[Prex] Determination of r208skin from reaction cross section for proton scattering

[Jay Benesch]

https://arxiv.org/abs/2010.02450

Determination of r208skin from reaction cross section for proton scattering
Shingo Tagami, Maya Takechi, Jun Matsui, Masanobu Yahiro

    Reaction cross sections are available for p scattering on 208Pb. We reanalyzed interaction cross sections for 42−51Ca+12C scattering, using the chiral (Kyushu) g-matrix folding model with the densities calculated with GHFB and GHFB+AMP. We determined rskin from the σI, using the folding model. One of the results is r48skin=0.164fm for 48Ca. Our aim is to determine r208skin from the central values of measured σR for p+208Pb scattering, using the Kyushu g-matrix folding model with the GHFB+AMP densities. The Kyushu g-matrix folding model with the GHFB+AMP densities reproduces σR in 40≤Ein≤180MeV. The rm(AMP) calculated with GHFB+AMP slightly overestimates the lower bound 5.54 fm of rm(PREX) by 0.3\%. We then identify the σR(AMP) with the lower bound of σR(PREX). The rp(PREX) and rn(PREX) in PREX are most reliable. The rp(AMP) and rn(AMP) slightly underestimate the central value rp(PREX)=5.45fm by 0.1\% and the central value rn(PREX)=5.78 fm by 3.6\%, respectively. The small deviation allows us to scale the GHFB+AMP densities to the central values of rp(PREX) and rn(PREX). The Kyushu g-matrix folding model with the scaled densities almost reproduces the central values of σR when Ein=40−81 MeV, so that both the σR(AMP) and σR(PREX) are in one σ of σR there. In Ein=40−81MeV, we determine the rm from the central values of σR and take the average for the rm. The averaged value is rm=5.61fm, leading to r208skin=0.25fm. 

Subjects: 	Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
Cite as: 	arXiv:2010.02450 [nucl-th]

https://arxiv.org/abs/2005.13197

Neutron skin of 48Ca consistent with experimental data on skins
Shingo Tagami, Jun Matsui, Maya Takechi, Masanobu Yahiro

    [Background]: In our previous paper, we predicted rskin, rp, rn, rm for 40−60,62,64Ca after determining the neutron dripline, using the Gogny-D1S HFB with and without the angular momentum projection (AMP). We found that effects of the AMP are small. Very lately, Tanaka {\it et al.} measured interaction cross sections σI for 42−51Ca, determined rm from the σI, and deduced skin rskin and rn from the rm and the rp(exp) evaluated from the electron scattering. Comparing our results with the data, we find for 42−48Ca that GHFB and GHFB+AMP reproduce the data on rskin, rn, rm, but not for rp(exp). [Aim]: Our purpose is to determine a value of r48skin by using GHFB+AMP and the constrained GHFB (cGHFB) in which the calculated value is fitted to rp(exp). [Results]: For 42,44,46,48Ca, cGHFB hardly changes rskin, rm, rn calculated with GHFB+AMP, except for r48skin. For r48skin, the cGHFB result is r48skin=0.190fm, while r48skin=0.159fm for GHFB+AMP. We should take the upper and the lower bound of GHFB+AMP and cGHFB. The result r48skin=0.159−0.190fm consists with the r48skin(σI) and the data r48skin(E1pE) obtained from high-resolution E1 polarizability experiment (E1pE). Using the r48skin-r208skin relation with strong correlation of Ref.[3], we transform the data r208skin determined by PREX and E1pE to the corresponding values, r48skin(tPREX) and r48skin(tE1pE). Our result is consistent also for r48skin(tPREX) and r48skin(tE1pE). 

Subjects: 	Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
Cite as: 	arXiv:2005.13197 [nucl-th]