Nuclear Theory·nucl-th

Tuesday·March 11, 2025

17 papers—8 primary·9 cross-listed

01
Reconstructing jet anisotropies with cumulants
Tanner Mengel🇺🇸 · Niseem Magdy🇺🇸 · Ron Belmont🇺🇸 · Anthony Timmins🇺🇸 · Christine Nattrass🇺🇸
In relativistic heavy-ion collisions, where quark-gluon plasma forms, hadron production is anisotropic at both low and high transverse momentum, driven by flow dynamics and spatial anisotropies. To better understand these mechanisms, we use multi-particle correlations to reconstruct jet anisotropies. We simulate data using \textsc{TennGen}\xspace as a hydro-like background and combine it with \textsc{Pythia-8}\xspace generated jets, clustering them with the anti- $k_{t}$ \xspace algorithm. Jet anisotropies are unfolded using a Bayesian technique, ensuring the robustness of the reconstructed signals. Our results demonstrate that multi-particle cumulant methods can accurately capture the differential jet azimuthal anisotropies, providing crucial insights into high- $p_{T} \xspace$ behavior and the dynamics within heavy-ion collisions.
nucl-thnucl-exPRC(2025)·0 citations
02
Electron capture cross sections and nuclear partition functions for fp-shell nuclei
Jameel-Un Nabi · Muhammad Riaz
We present calculation of electron capture cross sections (ECC), in the limit of zero momentum transfer, using the pn QRPA model in stellar matter. Towards this aim we make use of our recently introduced recipe for estimation of nuclear partition functions. For low momentum transfer q tends to zero, the nuclear matrix elements of the P{\sigma}{\tau} plus operator provide the leading contribution to the total cross section which we estimate using the pn QRPA model in a multi shell single particle space with a schematic interaction. Key f p shell nuclei (odd A, even even and odd odd) bearing astrophysical importance were selected for the calculation of ECC in stellar environment. These f p shell nuclei play crucial role in pre supernova evolution of massive stars and core collapse. We further present microscopic calculation of ground and excited states Gamow Teller strength distributions and stellar electron capture rates on these suite of nuclei. We used two different sets of empirically determined pairing gaps to calculate the ECC and electron capture rates. Results are compared with experimental data and previous computations. Our calculated ECC are systematically smaller at low electron incident energies as compared to the shell model results.
nucl-thJ.Phys.G(2019)·11 citations
03
Phase transitions in the inner crust of neutron stars within the superfluid band theory: Competition between $^{1} S_{0}$ pairing and spin polarization under finite temperature and magnetic field
Kenta Yoshimura · Kazuyuki Sekizawa
Phase transitions of matter under changes of external environment such as temperature and magnetic field have attracted great interests to various quantum many-body systems. Several phase transitions must have occurred in neutron stars as well such as transitions from normal to superfluid/superconducting phases and crust formation. In this work, we extend the superfluid band theory, which has been formulated in our previous work [K. Yoshimura and K. Sekizawa, Phys. Rev. C 109, 065804 (2024)] based on the Kohn-Sham density functional theory (DFT) for superfluid systems, into the finite temperature and finite magnetic field systems. As a result of the finite temperature calculations, we find that the superfluidity of neutrons dissapears at around $k_{B} T = 0.6$ -- $0.9$ MeV, and ``melting'' of nuclear slabs, that is, a structural change into the uniform matter, takes place at around $k_{B} T = 2.5$ -- $4.5$ MeV. We also reveal that these transition temperatures exhibit a systematical dependence on the baryon densities. By turning on the magnetic field, we find that protons' spin gets polarized at around $B = 1 0^{16}$ G, whereas neutrons' spin is kept unpolarized on average up to around $B = 1 0^{17}$ G. Intriguingly, our microscopic calculations reveal that neutrons' spin is actually polarized locally inside and outside of the slab already at $B \sim 1 0^{16}$ G, while keeping the system unpolarized in total. As a conclusion, we have demonstrated validity and usefulness of the fully self-consistent superfluid nuclear band theory for describing neutron star matter under arbitrary temperature and magnetic field. Critical temperatures and magnetic fields have been predicted for 1) superfluid to normal transition, 2) crust formation, and 3) spin polarization, under conditions relevant to realistic neutron star environments.
nucl-thastro-ph.HEcond-mat.quant-gasPRC(2025)·4 citations
04
Quartet correlations near the surface of $N = Z$ nuclei
Yixin Guo · Tomoya Naito · Hiroyuki Tajima · Haozhao Liang
We theoretically investigate Cooper quartet correlations in $N = Z$ doubly-magic nuclei ( $^{40} Ca$ , $^{100} Sn$ , and $^{164} Pb$ ). We first examine the quartet condensation fraction in infinite symmetric nuclear matter by using the quartet Bardeen-Cooper-Schrieffer theory. Together with the total nucleon density profiles of doubly-magic nuclei obtained from the Skyrme Hartree-Fock calculation, we discuss the spatial distribution of quartet correlations in finite nuclei within the local density approximation. Large quartet condensate fractions are found at the surface region of an atomic nucleus due to the strong neutron-proton attractive interaction responsible for the deuteron formation in vacuum. Moreover, we discuss a possible microscopic origin of the Wigner term in the context of nucleon-quartet scattering in dilute symmetric nuclear matter. The nucleon-quartet scattering effect on the Wigner term is numerically estimated to be about one order of magnitude of the total empirical strength, indicating the importance of multinucleon clusters in the symmetry energy and mass formula in addition to the neutron-proton pairing.
nucl-thcond-mat.quant-gasphysics.atom-phPRC(2025)·4 citations
05
Microscopic Calculations of Stellar Weak Rates for sd- and fp-Shell Nuclei for Astrophysical Applications
Jameel-Un-Nabi · H. V. Klapdor-Kleingrothaus
Proton neutron quasiparticle RPA is used for the first time to calculate weak interaction rates for sd and fp shell nuclei at high temperatures and densities. The calculated rates take into consideration the latest experimental energy levels and ft value compilations. Particle emission processes from excited states are taken into account. The calculation is done for 700 nuclei with mass number ranging from 18 to 100. The astrophysical applications of the calculated rates are highlighted.
nucl-thActa Phys.Polon.B(1999)·3 citations
06
Effect of Nuclear Deformation on Electron Capture Cross-section on Chromium Isotopes
Asim Ullah · Jameel-Un Nabi · Muhammad Riaz
The electron capture plays significant role in the pre supernova and supernova evolutions of massive stars which in turn are of great importance in synthesizing heavy elements beyond iron. In this paper we study the effect of nuclear deformation on the computed electron capture cross section on selected even even chromium isotopes (464850Cr). The nuclear deformation parameters were computed using two different theoretical models: Interacting Boson Model (IBM 1) and Macroscopic (Yukawa plus exponential) microscopic (Folded Yukawa) model (Mac mic model). A third value of deformation parameter was adopted from experimental data. We chose the pn QRPA model to perform our calculations. The predictive power of the chosen model was first tested by calculating Gamow Teller (GT) strength distributions of selected fp shell nuclei where measured GT data was available. The calculated GT strength distributions were well fragmented over the energy range 0 12 MeV and were noted to be in decent agreement with experimental data. The total GT strength was found to increase (decrease) with decrease (increase) in the value of deformation parameter for the three chromium isotopes. The computed GT strength distributions satisfied the model independent Ikeda sum rule. The ECC were calculated as a function of the deformation parameter at core temperature 1.0 MeV. Our results show that the calculated ECC increased with increasing value of nuclear deformation.
nucl-thInt.J.Mod.Phys.D(2019)·1 citation
07
Bound state formation within the Lindblad approach
Jan Rais🇩🇪 · Hendrik van Hees🇩🇪 · Carsten Greiner🇩🇪
The Lindblad master equation is a frequently used Markovian approach to describe open quantum systems in terms of the temporal evolution of a reduced density matrix. Here, the thermal environment is traced out to obtain an expression to describe the evolution of what is called a system: one particle or a chain of interacting particles, which is/are surrounded by a thermal heat bath. In this work, we investigate the formation of non-relativistic bound states, involving the Pöschl-Teller potential, in order to discuss the formation time and the thermal equilibrium, applying scales from nuclear physics. This problem is borrowed from the field of heavy-ion collisions, where the deuteron is a probe which is measured at temperature regimes around the chemical freeze out temperature, while the deuteron itself has a binding energy which is much lower. This is known and often described as a ``snowball in hell". We use a reformulated Lindblad equation, in terms of a diffusion-advection equation with sources and therefore provide a hydrodynamical formulation of a dissipative quantum master equation.
nucl-thquant-ph0 citations
08
Role of the isovector spin-orbit potential in mitigating the CREX-PREX dilemma
Athul Kunjipurayil · Marc Salinas · J. Piekarewicz
Pioneering electroweak measurements of the neutron skin thickness in lead-208 and calcium-48 are challenging our understanding of nuclear dynamics. Many theoretical models suggest that the slope of the symmetry energy controls the development of a neutron skin in neutron-rich nuclei. This led to the expectation that if lead-208 exhibits a large neutron skin, calcium-48 should as well. Given that the PREX collaboration reported a relatively thick neutron skin in lead, we anticipated that calcium would also have a significant neutron skin. Instead, the CREX collaboration reported a thin neutron skin in calcium. Although many suggestions have been proposed, the ``CREX-PREX dilemma" remains unsolved. Recently, an intriguing scenario has emerged, suggesting that an enhanced isovector spin-orbit interaction could simultaneously account for both results. Following this approach, we performed relativistic mean-field calculations with an increased isovector spin-orbit potential. Our findings indicate that while this modification significantly affects the structure of calcium-48, it has only a marginal impact on lead-208, thereby bringing the results into better agreement with experiment. However, the strong enhancement required to mitigate the CREX-PREX dilemma destroys the agreement with a successful spin-orbit phenomenology, primarily by modifying the well-known ordering of spin-orbit partners.
nucl-thnucl-exPRC(2025)·15 citations

Affiliations

first authorsco-authorsvia INSPIRE