Nuclear Theory·nucl-th

Tuesday·June 6, 2023

11 papers—4 primary·7 cross-listed

01
Shell model study of first-forbidden beta decay around $^{208}$ Pb
P. C. Srivastava · S. Sharma · A. Kumar · P. Choudhary
In the present work, we report a systematic theoretical study of the $lo g f t$ values for the forbidden $β^{-}$ decay transitions in the $^{208}$ Pb region. For this, we have considered $^{206}$ Hg $\to$ $^{206}$ Tl, $^{208}$ Hg $\to$ $^{208}$ Tl, $^{206}$ Tl $\to$ $^{206}$ Pb and $^{208}$ Tl $\to$ $^{208}$ Pb transitions. We have performed shell model calculations using KHH7B interaction in valence shell 58-114 for protons and 100-164 for neutrons by considering $1p - 1h$ excitations for both protons and neutrons simultaneously for daughter nuclei. This study presents the first shell model results of $β^{-}$ -decay corresponding to the recent experimental data.
nucl-thnucl-exJ.Phys.Conf.Ser.(2023)·4 citations
02
TRABZO: a novel combined model for heavy-ion fusion/capture accounting for zero-point shape oscillations and dissipative effects
Maria V. Chushnyakova
The fusion/capture cross sections (CSs) of complex nuclei (heavy ions) are often described in the literature within two approaches: i) the coupled channels model accounting for structure of the colliding nuclei and ii) trajectory models with friction and thermal fluctuations (dissipative effects). The first approach does not account for friction whereas the second one is not able to deal with sub-barrier CSs. In the present work, we have developed an algorithm for calculating the capture CSs of collision of spherical nuclei accounting for both zero-point oscillations (ZPO) of the nuclear shapes (structure effects) and for dissipative effects; i.e., in a sense we have combined the above two approaches. The bare nucleus-nucleus potential is evaluated using the semi-microscopic double-folding model with M3Y-Paris nucleon-nucleon forces. The nucleon densities are taken from the IAEA data base. For each collision partner several deformations of quadrupole and octupole type are accounted for with the probabilities corresponding to the harmonic oscillator at the ground state. The dissipative effects enter into our combined approach within the surface friction model well known in the literature. The final fate of a trajectory is decided by means of quantum transmission coefficients. There are two fitting parameters in the model, tau and K_R. Parameter tau reflects to what extent ZPO survives when the reagents approach each other. Parameter K_R is the friction strength for the radial motion. All calculations have been performed for 16O+92Zr reaction. The calculated CSs and barrier distribution are found in good agreement with the precision experimental data at reasonable values of tau and K_R. Calculations show that the CSs are mostly sensitive to tau at low (sub-barrier) collision energies whereas the value of K_R is important at the above barrier energies.
nucl-th0 citations
03
Role of three-body dynamics in nucleon-deuteron correlation functions
M. Viviani🇮🇹 · S. König🇺🇸 · A. Kievsky🇮🇹 · L. E. Marcucci🇮🇹 · B. Singh🇩🇪 · O. Vázquez Doce🇮🇹
Correlation functions of hadrons can be accessed in high-energy collisions of atomic nuclei, revealing information about the underlying interaction. This work complements experimental efforts to study nucleon-deuteron $N d$ -- with $N = p$ (proton) or $N = n$ (neutron) -- correlations with theory evaluations using different techniques. The correlation functions $C_{n d}$ and $C_{p d}$ are calculated based on scattering wave function, extending previous benchmarks for the $N d$ scattering matrix to this new observable. We use hyperspherical harmonics and Faddeev techniques with one of the widely used nucleon-nucleon ( $N N$ ) interactions, the Argonne $v_{18}$ potential. Moreover, in the low-energy region we perform additional calculations in the framework of pionless effective field theory. The $p d$ correlation function is computed in the large-energy region to make contact with a recent measurement by the ALICE Collaboration. We show that the scattering wave function has the proper dynamical input to describe an initial rise and subsequent oscillations of $C_{p d}$ as a function of the energy. Effects on the observables using different $N N$ and three-nucleon potentials are evaluated with the conclusion that variations of around $2%$ are observed. Although these effects are small, future measurements can go beyond this accuracy allowing for new detailed studies of strong interaction in light nuclear systems. The present study supports the current efforts devoted to the measurement of correlation functions in systems dominated by the strong interactions, such as $p d$ , $ppp$ , $Λ d$ and $pp Λ$ .
nucl-thhep-exPRC(2023)·32 citations
04
Dynamic Calculations of Magnetic Field and Implications on Spin Polarization and Spin Alignment in Heavy Ion Collisions
Hui Li🇨🇳 · Xiao-Liang Xia🇨🇳 · Xu-Guang Huang🇨🇳 · Huan Zhong Huang🇨🇳
Magnetic field plays a crucial role in various novel phenomena in heavy-ion collisions. We solve the Maxwell equations numerically in a medium with time-dependent electric conductivity by using the Finite-Difference Time-Domain (FDTD) algorithm. We investigate the time evolution of magnetic fields in two scenarios with different electric conductivities at collision energies ranging from $s_{NN} =$ 7.7 to 200 GeV. Our results suggest that the magnetic field may not persist long enough to induce a significant splitting between the global spin polarizations of $Λ$ and $Λ ˉ$ at freeze-out stage. However, our results do not rule out the possibility of the magnetic field influencing the spin (anti-)alignment of vector mesons.
nucl-thPRC(2023)·14 citations
05
Missing levels in intermediate spectra
María Hita-Pérez · Laura Muñoz · Rafael A. Molina
We derive an expression for the nearest-neighbor spacing distribution $P (s)$ of the energy levels of quantum systems with intermediate dynamics between regularity and chaos and missing levels due to random experimental errors. The expression is based on the Brody distribution, the most widely used for fitting mixed spectra as a function of one parameter. By using Monte Carlo simulations of intermediate spectra based on the $β$ -Hermite ensemble of Random Matrix Theory, we evaluate the quality of the formula and its suitability for fitting purposes. Estimations of the Brody parameter and the fraction of missing levels can be obtained by a least-square two-parameter fitting of the experimental $P (s)$ . The results should be important to distinguish the origins of deviations from RMT in experimental spectra.
↳ quant-phcond-mat.mes-hallnlin.CDnucl-th+1J.Phys.A(2023)·0 citations
06
133In: A Rosetta Stone for decays of r-process nuclei
Z. Y. Xu🇺🇸 · M. Madurga🇺🇸 · R. Grzywacz🇺🇸 · T. T. King🇺🇸 · A. Algora🇪🇸 · A. N. Andreyev🇬🇧 · J. Benito🇪🇸 · T. Berry🇬🇧 · M. J. G. Borge🇪🇸 · C. Costache🇷🇴 · H. De Witte🇧🇪 · A. Fijalkowska🇺🇸 and 37 other authors
The $β$ decays from both the ground state and a long-lived isomer of $^{133}$ In were studied at the ISOLDE Decay Station (IDS). With a hybrid detection system sensitive to $β$ , $γ$ , and neutron spectroscopy, the comparative partial half-lives (logft) have been measured for all their dominant $β$ -decay channels for the first time, including a low-energy Gamow-Teller transition and several First-Forbidden (FF) transitions. Uniquely for such a heavy neutron-rich nucleus, their $β$ decays selectively populate only a few isolated neutron unbound states in $^{133}$ Sn. Precise energy and branching-ratio measurements of those resonances allow us to benchmark $β$ -decay theories at an unprecedented level in this region of the nuclear chart. The results show good agreement with the newly developed large-scale shell model (LSSM) calculations. The experimental findings establish an archetype for the $β$ decay of neutron-rich nuclei southeast of $^{132}$ Sn and will serve as a guide for future theoretical development aiming to describe accurately the key $β$ decays in the rapid-neutron capture (r-) process.
↳ nucl-exnucl-thPRL(2023)·12 citations
07
Isomeric excitation energy for $^{99}$ In $^{m}$ from mass spectrometry reveals constant trend next to doubly magic $^{100}$ Sn
L. Nies (1 and 2)🇨🇭 · D. Atanasov (1 and 3)🇨🇭 · M. Athanasakis-Kaklamanakis (1 and 4)🇨🇭 · M. Au (1 and 5)🇨🇭 · K. Blaum (6)🇩🇪 · J. Dobaczewski (7 and 8)🇵🇱 · B. S. Hu (9)🇨🇦 · J. D. Holt (9 and 10)🇨🇦 · J. Karthein (11)🇺🇸 · I. Kulikov (12)🇩🇪 · Yu. A. Litvinov (12 and 13)🇩🇪 · D. Lunney (14)🇫🇷 and 7 other authors
The excitation energy of the 1/2 $^{-}$ isomer in $^{99}$ In at $N = 50$ is measured to be 671(37) keV and the mass uncertainty of the 9/2 $^{+}$ ground state is significantly reduced using the ISOLTRAP mass spectrometer at ISOLDE/CERN. The measurements exploit a major improvement in the resolution of the multi-reflection time-of-flight mass spectrometer. The results reveal an intriguing constancy of the $1/ 2^{-}$ isomer excitation energies in neutron-deficient indium that persists down to the $N = 50$ shell closure, even when all neutrons are removed from the valence shell. This trend is used to test large-scale shell model, \textit{ab initio}, and density functional theory calculations. The models have difficulties describing both the isomer excitation energies and ground-state electromagnetic moments along the indium chain.
↳ nucl-exnucl-thPRL(2023)·22 citations
08
Heavy-flavor transport and hadronization in pp collisions
Andrea Beraudo🇮🇹 · Arturo De Pace🇮🇹 · Daniel Pablos🇮🇹 · Francesco Prino🇮🇹 · Marco Monteno🇮🇹 · Marzia Nardi🇮🇹
Recent experimental results on the Lambda_c/D^0 ratio in proton-proton collisions have revealed a significant enhancement compared to expectations based on universal fragmentation fractions/functions across different colliding systems, from e+e- to pp. This unexpected enhancement has sparked speculation about the potential effects of a deconfined medium impacting hadronization, previously considered exclusive to heavy-ion collisions. In this study, we propose a novel approach that assumes the formation of a small, deconfined, and expanding fireball even in pp collisions, where charm quarks can undergo rescattering and hadronization. We make use of the same in-medium hadronization mechanism developed for heavy-ion collisions, which involves local color-neutralization through recombination of charm quarks with nearby opposite color charges from the background fireball. Our model incorporates the presence of diquark excitations in the hot medium, which promotes the formation of charmed baryons. Moreover, the recombination process, involving closely aligned partons from the same fluid cell, effectively transfers the collective flow of the system to the final charmed hadrons. We show that this framework can qualitatively reproduce the observed experimental findings in heavy-flavor particle-yield ratios, $p_{T}$ -spectra and elliptic-flow coefficients. Our results provide new, complementary supporting evidence that the collective phenomena observed in small systems naturally have the same origin as those observed in heavy-ion collisions
↳ hep-phhep-exnucl-exnucl-thPRD(2024)·43 citations
09
Perturbative QCD concerning light and heavy flavor in the EPOS4 framework
K. Werner🇫🇷 · B. Guiot🇨🇱
We recently introduced new concepts, implemented in EPOS4, which allow to consistently accommodate factorization and saturation in high energy proton-proton and nucleus-nucleus collisions, in a rigorous parallel scattering framework. EPOS4 has a modular structure and in this paper, we present in detail how the "single scattering module" (the main EPOS4 building block) is related to perturbative QCD, and how these calculations are performed, with particular care being devoted to heavy flavor contributions. We discuss similarities and differences compared to the usual pQCD approach based on factorization.
↳ hep-phnucl-thPRC(2023)·56 citations
10
Heavy quark drag and diffusion coefficients in the pre-hydrodynamic QCD plasma
Xiaojian Du🇪🇸
Kinetic and chemical equilibrations play important roles in the formation of the quark-gluon plasma (QGP) in relativistic heavy-ion collisions (HICs). These processes further influence the production of hard and electromagnetic probes in HICs, in particular, the thermalization of heavy quarks, which are produced at an extremely early time before the formation of the QGP. We calculate the drag and diffusion coefficients of heavy quarks in the pre-hydrodynamic quantum chromodynamic (QCD) plasma with the state-of-the-art QCD effective kinetic theory (EKT) solver. We present the time, momentum, and angular dependencies of these coefficients for gluon and quark contributions separately, showing the effects of isotropization and chemical equilibration from the QCD plasma. We also provide a simple formula to estimate the heavy quark drag and diffusion coefficients, as well as its energy loss, within the pre-hydrodynamic plasma at different coupling strengths based on the attractor theory. We then discuss the validity of these estimations with leading-order calculations and leading-logarithmic rescaling factors.
↳ hep-phnucl-thPRC(2024)·19 citations
11
Normal single-spin asymmetries in electron-proton scattering: two-photon exchange with intermediate state resonances
Jaseer Ahmed🇧🇩 · P. G. Blunden🇨🇦 · W. Melnitchouk🇺🇸
We calculate the beam ( $B_{n}$ ) and target ( $A_{n}$ ) normal single-spin asymmetries in electron-proton elastic scattering from two-photon exchange amplitudes with resonance intermediate states of spin-parity $1/ 2^{\pm}$ and $3/ 2^{\pm}$ and mass $W ≲ 1.8$ GeV. The latest CLAS exclusive meson electroproduction data are used as input for the transition amplitudes from the proton to the excited resonance states. For $B_{n}$ , the spin 3/2 resonances dominate by an order of magnitude over the spin 1/2 states. In general we observe cancellations between the negative contributions of the $Δ (1232)$ and $N (1520)$ across both beam energy and scattering angle, and the positive contributions of the $Δ (1700)$ and $N (1720)$ , leading to a rather large overall uncertainty band in the total $B_{n}$ . At forward angles and beam energies $E_{lab} < 1$ GeV, where the $Δ (1232)$ dominates, the calculated $B_{n}$ tend to overshoot the A4 and SAMPLE data. The calculated $B_{n}$ compare well with the measured values from the A4 and $Q_{weak}$ experiments with $E_{lab} > 1$ GeV.
↳ hep-phnucl-exnucl-thPRC(2023)·11 citations

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