arXiv subjects

S. S. Bao

Publications and source records attributed to S. S. Bao.

8 recordsLinked to original sources

arXiv2026

Measurement of the $Λ$ Electric Dipole Moment with an Entangled Baryon-Antibaryon System

The dominance of matter over antimatter in the universe has consistently driven the pursuit of new physics beyond the Standard Model that violates charge-parity symmetry. Strange baryons (hyperons) remain a largely unexplored territory in which interactions between hyperons and particles from new physics could induce a nontrivial electric dipole moment (EDM). However, direct measurements of hyperon EDMs through spin precession are highly challenging owing to their short lifetimes. In this work, we introduce a method to extract the EDM of the lightest hyperon, $Λ$, using the entangled $Λ$$\overlineΛ$ system. Our result is consistent with zero, achieving a three-orders-of-magnitude improvement over the previous upper limit established in the 1980s with comparable statistics, providing stringent constraints on potential new physics.

hep-ex↗

arXiv2022

Measurement of the Branching Fraction of the Singly Cabibbo-Suppressed Decay $Λ_{c}^{+}\toΛK^{+}$

We report a branching fraction measurement of the singly Cabibbo-suppressed decay $Λ_{c}^{+}\toΛK^{+}$ using a data sample collected with the BESIII detector at the BEPCII storage ring. The data span center-of-mass energies from 4.599 to 4.950 GeV and correspond to an integrated luminosity of 6.44 fb$^{-1}$. The branching fraction of $Λ_{c}^{+}\toΛK^{+}$ relative to that of the Cabibbo-favored decay $Λ_{c}^{+}\toΛπ^{+}$ is measured to be $\mathcal{R}=\frac{\mathcal{B}(Λ_{c}^{+}\toΛK^{+})}{\mathcal{B}(Λ_{c}^{+}\toΛπ^{+})}=(4.78\pm0.34\pm0.20)\%$. Combining with the world-average value of $\mathcal{B}(Λ_{c}^{+}\toΛπ^{+})$, we obtain $\mathcal{B}(Λ_c^+\toΛK^+)=(6.21\pm0.44\pm0.26\pm0.34)\times 10^{-4}$. Here the first uncertainties are statistical, the second systematic, and the third comes from the uncertainty of the $Λ_{c}^{+}\toΛπ^{+}$ branching fraction. This result, which is more precise than previous measurements, does not agree with theoretical predictions, and suggests that non-factorizable contributions have been under-estimated in current models.

hep-ex↗

arXiv2021

Impact of strong magnetic fields on the inner crust of neutron stars

We study the impact of strong magnetic fields on the pasta phases that are expected to exist in the inner crust of neutron stars. We employ the relativistic mean field model to describe the nucleon interaction and use the self-consistent Thomas-Fermi approximation to calculate the nonuniform matter in neutron star crust. The properties of pasta phases and crust-core transition are examined. It is found that as the magnetic field strength $B$ is less than $10^{17}$ G, the effects of magnetic field are not evident comparing with the results without magnetic field. As $B$ is stronger than $10^{18}$ G, the onset densities of pasta phases and crust-core transition density decrease significantly, and the density distributions of nucleons and electrons are also changed obviously.

nucl-th↗

arXiv2016

Effects of finite size and symmetry energy on the phase transition of stellar matter at subnuclear densities

We study the liquid-gas phase transition of stellar matter with the inclusion of the finite-size effect from surface and Coulomb energies. The equilibrium conditions for two coexisting phases are determined by minimizing the total free energy including the surface and Coulomb contributions, which are different from the Gibbs conditions used in the bulk calculations. The finite-size effect can significantly reduce the region of the liquid-gas mixed phase. The influence of the symmetry energy on the liquid-gas phase transition is investigated with the inclusion of finite-size effects. It is found that the slope of the symmetry energy plays an important role in determining the boundary and properties of the mixed phase.

nucl-th↗

arXiv2015

Impact of the symmetry energy on nuclear pasta phases and crust-core transition in neutron stars

We study the impact of the symmetry energy on properties of nuclear pasta phases and crust-core transition in neutron stars. We perform a self-consistent Thomas--Fermi calculation employing the relativistic mean-field model. The properties of pasta phases presented in the inner crust of neutron stars are investigated and the crust-core transition is examined. It is found that the slope of the symmetry energy plays an important role in determining the pasta phase structure and the crust-core transition. The correlation between the symmetry energy slope and the crust-core transition density obtained in the Thomas--Fermi approximation is consistent with that predicted by the liquid-drop model.

nucl-th↗

arXiv2014

Symmetry energy of hot nuclei in the relativistic Thomas-Fermi approximation

We develop a self-consistent description of hot nuclei within the relativistic Thomas--Fermi approximation using the relativistic mean-field model for nuclear interactions. The temperature dependence of the symmetry energy and other physical quantities of a nucleus are calculated by employing the subtraction procedure in order to isolate the nucleus from the surrounding nucleon gas. It is found that the symmetry energy coefficient of finite nuclei is significantly affected by the Coulomb polarization effect. We also examine the dependence of the results on nuclear interactions and make a comparison between the results obtained from relativistic and nonrelativistic Thomas-Fermi calculations.

nucl-th↗

arXiv2014

Effects of the symmetry energy on properties of neutron star crusts near the neutron drip density

We study the effects of the symmetry energy on the neutron drip density and properties of nuclei in neutron star crusts. The nonuniform matter around the neutron drip point is calculated by using the Thomas--Fermi approximation with the relativistic mean-field model. The neutron drip density and the composition of the crust are found to be correlated with the symmetry energy and its slope. We compare the self-consistent Thomas--Fermi approximation with other treatments of surface and Coulomb energies and find that these finite-size effects play an essential role in determining the equilibrium state at low density.

nucl-th↗

arXiv2014

Influence of the symmetry energy on nuclear pasta in neutron star crusts

We investigate the effects of the symmetry energy on nuclear pasta phases and the crust-core transition in neutron stars. We employ the relativistic mean-field approach and the coexisting phases method to study the properties of pasta phases presented in the inner crust of neutron stars. It is found that the slope of the nuclear symmetry energy at saturation density plays an important role in the crust-core transition and pasta phase properties. The correlation between the symmetry energy slope and the crust-core transition density obtained in this study is consistent with those obtained by other methods.

nucl-th↗