Nuclear Theory·nucl-th

Tuesday·December 5, 2023

11 papers—3 primary·8 cross-listed

04
Spin interaction of non-relativistic neutrons with an ultrashort laser pulse
Peter Christian Aichelburg · Christian Spreitzer
The non-relativistic Pauli equation is used to study the interaction of slow neutrons with a short magnetic pulse. In the extreme limit, the pulse is acting on the magnetic moment of the neutron only at one instant of time. We obtain the scattering amplitude by deriving the junction conditions for the Pauli wave function across the pulse. Explicit expressions are given for a beam of polarized plane wave neutrons subjected to a pulse of spatially constant magnetic field strength. Assuming that the magnetic field is generated by an ultrashort laser pulse, we provide crude numerical estimates.
↳ quant-phnucl-thInt.J.Mod.Phys.A(2024)·0 citations
05
Isospin diffusion from $^{40, 48}$ Ca $+^{40, 48}$ Ca experimental data at Fermi energies: Direct comparisons with transport model calculations
Q. Fable (L2IT)🇫🇷 · L. Baldesi (INFN, Sezione di Firenze)🇮🇹 · S. Barlini (INFN, Sezione di Firenze)🇮🇹 · Eric Bonnet (SUBATECH)🇫🇷 · Bernard Borderie (IJCLab)🇫🇷 · Remi Bougault (LPCC)🇫🇷 · A. Camaiani (INFN, Sezione di Firenze)🇮🇹 · G. Casini (INFN, Sezione di Firenze)🇮🇹 · A. Chbihi (GANIL)🇫🇷 · Caterina Ciampi (GANIL)🇫🇷 · J. A. Dueñas🇪🇸 · J.D. Frankland (GANIL)🇫🇷 and 21 other authors
This article presents an investigation of isospin equilibration in cross-bombarding $^{40, 48}$ Ca $+^{40, 48}$ Ca reactions at 35 MeV/nucleon, by comparing experimental data with filtered transport model calculations. Isospin diffusion is studied using the evolution of the isospin transport ratio with centrality. The asymmetry parameter $δ = (N - Z) / A$ of the quasiprojectile (QP) residue is used as isospin-sensitive observable, while a recent method for impact parameter reconstruction is used for centrality sorting. A benchmark of global observables is proposed to assess the relevance of the antisymmetrized molecular dynamics (AMD) model, coupled to GEMINI++, in the study of dissipative collisions. Our results demonstrate the importance of considering cluster formation to reproduce observables used for isospin transport and centrality studies. Within the AMD model, we prove the applicability of the impact parameter reconstruction method, enabling a direct comparison to the experimental data for the investigation of isospin diffusion. For both, we evidence a tendency to isospin equilibration with an impact parameter decreasing from 9 to 3 fm, while the full equilibration is not reached. A weak sensitivity to the stiffness of the equation of state employed in the model is also observed, with a better reproduction of the experimental trend for the neutron-rich reactions.
↳ nucl-exnucl-thPRC(2024)·9 citations
06
$J / ψ$ polarization in relativistic heavy ion collisions
Jiaxing Zhao🇫🇷 · Baoyi Chen🇨🇳
Understanding the polarization property of $J / ψ$ is critical to constrain its production mechanism. In addition, the polarization of $J / ψ$ can reveal the impact of strong electromagnetic and vorticity fields in relativistic heavy ion collisions. In this study, we analyzed the yield and polarization of $J / ψ$ in relativistic heavy ion collisions at different centrality and transverse momentum regions, using three different reference frames: the Collins-Soper frame, the helicity frame, and the event plane frame. The polarization of initially produced $J / ψ$ is determined by the NRQCD calculation and is similar to that of $pp$ collisions. However, both unpolarization and transverse polarization are considered for the regenerated $J / ψ$ . Our results indicate that the polarization at high $p_{T}$ is similar to that observed in $pp$ collisions. However, at low $p_{T}$ , where regenerated $J / ψ$ dominates, it is likely that the polarized charm quarks in the rotational QGP medium are responsible for this phenomenon. Our study supplies a baseline for future research on the effects of strong electromagnetic and vorticity fields on $J / ψ$ polarization.
↳ hep-phnucl-thEPJC(2024)·8 citations
07
Solving the left-hand cut problem in lattice QCD: $T_{cc} (3875)^{+}$ from finite volume energy levels
Lu Meng🇩🇪 · Vadim Baru🇩🇪 · Evgeny Epelbaum🇩🇪 · Arseniy A. Filin🇩🇪 · Ashot M. Gasparyan🇩🇪
We discuss a novel effective-field-theory-based approach for extracting two-body scattering information from finite volume energies, serving as an alternative to Lüscher's method. By explicitly incorporating one-pion exchange, we overcome the challenging left-hand cut problem in Lüscher's method and can handle finite volume energy levels both below and above the left-hand cut. Applied to the lattice data for $D D^{*}$ scattering at a pion mass of 280 MeV, as an illustrative example, our results reveal the significant impact of the one-pion exchange on P-wave and S-wave phase shifts. The pole position of the $T_{cc} (3875)^{+}$ state, extracted from the finite-volume energy levels at this pion mass while taking into account left-hand cut effects, range corrections and partial-wave mixing, is consistent with a near-threshold resonance. This study demonstrates, for the first time, that two-body scattering information can be reliably extracted from lattice spectra including the left-hand cut.
↳ hep-lathep-phnucl-thPRD(2024)·78 citations
08
Strange hidden-charm pentaquark poles from $B^{-} \to J / ψ Λ p ˉ$
Satoshi X. Nakamura (Shandong Univ.)🇨🇳 · Jia-Jun Wu (Univ. of Chinese Academy of Sciences)🇨🇳
Recent LHCb data for $B^{-} \to J / ψ Λ p ˉ$ show a clear peak structure at the $Ξ_{c} D ˉ$ threshold in the $J / ψ Λ$ invariant mass ( $M_{J / ψ Λ}$ ) distribution. The LHCb's amplitude analysis identified the peak with the first hidden-charm pentaquark with strangeness $P_{ψ s}^{Λ} (4338)$ . We conduct a coupled-channel amplitude analysis of the LHCb data by simultaneously fitting the $M_{J / ψ Λ}$ , $M_{J / ψ p ˉ}$ , $M_{Λ p ˉ}$ , and $cos θ_{K^{*}}$ distributions. Rather than the Breit-Wigner fit employed in the LHCb analysis, we consider relevant threshold effects and a unitary $Ξ_{c} D ˉ$ - $Λ_{c} D ˉ_{s}$ coupled-channel scattering amplitude from which $P_{ψ s}^{Λ}$ poles are extracted for the first time. In our default fit, the $P_{ψ s}^{Λ} (4338)$ pole is almost a $Ξ_{c} D ˉ$ bound state at $(4338.2 \pm 1.4) - (1.9 \pm 0.5) i$ MeV. Our default model also fits a large fluctuation at the $Λ_{c} D ˉ_{s}$ threshold, giving a $Λ_{c} D ˉ_{s}$ virtual state, $P_{ψ s}^{Λ} (4255)$ , at $4254.7 \pm 0.4$ MeV. We also found that the $P_{ψ s}^{Λ} (4338)$ peak cannot solely be a kinematical effect, and a nearby pole is needed.
↳ hep-phhep-exnucl-thEPJ Web Conf.(2024)·1 citation
09
Parameter optimisation using Bayesian inference for spallation models
Jason Hirtz🇫🇷 · Jean-Christophe David🇫🇷 · Joseph Cugnon🇧🇪 · Ingo Leya🇨🇭 · José Luís Rodríguez-Sánchez🇪🇸 · Georg Schnabel🇦🇹
The accuracy and precision of high-energy spallation models are key issues for the design and development of new applications and experiments. We present a method to estimate model parameters and associated uncertainties by leveraging the Bayesian version of the Generalised Least Squares method, which enables us to incorporate prior knowledge on the parameter values. This approach is designed to adjust parameters based on experimental data, accounting for experimental uncertainty information, and providing uncertainties for all adjusted parameters. This approach is designed in order both to improve the accuracy of models through the modification of free parameters of these models, which results in a better reproduction of experimental data, and to estimate the uncertainties of these parameters and, by extension, their impacts on the model output. We aim at demonstrating the Generalised Least Square method can be applied in the case of Monte Carlo models. We present a proof-of-concept for Monte Carlo models in the specific case of nuclear physics with the model combination INCL/ABLA. We discuss the challenges in the application of this method to high-energy spallation models, notably the large runtime and the stochasticity of the models. Our results indicate this framework can also be applied to analogous situations where parameters of a computationally expensive Monte Carlo code should be inferred/improved.
↳ hep-phnucl-thEPJA(2024)·4 citations
10
Far-from-equilibrium attractors for massive kinetic theory in the relaxation time approximation
Huda Alalawi🇺🇸 · Michael Strickland🇺🇸
In this proceedings contribution, we summarize recent findings concerning the presence of early- and late-time attractors in non-conformal kinetic theory. We study the effects of varying both the initial momentum-space anisotropy and initialization times using an exact solution of the 0+1D boost-invariant Boltzmann equation with a mass- and temperature-dependent relaxation time. Our findings support the existence of a longitudinal pressure attractor, but they do not support the existence of distinct attractors for the bulk viscous and shear pressures. Considering a large set of integral moments, we show that for moments with greater than one power of longitudinal momentum squared, both early- and late-time attractors are present.
↳ hep-phnucl-thEPJ Web Conf.(2024)·0 citations
11
Analysis of Neutron Star $f -$ mode Oscillations in General Relativity with Spectral Representation of Nuclear Equations of State
Debanjan Guha Roy · Tuhin Malik · Swastik Bhattacharya · Sarmistha Banik
We study quasinormal $f -$ mode oscillations in neutron star(NS) interiors within the linearized General Relativistic formalism. We utilize approximately 9000 nuclear Equations of State (EOS) using spectral representation techniques, incorporating constraints on nuclear saturation properties, chiral Effective Field Theory ( $χ$ EFT) for pure neutron matter, and perturbative Quantum Chromodynamics (pQCD) for densities pertinent to NS cores. The median values of f-mode frequency, $ν_{f}$ (damping time, $τ_{f}$ ) for NS with masses ranging from 1.4 - 2.0 $M_{⊙}$ lie between 1.80 - 2.20 kHz (0.13 - 0.22 s) for our entire EOS set. Our study reveals a weak correlation between $f -$ mode frequencies and individual nuclear saturation properties, prompting the necessity for more intricate methodologies to unveil multi-parameter relationships. We observe a robust linear relationship between the radii and $f -$ mode frequencies for different NS masses. Leveraging this correlation alongside NICER observations of PSR J0740+6620 and PSR J0030+0451, we establish constraints that exhibit partial and minimal overlap for observational data from Riley et al. and Miller et al. respectively with our nucleonic EOS dataset. Moreover, NICER data aligns closely with radius and frequency values for a few hadron-quark hybrid EOS models. This indicates the need to consider additional exotic particles such as deconfined quarks at suprasaturation densities. We conclude that future observations of the radius or $f -$ mode frequency for more than one NS mass, particularly at the extremes of viable NS mass scale, would either rule out nucleon-only EOS or provide definitive evidence in its favour.
↳ astro-ph.HEgr-qcnucl-thApJ(2024)·22 citations

Affiliations

first authorsco-authorsvia INSPIRE