  We study the consequences of the large dimuon asymmetry observed at D0.
Physics beyond the standard model (SM) in $B_s-\bar B_s$ mixing is required to
explain the data. We first present a detailed analysis for model independent
constraints on physics beyond the SM, and then study the implications for
theoretical models which modify the SM results in different ways, such as $Z'$
with FCNC and R-parity violating SUSY contributions.
