Nuclear Theory·nucl-th

Wednesday·September 27, 2023

12 papers—7 primary·5 cross-listed

01
Electron Dynamics in Neutron Scattering with Hydrogen Atoms
Mingzhao Xing · Libin Fu
In neutron-proton (n-p) scattering experiments, gas targets have been used to measure scattering length by detecting neutrons and recoil protons. Changes in electron dynamics within the gas target have a negligible effect on dynamics of neutrons and protons. However, electron dynamics are sensitive to the specific form of the n-p interaction during the scattering process, providing additional information to derive parameters in nuclear interaction models. We propose a theoretical approach to obtain these parameters from the momentum spectrum of ionized electrons within a hydrogen atomic gas target. This approach is based on a three-body scattering involving a neutron, a proton and an electron. We model the n-p interaction as the Yukawa potential and obtain the momentum spectrum of ionized electrons through the solution of the Time-Dependent Schrödinger Equation. Electron dynamics exhibit significant differences at various potential parameters. These parameters can be determined by comparing numerical calculations with experimental results. Moreover, this approach offers insights into detecting ultrafast scattering processes.
nucl-thquant-phCommun.Theor.Phys.(2025)·0 citations
02
$^{10}$ Be in the Cluster Shell Model
Omar Alejandro Diaz Caballero · Roelof Bijker
The Cluster Shell Model (CSM)describes light nuclei in terms of $k - α$ particles and $x$ extra nucleons, in which the extra nucleon move in the deformed field generated by the geometric configuration of $α$ -particles. We present the first study for the case $x = 2$ nucleons in application to $^{10} B e$ as a cluster of two $α$ -particles and two neutrons.
nucl-thJ.Phys.Conf.Ser.(2023)·1 citation
03
Structure of $^{13}$ C in the Cluster Shell Model
Adrian Santana-Valdés · Roelof Bijker
We study the structure of $^{13}$ C in the framework of the Cluster Shell Model. A comparison of the available experimental data with our model is made. Some predictions for level ordering and form factors are presented.
nucl-thJ.Phys.Conf.Ser.(2023)·1 citation
04
Probing the existence of \eta^3He mesic nucleus with a few-body approach
Qian Wu🇨🇳 · Gang Xie🇨🇳 · Xurong Chen🇨🇳
Motivated by the two recent observations in the WASA-at-COSY detector, we investigate the $η^{3}$ He nucleus with the $η N N N$ few body method. We construct the effective $s$ -wave energy dependent $η N$ potential which reproduce the $η N$ subthreshold scattering amplitude in the 2005 Green-Wycech model. It gives the $η$ separation energy and decay width of 0.19 MeV and 1.71 MeV, respectively. We also construct various sets of effective $s$ -wave energy independent $η N$ potentials where the corresponding complex scattering lengths (a) are within the range given in most theoretical models. We obtain the bound $η^{3}$ He nucleus with decay width of about 5 MeV when a is (1.0 fm, 0.3 fm), and of about 10 MeV when a is (1.0 fm, 0.5 fm).
nucl-thhep-phPLB(2024)·1 citation
05
The regime of applicability of Israel-Stewart hydrodynamics
David Wagner · Lorenzo Gavassino
Using analytical tools from linear response theory, we systematically assess the accuracy of several microscopic derivations of Israel-Stewart hydrodynamics near local equilibrium. This allows us to "rank" the different approaches in decreasing order of accuracy as follows: Inverse Reynolds Dominance (IReD), Denicol-Niemi-Molnár-Rischke (DNMR), second-order gradient expansion, and 14-moment approximation. We find that IReD theory is far superior to Navier-Stokes, being very accurate both in the asymptotic regime (i.e., for slow processes) and in the transient regime (i.e., on timescales comparable to the relaxation time). Also, the high accuracy of DNMR is confirmed, but neglecting second-order terms in the Knudsen number, which would render the equations parabolic, introduces serious systematic errors. Finally, in most cases, the second-order gradient expansion (a.k.a. non-resummed BRSSS) is found to be more inaccurate than Navier-Stokes in the transient regime. Overall, this analysis shows that Israel-Stewart hydrodynamics is falsifiable, and the relaxation time is observable, shedding new light on the debate on the viability of transient hydrodynamics as a well-defined physical theory distinguished from Navier-Stokes.
nucl-thastro-ph.HEgr-qcPRD(2024)·26 citations
06
Comparison of $N ˉ N$ optical models
Jaume Carbonell🇫🇷 · Guillaume Hupin🇫🇷 · Sławomir Wycech🇵🇱
We compare the strong part of the $N ˉ N$ interaction obtained by the Nijmegen partial wave analysis and the results of some of the most popular $N ˉ N$ optical potentials in configuration space. We have found severe discrepancies in most of the partial waves, especially above $p_{L ab}$ =400 MeV/c where the partial wave analysis displays a resonant-like structure in the $^{31}$ S $_{0}$ and $^{33}$ P $_{0}$ waves. Some theoretical difficulties to interpret this behaviour in terms of dynamical resonances are pointed pout and an alternative explanation is suggested. A much better stability is observed in the low energy parameters, apart from some discrepancies due to the presence of near-threshold quasi-bound states in particular waves. Large deviations have also been found between the corresponding potentials, at short and medium-range ( $r ≳ 1$ fm) distances.
nucl-thhep-exhep-phnucl-ex+1EPJA(2023)·12 citations
07
Model for compound nucleus formation in various heavy-ion systems
V. Yu. Denisov
The statistical model for the calculation of the compound nucleus formation cross section and the probability of compound nucleus formation in heavy-ion collisions is discussed in detail. The light, heavy, and super-heavy nucleus-nucleus systems are considered in this model in the framework of one approach. It is shown that the compound nucleus is formed in competition between passing through the compound-nucleus formation barrier and the quasi-elastic barrier. The compound-nucleus formation barrier is the barrier separating the system of contacting incident nuclei and the spherical or near-spherical ground state of the compound nucleus. The quasi-elastic barrier is the barrier between the contacting and well-separated deformed ions. It is shown that the compound nucleus formation cross-section is suppressed when the quasi-elastic barrier is lower than the compound nucleus formation barrier. The critical value of angular momentum, which limits the compound nucleus formation cross-section values for light and medium ion-ion systems at over-barrier collision energies, is discussed in the model. The suppression of the compound nucleus formation cross-section even at small partial waves for very heavy ion-ion systems is obtained in the model. The values of the capture and compound nucleus formation cross-sections calculated for various light, heavy, and super-heavy nucleus-nucleus systems as well as the probability of the compound nucleus formation for super-heavy nuclei are well agreed with the available experimental data.
nucl-thPRC(2024)·3 citations
08
Near-threshold hadron scattering with effective field theory
Katsuyoshi Sone🇯🇵 · Tetsuo Hyodo🇯🇵
When an exotic hadron locates near the threshold with the channel couplings, the internal structure of the exotic hadron is related to the scattering length. To incorporate the threshold effect, the Flatté amplitude has been often used to determine the scattering length. It is however known that an additional constraint is imposed on the Flatte amplitude near the threshold. We discuss this problem by using the effective field theory for the coupled-channel scattering.
↳ hep-phnucl-thEPJ Web Conf.(2024)·1 citation
09
Threshold-cusp explanation for $X$ and $Z_{cs}$ in $B^{+} \to J / ψ ϕ K^{+}$
S.X. Nakamura (Shandong Univ.)🇨🇳 · X. Luo (Anhui Univ.)🇨🇳
Several $X$ and $Z_{cs}$ exotic hadrons were claimed in the LHCb's amplitude analysis on $B^{+} \to J / ψ ϕ K^{+}$ . The data shows that all the peaks and also dips in the spectra are located at thresholds of seemingly relevant meson-meson channels. While the LHCb analysis fitted the peaks with Breit-Wigner resonances, threshold kinematical cusps might be the cause of such structures. We thus analyze the LHCb data considering the threshold cusps. Our model is simultaneously fitted to $J / ψ ϕ$ , $J / ψ K^{+}$ , and $K^{+} ϕ$ invariant mass distributions. The threshold cusps fit well all the $X$ , $Z_{cs}$ , and dip structures. Our analysis indicates that spin-parity of the $X (4274)$ and $X (4500)$ structures are $0^{-}$ and $1^{-}$ , respectively. This is different from the LHCb's spin-parity assignments ( $1^{+}$ and $0^{+}$ ). The number of fitting parameters can be significantly reduced by considering the relevant threshold cusps. Our analysis shows that $D_{s}^{(*)} D ˉ^{*}$ scattering lengths are consistent with zero. This disfavors an explanation of $Z_{cs} (4000)$ and $Z_{cs} (4220)$ as $D_{s}^{(*)} D ˉ^{*}$ molecules, which is consistent with lattice QCD via the SU(3) relation.
↳ hep-phhep-exnucl-thNuovo Cim.C(2024)·2 citations
10
Relativistic hydrodynamics with phase transition
F. Taghinavaz🇮🇷
Assessing the applicability of hydrodynamic expansions close to phase transition points is crucial from either theoretical or phenomenological points of view. We explore this within the gauge/gravity duality, using the Einstein-Klein-Gordon model, a bottom-up string theory construction. This model incorporates a parameter, $B_{4}$ , that simulates different types of phase transitions in the strongly coupled field theory existing at the boundary. We thoroughly examine the thermodynamics and dynamics of time-dependent, linearized perturbations in the spin-2, spin-1, and spin-0 sectors. Our findings suggest that "hydrodynamic series breakdown near transition points" is valid exclusively for second-order phase transitions, not for crossovers or first-order phase transitions. Additionally, we observe that the high-temperature and low-temperature limits of the radius of convergence for the hydrodynamic series ( $q_{c}^{2}$ ) are equal. We also discover that the relationship $(Max ∣ q_{c}^{2} ∣)_{spin-2} < (Max ∣ q_{c}^{2} ∣)_{spin-0} < (Max ∣ q_{c}^{2} ∣)_{spin-1}$ is consistent for different spin sectors, regardless of the phase transition type. At the chaos point, we observe the emergence of pole-skipping behavior for both gravity and scalar perturbations at $ω_{n} = - 2 π T ni$ . Lastly, comparing the chaos momentum with $q_{c}^{2}$ , we find that $q_{p s}^{2} < q_{c}^{2}$ , except for extremely high temperatures.
↳ hep-thhep-phnucl-thEPJC(2024)·3 citations
11
Hyperonic uncertainties in neutron stars, mergers and supernovae
Hristijan Kochankovski · Angels Ramos · Laura Tolos
In this work we delve into the temperature-dependent Equation of State (EoS) of baryonic matter within the framework of the FSU2H $^{*}$ hadronic model, which comprehensively incorporates hyperons and is suitable for relativistic simulations of neutron star mergers and supernovae. To assess the impact of the uncertainties in the hyperonic sector on astrophysical observables, we introduce two additional models, namely FSU2H $^{*}$ L and FSU2H $^{*}$ U. These models cover the entire spectrum of variability of hyperonic potentials, as derived from experimental data. Our investigations reveal that these uncertainties extend their influence not only to the relative abundances of various particle species but also to the EoS itself and, consequently, have an impact on the global properties of both cold and hot neutron stars. Notably, their effects become more pronounced at large temperatures, owing to the increased presence of hyperons. These findings have direct implications for the outcomes of relativistic simulations of neutron star mergers and supernovae, emphasizing the need of accounting for hyperonic uncertainties to ensure the accuracy and reliability of such simulations in astrophysical contexts.
↳ astro-ph.HEnucl-thMNRAS(2024)·13 citations
12
Coupled oscillator model of a trapped Fermi gas at the BEC-BCS crossover
Sergueï V. Andreev
We address theoretically the puzzling discontinuity of the radial quadrupole mode frequency observed in a trapped Fermi gas across the BEC-BCS crossover. We apply the scaling transformation to a two-channel model of a resonant Fermi superfluid and argue that the frequency downshift in the crossover region is due to Feshbach coupling of the molecular Bose-Einstein condensate (BEC) to the surrounding Fermi sea. The Bose and Fermi components of the gas act as coupled macroscopic oscillators. The frequency jump corresponds to the point where the closed-channel molecules are entirely converted into the Fermi sea. This implies linear scaling of the "critical" detuning between the scattering channels with the Fermi energy, which can be readily verified in an experiment.
↳ cond-mat.quant-gascond-mat.mes-hallcond-mat.str-elcond-mat.supr-con+1Physica A(2025)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE