Nuclear Theory·nucl-th

Monday·January 1, 2024

9 papers—3 primary·6 cross-listed

01
Low-energy structure and $β$ decay properties of neutron-rich nuclei in the region of a shape phase transition
Kosuke Nomura
The low-energy structure and $β$ decay properties of the neutron-rich even-mass nuclei near the neutron number $N = 60$ that are experimentally of much interest are investigated within the framework of the nuclear density functional theory and the interacting boson-fermion-fermion model. By using the results of the constrained self-consistent mean-field calculations based on the relativistic energy density functional, the interacting-boson Hamiltonian describing the even-even core nuclei, the boson-fermion, and the fermion-fermion interactions are determined. The Gamow-Teller transition strengths, with the corresponding operator being constructed without introducing further phenomenological adjustment, are computed by using the wave functions of the initial and final nuclei of the $β$ decay. The triaxial quadrupole potential energy surfaces computed for the $N = 60$ even-even isotones suggest a pronounced $γ$ softness. The calculated energy spectra for the even-even and odd-odd nuclei in the Rb to Cd isotopic chains exhibit an abrupt change in nuclear structure around $N = 60$ , as suggested experimentally. The predicted $β$ -decay $lo g_{10} f t$ values underestimate the measured values for the nuclei with low $Z$ and with $N ⩽ 60$ , exhibit a rapid increase for $N > 60$ , reflecting the nuclear structure evolution, and agree rather well with the measured values for those nuclei with $Z$ being not far from the proton major shell closure $Z = 50$ . Sensitivity of the predicted $β$ -decay properties to the model assumptions and parameters employed in the nuclear structure calculations is discussed, specifically, by comparing results obtained based on the different choices of the underlying energy density functional.
nucl-thnucl-exPRC(2024)·8 citations
02
Significance of the compound nucleus surface energy coefficients in the synthesis of the superheavy nuclei with $Z=112-120$
R. Zargini · S. A. Seyyedi
This paper investigates the impacts of the different surface energy coefficients on the compound nucleus decay modes during heavy ion fusion reactions, with focus given to the superheavy nuclei (SHN) in the range of $Z = 112 - 118$ . The evaporation-residue (ER) cross sections were calculated for different surface asymmetric constants, $k_{s}$ and surface energy constants, $γ_{0}$ . In these calculations, the di-nuclear system model and proximity potential, along with considering deformed nuclei, were employed. Comparing the experimental data and this theoretical approach, the best values of $k_{s}$ and $γ_{0}$ are $0.7546$ and $0.9180 MeV f m^{- 2}$ , respectively. Furthermore, this new model was used to investigate the probability of synthesis of experimentally unknown heavier systems with $Z = 119$ and $120$ . There exist five promising combinations to synthesize SHN with $Z = 119$ : a) $^{249} Cf (^{45} Sc, 3 n)^{291} 119$ , b) $^{249} Cf (^{45} Sc, 4 n)^{290} 119$ , c) $^{247} Bk (^{50} Ti, 3 n)^{294} 119$ , d) $^{254} Es (^{48} Ca, 3 n)^{299} 119$ , and e) $^{254} Es (^{48} Ca, 4 n)^{298} 119$ . In addition, it is found that the best combinations to synthesize SHN with $Z = 120$ are $^{249} Cf (^{50} Ti, 3 n)^{296} 120$ , and $^{251} Cf (^{50} Ti, 3 n)^{298} 120$ .
nucl-thPRC(2023)·6 citations
03
Enhancement of deuteron production in jets
Stanislaw Mrowczynski🇵🇱
A strong enhancement of deuteron production in jets has been recently observed in proton-proton collisions at LHC. We show that the effect is due to two independent factors: a collimation of jet nucleons and a smallness of nucleon source which is significantly smaller than a deuteron.
nucl-thhep-phActa Phys.Polon.B(2024)·2 citations
04
A new criterion for the existence of dark matter in neutron stars
Hongyi Sun🇨🇳 · Dehua Wen🇨🇳
The tidal deformability and the radius of neutron stars are observables, which have been used to constrain the neutron star equation of state and explore the composition in neutron stars. We investigated the radius and tidal deformability of dark matter admixed neutron stars (DANSs) by utilizing the two-fluid TOV equations. Assuming that the dark matter modeled as ideal fermi gas or self-interacting bosons, for a series of DANSs at a fixed mass, it is shown that there exists the DANSs with smaller normal matter radii but larger tidal deformabilities. This negative correlation does not exist in the normal neutron stars.In other words, if the observation finds that the neutron stars with a fixed mass exists such a situation, that is, having a smaller observed radius but a larger tidal deformability, it will indicate the existence of dark matter in neutron stars.In addition, the relevant neutron star observations can also be used to constrain the dark matter parameters.
↳ astro-ph.HEastro-ph.SRnucl-thPRD(2024)·17 citations
05
Empirical fits to inclusive electron-carbon scattering data obtained by deep-learning methods
Beata E. Kowal🇵🇱 · Krzysztof M. Graczyk🇵🇱 · Artur M. Ankowski🇵🇱 · Rwik Dharmapal Banerjee🇵🇱 · Hemant Prasad🇵🇱 · Jan T. Sobczyk🇵🇱
Employing the neural network framework, we obtain empirical fits to the electron-scattering cross sections for carbon over a broad kinematic region, extending from the quasielastic peak through resonance excitation to the onset of deep-inelastic scattering. We consider two different methods of obtaining such model-independent parametrizations and the corresponding uncertainties: based on the bootstrap approach and the Monte Carlo dropout approach. In our analysis, the $χ^{2}$ defines the loss function, including point-to-point and normalization uncertainties for each independent set of measurements. Our statistical approaches lead to fits of comparable quality and similar uncertainties of the order of $7$ %. To test these models, we compare their predictions to test datasets excluded from the training process and theoretical predictions obtained within the spectral function approach. The predictions of both models agree with experimental measurements and theoretical calculations. We also perform a comparison to a dataset lying beyond the covered kinematic region, and find that the bootstrap approach shows better interpolation and extrapolation abilities than the one based on the dropout algorithm.
↳ hep-phcs.LGhep-exnucl-ex+1PRC(2024)·9 citations
06
Population of tetraneutron continuum in reactions of $^{8}$ He on deuterium
I.A. Muzalevskii · N.B. Shulgina · A.A. Bezbakh · V. Chudoba · S.A. Krupko · S.G. Belogurov · D. Biare · I.A. Egorova · A.S. Fomichev · E.M. Gazeeva · A.V. Gorshkov · L.V. Grigorenko and 20 other authors
Search for the population of the low-energy continuum of a tetraneutron system was performed for reactions of the $^{8}$ He beam on a deuterium target. These studies are based on the data [I.A. Muzalevskii \textit{et al.}, Phys.\ Rev.\ C \textbf{103}, 044313 (2021)], previously used for the studies of $^{7}$ H and $^{6}$ H in the $^{2} H (^{8} He,^{3} He)^{7}$ H and $^{2} H (^{8} He,^{4} He)^{6}$ H reactions. Evidence for a hump in the $^{4}$ n continuum at $3.5 \pm 0.7$ and $3.2 \pm 0.8$ MeV was observed in the $^{2}$ H( $^{8}$ He, $^{6}$ Li) $^{4}$ n and $^{2}$ H( $^{8}$ He, $^{3}$ He) $^{7}$ H $\to^{3}$ H+ $^{4}$ n reactions, respectively. The observed statistics is quite low (6 events and up to 40 events) corresponding to very low cross sections of few microbarns or tens of microbarns. The background conditions for the $^{2}$ H( $^{8}$ He, $^{6}$ Li) $^{4}$ n reaction are shown to be good, favoring the physical nature of the observed events. The $^{2}$ H( $^{8}$ He, $^{3}$ He) $^{7}$ H $\to^{3}$ H+ $^{4}$ n process transforms to the $^{2}$ H( $^{8}$ He, $^{6}$ Li $^{*})^{4} n$ reaction in the limit of the highest $^{7}$ H decay energies. The population of the low-energy region in the $^{4}$ n spectrum is found to be perfectly correlated with the population of the lowest $^{6}$ Li state in the $^{3}$ He+ $^{3}$ H continuum with $E^{*} = 18$ MeV. Theoretical calculations of $^{8}$ He in a five-body $α$ + $4 n$ and of $^{4}$ n in a four-body hyperspherical models are presented. The $^{8}$ He wave function is shown to contain strong specific correlations, which may give rise to very low-energy structures in tetraneutron continuum in extreme-peripheral reaction scenarios.
↳ nucl-exnucl-thPRC(2025)·7 citations
07
Global coupled-channel analysis of $e^{+} e^{-} \to c c ˉ$ processes in $s = 3.75 - 4.7$ GeV
S.X. Nakamura (Shandong Univ.)🇨🇳 · X.-H. Li (USTC)🇨🇳 · H.-P. Peng (USTC)🇨🇳 · Z.-T. Sun (Shandong Univ.)🇨🇳 · X.-R. Zhou (USTC)🇨🇳
Recent high-precision $e^{+} e^{-} \to c c ˉ$ data from the BESIII and Belle are highly useful to understand vector charmonium ( $ψ$ ) pole structures and puzzling lineshapes due to the exotic hadron candidates $Y$ . We thus perform a global coupled-channel analysis of most of the available data (10 two-body, 9 three-body, and 1 four-body final states) in $s = 3.75 - 4.7$ GeV. Not only cross sections but also invariant-mass distributions of subsystems are fitted. The $e^{+} e^{-} \to μ^{+} μ^{-}$ cross sections are also predicted. Our model includes dozens of (quasi) two-body states that nonperturbatively couple with each other through bare $ψ$ excitations, particle-exchange, and short-range mechanisms; approximate three-body unitarity is considered. The amplitudes obtained from the fit are analytically continued to $ψ$ and $Z_{c}$ poles. We find $ψ$ states similar to those in the Particle Data Group listing and $Y (4320)$ . Moreover, several $ψ$ states, including new ones, are found close to open charm thresholds. Trajectories and compositeness of the near-threshold poles suggest dominant hadron-molecule contents in their internal structures. Two $Z_{c}$ poles are found as virtual states $\sim$ 40 MeV below the $D^{*} D ˉ^{(*)}$ thresholds, being consistent with lattice QCD results. This work presents the first global analysis to determine $ψ$ and $Z_{c}$ poles, thereby paving the way to extracting detailed properties of the prominent exotic hadron candidates from data.
↳ hep-phhep-exnucl-thPRD(2025)·48 citations
08
Spinodal enhancement of fluctuations in nucleus-nucleus collisions
Roman Poberezhnyuk🇺🇦 · Oleh Savchuk🇺🇸 · Volodymyr Vovchenko🇺🇸 · Volodymyr Kuznietsov🇺🇦 · Jan Steinheimer🇩🇪 · Mark Gorenstein🇺🇦 · Horst Stoecker🇩🇪
Subensemble Acceptance Method (SAM) [1,2] is an essential link between measured event-by-event fluctuations and their grand canonical theoretical predictions such as lattice QCD. The method allows quantifying the global conservation law effects in fluctuations. In its basic formulation, SAM requires a sufficiently large system such as created in central nucleus-nucleus collisions and sufficient space-momentum correlations. Directly in the spinodal region of the First Order Phase Transition (FOPT) different approximations should be used that account for finite size effects. Thus, we present the generalization of SAM applicable in both the pure phases, metastable and unstable regions of the phase diagram [3]. Obtained analytic formulas indicate the enhancement of fluctuations due to crossing the spinodal region of FOPT and are tested using molecular dynamics simulations. A rather good agreement is observed. Using transport model calculations with interaction potential we show that the spinodal enhancement of fluctuations survives till the later stages of collision via the memory effect [4]. However, at low collision energies the space-momentum correlation is not strong enough for this signal to be transferred to second and third order cumulants measured in momentum subspace. This result agrees well with recent HADES data on proton number fluctuations at $s_{N N} = 2.4$ GeV which are found to be consistent with the binomial momentum space acceptance [5].
↳ hep-phnucl-thEPJ Web Conf.(2024)·0 citations
09
Phases of 2d massless QCD with qubit regularization
Hanqing Liu🇺🇸 · Tanmoy Bhattacharya🇺🇸 · Shailesh Chandrasekharan🇺🇸 · Rajan Gupta🇺🇸
We investigate the possibility of reproducing the continuum physics of 2d SU(N) gauge theory coupled to a single flavor of massless Dirac fermions using qubit regularization. The continuum theory is described by N free fermions in the ultraviolet (UV) and a coset Wess-Zumino-Witten (WZW) model in the infrared (IR). In this work, we explore how well these features can be reproduced using the Kogut-Susskind Hamiltonian with a finite-dimensional link Hilbert space and a generalized Hubbard coupling. Using strong coupling expansions, we show that our model exhibits a gapped dimer phase and another phase described by a spin-chain. Furthermore, for N=2, using tensor network methods, we show that there is a second-order phase transition between these two phases. The critical theory at the transition can be understood as an SU(2)_1 WZW model, using which we determine the phase diagram of our model quantitatively. Using the confinement properties of the model we argue how the UV physics of free fermions could also emerge, but may require further modifications to our model.
↳ hep-latcond-mat.str-elhep-thnucl-th+1PRD(2025)·9 citations

Affiliations

first authorsco-authorsvia INSPIRE