Nuclear Theory·nucl-th

Friday·August 27, 2021

13 papers—7 primary·6 cross-listed

01
Implementation of residual nucleus de-excitations associated with proton decays in $^{12} C$ based on the GENIE generator and TALYS code
Hang Hu🇨🇳 · Wan-Lei Guo🇨🇳 · Jun Su🇨🇳 · Wei Wang🇨🇳 · Cenxi Yuan🇨🇳
We implement the de-excitation processes of residual nuclei associated with proton decays in $^{12} C$ based on the GENIE generator and TALYS code. To derive the reasonable excitation energy spectra of residual nuclei $^{11} B$ , $^{10} B$ and $^{10} Be$ , the default GENIE nucleon decay generator is modified in terms of the Spectral Function nuclear model. Then we use the TALYS code to estimate the de-excitation processes of residual nuclei. The TALYS calculation can partly account for the experimental data.
nucl-thhep-exhep-phnucl-exPLB(2022)·8 citations
02
Phenomenological study on correlation between flow harmonics and mean transverse momentum in nuclear collisions
Chunjian Zhang🇺🇸 · Jiangyong Jia🇺🇸 · Shengli Huang🇺🇸
To assess the properties of the quark-gluon plasma formed in nuclear collisions, the Pearson correlation coefficient between flow harmonics and mean transverse momentum, $ρ (v_{n}^{2}, [p_{T}])$ , reflecting the overlapped geometry of colliding atomic nuclei, is measured. $ρ (v_{2}^{2}, [p_{T}])$ was found to be particularly sensitive to the quadrupole deformation of the nuclei. We study the influence of the nuclear quadrupole deformation on $ρ (v_{n}^{2}, [p_{T}])$ in $Au + Au$ and $U + U$ collisions at RHIC energy using $AMPT$ transport model, and show that the $ρ (v_{2}^{2}, [p_{T}])$ is reduced by the prolate deformation $β_{2}$ and turns to change sign in ultra-central collisions (UCC).
nucl-thhep-exhep-phSciPost Phys.Proc.(2022)·0 citations
03
Probing the Structure of Deuteron at Very Short Distances
Frank Vera🇺🇸
We study the electrodisintegration of deuteron at quasi-elastic kinematics and high transferred momentum as a probe for the short distance structure in nuclei. In this reaction, an electron hits a nucleus of deuterium, which breaks up into a proton-neutron pair. We focus our attention on events where fast nucleons emerge, corresponding to nuclear configurations where the bound nucleons have a high relative momentum (exceeding 700 MeV/c). The present research is relevant to physical systems where high-density nuclear matter is present. This condition covers a wide range of physics, from neutron stars to nuclei stability and the repulsive nuclear core. The present work differs from previous studies in two crucial features. One is the definition of the deuteron wave function, which include terms of a relativistic origin that can be ordered based on their relative contribution to the deuteron's internal momentum distribution. These terms, related to the off-shell properties of the nucleon-nucleon bound-state, do not occur in non-relativistic quantum mechanics. However, they become increasingly important in describing configurations with a high nucleon-nucleon relative momentum. The second difference is that we account for the off-shell nature of the bound nucleon that enters on the definition of the (half-off-shell) electromagnetic current. We avoid many of the difficulties inherent to the relativistic nature of the processes involved by adopting a theoretical framework known as Light Front dynamics. Simultaneous simplifications in the definition of the relativistic wave function for the proton-neutron bound state and the treatment of the (half-off-shell) electromagnetic current for the bound nucleon are among the essential advantages resulting from the use of the Light Front dynamics.
nucl-th2 citations
04
A Systematic Study Of Nuclear Matter: Finite Nuclei To Neutron Star
Abdul Quddus🇮🇳
The main aim of the thesis is to study the properties of nuclear matter, i.e., finite nuclei to infinite nuclear matter, at zero and finite temperature within effective field theory motived relativistic mean-field model by using some of the recent parameter sets. For this, we have chosen exotic, superheavy, and natural/neutron-rich thermally fissile nuclei and studied ground as well as excited-state bulk and surface properties of nuclei. We have also tried to figure out the possible constraints on the DM variables by considering WIMP, a DM candidate, inside the NS core and using gravitational-wave data GW170817.
nucl-th0 citations
05
Renormalization of NN Chiral EFT, my personal mixed feelings
D.R. Entem🇪🇸
We are celebrating thirty-years from the seminal papers from Weinberg proposing to use the rules of Chiral Perturbation Theory to nucleon systems. His proposal was to build an Effective Field Theory (EFT) with Chiral symmetry as a key property. A big effort on this line have been made during these three decades, however the issue of renormalization of the theory is not settled. I will briefly review my path on this issue and give my personal view.
nucl-thFew Body Syst.(2021)·1 citation
06
Extraction of the second and fourth radial moments of nuclear charge density from the elastic electron-nucleus scattering
Jian Liu · Xiaoting Liu · Xuezhi Wang · Shuo Wang · Chang Xu · Zhongzhou Ren
The expression for the radial moments $⟨ r^{n} ⟩_{c}$ of the nuclear charge density has been discussed under the plane wave Born approximation (PWBA) method recently, which is significant to investigate the nuclear surface thickness and neutron distribution radius. In this paper, we extend the studies of extracting second-order moment $⟨ r^{2} ⟩_{c}$ and fourth-order moment $⟨ r^{4} ⟩_{c}$ from the Coulomb form factors $∣ F_{C} (q) ∣^{2}$ by the distorted wave Born approximation (DWBA) at the small momentum transfer $q$ region. Based on the relativistic mean-field (RMF) calculations, the DWBA form factors $F_{C}^{D W} (q)$ are expanded into $q^{4}$ , where the corresponding charge distributions are corrected by the contributions of neutron and spin-orbit densities. In the small $q$ region, it is found that the experimental $∣ F_{C} (q) ∣^{2}$ can be well reproduced by considering the contributions of the $⟨ r^{4} ⟩_{c}$ at the small $q$ region. Through further analyzing the second-order and fourth-order expansion coefficients of the $F_{C}^{D W} (q)$ , the relationship between the expansion coefficients and proton number $Z$ is obtained. By the relationship, we extract the $⟨ r^{2} ⟩_{c}$ and $⟨ r^{4} ⟩_{c}$ from the limited experimental data of form factors at the small $q$ region. Within the permissible range of error, the extracted $⟨ r^{n} ⟩_{c}$ are consistent with the experimental data in this paper.
nucl-thJ.Phys.G(2021)·5 citations
07
Neutrinoless double-beta decay from an effective field theory for heavy nuclei
Catharina Brase🇩🇪 · Javier Menéndez🇪🇸 · Eduardo Antonio Coello Pérez🇺🇸 · Achim Schwenk🇩🇪
We study neutrinoless double-beta decay in an effective field theory (EFT) for heavy nuclei, which are treated as a spherical core coupled to additional neutrons and/or protons. Since the low-energy constants of the EFT cannot be fitted to data for this unobserved decay, we follow an alternative strategy to constrain these through a correlation with double Gamow-Teller transitions. This correlation was recently found to hold for shell-model calculations, energy-density functionals, and other nuclear structure models. We therefore first calculate the nuclear matrix elements for double Gamow-Teller transitions in the EFT for heavy nuclei. The combination of the EFT uncertainty with the correlation uncertainty enables predictions of nuclear matrix elements for neutrinoless double-beta decay for a broad range of isotopes with quantified uncertainties. Generally the EFT predicts smaller nuclear matrix elements compared to other approaches, but our EFT results are consistent with recent ab initio calculations.
nucl-thnucl-exPRC(2022)·25 citations
08
From the lineshape of the $X (3872)$ to its structure
Angelo Esposito🇨🇭 · Luciano Maiani🇮🇹 · Alessandro Pilloni🇮🇹 · Antonio D. Polosa🇮🇹 · Veronica Riquer🇮🇹
From a study of the lineshape of the $X (3872)$ , the LHCb collaboration measures a sizeable negative effective range. This cannot be reconciled with a shallow $D D ˉ^{*}$ bound state hypothesis. Based on Weinberg's compositeness criterion, together with a theorem by Smorodinsky, it follows that the $X$ has to have a compact hidden charm structure, most likely a tetraquark, interacting with unbound $D D ˉ^{*}$ pairs via short-distance color forces. This conclusion is strengthened by the general pattern recently emerging for exotic mesons.
↳ hep-phnucl-thPRD(2022)·72 citations
09
Valence quark ratio in the proton
Zhu-Fang Cui🇨🇳 · Fei Gao🇩🇪 · Daniele Binosi🇮🇹 · Lei Chang🇨🇳 · Craig D. Roberts🇨🇳 · Sebastian M. Schmidt🇩🇪
Beginning with precise data on the ratio of structure functions in deep inelastic scattering (DIS) from $^{3}$ He and $^{3}$ H, collected on the domain $0.19 \leq x_{B} \leq 0.83$ , where $x_{B}$ is the Bjorken scaling variable, we employ a robust method for extrapolating such data to arrive at a model-independent result for the $x_{B} = 1$ value of the ratio of neutron and proton structure functions. Combining this with information obtained in analyses of DIS from nuclei, corrected for target-structure dependence, we arrive at a prediction for the proton's valence-quark ratio: $d_{v} / u_{v} ∣_{x_{B} \to 1} = 0.230 (57)$ . Requiring consistency with this result presents a challenge to many descriptions of proton structure.
↳ hep-phhep-exhep-latnucl-ex+1Chin.Phys.Lett.(2022)·24 citations
10
Near-threshold Spectrum from Uniformized Mittag-Leffler Expansion -Pole Structure of $Z (3900)$ -
Wren A. Yamada🇯🇵 · Osamu Morimatsu🇯🇵 · Toru Sato🇯🇵 · Koichi Yazaki🇯🇵
We demonstrate how S-matrix poles manifest themselves as the physical spectrum near the upper threshold in the context of the two-channel uniformized Mittag-Leffler expansion, an expression written as a sum of pole terms under an appropriate variable where the S-matrix is made single-valued (uniformization). We show that the transition of the spectrum is continuous as a S-matrix pole moves across the boundaries of the complex energy Riemann sheets and that the physical spectrum peaks at or near the upper threshold when the S-matrix pole is positioned sufficiently close to it on the uniformized plane. There is no essential difference on which sheet the pole is positioned. What is important is the existence of a pole near the upper threshold and the distance between the pole and the physical region, not on which complex energy sheet the pole is positioned. We also point out that when the pole is close to the upper threshold, the complex pole does not have the usual meaning of the resonance. Neither the real part represents the peak energy, nor the imaginary part represents the half width. Subsequently, we try to understand the current status of $Z (3900)$ from the viewpoint of the uniformized Mittag-Leffler expansion reflecting in particular, Phys.Rev.Lett.117, 242001 (2016) in which they concluded that $Z (3900)$ is not a conventional resonance but a threshold cusp. We point out that their results turn out to indicate the existence of S-matrix poles near the $D ˉ D^{*}$ threshold, which is most likely the origin of the peak found in their calculation of the near-threshold spectrum. In order to support our argument, we set up a separable potential model which shares common behavior of poles near the $D ˉ D^{*}$ threshold to the above-mentioned reference and show in our model that the structures near the $D ˉ D^{*}$ threshold are indeed caused by these near-threshold poles.
↳ hep-phnucl-thPRD(2022)·14 citations
11
Symmetry classification of uniform states in spin-2 Bose-Einstein condensates and neutron $^{3} P_{2}$ superfluids
Michikazu Kobayashi · Muneto Nitta
We clarify a relation between the Gross-Pitaevskii energy functional for spin-2 spinor Bose-Einstein condensates and the Ginzburg-Landau theory for neutron $^{3} P_{2}$ superfluidis (spin-triplet $P$ -wave pairing with total angular momentum two). We then classify all uniform states with nontrivial unbroken symmetries, with the help of geometric invariant theory.
↳ cond-mat.quant-gasnucl-thPRA(2021)·4 citations
12
Numerical Study on Beam-based Alignment of SXFEL Undulator Lattice
Liang Xu🇨🇳 · Nanshun Huang🇨🇳 · Qingmin Zhang🇨🇳 · Duan Gu🇨🇳 · Haixiao Deng🇨🇳
The undulator line of the Shanghai soft X-ray Free-electron Laser facility (SXFEL) has very tight tolerances on the straightness of the electron beam trajectory. However, the beam trajectory cannot meet the lasing requirements due to the influence of beam position, launch angle and quadrupole offsets. Traditional mechanical alignment can only control the rms of offsets to about 100 $μ$ m, which is far from reaching the requirement. Further orbit correction can be achieved by beam-based alignment (BBA) method based on electron energy variations. K modulation is used to determine whether the beam passes through the quadrupole magnetic center, and the Dispersion-Free Steering (DFS) method is used to calculate the offsets of quadrupole and BPM. In this paper, a detailed result of simulation is presented which demonstrates that the beam trajectory with rms and standard deviation ( $σ$ ) less than 10 $μ$ m can be obtained.
↳ physics.acc-phnucl-thProc.SPIE Int.Soc.Opt.Eng.(2022)·0 citations
13
Quantized electrical conductivity in binary neutron star mergers
Sreemoyee Sarkar🇮🇳 · Souvik Priyam Adhya🇵🇱
We examine nature of longitudinal electrical conductivity in magnetized electron-ion plasma in the context of binary neutron star mergers. In presence of strong magnetic field, high density and temperature, quantum oscillatory behaviour for electrons emerge due to breakdown of the classical description. For pronounced thermodynamic effects, we consider zeroth Landau level population of electrons for electrical conductivity. We solve Boltzmann equation in presence of magnetic field to obtain the dissipative component of the conductivity. The conductivity is formulated considering dynamically scattering centres in the medium with magnetically modified screening. Numerical estimations show that the effect of magnetically modified screening mass on electrical conductivity is less. On the other hand, we observe that frequency dependent screening reduces electrical conductivity leading to a reduction in the Ohmic decay time scale to become of the order of the characteristic timescale of the merger process in the low density regime. This indicates the relevance of dissipative process for the merger simulation in the above mentioned domain.
↳ hep-phastro-ph.HEnucl-thphysics.plasm-ph1 citation

Affiliations

first authorsco-authorsvia INSPIRE