Nuclear Theory·nucl-th

Tuesday·May 13, 2025

19 papers—13 primary·6 cross-listed

01
Phenomenology of baryon dynamics with directed flow in relativistic heavy-ion collisions
Tribhuban Parida
This thesis aims to elucidate the role of initial baryon stopping and its diffusion in heavy-ion collisions (HIC) using hydrodynamic model. In this regard, we have studied the observable-directed flow ( $v_{1}$ ) of identified hadrons, particularly the $v_{1}$ of baryons and antibaryons, as well as the splitting observed between them in detail. We propose a new ansatz for the initial baryon distribution. By employing this initial baryon deposition model alongside a tilted energy distribution as inputs to a hybrid framework, we successfully describe the rapidity-odd $v_{1}$ of identified hadrons, including the elusive baryon-antibaryon splitting of $v_{1}$ across a wide range of $s_{N N}$ . Our model, incorporating baryon stopping and it's subsequent diffusion within a relativistic hydrodynamic framework and employing a crossover equation of state derived from lattice QCD calculations, establishes a non-critical baryonic baseline. Moreover, we demonstrate that recent STAR measurements of the centrality and system-size dependence of $v_{1}$ splitting between oppositely charged hadrons-attributed to electromagnetic field effects-are significantly influenced by background contributions from baryon stopping and its diffusion. Furthermore, we show that the rapidity dependence of the splitting of the rapidity-even component of $v_{1}$ between $p$ and $p ˉ$ is highly sensitive to the initial baryon deposition scheme. If measured experimentally, this could constraint the rapidity dependence of the initial baryon deposition profile. Moreover, it could offer valuable phenomenological insights into the baryon junction picture and help refine constraints on the baryon diffusion coefficient of the medium. Notably, utilizing this phenomenologically successful baryon deposition model, we present the first estimation of the baryon diffusion coefficient for the strongly interacting QCD matter created in HIC.
nucl-thhep-exhep-phnucl-ex4 citations
02
Unique first-forbidden $β$ -decay transitions in odd-odd and even-even heavy nuclei
Jameel-Un Nabi · Necla Cakmak · Muhammad Majid · Cevad Selam
The allowed Gamow-Teller (GT) transitions are the most common weak nuclear processes of spin-isospin $(σ τ)$ type. These transitions play a key role in numerous processes in the domain of nuclear physics. Equally important is their contribution in astrophysics, particularly in nuclear synthesis and supernova-explosions. In situations where allowed GT transitions are not favored, first-forbidden transitions become significant, specifically in medium heavy and heavy nuclei. For neutron-rich nuclei, first-forbidden transitions are favored mainly due to the phase-space amplification for these transitions. In this work we calculate the allowed GT as well as unique first-forbidden (U1F) $∣Δ$ J $∣$ = 2 transitions strength in odd-odd and even-even nuclei in mass range $70 \leq A \leq 214$ . Two different pn-QRPA models were used with a schematic separable interaction to calculate GT and U1F transitions. The inclusion of U1F strength improved the overall comparison of calculated terrestrial $β$ -decay half-lives in both models. The \textit{ft} values and reduced transition probabilities for the $2^{-} ⟷ 0^{+}$ transitions were also calculated. We compared our calculations with the previously reported correlated RPA calculation and experimental results. Our calculations are in better agreement with measured data. For stellar applications we further calculated the allowed GT and U1F weak rates. These include $β^{\pm}$ -decay rates and electron/positron capture rates of heavy nuclei in stellar matter. Our study shows that positron and electron capture rates command the total weak rates of these heavy nuclei at high stellar temperatures.
nucl-thNPA(2017)·11 citations
03
Temperature-dependent nuclear partition functions and abundances in stellar interior
Jameel-Un Nabi · Abdel Nasser Tawfik · Nada Ezzelarab · Ali Abas Khan
We calculate temperature-dependent nuclear partition functions (TDNPFs) and nuclear abundances for $728$ nuclei assuming nuclear statistical equilibrium (NSE). The theories of stellar evolution support NSE. Discrete nuclear energy levels have been calculated \textit{microscopically}, using the pn-QRPA theory, up to an excitation energy of $10$ MeV in the calculation of TDNPFs. This feature of our paper distinguishes it from previous calculations. Experimental data is also incorporated wherever available to ensure reliability of our results. Beyond 10 MeV we employ simple Fermi gas model and perform integration over the nuclear level densities to approximate the TDNPFs. We calculate nuclidic abundances, using the Saha equation, as a function of three parameters: stellar density, stellar temperature and lepton-to-baryon content of stellar matter. All these physical parameters are considered to be extremely important in stellar interior. Results obtained in this paper show that the equilibrium configuration of nuclei remains unaltered by increasing stellar density (only calculated nuclear abundances increases by roughly same order of magnitude). Increasing the stellar temperature smooths the equilibrium configuration showing peaks at neutron-number magic nuclei.
nucl-thPhys.Scripta(2016)·7 citations
04
Half-vortex states in the rotating outer core of neutron stars
J. A. Gil Granados · A. Muñoz Mateo · X. Viñas
We probe the superfluid-superconductor dynamics of the rotating outer core of neutron stars through half-vortex states. By means of a generalized hydrodynamic model, where proton and neutron fluids are coupled by both dynamic entrainment and Skyrme SLy4 nucleon-nucleon interactions, we analyze single flux tubes in the proton-superconductor component of the system that thread proton vortices located faraway from neutron vortices. It is shown how they give rise to hydrodynamic perturbations in the coexisting neutron superfluid, and its structure remains unaltered for varying rotation rates and magnetic fields within ranges of observational values.
nucl-thPRC(2025)·2 citations
05
Continuum Lambda spectra for a 6Li_Lambda hypernucleus in the 6Li(K-, pi-) reaction
Toru Harada🇯🇵 · Yoshiharu Hirabayashi🇯🇵
We theoretically investigate Lambda production via a (K-, pi-) reaction on a 6Li target, using the distorted-wave impulse approximation (DWIA) with a Fermi-averaged K-n --> pi-Lambda amplitude. We calculate Lambda production spectra using the Green's function method for a 5Li nuclear core + Lambda system, employing a Lambda folding-model potential based on the 5Li nuclear density, which is constructed from alpha-p and 3He-d cluster wave functions. The results show that the calculated spectrum, which includes Lambda bound, resonance, and continuum states, agrees well with the experimental data from the (K-, pi-) reaction at p_K- = 790 MeV/c (0 deg.), where substitutional (0p_Lambda, 0p^{-1}_n) and (0s_Lambda, 0s^{-1}_n) configurations dominate in the near-recoilless reactions. A narrow peak corresponds to a high-lying excited state with spin-parity J^P= 1+ at E_Lambda= 13.8 MeV near the 3He + d + Lambda threshold, arising from interference effects between 5Li(3/2+)x(0s1/2)_Lambda and 5Li(1/2+)x(0s1/2)_Lambda components. This study offers a valuable framework for extracting essential information on the structure and production mechanisms of hypernuclear states from experimental data.
nucl-thnucl-exPRC(2025)·1 citation
06
Gamow-Teller strength distributions and stellar weak-interaction rates for $^{76}$ Ge and $^{82}$ Se using the deformed pn-QRPA model
Jameel-Un Nabi · Mavra Ishfaq
We calculate Gamow-Teller strength distributions for $β β$ -decay nuclei $^{76}$ Ge and $^{82}$ Se using the deformed pn-QRPA model. We use a deformed Nilsson basis and consider pairing correlations within the deformed BCS theory. Ground state correlations and two-particle and two-hole mixing states were included in our pn-QRPA model. Our calculated strength distributions were compared with experimental data and previous calculation. The total Gamow-Teller strength and centroid placement calculated in our model compares well with the measured value. We calculate $β$ -decay and positron capture rates on $^{76}$ Ge and $^{82}$ Se in supernovae environments and compare them to those obtained from experimental data and previous calculation. Our study shows that positron capture rates command the total weak rates at high stellar temperatures. We also calculate energy rates of $β$ -delayed neutrons and their emission probabilities.
nucl-thAstrophys.Space Sci.(2016)·0 citations
07
Quarkyonic picture of isospin QCD
Oleksii Ivanytskyi🇵🇱
We suggest a new look onto the thermodynamics of cold isospin QCD matter described within the quarkyonic framework, when confining forces are essential only for the momentum states close to the Fermi sphere and lead to formation of the quark-antiquark correlations with quantum numbers of pions. Within this picture cold isospin QCD matter is constituted by the Bose-Einstein condensate of pions and free (anti)quarks. We develop a simple confining model of pions existing as the lowest energy $P$ -state of in-medium three-dimensional harmonic oscillator and use it to show that under the conditions of isospin QCD quarkyonic matter can onset at densities significantly smaller than the overlap density of pions. Using the experimentally established pion charge radius we demonstrate that the onset density can be even lower than two nuclear saturation densities. To analyze the lattice QCD data we develop a field-theory inspired model of quark-antiquark-pion matter with vector-isovector repulsion among pions and (anti)quarks. The quark substructure of pions, which is one of the key elements of the model, is accounted for within the one-loop no-sea approximation and leads to an effective medium dependence of the pion mass. The latter is shown to be crucial for providing asymptotic vanishing of the pion density and pion condensate, which reflects pion dissociation due to asymptotic freedom of QCD. The proposed quarkyonic picture of isospin QCD agrees with the results of perturbative calculations on reaching the conformal limit of QCD and with the data of lattice simulations, which supports its viability and physical relevance.
nucl-thhep-phhep-thPRD(2025)·13 citations
08
Violation of NCQ scaling in hadron elliptic flow in Au+Au collisions at $\sqrt{s_{NN}}=3.0-7.7GeV
Xun Zhu🇨🇳 · Gao-Chan Yong🇨🇳
We investigate the number-of-constituent-quark (NCQ) scaling of elliptic flow for various hadrons in non-central Au+Au collisions at $\sqrt{s_{NN}} = 3.0\text{--}7.7\,\mathrm{GeV}$ using the AMPT model with string melting (SM) and pure hadron cascade (HC) modes. For the SM case, NCQ scaling is absent at $\sqrt{s_{NN}} =3.0\,\mathrm{GeV}$ but is largely restored by $\sqrt{s_{NN}} =3.9\,\mathrm{GeV}$. Although quark coalescence occurs at $\sqrt{s_{NN}} =3.0\,\mathrm{GeV}$, the lack of NCQ scaling is attributed to the insufficient development of quark elliptic flow and the limited production of strange quarks and antiquarks. This finding suggests that NCQ scaling could not be considered a definitive signature of quark-gluon plasma (QGP) formation in the RHIC fixed-target energy region. For the HC case, as expected, no NCQ scaling is observed. However, a mass ordering in the elliptic flow emerges at $\sqrt{s_{NN}} =4.5\,\mathrm{GeV}$, indicating that full thermalization may not be a prerequisite for mass ordering.
nucl-thhep-phnucl-exPLB(2025)·4 citations
09
The coexistence of possible magnetic and chiral rotation in $^{129} Cs$ and $^{131} La$ : a microscopic investigation
Jia-nuo Zang · Duo Chen · Rui Guo · Jian Li · Dong Yang · Yue Shi
A microscopic investigation of the rotational properties in $^{129} Cs$ and $^{131} La$ was carried out using the three-dimensional tilted axis cranking covariant density functional theory (3DTAC-CDFT). The calculations reveal the coexistence of magnetic and chiral rotation built on identical qusiparticle configurations $π h_{11/2}^{1} \otimes ν h_{11/2}^{- 2}$ in $^{129} Cs$ and $^{131} La$ , establishing a new type of shape coexistence. The calculations predict the deformation parameters for magnetic rotation in $^{129} Cs$ ( $β \approx 0.23$ , $γ \approx 4 1^{\circ}$ ) and $^{131} La$ ( $β \approx 0.25,$ $γ \approx 4 2^{\circ}$ ), along with those for possible chiral rotation in $^{129} Cs$ ( $β \approx 0.20,$ $γ \approx 2 9^{\circ}$ ) and in $^{131} La$ ( $β \approx 0.20,$ $γ \approx 2 7^{\circ}$ ). The energy spectra, the relation between the spin and the rotational frequency, and the reduced $M 1$ and $E 2$ transition probabilities are obtained with the various configurations. The experimental characteristics of band B8 in $^{129} Cs$ and band 13 in $^{131} La$ are well reproduced. Moreover, a distinctive rotational mode transition is uncovered in this work, progressing from the principal-axis rotation to the planar rotation and finally to the chiral rotation, as the rotational frequency evolves through different regimes.
nucl-thPRC(2025)·3 citations
10
Large quadrupole moment in $^{20}$ Ne:Localization and tensor-force effects
Xue Huai-Tong · Qiu Suo · Chen C. F. · Chen Q. B. · Zhou Xian-Rong · Ren Zhongzhou
Using the Beyond-Skyrme-Hartree-Fock approach with various Skyrme-type $N N$ effective interactions, we explore the large spectroscopic quadrupole moment $Q_{s}$ of the first excited $2_{1}^{+}$ state in $^{20}$ Ne. Our calculated $Q_{s} (2_{1}^{+}) \approx - 0.20 e b$ aligns closely with the experimental value of $- 0.22 (2) e b$ . Consistent with other theoretical methods, our results confirm the presence of an $α$ cluster structure in this state. We also investigate the robustness of the $α$ cluster against tensor-force, demonstrating that incorporating tensor components significantly enhances $Q_{s} (2_{1}^{+})$ and strengthens the cluster structure along the symmetrical axis.
nucl-thPRC(2025)·1 citation
11
Angular momentum of glasma
Margaret E. Carrington🇨🇦 · Stanislaw Mrowczynski🇵🇱
The earliest phase of an ultrarelativistic heavy ion collision can be described as a highly populated system of gluons called glasma. We study some glasma characteristics related to the system's angular momentum. The first one is the global angular momentum perpendicular to the reaction plane, which is spanned by the beam axis and impact parameter vector. We show that only a small fraction of the enormous initial angular momentum of the colliding ultrarelativistic nuclei is transferred to the glasma. Our main focus is the glasma angular momentum directed along the beam axis. This quantity has a local character and results from the inhomogeneous velocity field generated in the glasma. We calculate the vorticity and local angular momentum which show noticeably different behaviour. The results are analyzed in detail and discussed in the context of existing experimental data. We argue that neither vorticity nor thermal vorticity but instead the local angular momentum controls the polarization of final-state hadrons.
nucl-thhep-phPRC(2026)·5 citations
12
Astrophysical $S$ factor and reaction rate of the direct $^{12} C (p, γ)^{13} N$ capture process within a potential model approach
E.M. Tursunov · S.A. Turakulov · A.S. Kadyrov
The astrophysical direct nuclear capture reaction $^{12} C (p, γ)^{13} N$ is studied within the framework of a potential model. Parameters of the nuclear $p -^{12}$ C interaction potentials of the Woods-Saxon form are adjusted to reproduce experimental $p -^{12}$ C scattering phase shifts, as well as the binding energies and empirical values of the asymptotic normalization coefficient (ANC) for the $^{13}$ N(1/2 $^{-}$ ) ground state from the literature. The reaction rates are found to be very sensitive to the description of the value of the ANC of the $^{13}$ N( $1/ 2^{-}$ ) ground state and width of the $^{13}$ N( $1/ 2^{+}$ ) resonance at the $E_{x} = 2.365$ MeV excitation energy. The potential model, which yields the ANC value of 1.63 fm $^{- 1/2}$ for the $^{13}$ N( $1/ 2^{-}$ ) ground state and a value $Γ$ =39 keV for the $^{13}$ N( $1/ 2^{+}$ ) resonance width, is able to reproduce the astrophysical $S$ factor in the energy interval up to 2 MeV, the empirical values of the reaction rates in the temperature region up to $T = 1 0^{10}$ K of the LUNA Collaboration and the results of the R-matrix fit. The astrophysical factor $S (0) = 1.35$ keV b is found using the asymptotic expansion method of D. Baye. The obtained value is in a good agreement with the Solar Fusion II result. At the same time, the calculated value of 1.44 keV b of the astrophysical $S$ factor at the Solar Gamow energy is consistent with the result of the R-matrix fit of $S (25 keV) = 1.48 \pm 0.09$ keV b by Kettner {\it et al.}, but slightly less than the result of $S (25 keV) = 1.53 \pm 0.06$ keV b the LUNA Collaboration.
nucl-thastro-ph.SRPRC(2025)·0 citations
13
Nonparametric extensions of nuclear equations of state: probing the breakdown scale of relativistic mean-field theory
Isaac Legred🇺🇸 · Liam Brodie🇺🇸 · Alexander Haber🇺🇸 · Reed Essick🇨🇦 · Katerina Chatziioannou🇺🇸
Phenomenological calculations of the properties of dense matter, such as relativistic mean-field theories, represent a pathway to predicting the microscopic and macroscopic properties of neutron stars. However, such theories do not generically have well-controlled uncertainties and may break down within neutron stars. To faithfully represent the uncertainty in this breakdown scale, we develop a hybrid representation of the dense-matter equation of state, which assumes the form of a relativistic mean-field theory at low densities, while remaining agnostic to any nuclear theory at high densities. To achieve this, we use a nonparametric equation of state model to incorporate the correlations of the underlying relativistic mean-field theory equation of state at low pressures and transition to more flexible correlations above some chosen pressure scale. We perform astrophysical inference under various choices of the transition pressure between the theory-informed and theory-agnostic models. We further study whether the chosen relativistic mean-field theory breaks down above some particular pressure and find no such evidence. Using simulated data for future astrophysical observations at about two-to-three times the precision of current constraints, we show that our method can identify the breakdown pressure associated with a potential strong phase transition.
nucl-thastro-ph.HEgr-qcPRD(2025)·13 citations

Affiliations

first authorsco-authorsvia INSPIRE