  We investigate the detectability as well as reconstructibility of a light
pseudoscalar particle $A$, of mass in the 50 - 60 GeV range, which is still
allowed in a Type-X (lepton-specific) two-Higgs doublet scenario. Such a
pseudoscalar can be pair-produced in the decay $h\to AA$ of the 125 GeV scalar
$h$. The light pseudoscalar in the aforementioned range, helpful in explaining
the muon anomalous magnetic moment, has not only substantial branching ratio in
the $\tau^+\tau^-$ channel but also one of about $0.35\%$ in the $\mu^+\mu^-$
final state. We show how to faithfully reconstruct the $A$ mass using the
$\mu^+\mu^-$ mode, and establish the existence of a pseudoscalar around 50 - 60
GeV, using the process $pp\to h \to AA\to \mu^+\mu^-\,\tau^+\tau^-$. This is
the most reliable way of reconstructing the light $A$ mass, and is possible for
an integrated luminosity of about $100~\rm{fb}^{-1}$ or less at 14 TeV, with a
statistical significance that amounts to discovery.
