  ABRIDGED: We obtain new age and mass estimates for the star clusters in M82's
fossil starburst region B, based on improved fitting methods. Our new age
estimates confirm the peak in the age histogram attributed to the last tidal
encounter with M81; we find a peak formation epoch at slightly older ages than
previously published, log(t_peak / yr) = 9.04, with a Gaussian sigma of Delta
log(t_width) = 0.273. Cluster disruption has removed a large fraction of the
older clusters. Adopting the expression for the cluster disruption time-scale
of t_dis(M)= t_dis^4 (M/10^4 Msun)^gamma with gamma = 0.62 (Paper I), we find
that the ratios between the real cluster formation rates in the pre-burst phase
(log(t/yr) <= 9.4), the burst-phase (8.4 < log(t/yr) < 9.4) and the post-burst
phase (log(t/yr) <= 8.4) are about 1:2:1/40. The mass distribution of the
clusters formed during the burst shows a turnover at log(M_cl/Msun) ~ 5.3 which
is not caused by selection effects. This distribution can be explained by
cluster formation with an initial power-law mass function of slope alpha=2 up
to a maximum cluster mass of M_max = 3 x 10^6 Msun, and cluster disruption with
a normalisation time-scale t_dis^4 / t_burst = (3.0 +/- 0.3) x 10^{-2}. For a
burst age of 1 x 10^9 yr, we find that the disruption time-scale of a cluster
of 10^4 Msun is t_dis^4 ~ 3 x 10^7 years, with an uncertainty of approximately
a factor of two. This is the shortest disruption time-scale known in any
galaxy.
