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Nuclear Theory·nucl-th

Friday·July 19, 2019

9 papers—6 primary·3 cross-listed

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  1. 01

    Understanding Magic Numbers in Neutron-Rich Nuclei by Tensor Blocking Mechanism

    I. Tanihata · H. Toki · S. Terashima · H. -J. Ong

    A new paradigm for nuclear structure that includes blocking effects of tensor interactions is proposed. All of the recently discovered magic numbers (N=6, 14, 16, 32 and 34) in neutron-rich nuclei can be explained by the blocking effects. A large amount of binding energy is gained by high-momentum correlated pairs of nucleons produced by the tensor interaction. Such tensor correlations strongly depend on the configuration space available for exciting nucleons to 2p-2h states. When additional neutrons occupy a new orbital, the previously available configuration may be lost, resulting in a sudden loss of binding energy otherwise gained by the 2p-2h excitations. Such tensor blocking effects enlarge the energy gaps at all observed new magic numbers. Tensor blocking also explains consistently the observed peculiar configurations of neutron-rich nuclei at the borders of shells.

    nucl-th1 citation
  2. 02

    Search of cluster structure in nuclei via analysis of bremsstrahlung emission

    Sergei P. Maydanyuk (2 and 3)🇺🇦 · Peng-Ming Zhang (1 and 2)🇺🇦 · Li-Ping Zou (2) ((1) School of Physics and Astronomy, Sun Yat-Sen University, Zhuhai, China, (2) Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, 730000, China, (3) Institute for Nuclear Research, National Academy of Sciences of Ukraine, Kiev, 03680, Ukraine)🇨🇳

    We investigate emission of bremsstrahlung photons during scattering of -particles off nuclei. For that, we construct bremsstrahlung model for -nucleus scattering, where a new formalism for coherent and incoherent bremsstrahlung emissions in elastic scattering and mechanisms in inelastic scattering is added. Basing of this approach, we analyze experimental bremsstrahlung cross-sections in the scattering of -particles off the \isotope[59]{Co}, \isotope[116]{Sn}, \isotope[\rm nat]{Ag} and \isotope[197]{Au} nuclei at 50 MeV of -particles beam measured at the Variable Energy Cyclotron Centre, Calcutta. We observe oscillations in the calculated spectra for elastic scattering for each nucleus. But, for \isotope[59]{Co}, \isotope[116]{Sn} and \isotope[\rm nat]{Ag} we obtain good agreement between calculated coherent spectrum with incoherent contribution for elastic scattering with experimental data in the full photon energy region. For heavy nucleus \isotope[197]{Au} we find that (1) Oscillating behavior of the calculated spectrum of coherent emission in elastic scattering is in disagreement with experimental data, (2) Inclusion of incoherent emission improves description of the data, but summarized spectrum is in satisfactory agreement with the experimental data. To understand unknown modification of wave function for scattering, we add new mechanisms of inelastic scattering to calculations and extract information about unknown new amplitude of such mechanisms from experimental data analysis. This amplitude has maxima at some energies, that characterizes existence of states of the most compact structures (clusters) in nucleus-target. We explain origin of oscillations in the bremsstrahlung spectra for elastic scattering (at first time). New information about coherent and incoherent contributions is extracted for studied reactions.

    nucl-thhep-phnucl-ex2 citations
  3. 03

    Exact solutions and attractors of higher-order viscous fluid dynamics for Bjorken flow

    Sunil Jaiswal🇮🇳 · Chandrodoy Chattopadhyay🇺🇸 · Amaresh Jaiswal🇮🇳 · Subrata Pal🇮🇳 · Ulrich Heinz🇺🇸

    We consider causal higher order theories of relativistic viscous hydrodynamics in the limit of one-dimensional boost-invariant expansion and study the associated dynamical attractor. We obtain evolution equations for the inverse Reynolds number as a function of Knudsen number. The solutions of these equations exhibit attractor behavior which we analyze in terms of Lyapunov exponents using several different techniques. We compare the attractors of the second-order Müller-Israel-Stewart (MIS), transient DNMR, and third-order theories with the exact solution of the Boltzmann equation in the relaxation-time approximation. It is shown that for Bjorken flow the third-order theory provides a better approximation to the exact kinetic theory attractor than both MIS and DNMR theories. For three different choices of the time dependence of the shear relaxation rate we find analytical solutions for the energy density and shear stress and use these to study the attractors analytically. By studying these analytical solutions at both small and large Knudsen numbers we characterize and uniquely determine the attractors and Lyapunov exponents. While for small Knudsen numbers the approach to the attractor is exponential, strong power-law decay of deviations from the attractor and rapid loss of initial state memory is found even for large Knudsen numbers. Implications for the applicability of hydrodynamics in far-off-equilibrium situations are discussed.

    nucl-thhep-thPRC(2019)·82 citations
  4. 04

    New thermonuclear reaction rate equations for radiative neutron capture

    Vinay Singh · Joydev Lahiri · D. N. Basu

    The radiative neutron capture reaction rates have been studied at very low energies which are of interest for nuclear astrophysics. The rates for many of these reactions have remained independent of temperature so far. The temperature dependence of the thermonuclear reaction rates have been explored within the statistical model. Apart from the compound nuclear contribution, the pre-equilibrium as well as the direct effects have been taken into account. The corresponding Maxwellian-averaged thermonuclear reaction rates of relevance in astrophysical plasmas at temperatures in the range from 10 K to 10 K have been calculated. Analytical expression as a function of has been provided for Li(n,)Li by fitting the calculated reaction rate.

    nucl-thActa Phys.Polon.B(2021)·2 citations
  5. 05

    Searching for the QCD critical point with net-proton number fluctuations

    Michał Szymański🇵🇱 · Marcus Bluhm🇵🇱 · Krzysztof Redlich🇵🇱 · Chihiro Sasaki🇵🇱

    Net-proton number fluctuations can be measured experimentally and hence provide a source of important information about the matter created during relativistic heavy ion collisions. Particularly, they may give us clues about the conjectured QCD critical point. In this work the beam-energy dependence of ratios of the first four cumulants of the net-proton number is discussed. These quantities are calculated using a phenomenologically motivated model in which critical mode fluctuations couple to protons and anti-protons. Our model qualitatively captures both the monotonic behavior of the lowest-order ratio as well as the non-monotonic behavior of higher-order ratios, as seen in the experimental data from the STAR Collaboration. We also discuss the dependence of our results on the coupling strength and the location of the critical point.

    nucl-thUkr.J.Phys.(2019)·0 citations
  6. 06

    Nuclear electric dipole moment in the cluster model with a triton: Li and B

    Nodoka Yamanaka🇯🇵 · Taiichi Yamada🇯🇵 · Yasuro Funaki🇯🇵

    We calculate the electric dipole moment (EDM) of the nuclei Li and B in the cluster model with (He) and triton (H) clusters as degrees of freedom. The Li and B nuclei are treated in the two- and three-body problem, respectively, using the Gaussian expansion method, assuming the one-meson exchange P, CP-odd nuclear forces. We find that Li and B have larger sensitivity to the CP violation than the deuteron. It is also suggested that the EDMs of Li and B, together with those of Li, Be and the excited state of C, obey an approximate counting rule accounting for the EDM of the cluster and the polarization. We show their sensitivity on the hadronic level CP violation in terms of the chiral effective field theory, and discuss their role in probing new physics beyond the standard model.

    nucl-thhep-exhep-phnucl-exPRC(2019)·20 citations

Affiliations

first authorsco-authorsvia INSPIRE