Neutron skin of Pb in consistency with neutron star observations
نویسنده
چکیده
The renormalized meson-nucleon couplings are applied to the relativistic optical model of p-208Pb elastic scattering at Tlab = 200MeV. We calculate the strength of the vector potential at nuclear center as varying the neutron radius of 208Pb. The neutron skin thickness Sn is determined in the comparison of the calculated potential with the phenomenological one. We nd a value Sn = 0:118fm being consistent with the astronomical observations of massive neutron stars (NSs), the standard scenario of NS cooling and the experimental nuclear symmetry energy in terrestrial laboratory. The value is complementary to the previous result Sn = 0:119fm in the analysis of elastic scattering above Tlab = 500MeV within the relativistic impulse optical model. Recently, there are renewed interests on the neutron skin thickness Sn of Pb. The works [1] and [2] analyzed the nucleon-nucleus (NA) elastic scattering at low and intermediate energies within the nonrelativistic microscopic optical model, in which the nucleon-nucleon (NN) g-matrix interaction is folded by nuclear densities from the SkyrmeHartree-Fock [1] and the RPA [2] calculations of the nucleus. They derived the values Sn = 0:17fm and 0:13fm, respectively. The paper [3] analyzed the elastic scattering at high energies within the relativistic impulse optical model and obtained the value Sn = 0:119fm. To the contrary, Ref. [4] claimed that the elastic NA scattering is insensitive to neutron skin thickness. On the other hand, Ref. [5] derived Sn = 0:22fm in the analysis of heavy-ion collisions based on an isospinand momentum-dependent transport model, while Ref. [6] concluded Sn 0:22fm in the analysis of isovector giant monopole resonance within the accurately calibrated relativistic mean- eld (RMF) model. Consequently, at present, the neutron radius of Pb is not well known. The experiment of parity violating electron scattering planned at Je¤erson Laboratory [7] is however likely to resolve the di¤erences in the analyses. This paper presents a unique method to determine the neutron skin thickness of Pb. In the respect that we investigate the relativistic optical potential of p-Pb elastic scattering, our work is similar to Ref. [3]. On the other hand, we are based on the RMF model of nuclear matter in Ref. [8], which has the eld-dependent mesonnucleon coupling constants. The optical potential therefore includes the medium e¤ect.
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