Power corrections in the decay rate and distributions inB→Xsl+l

Abstract

We investigate the leading power corrections to the decay rates and distributions in the decay B→X s l ϩ l Ϫ in the standard model ͑SM͒ using heavy quark expansion ͑HQE͒ in (1/m b ) and a phenomenological model implementing the Fermi motion effects of the b quark bound in the B hadron. In the HQE method, we find that including the leading power corrections the decay width ⌫(B→X s l ϩ l Ϫ ) decreases by about 4% and the branching ratio B(B→X s l ϩ l Ϫ ) by about 1.5% from their ͑respective͒ parton model values.The dilepton invariant mass spectrum is found to be stable against power corrections over a good part of this spectrum. However, near the high-mass end point this distribution becomes negative with the current value of the nonperturbative parameter 2 ͑the 1 -dependent corrections are found to be innocuous͒, implying the breakdown of the HQE method in this region. Our results are at variance with the existing ones in the literature in both the decay rate and the invariant dilepton mass distribution calculated in the HQE approach. As an alternative, we implement the nonperturbative effects in the decay B→X s l ϩ l Ϫ using a phenomenologically motivated Gaussian Fermi motion model. We find small corrections to the branching ratio, but the nonperturbative effects are perceptible in both the dilepton mass distribution and the forward-backward asymmetry in the high dilepton mass region. Using this model for estimating the nonperturbative effects, modeling the dominant long distance contributions from the decays B→X s ϩ(J/,Ј, . . . )→X s l ϩ l Ϫ , and taking into account the next-to-leading order perturbative QCD corrections in b→sl ϩ l Ϫ , we present the decay rates and distributions for the inclusive process B→X s l ϩ l Ϫ in the SM. ͓S0556-2821͑97͒00107-0͔

Improved model-independent analysis of semileptonic and radiative rareBdecays

“…In particular, first measurements of semileptonic rare B-decays have been recently reported in the B → Kµ + µ − and B → Ke + e − modes by the BELLE collaboration [10], and upper limits have been put in a number of other related decay modes [10][11][12][13]. The current measurements of the exclusive modes are in agreement with the expectations in the SM [14,15], calculated in next-to-leading logarithmic (NLO) approximation, taking into account the experimental and theoretical errors. This, for example, can be judged from the comparison of the combined branching ratio for the decay modes B → K + − , = e, µ, reported by the BELLE collaboration B(B → K + − ) = 0.75 +0.…”

“…Instead, we compare the theoretical predictions with data which has been corrected for the experimental acceptance using SM-based theoretical distributions from Ref. [14,15]. In the present analysis, we are assuming that the acceptance corrections have been adequately incorporated in the experimental analysis in providing the branching ratios and upper limits listed above.…”

ProbeR-parity violating supersymmetry effects inB→K(*)ℓ+ℓ−

“…[9] and then in Refs. [10,11]. Long distance contributions can have different origins according to the value of the dilepton invariant mass.…”

“…Long distance contributions can have different origins according to the value of the dilepton invariant mass. The contributions of charmonium resonances to these decays by means of Vector Meson Dominance (VMD) have been studied carefully [10,12,13,14].…”

“…Analyses of new physics contribution have been performed in different models, for example, the two-Higgs doublet model [16] , the supersymmetric (SUSY) models [17,18], the SUSY SO (10) grand unification theory [19] and the top quark two-Higgs doublet model [20].…”