#### Physical Review C

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ISSN / EISSN : 0556-2813 / 1089-490X
Total articles ≅ 42,540
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Alpna Ojha, , Unnati Gupta, Pushpendra P. Singh, Abhishek Yadav, Devendra P. Singh, Mohd Shuaib, B. P. Singh, R. Prasad
Published: 14 September 2021
Physical Review C, Volume 104; https://doi.org/10.1103/physrevc.104.034615

Abstract:
Incomplete fusion processes and estimation of strength of incomplete fusion in heavy ion induced nuclear reactions have been explored for several combinations of projectile-target nuclei. Dynamics of these reactions is explained using an optical model. Parameters of the optical model affect the shape and depth of nuclear potential and hence influence the theoretical predictions. For heavy ion induced reactions, the optical model potential parameters are not unique and different sets of these parameters may be used for different ranges of mass number $A$ and incident energy $E$. To explore the effect of optical model potential parameters, a comparative study of available experimental data for excitation functions of four systems, , and ${}^{16}\mathrm{O}+{}^{74}\mathrm{Ge}$, with corresponding theoretically predicted excitation functions, made by PACE4 using different sets of optical model potential parameters, has been done. It has been observed that a single set of optical model potential parameters is not adequate for all the systems. The variations in these parameters change the theoretical cross-section predictions for various channels considerably, which in turn, change the correspondingly estimated fraction of incomplete fusion $\left({F}_{\mathrm{ICF}}\right)$. The effect of deformation of target nuclei on fractional incomplete fusion has also been investigated for the above mentioned systems. ${F}_{\mathrm{ICF}}$ has been plotted as a function of deformation parameter $\left({\beta }_{2}\right)$ of the target nuclei and it is found to increase as the deformation parameter of the corresponding target nuclei increases on either side of the intrinsic spherical symmetry.
, Mohd. Shuaib, Ishfaq Majeed, Manoj Kumar Sharma, , Abhishek Yadav, Devendra P. Singh, Pushpendra P. Singh, Unnati Gupta, Rudra N. Sahoo, et al.
Published: 14 September 2021
Physical Review C, Volume 104; https://doi.org/10.1103/physrevc.104.034616

Abstract:
In order to study incomplete fusion (ICF) reaction dynamics, the present work manifests the role of a non-$\alpha$-cluster ${}^{14}\mathrm{N}$ projectile on ${}^{181}\mathrm{Ta}$ target at energies $\approx 4–7$ MeV/nucleon using the offline $\gamma$-ray spectroscopy. The excitation functions for 15 reaction residues populated in ${}^{14}\mathrm{N}+{}^{181}\mathrm{Ta}$ system have been measured and analyzed within the framework of statistical model code PACE4. The experimentally measured excitation functions of evaporation residues populated via xn/pxn channels are found to be well reproduced by the predictions of code PACE4, which confirms their production solely via complete fusion process. However, an enhancement in the measured excitation function as compared to PACE4 calculations, particularly in tail portion of ${}^{192}\mathrm{Hg}$ residue ($3n$ channel) has been observed indicating the presence of precompound emission. A significant contribution from precursor decay in pxn channels has also been observed. An enhancement in the measured excitation functions for $\alpha$-emitting channels as compared to the PACE4 predictions has been observed and attributed to the incomplete fusion process. Further, the contribution from incomplete fusion process in the ${}^{14}\mathrm{N}+{}^{181}\mathrm{Ta}$ system has also been deduced in terms of strength function (${F}_{\mathrm{ICF}}$). The results have been discussed in terms of the parameters which influence the dynamics of ICF process. The ${F}_{\mathrm{ICF}}$ is found to depend strongly on projectile energies, the product of projectile and target charges, and $\alpha -Q$ value of the projectile.
, L. E. Marcucci, R. Schiavilla, M. Viviani
Published: 14 September 2021
Physical Review C, Volume 104; https://doi.org/10.1103/physrevc.104.035501

Abstract:
We report on a study of the Gamow-Teller matrix element contributing to ${}^{6}\mathrm{He}\phantom{\rule{4pt}{0ex}}\beta$ decay with similarity renormalization group (SRG) versions of momentum- and configuration-space two-nucleon interactions. These interactions are derived from two different formulations of chiral effective field theory ($\chi \mathrm{EFT}\right)$—without and with the explicit inclusion of $\mathrm{\Delta }$ isobars. We consider evolution parameters ${\mathrm{\Lambda }}_{\mathrm{SRG}}$ in the range between 1.2 and 2.0 ${\mathrm{fm}}^{-1}$ and, for the $\mathrm{\Delta }$-less case, also the unevolved (bare) interaction. The axial current contains one- and two-body terms, consistently derived at tree level (no loops) in the two distinct $\chi \mathrm{EFT}$ formulations we have adopted here. The ${}^{6}\mathrm{He}$ and ${}^{6}\mathrm{Li}$ ground-state wave functions are obtained from hyperspherical-harmonics (HH) solutions of the nuclear many-body problem. In $A=6$ systems, the HH method is limited at present to treat only two-body interactions and non-SRG evolved currents. Our results exhibit a significant dependence on ${\mathrm{\Lambda }}_{\text{SRG}}$ of the contributions associated with two-body currents, suggesting that a consistent SRG-evolution of these is needed in order to obtain reliable estimates. We also show that the contributions from one-pion-exchange currents depend strongly on the model (chiral) interactions and on the momentum- or configuration-space cutoffs used to regularize them. These results might prove helpful in clarifying the origin of the sign difference recently found in no-core-shell-model and quantum Monte Carlo calculations of the ${}^{6}\mathrm{He}$ Gamow-Teller matrix element.
Published: 14 September 2021
Physical Review C, Volume 104; https://doi.org/10.1103/physrevc.104.034904

Abstract:
We develop a flexible, relativistically covariant parametrization of the dense nuclear matter equation of state suited for inclusion in computationally demanding hadronic transport simulations. Within an implementation in the hadronic transport code smash, we show that effects due to bulk thermodynamic behavior are reproduced in dynamic hadronic systems, demonstrating that hadronic transport can be used to study critical behavior in dense nuclear matter, both at and away from equilibrium. We also show that two-particle correlations calculated from hadronic transport simulation data follow theoretical expectations based on the second-order cumulant ratio, and constitute a clear signature of the crossover region above the critical point.
Y. Bao, , Xian-Rong Zhou
Published: 14 September 2021
Physical Review C, Volume 104; https://doi.org/10.1103/physrevc.104.034312

Abstract:
In this paper we study the low-lying states of neutron-rich ${}^{122,124,126,128}\mathrm{Cd}$ and ${}^{130,132,134,136,138}\mathrm{Cd}$ within the nucleon-pair approximation of the shell model. We adopt the phenomenological Hamiltonian for ${}^{122,124,126,128}\mathrm{Cd}$, and the shell-model effective interaction $jj46$ for ${}^{130,132,134,136,138}\mathrm{Cd}$. The available experimental excitation energies and quadrupole transition probabilities are well reproduced by our calculation, and we also make predictions for very neutron-rich Cd nuclei. Based on our calculation, the $B\left(E2;{0}_{\mathrm{g}.\mathrm{s}.}^{+}\to {2}_{1}^{+}\right)$ values exhibit an asymmetric feature with respect to the $N=82$ shell closure, which mainly comes from the contributions of the proton transition matrix elements. We also investigate for the eight open-shell Cd nuclei, whether two low-lying yrast states with spins differing by 2 can be connected by a quadrupole-phonon excitation, and here we take the proton and neutron quadrupole operators multiplied by $1/{r}_{0}^{2}$ as our quadrupole phonon operators. We calculate explicit overlaps between the low-lying yrast states and the constructed quadrupole-phonon states based on the low-lying yrast states with lower spins, and the results indicate that, for all eight open-shell Cd nuclei, $|{2}_{1}^{+}〉$ and $|{4}_{1}^{+}〉$ can be well described to be the states constructed by coupling the proton or neutron phonon to $|{0}_{\mathrm{g}.\mathrm{s}.}^{+}〉$ and $|{2}_{1}^{+}〉$, respectively. Very interestingly, for ${}^{126,124,122}\mathrm{Cd}$ and ${}^{136,138}\mathrm{Cd}$, the ${2}_{1}^{+}$ state can be well described to be both the proton phonon state and the neutron phonon state, which indicates a nonorthogonal feature of these two phonon states. We further present an analytic relation for the overlap between these two phonon states, which implies that the proton and neutron phonon states constructed using the quadrupole operators and the ${0}_{\mathrm{g}.\mathrm{s}.}^{+}$ state in an open-shell nucleus are almost impossibly orthogonal.
, Mamta Sarswat, Sushant Arora, Satyendra Kumar, Mohd. Shuaib, Ishfaq Majeed, M. Shariq Asnain, B. P. Singh, R. Prasad, Vijay Raj Sharma, et al.
Published: 14 September 2021
Physical Review C, Volume 104; https://doi.org/10.1103/physrevc.104.l031601

Abstract:
A systematic analysis of the experimental cross-section data in odd mass number $\left(A\right)$ and odd atomic number $\left(Z\right)$ nuclei is reported to reveal a novel mass-energy systematics for the pre-compound emission of fast neutrons in $\alpha$-induced reactions at low energies. The experimental excitation functions have been analyzed within the framework of statistical model predictions to get information regarding pre-compound emission. The present analysis establishes for first time an interesting systematics, emphasizing that accessible excitation energy on peripheral nucleons of the systems is an exponential function of atomic mass number ($A$) of target nuclei. One of the most important features of this systematics is to provide a precise estimation of the pre-compound contribution for any nuclei, except closed-shell ones, over a wide range of mass number $63\le A\le 109$ in the nuclear landscape. New results of the present analysis emphasize an additional subtle interconnection between the structure of nuclei and the nuclear reaction mechanism of the pre-compound emission process at low energies, where the compound nucleus process is more likely to be dominant.
, L. C. Suárez González, A. Pérez Martínez, H. Pérez Rojas
Published: 13 September 2021
Physical Review C, Volume 104; https://doi.org/10.1103/physrevc.104.035803

Abstract:
We study the thermodynamic properties of a relativistic magnetized neutral vector boson gas at any temperature. By comparing the results with the low temperature and the nonrelativistic descriptions of this gas, we found that the fully relativistic case can be separated in two regimes according to temperature. For low temperatures, magnetic field effects dominate and the system shows a spontaneous magnetization, its pressure splits into two components, and, eventually, a transversal magnetic collapse might occur. In the high temperature region, the gas behavior is led by pair production. The presence of antiparticles preserves the isotropy in the pressure, and increases the magnetization and the total pressure of the system by several orders. Astrophysical implications of those behaviors are discussed.
A. J. Tropiano, S. K. Bogner,
Published: 13 September 2021
Physical Review C, Volume 104; https://doi.org/10.1103/physrevc.104.034311

Abstract:
Recent experiments have succeeded in isolating processes for which short-range correlation (SRC) physics is dominant and well accounted for by SRC phenomenology. But an alternative and compelling picture emerges from renormalization group (RG) evolution to low RG resolution. At high RG resolution, SRCs are identified as components in the nuclear wave function with relative pair momenta greater than the Fermi momentum. Scale separation results in wave-function factorization that can be exploited with phenomenologies such as the generalized contact formalism or the low-order correlation operator approximation. Evolution to lower resolution shifts SRC physics from nuclear structure to the reaction operators without changing the measured observables. We show how the features of SRC phenomenology manifested at high RG resolution are cleanly identified at low RG resolution using simple two-body operators and local-density approximations with uncorrelated wave functions, all of which can be systematically generalized. We verify that the experimental consequences to date follow directly at low resolution from well-established properties of nucleon-nucleon interactions such as the tensor force. Thus the RG reconciles the contrasting pictures of the same experiment and shows how to get correct results using wave functions without SRC components. Our demonstration has implications for the analysis of knockout reactions for which SRC physics is not cleanly isolated.
S. Mukhopadhyay, , Debasish Mondal, Deepak Pandit, Surajit Pal, Balaram Dey, Srijit Bhattacharya, A. De, T. K. Rana, S. Kundu, et al.
Published: 13 September 2021
Physical Review C, Volume 104; https://doi.org/10.1103/physrevc.104.l031304

Abstract:
An experimental study on the temperature ($T$) dependence of giant dipole resonance (GDR) width was performed for the medium mass nucleus ${}^{74}\mathrm{Kr}$ in the range of $T\approx 2–2.5$ MeV at an average angular momentum of $26\hslash$ using the ${}^{16}\mathrm{O}+{}^{58}\mathrm{Ni}$ fusion reaction. The emitted high-energy $\gamma$ rays and evaporated neutrons were measured in coincidence with low-energy discrete $\gamma$-ray multiplicities. The GDR parameters, nuclear level density parameter, and nuclear temperature were determined by the statistical model analysis of the high-energy $\gamma$-ray spectra as well as evaporated neutron spectra. The measured GDR width is found to increase monotonically with temperature, in contradiction with the recent observation of the width saturation in ${}^{88}\mathrm{Mo}$. Comparisons of the measured data with predictions of the adiabatic thermal shape fluctuation model and its refined version, the critical temperature included fluctuation model, are presented and discussed.
T. N. Szegedi, , , , M. Jacobi, G. G. Barnaföldi, , , A. Arcones
Published: 13 September 2021
Physical Review C, Volume 104; https://doi.org/10.1103/physrevc.104.035804

Abstract:
Background: Light ($30\le Z\le 45$) neutron-rich isotopes are thought to be synthesized in the neutrino-driven ejecta of core-collapse supernovae explosions via the weak $r$ process. Recent nucleosynthesis studies have demonstrated that $\left(\alpha ,xn\right)$ reactions play a particularly important role in the production of these isotopes. $\alpha$-nucleus optical model potentials ($\alpha$-OMPs) are used to model this nucleosynthesis scenario.