Nuclear Theory·nucl-th

Monday·January 15, 2024

9 papers—4 primary·5 cross-listed

01
Spin squeezed states and wobbling motion in collective Hamiltonian
Q. B. Chen · S. Frauendorf
A semiclassical approach is proposed to calculate the collective potential and mass parameters to formulate a collective Hamiltonian capable of describing the wobbling motion in both even-even and odd-mass systems. By diagonalizing the resulting collective Hamiltonian (CH), one can obtain the energies and wave functions associated with the wobbling states. Furthermore, a novel technique called spin squeezed state (SSS) maps is introduced based on the derived wave functions. To validate the results obtained from the collective Hamiltonian, a comparative analysis is conducted against predictions from the triaxial rotor model (TRM) and particle triaxial rotor (PTR) model. Notably, the SSS plots determined using the TRM and PTR models exhibit a strong correlation with the probability density distributions of the wave functions obtained from the CH. This correlation highlights the consistency and coherence between the different theoretical approaches when describing the wobbling phenomenon and associated rotational dynamics.
nucl-thnucl-exPRC(2024)·11 citations
02
Multinucleon transfer with time-dependent covariant density functional theory
D. D. Zhang · D. Vretenar · T. NikšIć · P. W. Zhao · J. Meng
The microscopic framework of time-dependent covariant density functional theory is applied to study multinucleon transfer reactions, with transfer probabilities calculated using the particle number projection method. It is found that similar total cross sections are obtained with two different relativistic density functionals, PC-PK1 and DD-ME2, as well as with the Skyrme functional SLy5 in a previous study, for multinucleon transfer in the reactions: $^{40} Ca +^{124} Sn$ at $E_{lab} = 170$ MeV, $^{40} Ca +^{208} Pb$ at $E_{lab} = 249$ MeV, and $^{58} Ni +^{208} Pb$ at $E_{lab} = 328.4$ MeV. We report the first microscopic calculation of total cross sections for the reactions: $^{40} Ar +^{208} Pb$ at $E_{lab} = 256$ MeV and $^{206} Pb +^{118} Sn$ at $E_{lab} = 1200$ MeV. Compared to the results obtained with the GRAZING model, the cross sections predicted by the time-dependent covariant density functional theory are in much better agreement with data, and demonstrate the potential of microscopic models based on relativistic density functionals for the description of reaction dynamics.
nucl-thPRC(2024)·26 citations
03
Neutron-rich nuclei and neutron skins from chiral low-resolution interactions
P. Arthuis · K. Hebeler · A. Schwenk
Neutron-rich nuclei provide important insights to nuclear forces and to the nuclear equation of state. Advances in ab initio methods combined with new opportunities with rare isotope beams enable unique explorations of their properties based on nuclear forces applicable over the entire nuclear chart. In this paper, we develop novel chiral low-resolution interactions that accurately describe bulk properties from $^{16}$ O to $^{208}$ Pb. With these, we investigate density distributions and neutron skins of neutron-rich nuclei. Our results show that neutron skins are narrowly predicted over all nuclei with interesting sensitivities for the most extreme, experimentally unexplored cases.
nucl-thnucl-exEPJA(2026)·57 citations
04
An analytic approach to the RTA Boltzmann attractor
Inês Aniceto🇬🇧 · Jorge Noronha🇺🇸 · Michał\ Spaliński🇵🇱
We reformulate the Boltzmann equation in the relaxation time approximation undergoing Bjorken flow in terms of a novel partial differential equation for the generating function of the moments of the distribution function. This is used to obtain an approximate analytic description of this system's far-from-equilibrium attractor via a series expansion at early times. This expansion possesses a finite radius of convergence and can be analytically continued to late times. We find that this procedure reproduces the known values of shear viscosity and other transport coefficients to high accuracy. We also provide a simple approximate analytic expression that describes the attractor in the entire domain of interest for studies of quark-gluon plasma dynamics.
nucl-thhep-phhep-thPRD(2025)·11 citations
05
The chiral phase transition and the axial anomaly
Robert D. Pisarski🇺🇸 · Fabian Rennecke🇩🇪
To date numerical simulations of lattice QCD have not found a chiral phase transition of first order which is expected to occur for sufficiently light pions. We show how the restoration of an exact global chiral symmetry can strongly decrease the breaking of the approximate, anomalous $U_{A} (1)$ symmetry. This is testable on the lattice through simulations for one through four flavors. In QCD a small breaking of the $U_{A} (1)$ symmetry in the chirally symmetric phase generates novel experimental signals.
↳ hep-phhep-lathep-thnucl-thPRL(2024)·43 citations
06
Instability windows of relativistic r-modes
Kirill Y. Kraav · Mikhail E. Gusakov · Elena M. Kantor
The detectability of the gravitational-wave signal from $r$ -modes depends on the interplay between the amplification of the mode by the CFS instability and its damping due to dissipative mechanisms present in the stellar matter. The instability window of $r$ -modes describes the region of stellar parameters (angular velocity, $Ω$ , and redshifted stellar temperature, $T^{\infty}$ ), for which the mode is unstable. In this study, we reexamine this problem in nonbarotropic neutron stars, taking into account the previously overlooked nonanalytic behavior (in $Ω$ ) of relativistic $r$ -modes and enhanced energy dissipation resulting from diffusion in superconducting stellar matter. We demonstrate that at slow rotation rates, relativistic $r$ -modes exhibit weaker amplification by the CFS instability compared to Newtonian ones. However, their dissipation through viscosity and diffusion is significantly more efficient. In rapidly rotating neutron stars within the framework of general relativity, the amplification of $r$ -modes by the CFS mechanism and their damping due to shear viscosity become comparable to those predicted by Newtonian theory. In contrast, the relativistic damping of the mode by diffusion and bulk viscosity remains significantly stronger than in the nonrelativistic case. Consequently, account for diffusion and general relativity leads to a substantial modification of the $r$ -mode instability window compared to the Newtonian prediction. This finding is important for the interpretation of observations of rotating neutron stars, as well as for overall understanding of $r$ -mode physics.
↳ astro-ph.HEgr-qcnucl-thPRD(2024)·9 citations
07
SIDIS at small $x$ at next-to-leading order: gluon contribution
Filip Bergabo🇺🇸 · Jamal Jalilian-Marian🇺🇸
We calculate the contribution of gluons to single inclusive hadron production at next-to-leading order (NLO) accuracy in Deep Inelastic Scattering (DIS) at small $x$ using the Color Glass Condensate formalism. It is shown that the only divergence present is the standard collinear divergence which is absorbed into evolution of gluon-hadron fragmentation function. Our calculations are performed at finite $N_{c}$ and we provide general finite $N_{c}$ expressions for the structure of Wilson lines appearing in inclusive dihadron and single hadron production cross sections. We also comment on how one can obtain rapidity distribution of hadron multiplicities from our results.
↳ hep-phnucl-exnucl-thPRD(2024)·15 citations
08
Incorporating $D D π$ effects and left-hand cuts in lattice QCD studies of the $T_{cc} (3875)^{+}$
Maxwell T. Hansen🇬🇧 · Fernando Romero-López🇺🇸 · Stephen R. Sharpe🇺🇸
We generalize the relativistic field-theoretic three-particle finite-volume scattering formalism to describe generic $D D π$ systems in the charm $C = 2$ sector. This includes the isospin-0 channel, in which the recently discovered doubly-charmed tetraquark $T_{cc} (3875)^{+}$ is expected to manifest as a pole in the $D D π \to D D π$ scattering amplitude. The formalism presented here can also be applied to lattice QCD settings in which the $D^{*}$ is bound and, in particular, remains valid below the left-hand cut in $D D^{*}$ scattering, thus resolving an issue in previous analyses of lattice-determined finite-volume energies.
↳ hep-lathep-phnucl-thJHEP(2024)·76 citations
09
Imaging Shapes of Atomic Nuclei in High-Energy Nuclear Collisions
STAR Collaboration
Atomic nuclei are self-organized, many-body quantum systems bound by strong nuclear forces within femtometer-scale space. These complex systems manifest a variety of shapes, traditionally explored using non-invasive spectroscopic techniques at low energies. However, at these energies, their instantaneous shapes are obscured by long-timescale quantum fluctuations, making direct observation challenging. Here we introduce the ``collective flow assisted nuclear shape imaging'' method, which images the nuclear global shape by colliding them at ultrarelativistic speeds and analyzing the collective response of outgoing debris. This technique captures a collision-specific snapshot of the spatial matter distribution within the nuclei, which, through the hydrodynamic expansion, imprints patterns on the particle momentum distribution observed in detectors. We benchmark this method in collisions of ground state Uranium-238 nuclei, known for their elongated, axial-symmetric shape. Our findings show a large deformation with a slight deviation from axial symmetry in the nuclear ground state, aligning broadly with previous low-energy experiments. This approach offers a new method for imaging nuclear shapes, enhances our understanding of the initial conditions in high-energy collisions and addresses the important issue of nuclear structure evolution across energy scales.
↳ nucl-exhep-exhep-phnucl-thNature(2024)·144 citations

Affiliations

first authorsco-authorsvia INSPIRE