${}^4\mathrm{He}$ vs. ${}^4\mathrm{Li}$ and production of light nuclei in relativistic heavy-ion collisions

Abstract

We propose to measure the yields of ${}^4\mathrm{He}$ and ${}^4\mathrm{Li}$ in relativistic heavy-ion collisions to clarify a mechanism of light nuclei production. Since the masses of ${}^4\mathrm{He}$ and ${}^4\mathrm{Li}$ are almost equal, the yield of ${}^4\mathrm{Li}$ predicted by the thermal model is 5 times bigger than that of ${}^4\mathrm{He}$ which reflects the different numbers of internal degrees of freedom of the two nuclides. Their internal structure is, however, very different: the alpha particle is well bound and compact while ${}^4\mathrm{Li}$ is weakly bound and loose. Within the coalescence model the ratio of yields of ${}^4\mathrm{Li}$ to ${}^4\mathrm{He}$ is shown to be significantly smaller than that in the thermal model and the ratio decreases fast from central to peripheral collisions of relativistic heavy-ion collisions because the coalescence rate strongly depends on the nucleon source radius. Since the nuclide ${}^4\mathrm{Li}$ is unstable and it decays into ${}^3\mathrm{He}$ and $p$ after roughly $30\mathrm{fm}/c$, the yield of ${}^4\mathrm{Li}$ can be experimentally obtained through a measurement of the ${}^3\mathrm{He}-p$ correlation function.

Comments: 4 pages, 1 figure, minor improvements, to appear in Mod. Phys. Lett. A