Nuclear Theory·nucl-th

Tuesday·May 2, 2023

9 papers—6 primary·3 cross-listed

01
[Submitted on 28 Apr 2023]
Determination of the neutron skin of $^{208}$ Pb from ultrarelativistic nuclear collisions
Giuliano Giacalone🇩🇪 · Govert Nijs🇺🇸 · Wilke van der Schee🇨🇭
Emergent bulk properties of matter governed by the strong nuclear force give rise to physical phenomena across vastly different scales, ranging from the shape of atomic nuclei to the masses and radii of neutron stars. They can be accessed on Earth by measuring the spatial extent of the outer skin made of neutrons that characterises the surface of heavy nuclei. The isotope $^{208}$ Pb, owing to its simple structure and neutron excess, has been in this context the target of many dedicated efforts. Here, we determine the neutron skin from measurements of particle distributions and their collective flow in $^{208}$ Pb+ $^{208}$ Pb collisions at ultrarelativistic energy performed at the Large Hadron Collider, which are sensitive to the overall size of the colliding $^{208}$ Pb ions. By means of state-of-the-art global analysis tools within the hydrodynamic model of heavy-ion collisions, we infer a neutron skin $Δ r_{n p} = 0.217 \pm 0.058$ fm, consistent with nuclear theory predictions, and competitive in accuracy with a recent determination from parity-violating asymmetries in polarised electron scattering. We establish thus a new experimental method to systematically measure neutron distributions in the ground state of atomic nuclei.
Comments:
8 pages, 6 figures. The Trajectum code can be found at https://sites.google.com/view/govertnijs/trajectum. Plotting routines can be found at http://wilkevanderschee.nl/trajectum. v2 expanded appendices, matches published version
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2305.00015 [pdf]
PRL(2023)·129 citations
02
[Submitted on 30 Apr 2023]
New 26P(p,{\gamma})27S thermonuclear reaction rate and its astrophysical implication in rp-process
S.Q. Hou · J.B. Liu · T. C. L. Trueman · J.G. Li · M. Pignatari · C. Bertulani · X.X. Xu
Accurate nuclear reaction rates for 26P(p,{\gamma})27S are pivotal for a comprehensive understanding of rp-process nucleosynthesis path in the region of proton-rich sulfur and phosphorus isotopes. However, large uncertainties still exist in the current rate of 26P(p,{\gamma})27S because of the lack of the nuclear mass and the energy level structure information of 27S. We reevaluate this reaction rate using the experimentally constrained 27S mass, together with the shell-model predicted level structure. It is found that the 26P(p,{\gamma})27S reaction rate is dominated by a direct-capture (DC) reaction mechanism despite the presence of three resonances at E = 1.104, 1.597, 1.777 MeV above the proton threshold in 27S. The new rate is overall smaller than the other previous rates from Hauser-Feshbach statistical model by at least one order of magnitude in the temperature range of X-ray burst interest. In addition, we consistently update the photodisintegration rate using the new 27S mass. The influence of new rates of forward and reverse reaction in the abundances of isotopes produced in rp-process is explored by post-processing nucleosynthesis calculations. The final abundance ratio of 27S/26P obtained using the new rates is only 10% of that from the old rate. The abundance flow calculations show the reaction path 26P(p,{\gamma})27S(\b{eta}+,{\nu})27P is not as important as thought previously for producing 27P. The adoption of the new reaction rates for 26P(p,{\gamma})27S only reduces the final production of aluminum by 7.1%, and has no discernible impact on the yield of other elements.
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR)
arXiv:
2305.00371 [pdf]
ApJ(2023)·2 citations
03
[Submitted on 1 May 2023]
Uncertainties in modeling the capture process in heavy-ion collisions
I. I. Gontchar
In the present paper, we study the uncertainties in modeling the collision of complex nuclei (heavy ions) resulting in capture of the nuclei into orbital motion. The effective interaction energy of the nuclei (effective potential) consists of three terms: the Coulomb potential, the strong nucleus-nucleus potential, and the centrifugal term related to the orbital motion. The last term usually is considered in the literature as the simplest one. However, we found in the literature at least two different approaches for the centrifugal potential. To see the effect of using these different prescriptions, we evaluate the capture cross sections using the standard quantum-mechanical formula with the transmission coefficients calculated within the quasi-classical approximation. For the Coulomb- and strong nuclear terms we apply the semi-microscopical double-folding model with the effective nucleon-nucleon forces of Yukawa type. For the nucleon densities the two parameter Fermi formula is used with the parameters from the IAEA data base. Our calculations show that the two approaches for the centrifugal potential result in theoretical capture cross sections which are 20-40 percent different. This result holds for any collision energies.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2305.00637 [pdf]
0 citations
04
[Submitted on 1 May 2023]
Systematic application of the M3Y NN forces for describing the capture process in heavy-ion collisions involving deformed target nuclei
I. I. Gontchar · M. V. Chushnyakova · O. M. Sukhareva
We present results of a systematic study of the capture process through the barrier penetration model. The nucleus-nucleus interaction potential is calculated using the double-folding model (DFM) with the M3Y Paris NN forces. The nucleon densities entering the model are generated from the experimental three-parameter Fermi charge densities. The DFM has been extended to the case of deformed target nuclei. It is shown that the density-dependent M3Y NN forces with the finite range exchange part can be mimicked successfully by the zero-range density-independent forces. The latter option significantly reduces the required computer time. For the nucleon densities and target nuclei deformations we employ the values from the commonly used data bases. Thus, we do not vary any parameters to reach a better agreement with the data. The resulting cross-sections are compared with data for 20 reactions with the product of the charge numbers Z_P*Z_T ranging from 216 up to 2576. We discuss the opinion met in the literature that the M3Y NN forces provide a poorer description of the capture cross-sections in heavy-ion collisions in comparison to the NN forces coming from the relativistic mean-field approach. Our calculations show that the M3Y NN forces give an agreement with the data which is not perfect yet is not worse than the one resulting from the RMF NN forces.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2305.00699 [pdf]
PRC(2022)·4 citations
05
[Submitted on 1 May 2023]
Impact of isovector pairing fluctuation on neutrinoless double-beta decay in multi-reference covariant density functional theory
C. R. Ding🇨🇳 · X. Zhang🇨🇳 · J. M. Yao🇨🇳 · P. Ring🇩🇪 · J. Meng🇨🇳
We extend the multi-reference covariant density functional theory (MR-CDFT) by including fluctuations in quadrupole deformations and average isovector pairing gaps simultaneously for the nuclear matrix elements (NMEs) of neutrinoless double-beta $(0 ν β β)$ decay in the candidate nuclei $^{76}$ Ge, $^{82}$ Se, $^{100}$ Mo, $^{130}$ Te, and $^{136}$ Xe assuming the exchange of either light or heavy neutrinos. The results indicate a linear correlation between the predicted NMEs and the isovector pairing strengths, as well as the excitation energies of $2_{1}^{+}$ and $4_{1}^{+}$ states. By adjusting the pairing strengths based on the excitation energies of the $2_{1}^{+}$ states, we calculate the NMEs for $0 ν β β$ decay, which are reduced by approximately $12%$ to $62%$ compared to the results obtained in the previous studies by Song et al. [Phys. Rev. C95, 024305 (2017)]. Additionally, upon introducing the average isovector pairing gap as an additional generator coordinate in the calculation, the NMEs increase by a factor ranging from $56%$ to $218%$ .
Comments:
11 pages with 4 tables and 8 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2305.00742 [pdf]
PRC(2023)·11 citations
06
[Submitted on 23 Apr 2023]
Comparisons of Matrices with Different Elements but Identical Eigenvalues
Daren Sitchepping Fosso · Castaly Fan · Larry Zamick
We show 2 matrices that have identical eigenvalues but different eigenfunctions. This shows that in obtaining two body nuclear matrix elements empirically, it is not sufficient to consider only energy levels. Other quantities like transitions must also be included.
Comments:
International Journal of Modern Physics E (2023)
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex); Quantum Physics (quant-ph)
arXiv:
2305.00811 [pdf]
IJMPE(2023)·0 citations
07
[Submitted on 28 Apr 2023] (cross-list from hep-ph)
Chiral symmetry restoration in a rotating medium
Irving I. Gaspar🇲🇽 · Luis A. Hernández🇲🇽 · Renato Zamora🇨🇱
We study the nature of the chiral symmetry restoration within the Yukawa model with spontaneous symmetry breaking. We work with scalar and fermion fields which are subject to the effects of a rotating system. In this work, we show the derivation of the scalar field propagator in a rotating medium using the Fock-Schwinger proper-time method. We compute analytically the effective potential in the high-temperature approximations, including the contribution of the ring diagrams to account for the plasma screening properties. We study the chiral transition as we vary the angular velocity $Ω$ , the boson self-coupling $λ$ and the fermion-boson coupling $g$ . We show that the critical temperature for the restoration of chiral symmetry always starts with decreasing behaviour, until it reaches a minimum and from there when increasing $Ω$ , we observe $T_{c}$ increases monotonically. In all the phase transition lines in the $T - Ω$ plane reported, we obtain that the rotating effects are able to change the order of the phase transition.
Comments:
14 pages and 6 figures. References added and typos corrected
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2305.00101 [pdf]
PRD(2023)·20 citations
08
[Submitted on 30 Apr 2023] (cross-list from hep-ph)
Estimation of collision centrality in terms of the number of participating nucleons in heavy-ion collisions using deep learning
Dipankar Basak🇮🇳 · Kalyan Dey🇮🇳
The deep learning technique has been applied for the first time to investigate the possibility of centrality determination in terms of the number of participants ( $N_{part}$ ) in high-energy heavy-ion collisions. For this purpose, supervised learning using both deep neural network (DNN) and convolutional neural network (CNN) is performed with labeled data obtained by modeling relativistic heavy-ion collisions utilizing A Multi-phase Transport Model (AMPT). Event-by-event distributions of pseudorapidity and azimuthal angle of charged hadrons weighted by their transverse momentum are used as input to train the DL models. The DL models did remarkably well in predicting $N_{part}$ values with CNN slightly outperforming the DNN model. The Mean Squared Logarithmic Error (MSLE) for the CNN model (Model-4) is determined to be 0.0592 for minimum bias collisions and 0.0114 for 0-60\% centrality class, indicating that the model performs better for semi-central and central collisions. Furthermore, the studied DL model is proven to be robust to changes in energy as well as model parameters of the input. The current study demonstrates that the data-driven technique has a distinct potential for determining centrality in terms of the number of participants in high-energy heavy-ion collision experiments.
Comments:
13 pages, and 7 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2305.00493 [pdf]
EPJA(2023)·5 citations
09
[Submitted on 1 May 2023] (cross-list from physics.hist-ph)
DT fusion through the $^{5}$ He $3/2 +$ "Bretscher state" accounts for $\geq 25%$ of our existence via nucleosynthesis and for the possibility of fusion energy
Mark B. Chadwick · Mark W. Paris · Brian M. Haines
In big bang nucleosynthesis (BBN), the deuterium-tritium (DT) fusion reaction, D(T,n) $α$ , enhanced by the 3/2 $^{+}$ resonance, is responsible for 99% of primordial $^{4}$ He. This has been known for decades and has been well documented in the scientific literature. However, following the tradition adopted by authors of learned articles, it was stated in a matter-of-fact manner and not emphasized; for most people, it has remained unknown. This helium became a source for the subsequent creation of $\geq$ 25% of the carbon and other heavier elements and, thus, a substantial fraction of our human bodies. (To be more precise than $\geq$ 25% will require future simulation studies on stellar nucleosynthesis.) Also, without this resonance, controlled fusion energy would be beyond reach. For example, for inertial confinement fusion (ICF), laser energy delivery for the National Ignition Facility (NIF) would have to be approximately 70 times larger for ignition. Because the resonance enhances the DT fusion cross section a hundredfold, we propose that the 3/2 $^{+}$ $^{5}$ He excited state be referred to as the "Bretscher state" in honor of the Manhattan Project scientist who discovered it, in analogy with the well-known 7.6 MeV "Hoyle state" in $^{12}$ C that allows for the resonant 3 $α$ formation.
Comments:
4 pages, 4 figures
Subjects:
History and Philosophy of Physics (physics.hist-ph); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2305.00647 [pdf]
4 citations

Affiliations

first authorsco-authorsvia INSPIRE