Nuclear Theory·nucl-th

Wednesday·August 14, 2024

13 papers—7 primary·6 cross-listed

01
Renormalized critical dynamics and fluctuations in model A
Nadine Attieh🇫🇷 · Nathan Touroux🇫🇷 · Marcus Bluhm🇫🇷 · Masakiyo Kitazawa🇯🇵 · Taklit Sami🇫🇷 · Marlene Nahrgang🇫🇷
In the context of relativistic heavy-ion collisions, we explore the stochastic and dissipative relaxational dynamics of a non-conserved order parameter in a $λ φ^{4}$ interaction. The cutoff of the theory is provided by the lattice spacing chosen for our numerical simulations. As a consequence, observables become dependent on that scale. We consider a possible first-order phase transition and an evolution close to a critical point. We demonstrate that using a lattice counterterm restores the expected behavior of the mean, variance and kurtosis: the mean and the variance become lattice spacing independent, and we recover the correct expectation value of the mean, the growth of the variance with the correlation length and the expected minimum in the kurtosis. Our findings hold true in equilibrium and during the dynamical relaxation, and therefore mark an important step towards a fully fluctuating fluid dynamical setup.
nucl-thPRC(2025)·2 citations
02
Chemical freeze-out curve in heavy-ion collisions and the QCD critical point
Artemiy Lysenko🇺🇦 · Mark I. Gorenstein🇺🇦 · Roman Poberezhniuk🇺🇦 · Volodymyr Vovchenko🇺🇸
The chemical freeze-out curve in heavy-ion collisions is investigated in the context of a quantum chromodynamics (QCD) critical point (CP) search at finite baryon densities. Taking the hadron resonance gas picture at face value, chemical freeze-out points at a given baryochemical potential provide a lower bound on the possible temperature of the QCD CP. We first verify that the freeze-out data in heavy-ion collisions are well described by a constant energy per particle curve, $E / N = const$ , under strangeness neutrality conditions ( $μ_{S} \neq = 0$ , $μ_{Q} \neq = 0$ ). We then evaluate the hypothetical lower bound on the freeze-out curve based on this criterion in the absence of strangeness neutrality ( $μ_{S} = 0$ , $μ_{Q} = 0$ ) and confront it with recent predictions on the CP location. We find that recent estimates based on Yang-Lee edge singularities from lattice QCD data on coarse lattices ( $N_{τ} = 6$ ) place the CP significantly below the freeze-out curve, hinting at the importance of performing continuum extrapolation within this method. Predictions based on functional methods and holography place the CP slightly above the freeze-out curve, indicating that the QCD CP may be located very close to the chemical freeze-out in $A$ + $A$ collisions at $s_{N N} = 3.5$ - $6$ GeV.
nucl-thPRC(2025)·29 citations
03
Application of the shift-invert Lanczos algorithm to a non-equilibrium Green function for transport problems
K. Uzawa · K. Hagino
Non-equilibrium Green's function theory and related methods are widely used to describe transport phenomena in many-body systems, but they often require a costly inversion of a large matrix. We show here that the shift-invert Lanczos method can dramatically reduce the computational effort. We apply the method to two test problems, namely a simple model Hamiltonian and to a more realistic Hamiltonian for nuclear fission. For a Hamiltonian of dimension 66103 we find that the computation time is reduced by a factor of 33 compared to the direct calculation of the Green's function.
nucl-thcond-mat.mes-hallcond-mat.stat-mechphysics.chem-phPRE(2024)·2 citations
04
Radial oscillations of proto-neutron stars
T. T. Sun🇨🇳 · H. Chen🇨🇳 · J. B. Wei🇨🇳 · Z. Y. Zheng🇨🇳 · G. F. Burgio🇮🇹 · H. -J. Schulze🇮🇹
We investigate radial oscillations of proto-neutron stars, employing equations of state described by the Brueckner-Hartree-Fock theory or the relativistic mean field model, and assuming isentropy and fixed lepton fractions for the internal structure. We calculate the eigenfrequencies and corresponding oscillation functions, which show different characteristics in different mass regions. In the low-mass region around 1.4 solar mass, the radial oscillation frequencies are lowered by large entropy and neutrino trapping, along with a reduction of the average adiabatic index. In the region close to the maximum mass, the fundamental oscillation frequency drops rapidly and vanishes at the maximum mass, in accordance with the critical stability criterion $\partial M / \partial ρ_{c} = 0$ , as for cold neutron stars.
nucl-thPRD(2025)·7 citations
05
The triton lifetime from nuclear lattice effective field theory
Serdar Elhatisari🇹🇷 · Fabian Hildenbrand🇩🇪 · Ulf-G. Meißner🇩🇪
In this work, we present a calculation of the triton $β$ -decay lifetime using Nuclear Lattice Effective Field Theory (NLEFT) at next-to-next-to-next-to-leading order in the chiral expansion. By incorporating a non-perturbative treatment of the higher-order corrections, we achieve consistent predictions for the Fermi and Gamow-Teller matrix elements, which are crucial for determining the triton lifetime. Our results are consistent with earlier theoretical calculations, confirming the robustness of our approach. This study marks a significant advancement in the systematic application of NLEFT to nuclear $β$ -decay processes, paving the way for future high-precision calculations in more complex nuclear systems. Additionally, we discuss potential improvements to our approach, including the explicit inclusion of two-pion exchange mechanisms and the refinement of three-nucleon forces. These developments are essential for extending the applicability of NLEFT to a broader range of nuclear phenomena, including neutrinoless double- $β$ decay.
nucl-thhep-lathep-phnucl-exPLB(2024)·10 citations
06
Multiboson Hanbury Brown-Twiss correlations for partially coherent sources in relativistic heavy-ion collisions in a multiphase transport model
Shi-Yao Wang🇨🇳 · Jun-Ting Ye🇨🇳 · Wei-Ning Zhang🇨🇳
We use a multi-phase transport (AMPT) model to study multi-pion and multi-kaon Hanbury Brown-Twiss (HBT) correlations for the partially coherent particle-emitting sources in relativistic heavy-ion collisions. A density-dependent longitudinal coherent emission length and density-dependent transverse coherent emission length are introduced in calculating the multi-boson HBT correlation functions of the partially coherent sources. We compare the model results of three- and four-pion HBT correlation functions with experimental data in Pb-Pb collisions at center-of-mass energy $s_{N N} =$ 2.76 TeV, and investigate the influences of boson coherent emissions on the multi-pion and multi-kaon correlation functions, respectively. We find that all of the three- and four-pion correlation functions of the partially coherent sources are consistent with experimental data. Coherent emission leads to the intercept decreases of the multi-boson correlation functions. The intercepts of the multi-kaon correlation functions of the partially coherent source are higher than those of the multi-pion correlation functions, because low kaon densities lead to smaller kaon coherent emission lengths than pion emission lengths. The intercepts of multi-boson correlation functions of partially coherent sources in high transverse momentum intervals are higher than those in low transverse momentum intervals because particle de Broglie wavelengths are small at high momenta.
nucl-thPRC(2024)·1 citation
07
Uncertainty quantification of optical models in fission fragment de-excitation
Kyle A. Beyer · Amy E. Lovell · Cole D. Pruitt · Nathan P. Giha · Brian C. Kiedrowski
We take the first step towards incorporating compound nuclear observables at astrophysically relevant energies into the experimental evidence used to constrain optical models, by propagating the uncertainty in two global optical potentials, one phenomenological and one microscopic, to correlated fission observables using the Monte Carlo Hauser-Feshbach formalism. We compare to a wide range of historic and recent experimental fission measurements, and discuss in detail regions of disagreement. We find that the parametric optical model uncertainty in neutron-fragment correlated observables involving neutron energy is significant. On the other hand, we observe that other experimental features, particularly neutron-fragment correlations near the $^{132}$ Sn shell-closure and the high energy component of neutron spectra, are unlikely to be explained by the optical potential, and will require further experimental and theoretical effort to explain.
nucl-thPRC(2025)·5 citations
08
Production characteristics of light nuclei, hypertritons and $Ω$ -hypernuclei in Pb+Pb collisions at $s_{N N} = 5.02$ TeV
Rui-Qin Wang🇨🇳 · Xin-Lei Hou🇨🇳 · Yan-Hao Li🇨🇳 · Jun Song🇨🇳 · Feng-Lan Shao🇨🇳
We extend an analytical nucleon coalescence model with hyperons to study productions of light nuclei, hypertritons and $Ω$ -hypernuclei in Pb+Pb collisions at $s_{N N} = 5.02$ TeV. We derive the formula of the momentum distribution of two bodies coalescing into dibaryon states and that of three bodies coalescing into tribaryon states. We explain the available data of the coalescence factors $B_{2}$ and $B_{3}$ , the transverse momentum spectra, the averaged transverse momenta, the yield rapidity densities, yield ratios of the deuteron, antihelium-3, antitriton, hypertriton measured by the ALICE collaboration, and give predictions of different $Ω$ -hypernuclei, e.g., $H (p Ω^{-})$ , $H (n Ω^{-})$ and $H (p n Ω^{-})$ . We find two groups of interesting observables, the averaged transverse momentum ratios of light (hyper-)nuclei to protons (hyperons) and the centrality-dependent yield ratios of theirs. The former group exhibits a reverse-hierarchy of the nucleus size, and the latter is helpful for the judgements of the nucleus production mechanism as well as the nucleus own size.
↳ hep-phnucl-thNucl.Sci.Tech.(2025)·6 citations
09
Semi-automatic Calculations of Multi-loop Feynman Amplitudes with AmpRed
Wen Chen🇨🇳
We present a Mathematica package AmpRed for the semi-automatic calculations of multi-loop Feynman amplitudes with high efficiency and precision. AmpRed implements the methods of integration by parts and differential equations in the Feynman-parameter representation. It allows for the calculations of general parametric integrals (which may not have momentum-space correspondences). Various user-friendly tools for multi-loop calculations, such as those to construct and solve differential equations for Feynman integrals, are provided. It can also deal with tensor algebras in non-relativistic field theories. Interfaces to some packages, like QGRAF and FORM, are also provided.
↳ hep-phhep-thnucl-thComput.Phys.Commun.(2025)·33 citations
10
Renormalization-group consistent treatment of color superconductivity in the NJL model
Hosein Gholami🇩🇪 · Marco Hofmann🇩🇪 · Michael Buballa🇩🇪
The Nambu-Jona-Lasinio (NJL) model and specifically its extension to color superconductivity (CSC) is a popular effective model for investigating dense quark matter. However, the reliability of its results is challenged by cutoff artifacts, which emerge if temperature or chemical potential are of the order of the cutoff energy scales. In this work, we generalize an idea from [Braun et al. SciPost Phys., 6:056, 2019], which is based on the requirement of renormalization-group (RG) consistency and has successfully been applied to the two-flavor Quark-Meson-Diquark model, to the NJL model for electrically and color-neutral three-flavor color-superconducting quark matter. To this end, we analyze the medium divergences of the model and eliminate them by appropriate counterterms, introducing three different schemes. We show that the RG-consistent treatment removes the cutoff artifacts of the conventional regularization and enables the investigation of CSC matter at higher densities by the model. Our studies reveal the emergence of a so-called d-quark superconducting (dSC) phase within the melting pattern of the Color-Flavor Locked (CFL) phase at high chemical potentials, consistent with earlier Ginzburg-Landau analyses.
↳ hep-phhep-thnucl-thPRD(2025)·47 citations
11
Nuclear Excitation by Near-Resonant Electron Transition in $^{229}$ Th $^{39 +}$ Ions
Karol Kozioł · Jacek Rzadkiewicz
Theoretical considerations are made for the nuclear excitation from the ground state to the 8 eV $^{229 m}$ Th isomer via near-resonant electron transitions in Sb-like ( $q = 39 +$ ) thorium ions. The energy of the first excited atomic state ( $J = 7/2$ ) in the $^{229}$ Th $^{39 +}$ ion is estimated to be 8.308 $\pm$ 0.069 eV, which is very close to the new reference value for the $^{229 m}$ Th nuclear isomer energy, 8.356 eV [Zhang et al., Nature 633, 63 (2024)]. Therefore, the $^{229}$ Th $^{39 +}$ ion provides a unique opportunity to study the nuclear excitation by electron transition process under well-defined atomic conditions in the regime of extremely low nuclear excitation energy. Our results indicate that the upper theoretical limit for the $^{229 m}$ Th isomer excitation rate reaches an enormous value of $1.27 \times 1 0^{16}$ s $^{- 1}$ at resonance ( $Δ = 0$ meV), but drops many orders of magnitude for the value of electronic transition energy within its uncertainty interval. Additionally, it was shown that using an electron beam ion trap, the production of the $^{229}$ Th isomer can reach rates ranging from a few to approximately $7 \times 1 0^{19}$ $^{- 1}$ .
↳ physics.atom-phnucl-exnucl-thquant-phPRC(2025)·4 citations
12
Pion to photon transition form factor: Beyond valence quarks
Xiaoyi Wu🇨🇳 · Zhimin Zhu🇨🇳 · Ziyang Lin🇨🇳 · Chandan Mondal🇨🇳 · Jiangshan Lan🇨🇳 · Xingbo Zhao🇨🇳 · James P. Vary🇺🇸
We investigate the singly virtual transition form factor (TFF) for the $π^{0} \to γ^{*} γ$ process in the space-like region using the hard-scattering formalism within the Basis Light-Front Quantization (BLFQ) framework. This form factor is expressed in terms of the perturbatively calculable hard-scattering amplitudes (HSAs) and the light-front wave functions (LFWFs) of the pion. We obtain the pion LFWFs by diagonalizing the light-front QCD Hamiltonian, which is determined for its constituent quark-antiquark and quark-antiquark-gluon Fock sectors with a three-dimensional confinement. We employ the HSAs up to next-to-leading order (NLO) in the quark-antiquark Fock sector and leading order (LO) in the quark-antiquark-gluon Fock sector. The NLO correction to the TFF in the quark-antiquark Fock sector is of the same order as the LO contribution to the TFF in the quark-antiquark-gluon Fock sector. We find that while the quark-antiquark-gluon Fock sector has minimal effect in the large momentum transfer ( $Q^{2}$ ) region, it has a noteworthy impact in the low- $Q^{2}$ region. Our results show that, after accounting for both Fock sectors, the TFF within the BLFQ framework aligns well with existing experimental data, particularly in the low $Q^{2}$ region.
↳ hep-phnucl-thPRD(2025)·4 citations
13
Shape Coexistence in $^{94}$ Zr from a Model-Independent Analysis
N. Marchini (1 and 2)🇮🇹 · M. Rocchini (1)🇮🇹 · M. Zielinska (3)🇫🇷 · A. Nannini (1)🇮🇹 · D.T. Doherty (4)🇬🇧 · N. Gavrielov (5)🇫🇷 · P.E. Garrett (6)🇨🇦 · K. Hadynska-Klek (7)🇵🇱 · A. Goasduff (8 and 9)🇮🇹 · D. Testov (8)🇮🇹 · S.D. Bakes (4 and 9 and 10)🇬🇧 · D. Bazzacco (8 and 9)🇮🇹 and 24 other authors
Low-lying states of $^{94}$ Zr were investigated via low-energy multi-step Coulomb excitation. From the measured $γ$ -ray yields, \textcolor{black}{16} reduced \textcolor{black}{E2} transition probabilities between low-spin states were determined, together with the spectroscopic quadrupole moments of the $2_{1, 2}^{+}$ states. Based on this information, for the first time in the Zr isotopic chain, the shapes of the $0_{1, 2}^{+}$ states including their deformation softness were inferred in a model-independent way using the quadrupole sum rules approach. The ground state of $^{94}$ Zr possesses a rather diffuse shape associated with a spherical configuration, while the $0_{2}^{+}$ state is \textcolor{black}{triaxial tending towards} oblate and more strongly deformed. {\color{black}The observed features of shape coexistence in $^{94}$ Zr are consistent with both Monte-Carlo shell-model predictions and IBM-CM calculations, and provide model-independent constraints on the shape character assigned in the IBM-CM to the intruder configuration in $^{92 - 96}$ Zr.}
↳ nucl-exnucl-thPLB(2026)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE