Rapidity distributions of Z=1 isotopes and the nuclear symmetry energy from Sn plus Sn collisions with radioactive beams at 270 MeV/nucleon

The rapidity distributions of hydrogen isotopes emitted from central collisions of neutron-rich Sn-132+Sn-124 and neutron-deficient Sn-108+Sn-112 systems at 270 MeV/nucleon were investigated at RIKEN-RIBF. The data are compared with antisymmetrized molecular dynamics (AMD) calculations and the rapidity distributions can be reproduced after adjusting the in-medium nucleon-nucleon cross sections. The double ratios between the two reaction systems taken for the relative yields of deuteron to proton (d/p) and triton to proton (t/p) are further examined in the midrapidity domain, where the adjustments in the AMD calculations do not affect much on them. The d/p and t/p double ratios at midrapidity agree well with the ratio of the system neutron numbers and its squared value, respectively, and the rapidity dependence of these double ratios is consistent with a picture of partial mixing of colliding nuclei. By comparing with the AMD model which shows a strong symmetry energy dependence of the t/p double ratio, the experimental result in the midrapidity domain favors the calculation with a symmetry-energy slope parameter around L = 46 MeV rather than L = 108 MeV. (C) 2021 The Author(s). Published by Elsevier B.V.

Automated summary

The rapidity distributions of hydrogen isotopes emitted from central collisions of neutron-rich and neutron-deficient systems at 270 MeV/nucleon were studied, and it was found that the distributions can be reproduced after adjusting the in-medium nucleon-nucleon cross sections in AMD calculations. The double ratios of deuteron to proton and triton to proton in the midrapidity domain agree well with the system neutron numbers and its squared value, respectively, indicating partial mixing of colliding nuclei. The experimental results in the midrapidity domain support a calculation with a symmetry-energy slope parameter around L = 46 MeV rather than L = 108 MeV in AMD model.