  A search for the flavour-changing neutral current decay D0 to mu+mu- is
performed in pp collisions at sqrt(s) = 7 TeV using 90 pb-1 of data collected
by the CMS experiment at the LHC. No evidence is found for this decay mode. The
upper limit on the branching fraction B(D0 to mu+mu-) is 5.4x10-7 at the 90%
confidence level.
