Nuclear Theory·nucl-th

Friday·July 19, 2019

9 papers—6 primary·3 cross-listed

01
[Submitted on 18 Jul 2019]
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.
Comments:
8 pages, 2 figures, 1 table
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1907.07902 [pdf]
1 citation
02
[Submitted on 18 Jul 2019]
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 $α$ -particles off nuclei. For that, we construct bremsstrahlung model for $α$ -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 $α$ -particles off the \isotope[59]{Co}, \isotope[116]{Sn}, \isotope[\rm nat]{Ag} and \isotope[197]{Au} nuclei at 50 MeV of $α$ -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.
Comments:
32 pages, 9 captured figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1907.07954 [pdf]
2 citations
03
[Submitted on 18 Jul 2019]
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.
Comments:
16 pages, 6 figures. Final version as appeared in Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Theory (hep-th)
arXiv:
1907.07965 [pdf]
PRC(2019)·82 citations
04
[Submitted on 18 Jul 2019]
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 $^{6}$ K to 10 $^{10}$ K have been calculated. Analytical expression as a function of $T_{9}$ has been provided for $^{6}$ Li(n, $γ$ ) $^{7}$ Li by fitting the calculated reaction rate.
Comments:
5 pages including 1 table and 1 figure
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1907.08054 [pdf]
Acta Phys.Polon.B(2021)·2 citations
05
[Submitted on 18 Jul 2019]
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.
Comments:
Proceedings of New Trends in High-Energy Physics conference, Odessa, Ukraine, May 12-18, 2019. 6 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1907.08056 [pdf]
Ukr.J.Phys.(2019)·0 citations
06
[Submitted on 18 Jul 2019]
Nuclear electric dipole moment in the cluster model with a triton: $^{7}$ Li and $^{11}$ B
Nodoka Yamanaka🇯🇵 · Taiichi Yamada🇯🇵 · Yasuro Funaki🇯🇵
We calculate the electric dipole moment (EDM) of the nuclei $^{7}$ Li and $^{11}$ B in the cluster model with $α$ ( $^{4}$ He) and triton ( $^{3}$ H) clusters as degrees of freedom. The $^{7}$ Li and $^{11}$ 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 $^{7}$ Li and $^{11}$ B have larger sensitivity to the CP violation than the deuteron. It is also suggested that the EDMs of $^{7}$ Li and $^{11}$ B, together with those of $^{6}$ Li, $^{9}$ Be and the $1/ 2_{1}^{+}$ excited state of $^{13}$ C, obey an approximate counting rule accounting for the EDM of the cluster and the $α - N$ 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.
Comments:
12 pages, 2 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1907.08091 [pdf]
PRC(2019)·20 citations
07
[Submitted on 18 Jul 2019] (cross-list from hep-ph)
Reduced uncertainty of the axial $γ Z$ -box correction to the proton's weak charge
Jens Erler🇩🇪 · Mikhail Gorchtein🇩🇪 · Oleksandr Koshchii🇩🇪 · Chien-Yeah Seng🇩🇪 · Hubert Spiesberger🇩🇪
We present the fully up-to-date calculation of the $γ Z$ -box correction which needs to be taken into account to determine the weak mixing angle at low energies from parity-violating electron proton scattering. We make use of neutrino and antineutrino inclusive scattering data to predict the parity-violating structure function $F_{3}^{γ Z}$ by isospin symmetry. Our new analysis confirms previous results for the axial contribution to the $γ Z$ -box graph, and reduces the uncertainty by a factor of~2. In addition, we note that the presence of parity-violating photon-hadron interactions induces an additional contribution via $F_{3}^{γ γ}$ . Using experimental and theoretical constraints on the nucleon anapole moment we are able to estimate the uncertainty associated with this contribution. We point out that future measurements are expected to significantly reduce this latter uncertainty.
Comments:
Version to appear in Phys.Rev.D
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1907.07928 [pdf]
PRD(2019)·13 citations
08
[Submitted on 18 Jul 2019] (cross-list from hep-ph)
What attracts to attractors?
Aleksi Kurkela🇨🇭 · Wilke van der Schee🇨🇭 · Urs Achim Wiedemann🇨🇭 · Bin Wu🇨🇭
Whether, how, and to what extent solutions of Bjorken-expanding systems become insensitive to aspects of their initial conditions is of importance for heavy-ion collisions. Here we study 1+1D and phenomenologically relevant boost-invariant 3+1D systems in which initial conditions approach a universal attractor solution. In Israel-Stewart theory (IS) and kinetic theory where the universal attractor extends to arbitrarily early times, we show that all initial conditions approach the attractor at early times by a power-law while their approach is exponential at late times. In these theories, the physical mechanisms of hydrodynamization operational at late times do not drive the approach to the attractor at early times, and the early-time attractor is reached prior to hydrodynamization. In marked contrast, the attractor in strongly coupled systems is realized concurrent with hydrodynamization. This qualitative difference may offer a basis for discriminating weakly and strongly coupled scenarios of heavy-ion collisions.
Comments:
12 pdf figures, revised version includes analysis of AdS/CFT attractor
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1907.08101 [pdf]
PRL(2020)·147 citations
09
[Submitted on 18 Jul 2019] (cross-list from hep-ph)
Strangeness neutrality and the QCD phase diagram
Fabian Rennecke🇺🇸 · Wei-jie Fu🇨🇳 · Jan M. Pawlowski🇩🇪
Since the incident nuclei in heavy-ion collisions do not carry strangeness, the global net strangeness of the detected hadrons has to vanish. We show that there is an intimate relation between strangeness neutrality and baryon-strangeness correlations. In the context of heavy-ion collisions, the former is a consequence of quark number conservation of the strong interactions while the latter are sensitive probes of the character of QCD matter. We investigate the sensitivity of baryon-strangeness correlations on the freeze-out conditions of heavy-ion collisions by studying their dependence on temperature, baryon- and strangeness chemical potential. The impact of strangeness neutrality on the QCD equation of state at finite chemical potentials will also be discussed. We model the low-energy sector of QCD by an effective Polyakov loop enhanced quark-meson model with 2+1 dynamical quark flavors and use the functional renormalization group to account for the non-perturbative quantum fluctuations of hadrons.
Comments:
15 pages, 6 Figures; Contribution to the proceedings of the CPOD2018 conference
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1907.08179 [pdf]
PoS(2019)·9 citations

Affiliations

first authorsco-authorsvia INSPIRE