  (Abridged)We present a combined analysis of mass estimates in the central
cores of galaxy clusters from the strong lensing, the X-ray measurements and
the universal density profile (NFW). Special attention is paid to the questions
(1)whether the previously claimed mass discrepancy between the strong lensing
and X-ray measurements is associated with the presence of cooling/non-cooling
flows, (2)whether the cusped NFW density model can provide a consistent cluster
mass with the strong lensing result and (3)whether a non-zero cosmological
constant can be of any help to reducing the strong lensing - X-ray mass ratios.
We analyse a sample of 26 arc-like images among 21 clusters. The X-ray and NFW
cluster masses are obtained by assuming that the intracluster gas is isothermal
and in hydrostatic equilibrium with the underlying gravitational potential of
the clusters. A statistical comparison of these three mass estimates reveals
that the mass discrepancies for all the events are well within a factor of 2.
We confirm the result of Allen that the larger mass discrepancy is only
detected in the intermediate cooling, especially non-cooling flow clusters,
thus attributing the mass discrepancy to the local dynamical activities in the
central regions. We show that the NFW profile yields a consistent cluster mass
with the conventional X-ray measurement, and any difference between these two
models must occur at even smaller radii (e.g. within the arc-like images) or at
large radii. Finally, a non-zero cosmological constant is able to moderately
reduce the mass ratios of m_lens to m_xray.
