Nuclear Theory·nucl-th

Tuesday·July 16, 2024

25 papers—11 primary·14 cross-listed

12
Accelerating Eigenvalue Computation for Nuclear Structure Calculations via Perturbative Corrections
Dong Min Roh · Esmond Ng · Chao Yang · Dean Lee · Pieter Maris · James P. Vary
We present a new method for computing the lowest few eigenvalues and the corresponding eigenvectors of a nuclear many-body Hamiltonian represented in a truncated configuration interaction subspace, i.e., the no-core shell model (NCSM). The method uses the hierarchical structure of the NCSM Hamiltonian to partition the Hamiltonian as the sum of two matrices. The first matrix corresponds to the Hamiltonian represented in a small configuration space, whereas the second is viewed as the perturbation to the first matrix. Eigenvalues and eigenvectors of the first matrix can be computed efficiently. Perturbative corrections to the eigenvectors of the first matrix can be obtained from the solutions of a sequence of linear systems of equations defined in the small configuration space. These correction vectors can be combined with the approximate eigenvectors of the first matrix to construct a subspace from which more accurate approximations of the desired eigenpairs can be obtained. We call this method a Subspace Projection with Perturbative Corrections (SPPC) method. We show by numerical examples that the SPPC method can be more efficient than conventional iterative methods for solving large-scale eigenvalue problems such as the Lanczos, block Lanczos and the locally optimal block preconditioned conjugate gradient (LOBPCG) method. The method can also be combined with other methods to avoid convergence stagnation.
↳ physics.comp-phcs.NAmath.NAnucl-thJ.Comput.Phys.(2025)·0 citations
13
Soft-gluon exchange matters: isotropic screening in QCD kinetic theory
Kirill Boguslavski🇦🇹 · Florian Lindenbauer🇦🇹
QCD kinetic theory simulations are a prominent tool for studying the nonequilibrium initial stages in heavy-ion collisions. Despite their success, all implementations rely on approximations of the hard thermal loop (HTL) screened matrix elements in the collision terms. In this paper, we present our results for different isotropic screening prescriptions in the elastic collision term for gluons. In particular, we go beyond the simple Debye-like screening form that is used in all current implementations and apply the isotropic HTL matrix element instead. For isotropic systems, the evolution is nearly unchanged, but when studying the equilibration process in a Bjorken expanding plasma, we find qualitative and quantitative differences in a range of moments of the distribution function, such as a decrease in the maximum pressure anisotropy by up to 50%. In contrast, we find no significant qualitative impact on the jet quenching parameter or on the late-time hydrodynamization dynamics of anisotropic plasmas but observe systematically smaller values of $η / s$ by about 10% that coincide with perturbative calculations at small couplings. Our study reveals that the choice of the screening prescription can lead to large corrections at early times, but is less important close to equilibrium.
↳ hep-phnucl-thPRD(2024)·16 citations
14
Coupling and Recoupling Coefficients for Wigner's U(4) Supermultiplet Symmetry
Phong Dang🇺🇸 · Jerry P. Draayer🇺🇸 · Feng Pan🇺🇸 · Tomas Dytrych🇺🇸 · Daniel Langr🇨🇿 · David Kekejian🇺🇸 · Kevin S. Becker🇺🇸 · Noah Thompson🇺🇸
A novel procedure for evaluating Wigner coupling coefficients and Racah recoupling coefficients for U(4) in two group-subgroup chains is presented. The canonical U(4)->U(3)->U(2)->U(1) coupling and recoupling coefficients are applicable to any system that possesses U(4) symmetry, while the physical U(4)->SU_S(2)xSU_T(2) coupling coefficients are more specific to nuclear structure studies that utilize Wigner's Supermultiplet Symmetry concept. The procedure that is proposed sidesteps the use of binomial coefficients and alternating sum series, and consequently enables fast and accurate computation of any and all U(4)-underpinned features. The inner multiplicity of a (S,T) pair within a single U(4) irreducible representation is obtained from the dimension of the null space of the SU(2) raising generators; while the resolution for the outer multiplicity follows from the work of Alex et al. on U(N). It is anticipated that a C++ library will ultimately be available for determining generic coupling and recoupling coefficients associated with both the \textit{canonical} and the \textit{physical} group-subgroup chains of U(4).
↳ math-phhep-thmath.MPnucl-thEur.Phys.J.Plus(2025)·5 citations
15
Simultaneous Extraction of the Weak Radius and the Weak Mixing Angle from Parity-Violating Electron Scattering on $^{12} C$
Matteo Cadeddu🇮🇹 · Nicola Cargioli🇮🇹 · Jens Erler🇩🇪 · Mikhail Gorchtein🇩🇪 · Jorge Piekarewicz🇺🇸 · Xavier Roca-Maza🇮🇹 · Hubert Spiesberger🇩🇪
We study the impact of nuclear structure uncertainties on a measurement of the weak charge of $^{12} C$ at the future MESA facility in Mainz. Information from a large variety of nuclear models, accurately calibrated to the ground-state properties of selected nuclei, suggest that a $0.3$ % precision measurement of the parity-violating asymmetry at forward angles will not be compromised by nuclear structure effects, thereby allowing a world-leading determination of the weak charge of $^{12} C$ . Furthermore, we show that a combination of measurements of the parity-violating asymmetry at forward and backward angles for the same electron beam energy can be used to extract information on the nuclear weak charge distribution. We conclude that a $0.34$ % precision on the weak radius of $^{12} C$ may be achieved by performing a $3$ % precision measurement of the parity-violating asymmetry at backward angles.
↳ hep-phnucl-thPRC(2024)·11 citations
16
Influence of magnetic field-induced anisotropic gluon pressure during pre-equilibrium in heavy-ion collisions: A faster road towards isotropization
A. Ayala🇲🇽 · A. Mizher🇧🇷
Magnetic fields of a large intensity can be generated in peripheral high-energy heavy-ion collisions. Although their intensity drops fast and, moreover, it is not clear whether these fields last long enough to induce a magnetization during the quark-gluon plasma phase, most of the models and simulations predict a significant intensity that lasts up to proper times of order 1 fm after the beginning of the reaction, which is a typical time for the hydrodynamical phase to start. This interval of time is referred to as the pre-equilibrium stage. The evolution of the reaction during pre-equilibrium is thus likely to be influenced by these fields. In this work we adopt a strong field approximation to study the effects of the magnetic field-induced anisotropy on the gluon pressure. We include this anisotropy within the description obtained by means of Effective Kinetic Theory and explore the consequences to reach isotropization at proper times of order 1 fm. We show that when including the magnetic field effects, isotropization is achieved faster.
↳ hep-phhep-thnucl-thPRD(2024)·10 citations
17
Properties of neutron stars and strangeness-mixed stars from a pion mean-field approach
Nam-Yong Ghim🇰🇷 · Hyun-Chul Kim🇰🇷 · Ulugbek Yakhshiev🇰🇷 · Ghil-Seok Yang🇰🇷
We investigate the properties of the static neutron stars and strangeness-mixed stars, based on the equations of state derived from a pion mean-field approach. Using the empirical data on the pion-nucleus scattering and bulk properties of nuclear matter, we have already fixed all the parameters in a previous work, where the nucleons and hyperons were shown to be modified in various nuclear medium. In the current work, we first examine the energy and pressure inside a neutron star. We show that the central densities in various neutron stars vary within the range of $(3 - 4) ρ_{0}$ , where $ρ_{0}$ is the normal nuclear matter density. The mass-radius relations are obtained and discussed. As the slope parameter for neutron matter increases, the radii of the neutron stars increase with their masses fixed. We also study the strangeness-mixed stars or the hyperon stars using the same sets of the parameters. As the strangeness content of strange matter increases, the binding energy per nucleon is saturated and the corresponding equation of state becomes softened. Consequently, the central densities of the strangeness-mixed stars increase. Assuming that recently observed neutron stars are the strangeness-mixed ones, we find that the central densities increase.
↳ hep-phastro-ph.HEastro-ph.SRnucl-thPRD(2025)·0 citations
18
Probing gluon saturation and nuclear structure in photon-nucleus collisions
Heikki Mäntysaari · Farid Salazar · Björn Schenke · Chun Shen · Wenbin Zhao🇺🇸
We calculate exclusive vector meson photoproduction within the Color Glass Condensate framework in high-energy photon-nucleus scattering probed experimentally in ultra peripheral heavy ion collisions at RHIC and at the LHC. When the free parameters are constrained by the $γ + p$ data from HERA, we predict significant nuclear suppression for both the coherent and incoherent photoproduction cross section in the TeV range. Our results indicate that the LHC data prefers even stronger saturation effects at the highest collision energies. Furthermore, we demonstrate how the linear polarization of photons in ulra peripheral collisions generates azimuthal modulations in the decay products of the exclusively produced vector meson. We show how these measurements can probe details of the nuclear geometry, specifically the deformed structure of the uranium nuclei.
↳ hep-phnucl-thPoS(2025)·1 citation
19
Two-pion emission decays of negative parity singly heavy baryons
Nongnapat Ponkhuha🇹🇭 · Ahmad Jafar Arifi🇯🇵 · Daris Samart🇹🇭
We investigate two-pion emission decays of singly charmed and bottom baryons, focusing on $Λ_{Q}^{*} (1 P)$ and $Ξ_{Q}^{*} (1 P)$ with $Q = c$ (charm) or $b$ (bottom) quarks and $J^{P} = 1/ 2^{-}, 3/ 2^{-}$ , belonging to antisymmetric flavor triplet $3 ˉ_{F}$ . Our analysis encompasses both sequential processes, involving intermediate states belonging to symmetric flavor sextet $6_{F}$ such as $Σ_{Q} (1 S)$ and $Ξ_{Q}^{'} (1 S)$ respectively with $J^{P} = 1/ 2^{+}, 3/ 2^{+}$ , derived from the chiral quark model, and direct process crucial for comparison with experimental data, whose coupling constants estimated using the chiral-partner scheme. We also incorporate the convolution of the parent particle's mass for the Dalitz plot, enabling a more realistic comparison with experimental data. We scrutinize the Dalitz plots of these negative parity states in light of recent Belle measurements for $Λ_{c} (2625)^{+}$ . Our findings support the assignment of $Λ_{c} (2625)^{+}$ as the $λ$ -mode excitation with $J^{P} = 3/ 2^{-}$ in the quark model, deduced from the the $Λ_{c} π$ invariant mass distribution, and we then give predictions for other cases, including the $Ξ_{Q}^{*}$ decays. The observed asymmetry in the $π π$ invariant mass distribution underscores the important role of the direct process, reflecting the chiral-partner structure in the heavy baryon sector. It is evident that the presence of the direct process is not significant in the three-body decays unless the $S$ -wave resonance contribution is suppressed. We suggest further experimental verification to test our predictions and get more insights into the structure of heavy baryons.
↳ hep-phnucl-thPRD(2024)·2 citations
20
Strangeness Production in $s_{NN} = 3$ GeV Au+Au Collisions at RHIC
The STAR Collaboration
We report multi-differential measurements of strange hadron production ranging from mid- to target-rapidity in Au+Au collisions at a center-of-momentum energy per nucleon pair of $s_{NN} = 3$ GeV with the STAR experiment at RHIC. $K_{S}^{0}$ meson and $Λ$ hyperon yields are measured via their weak decay channels. Collision centrality and rapidity dependences of the transverse momentum spectra and particle ratios are presented. Particle mass and centrality dependence of the average transverse momenta of $Λ$ and $K_{S}^{0}$ are compared with other strange particles, providing evidence of the development of hadronic rescattering in such collisions. The 4 $π$ yields of each of these strange hadrons show a consistent centrality dependence. Discussions on radial flow, the strange hadron production mechanism, and properties of the medium created in such collisions are presented together with results from hadronic transport and thermal model calculations.
↳ nucl-exnucl-thJHEP(2024)·32 citations
21
Charge radii of $^{11 - 16}$ C, $^{13 - 17}$ N and $^{15 - 18}$ O determined from their charge-changing cross-sections and the mirror-difference charge radii
J.W. Zhao · B.-H. Sun · I. Tanihata · J.Y. Xu · K.Y. Zhang · A. Prochazka · L.H. Zhu · S. Terashima · J. Meng · L.C. He · C.Y. Liu · G.S. Li and 15 other authors
Charge-changing cross-sections of $^{11 - 16}$ C, $^{13 - 17}$ N and $^{15 - 18}$ O on a carbon target have been determined at energies around 300 MeV/nucleon. A nucleon separation energy-dependent correction factor has been introduced to the Glauber model calculation for extracting the nuclear charge radii from the experimental CCCSs. The charge radii of $^{11}$ C, $^{13, 16}$ N and $^{15}$ O thus were determined for the first time. With the new radii, we studied the experimental mirror-difference charge radii ( $Δ R_{ch}^{mirror}$ ) of $^{11}$ B- $^{11}$ C, $^{13}$ C- $^{13}$ N, $^{15}$ N- $^{15}$ O, $^{17}$ N- $^{17}$ Ne pairs for the first time. We find that the $Δ R_{ch}^{mirror}$ values of $^{13}$ C- $^{13}$ N and $^{15}$ N- $^{15}$ O pairs follow well the empirical relation to the isospin asymmetry predicted by the $ab$ $ini t i o$ calculations, while $Δ R_{ch}^{mirror}$ of $^{11}$ B- $^{11}$ C and $^{17}$ N- $^{17}$ Ne pairs deviate from such relation by more than two standard deviations.
↳ nucl-exnucl-thPLB(2024)·26 citations
22
3D structure of hadrons and energy-momentum tensor
Cédric Lorcé (Ecole Polytechnique)🇫🇷
The three-dimensional spatial structure of hadrons is encoded in their form factors. Via appropriate Fourier transform, the latter describe how charge, energy, linear and angular momentum, but also pressure are distributed inside these systems. Electromagnetic form factors of the nucleon have been measured for a long time, but it is only recently that some gravitational form factors have been extracted from experimental data, creating a great deal of enthusiasm in the hadronic community. Here we summarize some of the recent developments on the interpretation of these form factors, and provide a quick overview of what we can learn about the nucleon mass, spin and internal pressure.
↳ hep-phnucl-thPoS(2025)·1 citation
23
Confronting the low-scale seesaw and leptogenesis with neutrinoless double beta decay
J. de Vries🇳🇱 · M. Drewes🇧🇪 · Y. Georis🇧🇪 · J. Klarić🇳🇱 · V. Plakkot🇳🇱
We revisit the impact of heavy neutrinos with masses in the MeV-GeV range on neutrinoless double beta decay ( $0 ν β β$ ) in view of updated results for the lifetime of this process. Working in a minimal realistic extension of the Standard Model by two right-handed neutrino flavours, we show that the non-observation of $0 ν β β$ will impose strong bounds on the heavy neutrino properties that are complementary to the limits obtained from Big Bang Nucleosynthesis and collider searches. For an inverted mass hierarchy of the light neutrinos we find that improved limits on $0 ν β β$ from next-generation experiments, assuming an improvement of two orders of magnitude on the current $0 ν β β$ limits will restrict the allowed parameter space for fixed mass splitting to narrow bands in the mass-mixing plane. Further combining this with the requirement to explain the baryon asymmetry of the universe via leptogenesis reduces these bands to windows in parameter space that are constrained in all directions and can be targeted by direct searches at accelerators, and restricts the mass splitting to values that can be resolved at experiments. For a normal mass hierarchy, restricting the allowed parameter will require even stronger $0 ν β β$ limits, and only parts of the parameter space can then be probed.
↳ hep-phastro-ph.COnucl-thJHEP(2025)·25 citations
24
Classification of Coupled-Channel Near-Threshold Structures
Zhen-Hua Zhang🇨🇳 · Feng-Kun Guo🇨🇳
Since 2003, plenty of resonant structures have been observed in the heavy quarkonium regime. Many of them are close to the thresholds of a few pairs of heavy hadrons. They are candidates of exotic hadrons and have attracted immense attentions. Based on a coupled-channel nonrelativistic effective field theory, we classify the near-threshold structures of a symmetry-related two-channel system by studying the evolution of the scattering amplitude line shapes and pole positions with the variation of the single-channel scattering length and channel coupling strength. We show that the evolution of the scattering amplitude line shapes can be understood from the pole trajectories in the complex energy plane, and the pole evolution can be traced back to the renormalization group fixed points. We provide a dictionary of correspondence between the evolution of line shapes and pole trajectories along with varying interaction and channel coupling strengths, which can be used to understand the experimental observations of the near-threshold structures.
↳ hep-phhep-exnucl-thPLB(2025)·26 citations
25
Global analysis of nuclear parton distribution functions
M. Klasen🇩🇪
We review the theoretical foundations, methodological approaches and current status of the determination of nuclear parton distribution functions (PDFs). A large variety of measurements in fixed-target and collider experiments provide increasingly precise constraints on various aspects of nuclear PDFs, including shadowing, antishadowing, the EMC effect, Fermi motion, flavour separation, deuteron binding, target-mass and other higher-twist effects. We give particular emphasis to measurements carried out in proton-lead collisions at the Large Hadron Collider, which have revolutionised the global analysis during the past decade. These measurements include electroweak boson, isolated photon, single inclusive hadron, jet, and heavy-flavour observables.
↳ hep-phhep-exnucl-exnucl-thPoS(2025)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE