Search forB+→ℓ+νℓrecoiling againstB−→D0

Abstract

We present a search for the decay B + → ℓ + ν ℓ (ℓ = τ, µ, or e) in (458.9±5.1)×10 6 Υ (4S) decays recorded with the BABAR detector at the SLAC PEP-II B-Factory. A sample of events with one reconstructed exclusive semi-leptonic B decay (B − → D 0 ℓ −ν X) is selected, and in the recoil a search for B + → ℓ + ν ℓ signal is performed. The τ is identified in the following channels: τ + → e + ν e ν τ , τ + → µ + ν µ ν τ , τ + → π + ν τ , and τ + → π + π 0 ν τ . The analysis strategy and the statistical procedure is set up for branching fraction extraction or upper limit determination. We determine from the dataset a preliminary measurement of B(B + → τ + ν τ ) = (1.8 ± 0.8 ± 0.1) × 10 −4 , which excludes zero at 2.4σ, and f B = 230 ± 57 MeV. Combination with the hadronically tagged measurement yields B(B + → τ + ν τ ) = (1.8 ± 0.6) × 10 −4 . We also set preliminary limits on the branching fractions at B(B + → e + ν e ) < 7.7 × 10 −6 (90% C.L.), B(B + → µ + ν µ ) < 11 × 10 −6 (90% C.L.), and B(B + → τ + ν τ ) < 3.2 × 10 −4 (90% C.L.).

Minimal flavor violating two-Higgs-doublet model at the LHC

“…The red region above the dashed contour is excluded by the latest combination of B u ! data from BaBar [111,112] and Belle [113,114], that is in reasonable agreement with SM expectations. The bounds from top decays only exist for M H AE & 160 GeV, while obviously no such restriction exists for the constraint from B u !…”

FCNC portals to the dark sector

“…The persistent tension between the Belle and BaBar measurements of B(B → τ ν) = (1.68 ± 0.31) · 10 −4 [35][36][37][38] and the predictions of the global CKM fits within the SM (see ref. [39] for a recent review) can be addressed provided m ψ < 3.5 GeV.…”

The CKM Parameters

“…Additional decay modes need to be added in order to obtain a global picture for |V ub | and |V cb |. The leptonic decay B → τ ν τ has been studied at B factories [73][74][75][76], favouring values closer to the inclusive determination. The value of this branching ratio used to be at odds with expectations from global fits [77], but recent determinations from Belle reduced the discrepancy to 1.2σ.…”