Nuclear Theory·nucl-th

Friday·November 18, 2022

16 papers—8 primary·8 cross-listed

01
Helicity and vorticity in heavy-ion collisions at NICA energies
N. S. Tsegelnik🇷🇺 · E. E. Kolomeitsev🇷🇺 · V. Voronyuk🇷🇺
Heavy-ion collisions at center-of-mass nucleon collision energies 4.5--11.5 GeV are analyzed within the PHSD transport model. Spectator nucleons are separated, and the transfer of the initial angular momentum of colliding nuclei to the fireball formed by participants is studied. The maximal angular momentum is carried by the fireball in gold-gold collisions with the impact parameter about 5 fm corresponding to centrality class 10--20\%. The obtained participant distributions were fluidized and the energy and baryon number densities, temperature, and velocity fields are obtained in the Landau frame. It is shown that the velocity field has dominantly Hubble-like transversal and longitudinal expansion with the vortical motion being only a small correction on top of it. The vorticity field is calculated and illustrated in detail. The formation of two oppositely-rotating vortex rings moving in opposite directions along the $z$ axis is demonstrated. Other characteristics of the vortical motion such as the Lamb vector field and the kinematic vorticity number are considered. The magnitude of the latter one is found to be smaller than that for the Poiseuille flow and close to the pure shear deformation corresponding to just a flattening of fluid cells. The field of hydrodynamic helicity, which is responsible for the axial vortex effect, is calculated. The separation of positive and negative helicities localized upper and lower semi-planes with respect to the reaction plane is shown. It is proved that the areas with various helicity signs can be probed by the selection of $Λ$ hyperons with positive and negative projections of their momenta orthogonal to the reaction plane.
nucl-thhep-phPRC(2023)·24 citations
02
Weinberg and few-nucleon forces
U. van Kolck🇫🇷
Weinberg's contributions to the power counting and derivation of few-nucleon forces in Chiral EFT are briefly recalled. Subsequent improvements are reviewed, concluding with the recent suggestion of a combinatorial enhancement.
nucl-thhep-phJ.Phys.Conf.Ser.(2022)·0 citations
03
The interplay of single-particle and collective motions in the low-lying states of $_{Λ}^{21}$ Ne with quadrupole-octupole correlations
H. J. Xia🇨🇳 · X. Y. Wu🇨🇳 · H. Mei🇷🇺 · J. M. Yao🇨🇳
The beyond mean-field approach for low-lying hypernuclear states is extended by mixing the configurations associated with both single-particle and quadrupole-octupole collective excitations within the generator coordinate method based on a covariant density functional theory. The method is demonstrated in the application to the low-lying states of $_{Λ}^{21}$ Ne, where the configurations with the $Λ$ hyperon occupying the first ( $Λ_{s}$ ) and second ( $Λ_{p}$ ) lowest-energy states are considered. The results indicate that the positive-parity states are dominated by the $α +^{12}$ C+ $α + Λ_{s}$ structure. In contrast, the low-lying negative-parity states are dominated by a strong admixture of $α +^{16}$ O+ $Λ_{s}$ structure and $α +^{12}$ C+ $α + Λ_{p}$ structure due to the inclusion of octupole correlations. As a result, the low-lying negative-parity states become much lower than what is expected from the previous studies without the mixing, and the electric multipole transition strengths are significantly quenched.
nucl-thnucl-exSCPMA(2023)·10 citations
04
Isotopic dependence of $(n, α)$ reaction cross sections for Fe and Sn nuclei
Sema Kucuksucu · Mustafa Yigit · Nils Paar
The $(n, α)$ reactions play an important role for the energy generation and the synthesis of chemical elements in the stars, as well as for nuclear engineering and medical applications. The aim of this study is to explore the evolution of $(n, α)$ reactions in Fe and Sn isotope chains in order to assess their properties with the increase of neutrons in target nucleus, and compare with other relevant neutron induced reactions. Model calculations of the cross sections are based on the statistical Hauser-Feshbach model in TALYS implementation, using global optical model potential that is additionally adjusted by the $(n, α)$ cross section data for $^{54}$ Fe and $^{118}$ Sn. The calculations of $(n, α)$ reactions in Fe and Sn isotopes provide the insight into their isospin dependence and properties over the complete relevant range of neutron energies. The results show the evolution of the cross sections with pronounced maxima at low-mass isotopes, and rather strong decrease for neutron-rich nuclei consistent with the reduction of the reaction $Q$ -value and increased contributions from other exit channels from compound nucleus. The analysis of the Maxwellian averaged cross sections at temperatures in stellar environment shows that while the $(n, α)$ reactions contribute for the low-mass isotopes, in neutron induced reactions with nuclei with neutron excess, $γ$ and neutron emission dominate.
nucl-thastro-ph.SRnucl-exNPA(2024)·1 citation
05
Fermi operator expansion method for nuclei and inhomogeneous matter with nuclear energy density functional
Takashi Nakatsukasa
The nuclear energy density functional method at finite temperature is a useful tool for studies of nuclear structure at high excitation, and also for researches of nuclear matter involved in explosive stellar phenomena and neutron stars. However, its unrestricted calculation requires large computational costs for the three-dimensional coordinate-space solvers, especially for the Hamiltonian matrix diagonalization and (or) the Gram-Schmidt orthonormalization of the single-particle wave functions. We test numerical performance of the Fermi operator expansion method, that requires neither the diagonalization nor the Gram-Schmidt orthonormalization, for finite nuclei and inhomogeneous nuclear matter. The method is applied to isolated finite N=Z nuclei and to non-uniform symmetric nuclear matter at finite temperature, which turns out be very effective with the three-dimensional coordinate-space representation, especially at high temperature. The Fermi operator expansion method is a useful tool for studies of various nuclear phases at finite temperature with the energy density functional calculations. The method is suitable for massively parallel computing with distributed memory. Furthermore, when the space size is large, the calculation may benefit from its order-N scaling property.
nucl-thPRC(2023)·2 citations
06
Cluster mean field description of alpha emission
A. Dumitrescu · D. S. Delion
We show that the Hartree-Fock-Bogoliubov (HFB) method is able to describe experimental values of alpha decay widths by including a residual nucleon-nucleon Surface Gaussian Interaction (SGI) within the standard procedure used to calculate the nuclear mean field. We call this method the Cluster HFB (CHFB) approach. In this way we correct the deficient asymptotic behaviour of the corresponding single-particle (sp) wave functions generated by the standard mean field. The corrected mean field becomes a sum between the standard mean Woods-Saxon-like field and a cluster Gaussian component centered at the same radius as the SGI. Thus, we give a confirmation of the mean field plus cluster potential structure, which was assumed in our previous work on alpha-decay widths. Systematic calculations evidence the linear correlation between the SGI strength and fragmentation potential, allowing for reliable predictions concerning the half lives of superheavy emitters.
nucl-thPRC(2023)·8 citations
07
Charge diffusion in relativistic resistive second-order dissipative magnetohydrodynamics
Ashutosh Dash🇩🇪 · Masoud Shokri🇩🇪 · Luciano Rezzolla🇩🇪 · Dirk H. Rischke🇩🇪
We study charge diffusion in relativistic resistive second-order dissipative magnetohydrodynamics. In this theory, charge diffusion is not simply given by the standard Navier-Stokes form of Ohm's law, but by an evolution equation which ensures causality and stability. This, in turn, leads to transient effects in the charge diffusion current, the nature of which depends on the particular values of the electrical conductivity and the charge-diffusion relaxation time. The ensuing equations of motion are of so-called stiff character, which requires special care when solving them numerically. To this end, we specifically develop an implicit-explicit Runge-Kutta method for solving relativistic resistive second-order dissipative magnetohydrodynamics and subject it to various tests. We then study the system's evolution in a simplified 1+1-dimensional scenario for a heavy-ion collision, where matter and electromagnetic fields are assumed to be transversely homogeneous, and investigate the cases of an initially non-expanding fluid and a fluid initially expanding according to a Bjorken scaling flow. In the latter case, the scale invariance is broken by the ensuing self-consistent dynamics of matter and electromagnetic fields. However, the breaking becomes quantitatively important only if the electromagnetic fields are sufficiently strong. The breaking of scale invariance is larger for smaller values of the conductivity. Aspects of entropy production from charge diffusion currents and stability are also discussed.
nucl-thhep-phphysics.flu-dynPRD(2023)·27 citations
08
Calculating QCD Phase Diagram Trajectories of Nuclear Collisions using a Semi-analytical Model
Todd Mendenhall🇺🇸 · Zi-Wei Lin🇺🇸
At low to moderate collision energies where the parton formation time $τ_{F}$ is not small compared to the nuclear crossing time, the finite nuclear thickness significantly affects the energy density $ϵ (t)$ and net conserved-charge densities such as the net-baryon density $n_{B} (t)$ produced in heavy ion collisions. As a result, at low to moderate energies the trajectory in the QCD phase diagram is also affected by the finite nuclear thickness. Here, we first discuss our semi-analytical model and its results on $ϵ (t)$ , $n_{B} (t)$ , $n_{Q} (t)$ , and $n_{S} (t)$ in central Au+Au collisions. We then compare the $T (t)$ , $μ_{B} (t)$ , $μ_{Q} (t)$ , and $μ_{S} (t)$ extracted with the ideal gas equation of state (EoS) with quantum statistics to those extracted with a lattice QCD-based EoS. We also compare the $T - μ_{B}$ trajectories with the RHIC chemical freezeout data. Finally, we discuss the effect of transverse flow on the trajectories.
nucl-thEPJ Web Conf.(2023)·1 citation
09
Maximum entropy freezeout of hydrodynamic fluctuations
Maneesha Sushama Pradeep🇺🇸 · Mikhail Stephanov🇺🇸
We propose a general approach to freezing out fluctuations in heavy-ion collisions using the principle of maximum entropy. We find the results naturally expressed as a direct relationship between the irreducible relative correlators quantifying the deviations of hydrodynamic as well as hadron gas fluctuations from the ideal hadron gas baseline. The method also allows us to determine heretofore unknown parameters crucial for the freezeout of fluctuations near the QCD critical point in terms of the QCD equation of state.
↳ hep-phhep-thnucl-thPRL(2023)·34 citations
10
Rethinking the $P_{c} (4457)^{+}$ as the $P_{ψ}^{Δ^{+}} (4457)$ isoquartet $D ˉ^{*} Σ_{c}$ molecule
Fang-Zheng Peng🇨🇳 · Mao-Jun Yan🇨🇳 · Mario Sánchez Sánchez🇫🇷 · Manuel Pavon Valderrama🇨🇳
The nature of the $P_{c} (4312)$ , $P_{c} (4440)$ and $P_{c} (4457)$ pentaquarks is a fascinating theoretical question. Within the molecular picture their more usual interpretation is that of $I = \frac{1}{2}$ $D ˉ Σ_{c}$ and $D ˉ^{*} Σ_{c}$ bound states. Here we argue in favor of interpreting the $P_{c} (4457)$ pentaquark as a $I = \frac{3}{2}$ $D ˉ^{*} Σ_{c}$ bound state (with spin $J = \frac{1}{2}$ ) instead. Owing to isospin symmetry breaking effects, with this identification the partial decay width of the $P_{c} (4457)^{+}$ into $J / ψ p$ will be of the same order of magnitude as the $P_{c} (4312)^{+}$ and $P_{c} (4440)^{+}$ , in contrast with the considerably larger partial decay width in the $I = \frac{1}{2}$ scenario. In turn, this leads to a different hidden-charm molecular pentaquark spectrum, in which there are only four or five $P_{ψ}^{N}$ bound states instead of the usual seven, which might explain why the predicted $J = \frac{1}{2}$ and $\frac{3}{2}$ ( $I = \frac{1}{2}$ ) $D ˉ^{*} Σ_{c}^{*}$ molecular partners of the $P_{c} (4312)$ and $P_{c} (4440)$ have not been observed.
↳ hep-phhep-exnucl-thPLB(2023)·9 citations
11
Colliding localized, lumpy holographic shocks with a granular nuclear structure
Sebastian Waeber🇮🇱 · Laurence G. Yaffe🇺🇸
We apply a recent and simple technique which speeds up the calculation of localized collisions in holography to study more realistic models of heavy ion collisions via the gauge/gravity duality. The initial data takes into account the lumpy nuclear structure of real heavy ions and the projectiles' aspect ratio mimics the Lorentz contraction of nuclei during RHIC collisions. At the hydrodynamization time of the central region of the quark gluon plasma developed during the collision, we find that most of the vorticity three vector's absolute value is deposited far away from the hydrodynamized part of the plasma. Only the relativistic corrections to the thermal vorticity in the hydrodynamized region are non-negligible. We compare the transverse flow after the collision determined in this work with previous results, without granular initial conditions and determine the proper energy density and fluid velocity in a hydrodynamized subregion of the plasma.
↳ hep-thgr-qchep-phnucl-thJHEP(2023)·5 citations
12
Exotic states with triple charm
M. Bayar🇹🇷 · A. Martinez Torres🇪🇸 · K. P. Khemchandani🇪🇸 · R. Molina🇪🇸 · E. Oset🇪🇸
In this work we investigate the possibility of the formation of states from the dynamics involved in the $D^{*} D^{*} D^{*}$ system by considering that two $D^{*}$ 's generate a $J^{P} = 1^{+}$ bound state, with isospin 0, which has been predicted in an earlier theoretical work. We solve the Faddeev equations for this system within the fixed center approximation and find the existence of $J^{P} = 0^{-}$ , $1^{-}$ and $2^{-}$ states with charm $3$ , isospin $1/2$ , masses $\sim 6000$ MeV, which are manifestly exotic hadrons, i.e., with a multiquark inner structure.
↳ hep-phnucl-thEPJC(2023)·15 citations
13
Quantification of the hadronic CP violation contribution to the atomic EDMs
Nodoka Yamanaka🇯🇵
CP violating interactions are required to realize the matter abundance of our Universe. It is however known that the standard model of particle physics does not contain sufficient CP violation. The electric dipole moment (EDM) of atomic systems is a very sensitive experimental probe of CP violation beyond the standard model, and it is very actively studied in experiments. The atomic EDM has a significant sensitivity to hadronic CP violation, but its quantification has for long been obstructed by the nonperturbative physics of quantum chromodynamics. Quite recently, the contribution of the Weinberg operator (CP violating three-gluon interaction) to the atomic EDM has been analyzed, and we are almost attaining the quantification era of the CP violating hadronic interaction in the leading order of standard model effective field theory. In this proceedings contribution, we summarize the current attempt to quantify the hadronic CP violation contribution to the EDM of atoms.
↳ hep-phhep-exnucl-thphysics.atom-phAIP Conf.Proc.(2024)·1 citation
14
Definition of gravitational local spatial densities for spin-0 and spin-1/2 systems
J. Yu. Panteleeva🇩🇪 · E. Epelbaum🇩🇪 · J. Gegelia🇩🇪 · U.-G. Meißner🇩🇪
We work out details of defining the spatial densities corresponding to the gravitational form factors of spin-0 and spin-1/2 systems using spherically symmetric sharply localized wave packets. The expressions for the spatial densities are provided in the frames with both zero and non-zero expectation values of the momentum operator.
↳ hep-phhep-thnucl-thEPJC(2023)·29 citations
15
Baryon and meson masses in the Nambu--Jona-Lasinio model: A Bayesian approach
Antoine Pfaff🇫🇷 · Hubert Hansen🇫🇷 · Juan M. Torres-Rincon🇪🇸 · Joerg Aichelin🇫🇷
We investigate the capabilities of the Nambu--Jona-Lasinio model to describe and reproduce fundamental vacuum properties of Quantum Chromodynamics, notably the hadronic spectrum. Mesons are described as quark-antiquark bound states at the level of the random phase approximation of the Bethe-Salpeter equation, while baryons are characterized as quark-diquark bound states within the static approximation of the Faddeev equation. Within a Bayesian framework, we constrain the model by phenomenologically known quantities and study the implications on its parameters and predictions in vacuum, as well as the correlations between the two. We find that within our framework, the vacuum masses of mesons and baryons can be reasonably well reproduced. Scalar diquarks need to be significantly bound in order to correctly reproduce the masses of the baryon octet, therefore enforcing values of the scalar diquark coupling larger than what is suggested by the canonical Fierz values. These findings could have important implications on the phenomenology of strongly-interacting matter at high temperature and density as well as of compact star physics.
↳ hep-phnucl-thPRC(2023)·1 citation
16
Colliding poles with colliding nuclei
Alexander Soloviev🇦🇹
In these proceedings, I will discuss collisions of poles in the complex plane as a signature of phase transitions for theories relevant to the quark gluon plasma. I will begin with an illustrative example, namely the chiral phase transition, which can be characterized by colliding poles as a function of temperature. Then, recognizing the interplay between weak and strong coupling sectors in a typical collision, I will introduce a hybrid model with a weakly broken symmetry, which has a rich quasi-hydrodynamic phenomenological description where hydrodynamic and non-hydrodynamic poles are unified by a common dispersion relation. I will show that energy is transferred initially from the soft to the hard sector before irreversibly transferring back to the soft sector at late times, and that the model reproduces many features common to dissipative systems with a weakly broken symmetry including the k-gap.
↳ hep-phnucl-thEPJ Web Conf.(2022)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE