Nuclear Theory·nucl-th

Friday·May 18, 2018

5 papers—3 primary·2 cross-listed

01
Evolution of shell structure in exotic nuclei
Takaharu Otsuka🇯🇵 · Alexandra Gade🇺🇸 · Olivier Sorlin🇫🇷 · Toshio Suzuki🇯🇵 · Yutaka Utsuno🇯🇵
The atomic nucleus is a quantum many-body system whose constituent nucleons (protons and neutrons) are subject to complex nucleon-nucleon interactions that include spin- and isospin-dependent components. For stable nuclei, already several decades ago, emerging seemingly regular patterns in some observables could be described successfully within a shell-model picture that results in particularly stable nuclei at certain magic fillings of the shells with protons and/or neutrons: N,Z = 8, 20, 28, 50, 82, 126. However, in short-lived, so-called exotic nuclei or rare isotopes, characterized by a large N/Z asymmetry and located far away from the valley of beta stability on the nuclear chart, these magic numbers, viewed through observables, were shown to change. These changes in the regime of exotic nuclei offer an unprecedented view at the roles of the various components of the nuclear force when theoretical descriptions are confronted with experimental data on exotic nuclei where certain effects are enhanced. This article reviews the driving forces behind shell evolution from a theoretical point of view and connects this to experimental signatures.
nucl-thnucl-exRMP(2020)·434 citations
02
Temperature Dependence of the Neutron Lifespan
Cheng Tao Yang🇺🇸 · Jeremiah Birrell🇺🇸 · Johann Rafelski (Arizona)🇺🇸
Current precision big bang nucleosynthesis (BBN) studies motivate us to revisit the neutron lifespan in the plasma medium of the early universe. The mechanism we explore is the Fermi-blocking of decay electrons and neutrinos by plasma. As result, neutrons live longer and we find a significant 6.4\% modification of neutron abundance in the BBN era arising from in plasma modification of the neutron lifetime. This effect can influence the final abundances of the light elements in BBN.
nucl-thastro-ph.COphysics.plasm-ph3 citations
03
Chiral symmetry restoration by parity doubling and the structure of neutron stars
Michał Marczenko🇵🇱 · David Blaschke🇵🇱 · Krzysztof Redlich🇵🇱 · Chihiro Sasaki🇵🇱
We investigate the equation of state for a recently developed hybrid quark-meson-nucleon model under neutron star conditions of $β -$ equilibrium and charge neutrality. The model has the characteristic feature that at increasing baryon density chiral symmetry is restored in a first order transition within the hadronic phase by lifting the mass splitting between chiral partner states, before quark deconfinement takes place. Most important for this study are the nucleon (neutron, proton) and $N (1535)$ states. We present three sets for the two free parameters which result in compact star mass-radius relations in accordance with modern constraints on the mass from PSR~J0437-4715 and on the compactness from GW170817. We also consider the threshold for the direct URCA process for which a new relationship is given and suggest as an additional constraint on the parameter choice of the model that this process shall become operative at best for stars with masses above the range for binary radio pulsars, $M > 1.4 M_{⊙}$ .
nucl-thastro-ph.HEhep-phPRD(2018)·67 citations
04
Analysis of the $b_{1}$ meson decay in local tensor bilinear representation
Kie Sang Jeong🇰🇷 · Su Houng Lee🇰🇷 · Yongseok Oh🇰🇷
We explore the validity of vector meson dominance in the radiative decay of the $b_{1} (1235)$ meson. In order to explain the violation of the vector meson dominance hypothesis in this decay process, we investigate a model where the $b_{1}$ meson strongly couples with the local current in tensor bilinear representation. The tensor representation is investigated in the framework of the operator product expansion and we found a low energy decay process that does not follow the usual vector meson dominance hypothesis. The $ω$ -like intermediate meson state of quantum numbers $I^{G} (J^{P C}) = 0^{-} (1^{--})$ is found to have a nontrivial role in the decay process of the $b_{1}$ meson. The spectral structure of the $ω$ -like state is found to be close to a $π$ - $ρ$ hybrid state, which provides a mechanism that evades the usual vector meson dominance hypothesis. Precise measurements of various decay channels of the $b_{1}$ meson are, therefore, required to unravel the internal structure of axial vector mesons.
↳ hep-phhep-exnucl-thJHEP(2018)·7 citations
05
Decay behavior of the strange and beauty partners of $P_{c}$ hadronic molecules
Yong-Hui Lin🇨🇳 · Chao-Wei Shen🇨🇳 · Bing-Song Zou🇨🇳
We extend our previous study on the decay behavior of $P_{c}$ hadronic molecules to their strange and beauty partners. While $P_{c} (4380)$ and $P_{c} (4450)$ locate just below the $D ˉ Σ_{c}^{*}$ and $D ˉ^{*} Σ_{c}$ thresholds, respectively, their proposed strange partners $N (1875)$ and $N (2080)$ sit just below the $K Σ^{*}$ and $K^{*} Σ$ thresholds, respectively. Using the effective Lagrangian approach as the same as for the study of $P_{c}$ hadronic molecular states and with the couplings determined by the $SU (3)$ flavor symmetry, the decay patterns of $N (1875)$ and $N (2080)$ are obtained assuming them to be the $S$ -wave $K Σ^{*}$ and $K^{*} Σ$ molecules, respectively. It is found that the measured decay properties of $N (1875)$ and $N (2080)$ are reproduced well. Our results suggest that both $N (1875)$ and $N (2080)$ can be ascribed as the hadronic molecular pentaquark states in the hidden strangeness sector with quantum number $I (J^{P}) = 1/2 (3/2^{-})$ . Further checks on their hadronic molecule nature by various experiments are proposed. With the same approach, we also give our predictions for the decay behavior of the possible beauty partners of the $P_{c}$ hadronic molecular states. The $B^{*} Λ_{b}$ is found to be the largest decay mode for both $B Σ_{b}^{*}$ and $B^{*} Σ_{b}$ hadronic molecules, hence can be used to look for the hidden beauty pentaquark states in forthcoming experiments.
↳ hep-phnucl-thNPA(2018)·41 citations

Affiliations

first authorsco-authorsvia INSPIRE

Evolution of shell structure in exotic nuclei

Temperature Dependence of the Neutron Lifespan

Chiral symmetry restoration by parity doubling and the structure of neutron stars

Analysis of the b1​ meson decay in local tensor bilinear representation

Decay behavior of the strange and beauty partners of Pc​ hadronic molecules

Affiliations

Analysis of the $b_{1}$ meson decay in local tensor bilinear representation

Decay behavior of the strange and beauty partners of $P_{c}$ hadronic molecules