Nuclear Theory·nucl-th

Monday·April 8, 2024

9 papers—2 primary·7 cross-listed

01
Gamow-Teller strength distributions of 18O and well-deformed nuclei 24,26Mg by deformed QRPA
Eunja Ha · Myung-Ki Cheoun · H. Sagawa · Gianluca Colo
We investigate the Gamow-Teller (GT) transition strength distributions of {strongly} deformed nuclei, $^{24, 26}$ Mg, as well as of $^{18}$ O. The calculations are performed within a deformed quasi-particle random phase approximation (DQRPA) which explicitly includes the deformation degree of freedom in the Skyrme-Hartree-Fock (SHF) and RPA calculations. The residual particle-particle ( $p - p$ ) interaction as well as the particle-hole ( $p - h$ ) interaction are extracted from Brückner $G$ -matrix calculations. The {residual interaction} dependence of the low-lying GT strength of these strongly deformed nuclei is examined by changing the strength of the residual $p - p$ and $p - h$ interactions. We have found that the low-lying GT peaks are quite similar in energy to those found in {spherical} $N = Z$ and $N = Z + 2$ nuclei near magic shells, but the configurations {of $^{24, 26}$ Mg are largely mixed by} the pairing correlations and the deformation. Our results are compared to the experimental GT $(\pm)$ transition data by ( $t$ , $^{3}$ He) and ( $^{3}$ He, $t$ ) reactions, {and found to reproduce the main features of GT strength distributions.
nucl-thPRC(2024)·3 citations
02
Significance of the refraction effect on the $p$ - $d$ elementary process in the ( $p$ , $p d$ ) reaction
Kazuki Yoshida · Yoshiki Chazono · Kazuyuki Ogata
The proton-induced deuteron knockout reaction, ( $p$ , $p d$ ), is one of the interests in the studies for probing the deuteron-like $p$ - $n$ correlation in nuclei. According to a recent study of the inclusive deuteron-induced reaction, $(d, d^{'} x)$ , the refraction effect of the deuteron has a significant effect on the elementary process, nucleon-deuteron ( $N$ - $d$ ) binary scattering inside a nucleus, of the reaction. In the paper, it is shown that proper treatment of the local $N$ - $d$ relative momentum in the elementary process is crucial in $(d, d^{'} x)$ reactions at $100$ MeV and below. In the present work, we investigate the deuteron refraction effect in the exclusive ( $p$ , $p d$ ) reactions. We also discuss the incident energy dependence of the refraction effect. The refraction effect on the $p$ - $d$ elementary process is taken into account by the local semiclassical approximation to the distorted waves. The results are compared with those obtained with the asymptotic momentum approximation, which is standardly applied to the distorted wave impulse approximation framework. It is shown that the refraction effect drastically changes the energy sharing distribution of the $^{16}$ O( $p$ , $p d$ ) $^{14}$ N reaction at 101.3 MeV and gives a better agreement with experimental data. In contrast, it is confirmed that the effect is negligibly small at 250 MeV. We have clarified that the deuteron refraction effect is significant in the $^{16}$ O( $p$ , $p d$ ) $^{14}$ N reaction at 101.3 MeV and the experimental data are well reproduced. The refraction effect plays a significant role in both the shape and magnitude of the ( $p$ , $p d$ ) cross section, while the effect is negligible at 250 MeV.
nucl-thnucl-exPRC(2024)·5 citations
03
Target normal single-spin asymmetry in inclusive electron-nucleon scattering in the 1/Nc expansion
Jose L. Goity · Christian Weiss
The target normal single-spin asymmetry in electron nucleon scattering is studied in the framework of the 1/Nc expansion of QCD, which allows for a rigorous description in the energy range that includes the Delta resonance and below the second baryon resonance region. The asymmetry is driven by the absorptive part of the two-photon exchange component of the scattering amplitude, being therefore the most unambiguous two-photon exchange effect. Such amplitude is shown to be described up to the next to leading order in the 1/Nc expansion only in terms of the charge and magnetic form factors of the nucleons, consequence of the approximate $S U (4)$ spin flavor symmetry valid in the large Nc limit for baryons. A discussion is provided of the 1/Nc expansion framework along with the results for the asymmetries in elastic, inelastic, and inclusive electron-nucleon scattering.
↳ hep-phnucl-th0 citations
04
Nuclear uncertainties associated with the ejecta of a neutron-star black-hole accretion disk
M. R. Mumpower · T. M. Sprouse · J. M. Miller · K. A. Lund · J. Cabrera Garcia · N. Vassh · G. C. McLaughlin · R. Surman
The simulation of heavy element nucleosynthesis requires input from yet-to-be-measured nuclear properties. The uncertainty in the values of these off-stability nuclear properties propagates to uncertainties in the predictions of elemental and isotopic abundances. However, for any given astrophysical explosion, there are many different trajectories, i.e. temperature and density histories, experienced by outflowing material and thus different nuclear properties can come into play. We consider combined nucleosynthesis results from 460,000 trajectories from a neutron star-black hole accretion disk and the find spread in elemental predictions due solely to unknown nuclear properties to be a factor of a few. We analyze this relative spread in model predictions due to nuclear variations and conclude that the uncertainties can be attributed to a combination of properties in a given region of the abundance pattern. We calculate a cross-correlation between mass changes and abundance changes to show how variations among the properties of participating nuclei may be explored. Our results provide further impetus for measurements of multiple quantities on individual short-lived neutron-rich isotopes at modern experimental facilities.
↳ astro-ph.HEastro-ph.SRnucl-exnucl-thApJ(2024)·7 citations
05
Photo-production of $η_{c, b}$ near Threshold
Wei-Yang Liu🇺🇸 · Ismail Zahed🇺🇸
We analyze the photo-production of $η_{c, b}$ off a proton in the threshold region, in terms of C-odd gluonic correlations in the off-forward proton matrix element. Near threshold, the skewness is large leading to a production amplitude that is dominated by four C-odd twist-3 gluon GPDs. We use the QCD instanton vacuum to estimate these C-odd contributions in the proton. The results are used to estimate the differential cross sections for coherent photo-production of $η_{c, b}$ in the threshold region, at current electron facilities.
↳ hep-phnucl-thPRD(2024)·9 citations
06
Maximal mass of the neutron star with a deconfined quark core
Muhammed Shafeeque🇮🇳 · Arun Mathew🇮🇪 · Malay K. Nandy🇮🇳
The nature of equation of state for the matter in the neutron star plays an important role in determining its maximal mass. In addition, it must comply with the condition of causality. Noting that the central density of a maximally massive neutron star is well above the nuclear saturation density, a deconfined quark core in the central region is motivated in this paper. We analyze this scenario by employing the MIT bag model to represent the core region and one of the unified equations of state for the region outside the core. Such combination is found to solve the problem of causality violation. In each case of the combined equations of state, the radial profile of $ρ r^{2}$ displays a peak and dominant contribution to the total mass of the star comes from the region around the peak value of $ρ r^{2}$ , whereas the contribution is small from the regions near the center and the surface. This peak occurs in the region of hadronic matter for the combinations considered in this paper. Importantly, we find that the position of the peak in $ρ r^{2}$ is well-correlated with the maximal mass -- the highest value of $1.98 M_{⊙}$ obtains for the case with the peak occurring farthest from the center. This gravitational threshold being obtained for a non-rotating neutron star, we expect the threshold to lie well above 2 $M_{⊙}$ for a rapidly rotating neutron star, that may explain the existance of massive pulsars from recent astronomical observations.
↳ astro-ph.HEgr-qcnucl-thJ.Astrophys.Astron.(2023)·3 citations
07
Unified equations of state for cold nonaccreting neutron stars with Brussels-Montreal functionals. V. Improved parametrization of the nucleon density distributions
N.N. Shchechilin · N. Chamel · J.M. Pearson · A.I. Chugunov · A.Y. Potekhin
We previously studied the inner crust and the pasta mantle of a neutron star within the 4th-order extended Thomas-Fermi (ETF) approach with consistent proton shell corrections added perturbatively via the Strutinsky integral (SI) theorem together with the contribution due to pairing. To speed up the computations and avoid numerical problems, we adopted parametrized nucleon density distributions. However, the errors incurred by the choice of the parametrization are expected to become more significant as the mean baryon number density is increased, especially in the pasta mantle where the differences in the energy per nucleon of the different phases are very small, typically a few keV. To improve the description of these exotic structures, we discuss the important features that a nuclear profile should fulfill and introduce two new parametrizations. Performing calculations using the BSk24 functional, we find that these parametrizations lead to lower ETF energy solutions for all pasta phases than the parametrization we adopted before and more accurately reproduce the exact equilibrium nucleon density distributions obtained from unconstrained variational calculations. Within the ETFSI method, all parametrizations predict the same composition in the region with quasi-spherical clusters. However, the two new parametrizations lead to a different mantle structure at mean baryon densities above about 0.07 fm^-3, at which point lasagna is energetically favored. Interestingly, spherical clusters reappear in the pasta region. The inverted pasta phases such as bucatini and Swiss cheese are still found in the densest region above the core in all cases.
↳ astro-ph.HEnucl-thPRC(2024)·18 citations
08
Strangeness $+ 1$ light multiquark baryons
Brenda B. Malabarba🇧🇷 · K. P. Khemchandani🇰🇷 · A. Martinez Torres🇧🇷 · Seung-il Nam🇰🇷
In view of the renewing experimental interest for searching strangeness $+ 1$ baryons at J-PARC, we study the existence of light baryon resonances with strangeness +1 generated in the $K$ - $(N^{*} / Δ^{*})$ system, where $N^{*}$ represents either $N^{*} (1535)$ / $N^{*} (1650)$ / $N^{*} (1700)$ , and $Δ^{*}$ corresponds to $Δ (1620)$ . The description of the properties of the aforementioned states requires considering the dynamics involved in the coupled pseudoscalar-baryon and vector-baryon systems with strangeness $S = 0$ in the s-wave. For the purpose of our current study, we consider the pseudoscalar-baryon (PB) and vector-baryon channels (VB) to which the mentioned $N^{*}$ and $Δ^{*}$ resonances couple and solve the Faddeev equations for the coupled channel system $K$ - $PB$ , $K$ - $VB$ , with all interactions being in the s-wave. Despite some strong attraction present in two of the subsystems, we do not find clear evidence supporting the formation of strangeness +1 states, with spin-parity $J^{P} = 1/ 2^{+}$ , in the energy region $2000 - 2200$ MeV. However, the case of spin-parity $J^{P} = 3/ 2^{+}$ seems more promising, showing the formation of a resonance with a mass around 2167 MeV, with a width of 90-100 MeV. We suggest that a signal of such a state could be found in processes with final states like $K N$ , $K^{*} (892) N$ .
↳ hep-phnucl-thPRD(2025)·8 citations
09
Jet angularities in dijet production in proton-proton and heavy-ion collisions at RHIC
Yang-Ting Chien🇺🇸 · Oleh Fedkevych🇺🇸 · Daniel Reichelt🇬🇧 · Steffen Schumann🇩🇪
We study jet angularities for dijet production at the Relativistic Heavy Ion Collider (RHIC) in proton-proton (pp) and nucleus-nucleus (AA) collisions at 200 GeV nucleon-nucleon center-of-mass collision energy. In particular, we provide $NLL$ resummed predictions for angularity observables of groomed and ungroomed jets produced in $pp$ collisions matched to next-to-leading order QCD calculations resulting in $NLO + NL L^{'}$ accuracy. Our parton-level predictions are corrected for non-perturbative effects, such as hadronization and underlying event, using parton-to-hadron level transfer matrices obtained with the Sherpa event generator. Furthermore, we use the Q-Pythia and JEWEL generators to estimate the impact of the interaction between quarks and gluons produced by the parton shower with the dense medium formed in heavy-ion collisions on the considered jet angularities.
↳ hep-phhep-exnucl-exnucl-thJHEP(2024)·18 citations

Affiliations

first authorsco-authorsvia INSPIRE