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Nuclear Theory·nucl-th

Friday·February 3, 2017

7 papers—6 primary·1 cross-listed

All7Primary6Cross-lists1
  1. 01

    Subthreshold resonances and resonances in the -matrix method for binary reactions and in the Trojan Horse method

    A. M. Mukhamedzhanov · Shubhchintak · C. A. Bertulani

    In this paper we discuss the -matrix approach to treat the subthreshold resonances for the single-level and one channel, and for the single-level and two channel cases. In particular, the expression relating the ANC with the observable reduced width, when the subthreshold bound state is the only channel or coupled with an open channel, which is a resonance, is formulated. Since the ANC plays a very important role in nuclear astrophysics, these relations significantly enhance the power of the derived equations. We present the relationship between the resonance width and the ANC for the general case and consider two limiting cases: wide and narrow resonances. Different equations for the astrophysical S-factors in the -matrix approach are presented. After that we discuss the Trojan Horse Method (THM) formalism. The developed equations are obtained using the surface-integral formalism and the generalized -matrix approach for the three-body resonant reactions. It is shown how the Trojan Horse (TH) double differential cross section can be expressed in terms of the on-the-energy-shell astrophysical S-factor for the binary sub-reaction. Finally, we demonstrate how the THM can be used to calculate the astrophysical S-factor for the neutron generator in low-mass AGB stars. At astrophysically relevant energies this astrophysical S-factor is controlled by the threshold level keV. Here, we reanalyzed recent TH data taking into account more accurately the three-body effects and using both assumptions that the threshold level is a subthreshold bound state or it is a resonance state.

    nucl-thnucl-exPRC(2017)·14 citations
  2. 02

    The and dependence of , quasi-particles and the JET puzzle

    Evan Bianchi🇺🇸 · Jacob Elledge🇺🇸 · Amit Kumar🇺🇸 · Abhijit Majumder🇺🇸 · Guang-You Qin🇺🇸 · Chun Shen🇺🇸

    We present the first attempt to extract the "" dependence of the parton distribution function (PDF) of the quark gluon plasma (QGP). In the absence of knowledge regarding the mass of a QGP constituent, we define the new variable , the nucleonic momentum fraction, which represents the ratio of the momentum of the parton to that of a self-contained section of the plasma that has the mass of a nucleon. Calculations are compared to data for single hadron suppression in terms of the nuclear modification factor and the azimuthal anisotropy parameter , as a function of transverse momentum , centrality and energy of the collision. It is demonstrated that the scale evolution of the QGP-PDF is responsible for the reduction in normalization of the jet transport coefficient , between fits to Relativistic Heavy-Ion Collider (RHIC) and Large Hadron Collider (LHC) data; a puzzle, first discovered by the JET collaboration. Best fits to data are suggestive of the presence of quasi-particles with wide dispersion relations in the QGP.

    nucl-thhep-phnucl-ex33 citations
  3. 03

    Exotic Hadrons from Heavy Ion Collisions

    ExHIC Collaboration: Sungtae Cho🇰🇷 · Tetsuo Hyodo🇯🇵 · Daisuke Jido🇯🇵 · Che Ming Ko🇺🇸 · Su Houng Lee🇰🇷 · Saori Maeda🇯🇵 · Kenta Miyahara🇯🇵 · Kenji Morita🇯🇵 · Marina Nielsen🇧🇷 · Akira Ohnishi🇯🇵 · Takayasu Sekihara🇯🇵 · Taesoo Song🇩🇪 · Shigehiro Yasui🇯🇵 · Koichi Yazaki🇯🇵

    Heavy ion collisions (HIC) at high energies are excellent ways for producing heavy hadrons and composite particles. With upgraded detectors at RHIC and LHC, it has become possible to measure hadrons beyond their ground states. Therefore, HIC provide a new method for studying exotic hadrons that are either hadronic molecular states or compact multiquark systems. Because their structures are related to the fundamental properties of QCD, studying exotic hadrons is currently one of the most active areas of research in hadron physics. Experiments carried out at various accelerator facilities have indicated that some exotic hadrons may have already been produced. The present review is a summary of the current understanding of a selected set of exotic particle candidates that can be potentially measured in HIC. It also includes discussions on the production of exotic hadrons in HIC based on the coalescence and statistical models. A more detailed discussion leads to the conclusion that the yield of a hadron is typically an order of magnitude smaller when it is a compact multiquark state than that of an excited hadronic state with normal quark numbers and/or a molecular configuration. Attention is also given to some of the proposed heavy exotic hadrons that could be produced with sufficient abundance in HIC because of the significant numbers of charm and bottom quarks produced at RHIC and LHC, making it possible to study them in these experiments. Further included in the discussion are the general formalism for the coalescence model that involves resonance particles and its implication on the present estimated yield for resonance production. Finally, a review is given on recent studies to constrain the hadron-hadron interaction through correlation measurements in HIC and their implications on the interpretation and the possible existence of exotic states in hadronic interactions.

    nucl-thhep-phnucl-exPPNP(2017)·201 citations
  4. 04

    Effects of meson-nucleon dynamics in a relativistic approach to medium-mass nuclei

    Elena Litvinova🇺🇸 · Caroline Robin🇺🇸

    Recent developments in the relativistic nuclear field theory (RNFT) are reviewed. Based on the covariant meson-nucleon Lagrangian of quantum hadrodynamics, RNFT connects consistently the high-energy scale of heavy mesons, medium-energy range of pion and the low-energy domain of emergent collective vibrations (phonons) in a parameter-free way. Mesons and phonons build up the effective interaction in various channels, in particular, the phonon-exchange part takes care of the retardation effects, which are of great importance for the fragmentation of single-particle states, spreading of collective giant resonances and soft modes, quenching and beta-decay rates with significant consequences for astrophysics and for the theory of weak processes in nuclei. As examples, the recently discovered impact of isospin dynamics on the nuclear shell structure and the isospin-flip pairing vibrations are discussed.

    nucl-thPoS(2017)·0 citations
  5. 05

    Additive empirical parametrization and microscopic study of the deuteron breakup

    M. Avrigeanu · V. Avrigeanu

    Comparative assessment of the total breakup proton-emission cross sections measured for 56 MeV deuteron interaction with target nuclei from C to Bi, with an empirical parametrization and recently calculated microscopic neutron-removal cross sections has been done at the same time with similar data measured at 15, 25.5, 70, and 80 MeV. Comparable mass dependances of the elastic-breakup (EB) cross sections provided by the empirical parametrization and the microscopic results have been also found at the deuteron energy of 56 MeV, while the assessment of absolute-values variance up to a factor of two has been not possible due to the lack of EB measurements at energies higher than 25.5 MeV. While the similarities represent an additional validation of the microscopic calculations, the cross-section difference should be considered within the objectives of further measurements.

    nucl-thPRC(2017)·18 citations
  6. 06

    Temperature dependence of the symmetry energy and neutron skins in Ni, Sn, and Pb isotopic chains

    A.N. Antonov · D.N. Kadrev · M.K. Gaidarov · P. Sarriguren · E. Moya de Guerra

    The temperature dependence of the symmetry energy for isotopic chains of even-even Ni, Sn, and Pb nuclei is investigated in the framework of the local density approximation (LDA). The Skyrme energy density functional with two Skyrme-class effective interactions, SkM* and SLy4, is used in the calculations. The temperature-dependent proton and neutron densities are calculated through the HFBTHO code that solves the nuclear Skyrme-Hartree-Fock-Bogoliubov problem by using the cylindrical transformed deformed harmonic-oscillator basis. In addition, two other density distributions of Pb, namely the Fermi-type density determined within the extended Thomas-Fermi (TF) method and symmetrized-Fermi local density obtained within the rigorous density functional approach, are used. The kinetic energy densities are calculated either by the HFBTHO code or, for a comparison, by the extended TF method up to second order in temperature (with term). Alternative ways to calculate the symmetry energy coefficient within the LDA are proposed. The results for the thermal evolution of the symmetry energy coefficient in the interval MeV show that its values decrease with temperature. The temperature dependence of the neutron and proton root-mean-square radii and corresponding neutron skin thickness is also investigated, showing that the effect of temperature leads mainly to a substantial increase of the neutron radii and skins, especially in the more neutron-rich nuclei, a feature that may have consequences on astrophysical processes and neutron stars.

    nucl-thPRC(2017)·35 citations

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first authorsco-authorsvia INSPIRE