Search for rare and forbidden 3-body di-muon decays of the charmed mesons D+ and Ds+

Using a high statistics sample of photo-produced charm particles from the FOCUS experiment at Fermilab, we report results of a search for eight rare and Standard-Model-forbidden decays: D+, D-S(+) --> h(+/-)mu(-/+)mu(+) (with h = pi, K). Improvement over previous results by a factor of 1.7-14 is realized. Our branching ratio upper limit D+ --> pi(+)mu(-)mu(+) of 8.8 x 10(-6) at the 90% C.L. is below the current MSSM R-parity violating constraint. (C) 2003 Published by Elsevier B.V.