Nuclear Theory·nucl-th

Thursday·September 30, 2021

8 papers—3 primary·5 cross-listed

01
[Submitted on 28 Sept 2021]
Systematical studies of the E1 photon strength functions combining Skyrme-HFB+QRPA model and experimental giant dipole resonance properties
Y. Xu🇷🇴 · S. Goriely🇧🇪 · E. Khan🇫🇷
Valuable theoretical predictions of nuclear dipole excitations in the whole nuclear chart are of great interest for different applications, including in particular nuclear astrophysics. We present here the systematic study of the electric dipole (E1) photon strength functions (PSFs) combining the microscopic Hartree-Fock-Bogoliubov plus Quasiparticle Random Phase Approximation (HFB+QRPA) model and the parametrizations constrained by the available experimental giant dipole resonance (GDR) data. For about 10000 nuclei with 8<Z<124 lying between the proton and the neutron drip-lines on nuclear chart, the particle-hole strength distributions are computed using the HFB+QRPA model under the assumption of spherical symmetry and making use of the BSk27 Skyrme effective interaction derived from the most accurate HFB mass model (HFB-27) so far achieved. Large-scale calculations of the BSk27+QRPA E1 PSFs are performed in the framework of a specific folding procedure, in which three phenomenological improvements are considered. First, two interference factors are introduced and adjusted to reproduce at best the available experimental GDR data. Second, an empirical expression accounting for the deformation effect is applied to describe the peak splitting of the strength function. Third, the width of the strength function is corrected by a temperature-dependent term, which effectively increases the de-excitation photon strength function at low-energy. The E1 PSFs as well as the extracted GDR peaks and widths are compared with available experimental data. A relatively good agreement with data indicates the reliability of the calculations. Eventually, the astrophysical (n,g) rates for all the 10000 nuclei with 8<Z<124 are estimated using the present E1 PSFs. The resulting reaction rates are compared with previous BSk7+QRPA results and Gogny-HFB+QRPA predictions based on the D1M interaction.
Comments:
16 pages, 14 figures, to be published on Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex)
arXiv:
2109.13968 [pdf]
PRC(2021)·18 citations
02
[Submitted on 28 Sept 2021]
Gaussian process error modeling for chiral effective-field-theory calculations of $n p \leftrightarrow d γ$ at low energies
Bijaya Acharya🇩🇪 · Sonia Bacca🇩🇪
We calculate the energy-dependent cross section of the $n p \leftrightarrow d γ$ process in chiral effective field theory and apply state-of-the-art tools for quantification of theory uncertainty. We focus on the low-energy regime, where the magnetic dipole and the electric dipole transitions cross over, including the range relevant for big-bang nucleosynthesis. Working with the leading one- and two-body electromagnetic currents, we study the order-by-order convergence of this observable in the chiral expansion of the nuclear potential. We find that the Gaussian process error model describes the observed convergence very well, allowing us to present Bayesian credible intervals for the truncation error with correlations between the cross sections at different energies taken into account. We obtain a 1 $σ$ estimate of about 0.2\% for the uncertainty from the truncation of the nuclear potential. This is an important step towards calculations with statistically interpretable uncertainties for astrophysical reactions involving light nuclei.
Subjects:
Nuclear Theory (nucl-th); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
arXiv:
2109.13972 [pdf]
PLB(2022)·22 citations
03
[Submitted on 29 Sept 2021]
The sixth order cumulant of net-proton number in Binomial distribution at $s_{N N} =$ 200 GeV
Li-Zhu Chen🇨🇳 · Ye-Yin Zhao🇨🇳 · Jin Wu🇨🇳 · Zhi-Ming Li🇨🇳 · Yuan-Fang Wu🇨🇳
It is proposed that ratios of the sixth order to the second order cumulant ( $C_{6} / C_{2}$ ) of conserved quantities are sensitive to the chiral crossover transition. Recently, the negative $C_{6} / C_{2}$ was obtained both in theoretical Lattice QCD and experiments at $s_{N N} =$ 200 GeV. In this study, we investigate the behavior of net-proton $C_{6} / C_{2}$ in statistical Binomial distribution (BD) at $s_{N N} =$ 200 GeV in Au + Au collisions. With the BD parameters extracted from RHIC/STAR, it is found that $C_{6} / C_{2}$ can be negative. Furthermore, the obtained $C_{6} / C_{2}$ becomes smaller when applying the same magnitude of experimental statistics and calculation method to simulations. In 0-10\% centrality, there is a significant difference between the simulated result and theoretical expectation. Based on the extracted parameters and experimentally collected statistics, the baseline of net-proton $C_{6} / C_{2}$ in BD is presented.
Comments:
8 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2109.14169 [pdf]
CPC(2021)·7 citations
04
[Submitted on 28 Sept 2021] (cross-list from hep-th)
Dense matter equation of state and phase transitions from a Generalized Skyrme model
Christoph Adam🇪🇸 · Alberto Garcia Martin-Caro🇪🇸 · Miguel Huidobro🇪🇸 · Ricardo Vazquez🇪🇸 · Andrzej Wereszczynski🇵🇱
Skyrmion crystals are the field configurations which minimize the energy per baryon in the infinitely large topological charge sector of the Skyrme model, at least for sufficiently high density. They are, therefore, an important tool to describe the ground state of cold, symmetric nuclear matter at high density regimes. In this work, we analyze different crystalline phases and the existence of phase transitions between them within the generalized Skyrme model, with the ultimate goal of describing symmetric nuclear matter in a wide regime of densities. Furthermore, we propose a new energy-minimizing phase for densities lower than the nuclear saturation point ( $n_{0}$ ) which also presents a good qualitative behavior in the zero density limit, thereby improving the description of strongly interacting matter in the region $n < n_{0}$ .
Comments:
16 pages, 10 figures; v2: presentation slightly improved, some references added
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2109.13946 [pdf]
PRD(2022)·15 citations
05
[Submitted on 29 Sept 2021] (cross-list from astro-ph.SR)
Theoretical estimate of the half-life for the radioactive $^{134}$ Cs and $^{135}$ Cs in astrophysical scenarios
S. Taioli · D. Vescovi · M. Busso · S. Palmerini · S. Cristallo · A. Mengoni · S. Simonucci
We analyze the $_{55}^{134}$ Cs $\to_{56}^{134}$ Ba and $_{55}^{135}$ Cs $\to_{56}^{135}$ Ba $β^{-}$ decays, which are crucial production channels for Ba isotopes in Asymptotic Giant Branch (AGB) stars. We reckon, from relativistic quantum mechanis, the effects of multichannel scattering onto weak decays, including nuclear and electronic excited states (ES) populated above $≃$ 10 keV, for both parent and daughter nuclei. We find increases in the half-lives for $T > 1 0^{8}$ K (by more than a factor 3 for $^{134}$ Cs) as compared to previous works based on systematics. We also discuss our method in view of these previous calculations. An important impact on half-lives comes from nuclear ES decays, while including electronic temperatures yields further increases of about 20\% at energies 10-30 keV, typical of AGB stars of moderate mass ( $M ≲ 8 M_{⊙}$ ). Despite properly considering these effects, the new rates remain sensitively lower than the TY values, implying longer half-lives at least above 8-9 keV. Our rate predictions are in substantial accord with recent results based on the shell model, and strongly modify branching ratios along the $s$ -process path previously adopted. With our new rate, nucleosynthesis models well account for the isotopic admixtures of Ba in presolar SiC grains and in the Sun.
Comments:
15 pages, 3 figures, 5 tables. Accepted for publication in ApJ
Subjects:
Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
2109.14230 [pdf]
ApJ(2022)·12 citations
06
[Submitted on 29 Sept 2021] (cross-list from hep-ph)
Enhancement of baryon-to-meson ratios around jets as a signature of medium response
Ao Luo🇨🇳 · Ya-Xian Mao🇨🇳 · Guang-You Qin🇨🇳 · En-Ke Wang🇨🇳 · Han-Zhong Zhang🇨🇳
We present a unique signal of jet-induced medium excitations: the enhancement of baryon-to-meson ratios around the quenched jets.To illustrate this, we study jet-particle correlations and the distributions of jet-induced identified particles with respect to the jet direction in Pb+Pb collisions at the LHC via a multi-phase transport model.We find a strong enhancement of baryon-to-meson ratios for associated particles at intermediate transverse momentum around the triggered jets in Pb+Pb collisions relative to p+p collisions, due to the coalescence of jet-excited medium partons.Since the lost energy from jets can diffuse to large angles, such baryon-to-meson-ratio enhancement is more pronounced for larger relative distance from the jet axis.We argue that the experimental confirmation of the enhancement of jet-induced baryon-to-meson ratios around the jets will provide an unambiguous evidence for the medium response to jet quenching in heavy-ion collisions.
Comments:
6 pages, 3 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2109.14314 [pdf]
PLB(2023)·35 citations
07
[Submitted on 29 Sept 2021] (cross-list from hep-ph)
Induced fission-like process of hadronic molecular states
Jun He🇨🇳 · Dian-Yong Chen🇨🇳 · Zhan-Wei Liu🇨🇳 · Xiang Liu🇨🇳
In this work, we predict a new physical phenomenon, induced fission-like process and chain reaction of hadronic molecular states. As a molecular state, if induced by a $D$ meson, the $X (3872)$ can split into $D D ˉ$ final state which is forbidden due to the spin-parity conservation. The breeding of the $D$ meson of the reaction, such as $D^{0} X (3872) \to D^{0} D ˉ^{0} D^{0}$ , makes the chain reaction of $X (3872)$ matter possible. We estimate the cross section of the $D$ meson induced fission-like process of $X (3872)$ into two $D$ mesons. With very small $D^{0}$ beam momentum of 1 eV, the total cross section reaches an order of 1000 b, and decreases rapidly with the increasing of beam momentum. With the transition of $D^{*}$ meson in molecular states to a $D$ meson, the $X (3872)$ can release large energy, which is acquired by the final mesons. The momentum distributions of the final $D$ mesons are analyzed. In the laboratory frame, the spectator $D$ meson in molecular state concentrates in the low momentum area. The energy from the transition frim $D^{*}$ to $D$ meson is mainly acquired by two scattered $D$ mesons. The results suggest that the $D$ meson environment will lead to the induced fission-like process and chain reaction of the $X (3827)$ . Such phenomenon can be extended to other hadronic molecular states.
Comments:
5 pages and 3 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2109.14395 [pdf]
Chin.Phys.Lett.(2022)·5 citations
08
[Submitted on 29 Sept 2021] (cross-list from nucl-ex)
Search for a bound di-neutron by comparing $^{3}$ He(e,e'p)d and $^{3}$ H(e,e'p)X measurements
D. Nguyen🇺🇸 · C. Neuburger🇮🇱 · R. Cruz-Torres🇺🇸 · A. Schmidt🇺🇸 · D.W. Higinbotham🇺🇸 · J. Kahlbow🇺🇸 · P. Monaghan🇺🇸 · E. Piasetzky🇮🇱 · O. Hen🇺🇸
We report on a search for a bound di-neutron by comparing electron-induced proton-knockout $(e, e^{'} p)$ measurements from Helium-3 ( $^{3}$ He) and Tritium ( $^{3}$ H). The measurements were performed at Jefferson Lab Hall A with a 4.326 GeV electron beam, and kinematics of large momentum transfer $Q^{2} \approx 1.9$ (GeV/ $c$ ) $^{2}$ and $x_{B} > 1$ , to minimize contributions from non quasi-elastic (QE) reaction mechanisms. Analyzing the measured $^{3}$ He missing mass ( $M_{mi ss}$ ) and missing energy ( $E_{mi ss}$ ) distributions, we can distinguish the two-body break-up reaction, in which the residual proton-neutron system remains bound as a deuteron. In the $^{3}$ H mirror case, under the exact same kinematic conditions, we do not identify a signature for a bound di-neutron with similar binding energy to that of the deuteron. We calculate exclusion limits as a function of the di-neutron binding energy and find that, for binding equivalent to the deuteron, the two-body break-up cross section on $^{3}$ H is less than 0.9% of that on $^{3}$ He in the measured kinematics at the 95% confidence level.
Comments:
6 pages, 3 figures
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2109.14524 [pdf]
PLB(2022)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE