Flavor changing top decay t -> c(nu)over-tilde or (nu)over-tilde -> t(c)over-bar in the MSSM without R parity - art. no. 035007.

Widths for the new flavor-changing top quark decay t --> c<(nu)over tilde> or for the reversed sneutrino decay <(nu)over tilde> --> t (c) over bar are calculated in the minimal supersymmetric standard model without R-parity c onservation. For large tan beta, e.g., tan beta similar to m(t)/m(b) simila r to 40, Br(t --> c<(nu)over tilde>) > 10(-5) or Br(<(nu)over tilde> --> t (c) over bar) > 10(-6) in a relatively wide range of the supersymmetric par ameter space as long as there is more than one nonzero R-parity violating c oupling. In the best cases, with a typical squark mass around 100 GeV, we f ind that Br(t --> c<(nu)over tilde>) similar to 10(-4) - 10(-3) or Br(<(nu) over tilde> --> t (c) over bar) similar to 10(-5) - 10(-4). For tan beta-O( 1) the corresponding branching ratios for both top or sneutrino decays are too small to be measured at the CERN Large Hadron Collider (LHC). Therefore , the decays t --> c<(nu)over tilde> or <(nu)over tilde> --> t (c) over bar appear to be sensitive to tan beta and may be detected at the LHC. The bra nching ratios of the corresponding decays to an up quark instead of a charm quark, e.g.,t --> u<(nu)over tilde> or <(nu)over tilde> --> t (u) over bar , may also be similar. [S0556-2821(99)04911-5].