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

TL;DR

This paper compares the production mechanisms of $^4$He and $^4$Li$ in relativistic heavy-ion collisions, proposing experimental methods to distinguish between thermal and coalescence models based on yield ratios and decay signatures.

Contribution

It introduces a comparative analysis of $^4$He and $^4$Li$ production in heavy-ion collisions, highlighting differences predicted by thermal and coalescence models and suggesting experimental detection strategies.

Findings

Thermal model predicts $^4$Li$ yield to be 5 times $^4$He$ yield.

Coalescence model predicts a smaller and collision-centrality-dependent $^4$Li$ to $^4$He$ ratio.

$^4$Li$ decay into $^3$He$ and $p$ allows experimental detection via correlation functions.

Abstract

We propose to measure the yields of $^4{\rm He}$ and $^4{\rm Li}$ in relativistic heavy-ion collisions to clarify a mechanism of light nuclei production. Since the masses of $^4{\rm He}$ and $^4{\rm Li}$ are almost equal, the yield of $^4{\rm Li}$ predicted by the thermal model is 5 times bigger than that of $^4{\rm He}$ 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 $^4{\rm Li}$ is weakly bound and loose. Within the coalescence model the ratio of yields of $^4{\rm Li}$ to $^4{\rm He}$ 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 $^4{\rm Li}$ is unstable and it decays into $^3{\rm He}$ and $p$ after roughly $30~{\rm fm}/c$, the yield of $^4{\rm Li}$ can be experimentally obtained through a measurement of the $^3{\rm He}\!-\!p$ correlation function.