Model for hypernucleus production in heavy ion collisions

Abstract

We estimate the production cross sections of hypernuclei in projectile-like fragments (PLFs) in heavy ion collisions. The discussed scenario for the formation cross section of a $\ensuremath{\Lambda}$ hypernucleus is (a) $\ensuremath{\Lambda}$ particles are produced in the participant region but have a considerable rapidity spread and (b) $\ensuremath{\Lambda}$ with rapidity close to that of the PLF and total momentum (in the rest system of the PLF) up to Fermi motion can then be trapped and produce hypernuclei. Process (a) is considered here within the heavy ion jet interaction generator (HIJING/B$\overline{\mathrm{B}}$) model, and process (b) in the canonical thermodynamic model (CTM). We estimate the production cross sections for a hypernucleus ${}_{\ensuremath{\Lambda}}^{{A}_{F}}Z$ where $Z=1$, $2$, $3$, and $4$ for C $+$ C at total nucleon-nucleon center of mass (c.m.) energy $\sqrt{{s}_{\mathit{NN}}}=3.7$ GeV, and for Ne $+$ Ne and Ar $+$ Ar collisions at $\sqrt{{s}_{\mathit{NN}}}=5.0$ GeV. By taking into account explicitly the impact parameter dependence of the colliding systems, it is found that the cross section is different from that predicted by the coalescence model, and large discrepancy is obtained for ${}_{\ensuremath{\Lambda}}^{6}$He and ${}_{\ensuremath{\Lambda}}^{9}$Be hypernuclei.