model which is reliable at any arbitrarily low value of the temperature, with potential applications for neutron star cooling and accretion problems. We present different illustrative results with several mass models and effective interactions, showing the importance of accounting for the nuclear species distribution even at temperatures lower than 1 MeV.

    nucl-thPRC(2015)·177 citations
  6. 06

    Limit Cycles from the Similarity Renormalization Group

    P. Niemann · H.-W. Hammer (TU Darmstadt)

    We investigate renormalization group limit cycles within the similarity renormalization group (SRG) and discuss their signatures in the evolved interaction. A quantitative method to detect limit cycles in the interaction and to extract their period is proposed. Several SRG generators are compared regarding their suitability for this purpose. As a test case, we consider the limit cycle of the inverse square potential.

    nucl-thquant-phFew Body Syst.(2015)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE