Dilepton asymmetries atBfactories in search ofΔB=−ΔQtransitions

Abstract

In order to detect the possible presence of ⌬BϭϪ⌬Q amplitudes in neutral B meson decays, we consider the measurement of decay time asymmetries involving like-sign dilepton events at the B factories. ͓S0556-2821͑96͒03721-6͔PACS number͑s͒: 13.20. He, 11.30.Er Bottom meson decay is a promising place to look for CP violation outside the neutral kaon system. It will also facilitate a test of the CP-violation mechanism of the standard model ͓1͔. One way to achieve this aim would be to measure decay time asymmetries at the asymmetric B factories presently under construction ͓2͔. But violations of the standard model may show up in B physics in other ways also. Here, we focus on the interesting possibility of the breakdown of ⌬Bϭ⌬Q rule in semileptonic decays of neutral bottom mesons. This rule is not exact as it is violated in higher order weak interactions. For instance, a ⌬BϭϪ⌬Q amplitude is generated in the decay B(bd)→ ϩ e Ϫ ¯e by two tree-level transitions b→qud and d→qe Ϫ ¯e by exchanging the quark qϭu,c,t. However, an estimate of this amplitude may be misleading because we could have additional contributions ͓at the same order and with the same Cabibbo-Kobayashi-Maskawa ͑CKM͒ factors͔ from the b→d penguin transition, and the effects due to new particle exchanges in the penguin loop are unknown ͓3͔. In any case, an experimental check of the ⌬Bϭ⌬Q rule as a phenomenological question is important in its own right; the rule forms the basis of lepton tagging of bottom flavor. For this check, we shall examine the decay time asymmetries involving likesign dilepton events produced at asymmetric factories of ⌼(4S).The parameters of interest are the ratios of semileptonic decay amplitudes for B and B mesons to decay into the chan-

Second order direct CP asymmetry in B_(s) -> X l nu

“…Second order amplitudes for B 0 k → Xℓ − νℓ have been discussed in Ref. [24] without estimating their magnitudes. For completeness, as we have studied tiny CP asymmetries from second order amplitudes, we will estimate the ratio of second order amplitudes for "wrong-sign" leptons and first order amplitudes for "right-sign" leptons, showing that this ratio is negligibly small.…”

A Model-Independent and Rephase-Invariant Parametrization of Cp Violation

“…Assuming the ∆B = ∆Q rule conserved [ 6 ], the amount of its magnitude can then be extracted from the decay rate asymmetry between the semileptonic channels B →…”