Nuclear Theory·nucl-th

Thursday·September 1, 2022

11 papers—3 primary·8 cross-listed

04
Nature of excited $Ξ$ baryons with threshold effects
Takuma Nishibuchi🇯🇵 · Tetsuo Hyodo🇯🇵
Spectroscopy of excited baryons with strangeness $S = - 2$ is stimulated by recent experimental developments. Here we focus on the $Ξ (1620)$ which locates close to the $K ˉ Λ$ threshold. To take into account the threshold effects, we construct the coupled-channels meson-baryon scattering amplitude where the $Ξ (1620)$ appears as a resonance. We demonstrate that the $K ˉ Λ$ threshold effects distort the peak of the $Ξ (1620)$ resonance from the simple Breit-Wigner distribution.
↳ hep-phnucl-thEPJ Web Conf.(2022)·9 citations
05
Towards three-dimensional nucleon structures at the Electron-Ion Collider in China: A study of the Sivers function
Chunhua Zeng🇨🇳 · Tianbo Liu🇨🇳 · Peng Sun🇨🇳 · Yuxiang Zhao🇨🇳
Transverse momentum-dependent parton distribution functions (TMDs) provide three-dimensional imaging of the nucleon in the momentum space. With its fundamental importance in understanding the spin structure of the nucleon, the precise measurement of TMDs is considered as one of the main physics topics of the proposed Electron-Ion Collider in China (EicC). In this paper, we investigate the impact of future semi-inclusive deep inelastic scattering (SIDIS) data from EicC on the extraction of TMDs. Taking the Sivers function as an example, we revisited the world SIDIS data, which serves as the input for the simulated EicC data. By performing a combined analysis of the world data and the EicC simulated data, we quantitatively demonstrate that the Sivers functions can be precisely determined for various quark flavors, especially for sea quarks, in the region, $x > 0.005$ , directly covered by the EicC.
↳ hep-phhep-exnucl-exnucl-thPRD(2022)·15 citations
06
Impacts of the direct URCA and Superfluidity inside a Neutron Star on Type-I X-Ray Bursts and X-Ray Superbursts
Akira Dohi · Nobuya Nishimura · Hajime Sotani · Tsuneo Noda · Helei Liu · Shigehiro Nagataki · Masa-aki Hashimoto
We investigate the impacts of neutrino cooling mechanism inside the neutron star (NS) core on the light curves of type-I X-ray bursts and X-ray superbursts. From several observations of NS thermal evolution, physical processes of fast neutrino cooling, such as the direct Urca (DU) process, are indicated. They significantly decrease the surface temperature of NSs, though the cooling effect could be suppressed by nucleon superfluidity. In the present study, focusing on the DU process and nucleon superfluidity, we investigate the effects of NS cooling on the X-ray bursts using a general-relativistic stellar-evolution code. We find that the DU process leads find the longer recurrence time and the higher peak luminosity, which could be obstructed by the neutrons superfluidity. We also apply our burst models to the comparison with {\it Clocked burster} GS 1826 $-$ 24, and to the recurrence time of superburst triggered by carbon ignition. These effects are significant within a certain range of binary parameters and uncertainty of the NS equation of state.
↳ astro-ph.HEnucl-thApJ(2022)·16 citations
07
Extraction of the Coulomb Sum Rule, Transverse Enhancement, and Longitudinal Quenching from an Analysis of all Available e- $^{12}$ C and e- $^{16}$ O Cross Section Data
A. Bodek🇺🇸 · M. E. Christy🇺🇸
We report on a phenomenological analysis of all available electron scattering data on $^{12} C$ (about 6600 differential cross section measurements) and on $^{16} O$ (about 250 measurements) within the framework of the quasielastic (QE) superscaling model (including Pauli blocking). All QE and inelastic cross section measurements are included down to the lowest momentum transfer $q$ (including photo-production data). We find that there is enhancement of the transverse QE response function ( $R_{T}^{QE}$ ) and quenching of the QE longitudinal response function ( $R_{L}^{QE}$ ) at low $q$ (in addition to Pauli blocking). We extract parameterizations of a $m u l t i pl i c a t i v e$ low $q$ "Longitudinal Quenching Factor" and an $a dd i t i v e$ "Transverse Enhancement" contribution. Additionally, we find that the excitation of nuclear states contribute significantly (up to 30\%) to the Coulomb Sum Rule $S L (q)$ . We extract the most accurate determination of $S L (q)$ to date and find it to be in reasonable agreement with recent theoretical calculations.
↳ hep-phhep-exnucl-exnucl-thPRC(2022)·18 citations
08
Applicability of Hydrodynamics in Hadronic Phase of Heavy-Ion Collisions
Ronald Scaria🇮🇳 · Captain R. Singh🇮🇳 · Raghunath Sahoo🇮🇳
The hadronic phase and its dynamics in relativistic heavy-ion collisions are topics of immense discussion. The hadronic phase contains various massive hadrons with an abundance of the lightest hadron, i.e., $π$ -mesons (pions). In this paper, we consider that pions are in thermal equilibrium in the hadronic phase and use second-order viscous hydrodynamics for a medium of massive pions to obtain its expansion to the boundary of the kinetic freeze-out. We achieve the kinetic freeze-out boundary with the Knudsen number $K n > 1$ limit. When this condition is met, hydrodynamics expansion breaks down, and the mean free path becomes sufficiently large in comparison with the system size so that the particle yields are preserved. Further, we investigate the effect of the massive fluid on the resonance particle yields, including re-scattering and regeneration, along with the natural decay widths of the resonances. The resonances can play an essential role in determining the characteristics of the hadronic phase as they have sufficiently small lifetimes, which may be comparable to the hadronic phase lifetime. In the current study, we predict the hadronic phase lifetime, which is further used to determine the $K^{*} (892)^{0} / K$ , $ϕ (1020) / K$ , and $ρ (770)^{0} / π$ yield ratios at the kinetic freeze-out. We calculate these ratios as a function of charged particle multiplicity and transverse momentum and compare the findings with experimental data. Our calculations qualitatively agree with the experimental data, indicating a possible hydrodynamical evolution of the hadronic phase.
↳ hep-phhep-exnucl-exnucl-thPhysics(2025)·6 citations
09
Dispersion-theoretical analysis of the electromagnetic form factors of the $Λ$ hyperon
Yong-Hui Lin🇩🇪 · Hans-Werner Hammer🇩🇪 · Ulf-G. Meißner🇩🇪
The electromagnetic form factors of the $Λ$ hyperon in the time-like region are determined precisely through a dispersion-theoretical analysis of the world data for the cross section of the annihilation process $e^{+} e^{-} \to Λ ˉ Λ$ . The spectral function is represented by a superposition of narrow and broad vector meson poles. We test different scenarios for the spectral function and obtain a good description of the world data in the time-like region. The uncertainties in the extracted form factors are estimated by means of the bootstrap sampling method. The analytical continuation of the form factors to the space-like region introduces large errors due to the lack of data. When the electric $Λ$ radius from chiral perturbation theory is taken as a constraint, the magnetic radius is predicted as $r_{M} = 0.681 \pm 0.002$ fm. We also extract various vector meson to baryon coupling constants.
↳ hep-phhep-exnucl-exnucl-thEPJC(2022)·12 citations
10
Molecular $Ω_{cc}$ , $Ω_{bb}$ and $Ω_{b c}$ states
Wen-Fei Wang🇨🇳 · Albert Feijoo🇪🇸 · Jing Song🇨🇳 · Eulogio Oset🇪🇸
We study the interaction of meson-baryon coupled channels carrying quantum numbers of $Ω_{cc}$ , $Ω_{bb}$ and $Ω_{b c}$ presently under investigation by the LHCb collaboration. The interaction is obtained from an extension of the local hidden gauge approach to the heavy quark sector that has proved to provide accurate results compared to experiment in the case of $Ω_{c}$ , $Ξ_{c}$ states and pentaquarks, $P_{c}$ and $P_{cs}$ . We obtain many bound states, with small decay widths within the space of the chosen coupled channels. The spin-parity of the states are $J^{P} = \frac{1}{2}^{-}$ for coupled channels of pseudoscalar-baryon ( $\frac{1}{2}^{+}$ ), $J^{P} = \frac{3}{2}^{-}$ for the case of pseudoscalar-baryon ( $\frac{3}{2}^{+}$ ), $J^{P} = \frac{1}{2}^{-}, \frac{3}{2}^{-}$ for the case of vector-baryon ( $\frac{1}{2}^{+}$ ) and $J^{P} = \frac{1}{2}^{-}, \frac{3}{2}^{-}, \frac{5}{2}^{-}$ for the vector-baryon ( $\frac{3}{2}^{+}$ ) channels. We look for poles of the states and evaluate the couplings to the different channels. The couplings obtained for the open channels can serve as a guide to see in which reaction the obtained states are more likely to be observed.
↳ hep-phhep-exnucl-thPRD(2022)·22 citations
11
Report on Progress in Physics: Observation of the Breit-Wheeler Process and Vacuum Birefringence in Heavy-Ion Collisions
James Daniel Brandenburg🇺🇸 · Janet Seger🇺🇸 · Zhangbu Xu🇺🇸 · Wangmei Zha🇨🇳
This Report reviews the effort over several decades to observe the linear Breit-Wheeler process ( $γ γ \to e^{+} e^{-}$ ) and vacuum birefringence in high-energy particle and heavy-ion collider experiment. This Report, motivated by STAR's recent observations, attempts to summarize the key issues related to the interpretation of polarized $γ γ \to l^{+} l^{-}$ measurements in high-energy experiments. To that end, we start by reviewing the historical context and essential theoretical developments, before focusing on the decades of progress made in high-energy collider experiments. Special attention is given to the evolution in experimental approaches in response to various challenges and the demanding detector capabilities required to unambiguously identify the linear Breit-Wheeler process and to detect the signatures of vacuum birefringence. We close the report with a discussion, followed by a look at near-future opportunities for utilizing these discoveries and for testing QED in previously unexplored regimes.
↳ hep-phnucl-exnucl-thRept.Prog.Phys.(2023)·39 citations

Affiliations

first authorsco-authorsvia INSPIRE