Production of antimatter $^{5,6}$Li nuclei in central Au+Au collisions
  at $\sqrt{s_{NN}} = 200$ GeV
  Combining the covariant coalescence model and a blast-wave-like analytical
parametrization for (anti-)nucleon phase-space freezeout configuration, we
explore light (anti-)nucleus production in central Au+Au collisions at
$\sqrt{s_{NN}} = 200$ GeV. Using the nucleon freezeout configuration (denoted
by FO1) determined from the measured spectra of protons (p), deutrons (d) and
$^{3}$He, we find the predicted yield of $^{4}$He is significantly smaller than
the experimental data. We show this disagreement can be removed by using a
nucleon freezeout configuration (denoted by FO2) in which the nucleons are
assumed to freeze out earlier than those in FO1 to effectively consider the
effect of large binding energy value of $^{4}$He. Assuming the binding energy
effect also exists for the production of $^5\text{Li}$,
$^5\overline{\text{Li}}$, $^6\text{Li}$ and $^6\overline{\text{Li}}$ due to
their similar binding energy values as $^{4}$He, we find the yields of these
heavier (anti-)nuclei can be enhanced by a factor of about one order, implying
that although the stable (anti-)$^6$Li nucleus is unlikely to be observed, the
unstable (anti-)$^5$Li nucleus could be produced in observable abundance in
Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV where it may be identified
through the p-$^4\text{He}$ ($\overline{\text{p}}$-$^4\overline{\text{He}}$)
invariant mass spectrum. The future experimental measurement on
(anti-)$^5\text{Li}$ would be very useful to understand the production
mechanism of heavier antimatter.
