Nuclear Theory·nucl-th

Friday·August 30, 2024

10 papers—7 primary·3 cross-listed

01
[Submitted on 28 Aug 2024]
Neutron skins: A perspective from dispersive optical models
M. C. Atkinson · W. H. Dickhoff
An overview is presented of neutron skin predictions obtained using an empirical nonlocal dispersive optical model (DOM). The DOM links both scattering and bound-state experimental data through a subtracted dispersion relation which allows for fully-consistent, data-informed predictions for nuclei where such data exists. Large skins were predicted for both $^{48}$ Ca ( $R_{skin}^{48} = 0.25 \pm 0.023$ fm in 2017) and $^{208}$ Pb ( $R_{skin}^{208} = 0.25 \pm 0.05$ fm in 2020). While the DOM prediction in $^{208}$ Pb is within 1 $σ$ of the subsequent PREX-2 measurement, the DOM prediction in $^{48}$ Ca is over 2 $σ$ larger than the thin neutron skin resulting from CREX. From the moment it was revealed, the thin skin in $^{48}$ Ca has puzzled the nuclear-physics community as no adequate theories simultaneously predict both a large skin in $^{208}$ Pb and a small skin in $^{48}$ Ca. The DOM is unique in its ability to treat both structure and reaction data on the same footing, providing a unique perspective on this $R_{skin}$ puzzle. It appears vital that more neutron data be measured in both the scattering and bound-state domain for $^{48}$ Ca to clarify the situation.
Comments:
21 pages, 9 figures, 2 tables. arXiv admin note: substantial text overlap with arXiv:1911.09020
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2408.16097 [pdf]
0 citations
02
[Submitted on 29 Aug 2024]
Gamow shell model description of neutron-rich He hyper-isotopes
Xin Li · N. Michel · J. G. Li · Xian-Rong Zhou
The Gamow shell model (GSM) framework has been extended to the study of weakly bound hypernuclei. As a first application, the neutron-rich He hyper-isotope chains, from 6{\Lambda}He to 9{\Lambda}He have been investigated to accurately account for the loosely bound or neutron-unbound character of hypernuclear many-body states. The energy spectra calculated with a phenomenological Hamiltonian show good agreement with experimental data. In particular, neutron-emitting resonant states are predicted for the neutron-rich nuclei 5-7He and the hypernucleus 6{\Lambda}He. Furthermore, one-neutron densities exhibit the long-range character of weakly bound and resonant states. This study demonstrates that GSM is a practical tool for describing the complex structure of hypernuclei, especially for those close to drip lines.
Comments:
3 pages
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2408.16223 [pdf]
PLB(2025)·7 citations
03
[Submitted on 29 Aug 2024]
Role of nuclear deformation and orientation about symmetry axis of target nucleus on heavy-ion fusion dynamics
Shilpa Rana · M. Bhuyan · Raj Kumar · B. V. Carlson
Nuclear shape and orientation degrees of freedom are incorporated into the calculation of the double-folding nuclear potential within the relativistic mean-field (RMF) formalism. The quadrupole deformations ( $β_{2}$ ), nuclear densities and the effective nucleon-nucleon (NN) interaction potential are obtained using the RMF approach for the Hybrid, NL3 $^{*}$ and NL3 parameterizations. The calculated quadrupole deformations are included in the target densities through the nuclear radius. The deformation and orientation-dependent microscopic nuclear potentials are further employed to obtain fusion barrier characteristics and cross-sections for 12 even-even heavy-ion reactions with doubly magic spherical $^{16}$ O and $^{48}$ Ca as projectiles along with deformed targets from different mass regions. The results obtained for the relativistic R3Y NN potential are compared with those of the Reid version of the non-relativistic M3Y NN potential as well as with the available experimental data. A decrease in the barrier height and increase in the cross-section is observed upon the inclusion of target quadrupole deformations in the nuclear density distributions at the target orientation angles, $θ_{2} \leq 5 8^{\circ}$ for the R3Y NN potential and at $θ_{2} \leq 6 0^{\circ}$ for the M3Y NN potential. On comparing the $θ_{2}$ -integrated cross-section calculated using M3Y and R3Y NN potentials with spherical and deformed densities, one observes that the deformed densities and the relativistic R3Y NN potential obtained for the Hybrid parameter set provide better agreement with the available experimental data for all the considered reactions. Moreover, the modifications in the characteristics of the fusion barrier and hence in the cross-section with the inclusion of nuclear shape degrees of freedom and orientations are found to become more prominent in reactions forming heavier compound nuclei.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2408.16436 [pdf]
PRC(2024)·4 citations
04
[Submitted on 29 Aug 2024]
Persistence of the N = 50 shell closure over the isotopic chains of Sc, Ti, V and Cr nuclei using relativistic energy density functional
Praveen K. Yadav · Raj Kumar · M. Bhuyan
The analytical expression of the density-dependent binding energy per nucleon for the relativistic mean field (RMF), also known as the relativistic energy density functional (Relativistic-EDF), is used to obtain the isospin-dependent symmetry energy and its components for the isotopic chain of Sc, Ti, V, and Cr nuclei. The procedure of the coherent density fluctuation model is employed to formulate the Relativistic-EDF and Brueckner energy density functional (Brueckner-EDF) at local density. A few signatures of shell and/or sub-shell closure are observed in the symmetry energy and its components, i.e., surface and volume symmetry energy, far from the beta-stable region for odd-A Sc and V, and even-even Ti and Cr nuclei with non-linear NL3 and G3 parameter sets. A comparison is made with the results obtained from Relativistic-EDF and Brueckner-EDF with both NL3 and G3 for the considered isotopic chains. We find Relativistic-EDF outperforms the Brueckner-EDF in predicting the shell and/or sub-shell closure of neutron-rich isotopes at N = 50 for these atomic nuclei. Moreover, a relative comparison has been made for the results obtained with the non-linear NL3 and G3 parameter sets.
Comments:
18 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); Computational Physics (physics.comp-ph)
arXiv:
2408.16588 [pdf]
Mod.Phys.Lett.A(2023)·3 citations
05
[Submitted on 29 Aug 2024]
Distinguishing the sources of dielectron anisotropic flow at low beam energies
Renan Hirayama🇩🇪 · Hannah Elfner🇩🇪
We present calculations of dielectron anisotropic flow in heavy-ion collisions at HADES beam energies from a hadronic transport approach. The ongoing experimental analysis employs the traditional reaction plane method to evaluate the flow coefficients $v_{n}$ and claims to see isotropic radiation from the thermal quark-gluon plasma. We show in this work, that in the region above the pion mass, the dilepton flow measurement might suffer from cancellation effects that mask the complicated underlying dynamics. Contributions from different baryonic and mesonic resonances show collective behaviour with different signs and lead to an overall vanishing elliptic flow. To differentiate the different contributions, we propose to employ the scalar product method, which exploits the previously measured hadronic flow to create different reference planes. As a proof of concept, we calculate the $v_{2}$ of dielectrons for Ag+Ag collisions at $s_{N N} = 2.55$ $GeV$ with both methods and investigate the contribution of each source, concluding that the scalar product method provides the proton and pion tagged flow coefficients as two distinct measurements, disentangling the various dilepton sources.
Comments:
10 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2408.16603 [pdf]
PRC(2024)·7 citations
06
[Submitted on 29 Aug 2024]
Bounds on the minimum sound speed above neutron star densities
Dake Zhou🇺🇸
We show that the existence of massive neutron stars and asymptotic freedom of QCD place robust upper bounds on the lowest sound speed of the ultra-dense matter unattainable in neutron stars. Centered on worst-case scenarios, our limits are the most conservative among physical equations of state in the density range $\sim 2 - 40 n_{0}$ . Discovery of $≳ 2.6 M_{⊙}$ neutron stars, in combination with current multimessenger astrophysical constraints on the equation of state, would strongly support first-order phase transitions at high baryon densities.
Comments:
v2: broadened low-density uncertainties and updated refs
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th)
arXiv:
2408.16738 [pdf]
1 citation
07
[Submitted on 29 Aug 2024]
The X17 boson and the d(p,e+ e-)3He and d(n,e+ e-)3H processes: a theoretical analysis
M. Viviani🇮🇹 · E. Filandri🇮🇹 · L. Girlanda🇮🇹 · C. Gustavino🇮🇹 · A. Kievsky🇮🇹 · L.E. Marcucci🇮🇹
The present work deals with the e+ e- pair production in the d(p,e+e-)3He and d(n,e+ e-)3H processes, in order to evidentiate possible effects due to the exchange of a hypothetical low-mass boson, the so-called X17. These processes are studied for energies of the incident beams in the range 18-30 MeV, in order to have a sufficient energy to produce such a boson, whose mass is estimated to be around 17 MeV. We first analyze them as a purely electromagnetic processes, in the context of a state-of-the-art approach to nuclear strong-interaction dynamics and nuclear electromagnetic currents, derived from chiral effective field theory chiEFT. Next, we examine how the exchange of a hypothetical low-mass boson would impact the cross sections for such processes. We consider several possibilities, that this boson is either a scalar, pseudoscalar, vector, or axial particle. The main aim of the study is to exploit the specular structure of the 3He and 3H nuclei to investigate the isospin dependency of the X17-nucleon interaction, as the alleged "proto-phobicity".
Comments:
19 pages, 15 figures, new version with more details, added two appendices. arXiv admin note: text overlap with arXiv:2104.07808
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2408.16744 [pdf]
PRC(2025)·2 citations
08
[Submitted on 29 Aug 2024] (cross-list from quant-ph)
Quantum decoherence from complex saddle points
Jun Nishimura · Hiromasa Watanabe
Quantum decoherence is the effect that bridges quantum physics to well-understood classical physics. As such, it plays a crucial role in understanding the mysterious nature of quantum physics. Quantum decoherence is also a source of quantum noise that has to be well under control in quantum computing and in various experiments based on quantum technologies. Here we point out that quantum decoherence can be captured by $complex$ saddle points in the Feynman path integral in much the same way as quantum tunneling can be captured by instantons. In particular, we present some first-principle calculations in the Caldeira-Leggett model, which reproduce the predicted scaling behavior of quantum decoherence with respect to the parameters of the environment, such as the temperature and the coupling to the system of interest. We also discuss how to extend our approach to general models by Monte Carlo calculations using a recently developed method to overcome the sign problem.
Comments:
6 pages, 3 figures; v2: the version accepted for publication in Physical Review Letters
Subjects:
Quantum Physics (quant-ph); Statistical Mechanics (cond-mat.stat-mech); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2408.16627 [pdf]
PRL(2025)·3 citations
09
[Submitted on 29 Aug 2024] (cross-list from nucl-ex)
Flavor Dependence of Charged Pion Fragmentation Functions
H. Bhatt🇺🇸 · P. Bosted🇺🇸 · S. Jia🇺🇸 · W. Armstrong🇺🇸 · D. Dutta🇺🇸 · R. Ent🇺🇸 · D. Gaskell🇺🇸 · E. Kinney🇺🇸 · H. Mkrtchyan🇦🇲 · S. Ali🇺🇸 · R. Ambrose🇨🇦 · D. Androic🇭🇷 and 58 other authors
We have measured the flavor dependence of multiplicities for pi^+ and pi^- production in semi-inclusive deep-inelastic scattering (SIDIS) on proton and deuteron targets to explore a possible charge symmetry violation in fragmentation functions. The experiment used an electron beam with energies of 10.2 and 10.6 GeV at Jefferson Lab and the Hall-C spectrometers. The electron kinematics spanned the range 0.3<x<0.6, 2<Q^2<5.5 GeV^2, and 4<W^2<11 GeV^2. The pion fractional momentum range was 0.3< z <0.7, and the transverse momentum range was 0<p_T<0.25 GeV/c. Assuming factorization at low p_T and allowing for isospin breaking, we find that the results can be described by two "favored" and two "un-favored" effective low $p_{T}$ fragmentation functions that are flavor-dependent. However, they converge to a common flavor-independent value at the lowest x or highest W of this experiment.
Comments:
6 pages, 3 figures with 11 pages of supplementary material which has 9 figures
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2408.16640 [pdf]
PLB(2025)·7 citations
10
[Submitted on 29 Aug 2024] (cross-list from cond-mat.quant-gas)
Pseudogap regime of the unitary Fermi gas with lattice auxiliary-field quantum Monte Carlo in the continuum limit
S. Jensen · C. N. Gilbreth · Y. Alhassid
The unitary Fermi gas (UFG) is a strongly correlated system of two-species (spin-1/2) fermions with a short-range attractive interaction modeled by a contact interaction and has attracted much interest across different disciplines. The UFG is considered a paradigm for strongly correlated superfluids and has been investigated extensively, with generally good agreement found between theory and experiment. However, the extent of a pseudogap regime above the critical temperature $T_{c}$ for superfluidity is still debated both theoretically and experimentally. Here we study thermodynamic properties of the UFG across the superfluid phase transition using finite-temperature lattice auxiliary-field quantum Monte Carlo (AFMC) methods in the canonical ensemble of fixed particle numbers. We extrapolate our lattice AFMC results to the continuous time and continuum limits, thus removing the systematic error associated with the finite filling factor of previous AFMC studies. We determine the critical temperature to be $T_{c} = 0.16 (1) T_{F}$ . For the largest particle number studied $N = 114$ , the energy-staggering pairing gap is suppressed above a pairing scale temperature of $T^{*} \approx 0.2 T_{F}$ . The spin susceptibility displays moderate suppression above $T_{c}$ with a spin gap temperature of $T_{s} \approx 0.2 T_{F}$ . We also calculate a free energy-staggering pairing gap, which shows substantially reduced statistical errors when compared with the energy-staggering gap, allowing for a clear signature of pairing correlations in the finite-size system. All results indicate that the pseudogap regime is narrow, with pseudogap signatures emerging at temperatures below $T^{*} \approx 0.2 T_{F}$ . The reduced statistical errors of the free energy gap enable an extrapolation at low temperatures, allowing an estimate of the zero-temperature pairing gap $Δ_{E} = 0.576 (24) ϵ_{F}$ .
Comments:
18 pages, 7 figures
Subjects:
Quantum Gases (cond-mat.quant-gas); Superconductivity (cond-mat.supr-con); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2408.16676 [pdf]
1 citation

Affiliations

first authorsco-authorsvia INSPIRE