  Accurate knowledge about the neutron skin thickness $\Delta R_{np}$ in
$^{208}$Pb has far-reaching implications for different communities of nuclear
physics and astrophysics. Yet, the novel Lead Radius Experiment (PREX) did not
yield stringent constraint on the $\Delta R_{np}$ recently. We employ a more
practicable strategy currently to probe the neutron skin thickness of
$^{208}$Pb based on a high linear correlation between the $\Delta R_{np}$ and
$J-a_{\text{sym}}$, where $J$ and $a_{\text{sym}}$ are the symmetry energy
(coefficient) of nuclear matter at saturation density and of $^{208}$Pb. An
accurate $J-a_{\text{sym}}$ thus places a strong constraint on the $\Delta
R_{np}$. Compared with the parity-violating asymmetry $A_{\text{PV}}$ in the
PREX, the reliably experimental information on the $J-a_{\text{sym}}$ is much
more easily available attributed to a wealth of measured data on nuclear masses
and on decay energies. The density dependence of the symmetry energy is also
well constrained with the $J-a_{\text{sym}}$. Finally, with a `tomoscan'
method, we find that one just needs to measure the nucleon densities in
$^{208}$Pb starting from $R_{m} = 7.61\pm0.04$ fm to obtain the $\Delta R_{np}$
in hadron scattering experiments, regardless of its interior profile that is
hampered by the strong absorption.

Nuclear Theory