A Comparative Study of the Decays B ! ( K ; K ) ` + ` � in Standard Model and Supersymmetric Theories

Using improved theoretical calculations of the decay form factors in the Light Cone-QCD sum rule approach, we investigate the decay rates, dilepton invariant mass spectra and the forward-backward (FB) asymmetry in the decays B ! (K;K )`` (` = e ; ; ) in the standard model (SM) and a number of popular variants of the supersymmetric (SUSY) models. Theoretical precision on the di erential decay rates and FB-asymmetry is estimated in these theories taking into account various parametric uncertainties. We show that existing data on B ! Xs and the experimental upper limit on the branching ratio B(B ! K + ) provide interesting bounds on the coe cients of the underlying e ective theory. We argue that the FB-asymmetry in B ! K `` constitutes a precision test of the SM and its measurement in forthcoming experiments may reveal new physics. In particular, the presently allowed largetan solutions in SUGRA models, as well as more general avor-violating SUSY models, yield FB-asymmetries which are characteristically di erent from the corresponding ones in the SM. submitted to Physical Review D Pacs numbers: 13.20.He, 13.25.Hw Work supported by the Department of Energy, Contract DE-AC03-76SF00515 y E-mail : [email protected] z E-mail : [email protected] x E-mail : [email protected] { E-mail : [email protected], [email protected]; Current address: SLAC, P.O.Box 4349, Stanford, CA 94309.