Measurement of|Vcb|and the Form-Factor Slope inB¯→Dℓ−

Abstract

We present a measurement of the Cabibbo-Kobayashi-Maskawa matrix element |V(cb)| and the form-factor slope rho2 in B --> Dl- nu(l) decays based on 460x10(6) BB events recorded at the Upsilon(4S) resonance with the BABAR detector. B --> Dl- nu(l) decays are selected in events in which a hadronic decay of the second B meson is fully reconstructed. We measure B(B- --> D0 l- nu(l))/B(B- --> Xl- nu(l)) = (0.255+/-0.009+/-0.009) and B(B0 --> D+ l- nu(l))/B(B0 --> Xl- nu(l)) = (0.230+/-0.011+/-0.011), along with the differential decay distribution in B --> Dl- nu(l) decays. We then determine G(1)|V(cb)| = (42.3+/-1.9+/-1.4)x10(-3) and rho2 = 1.20+/-0.09+/-0.04, where G(1) is the hadronic form factor at the point of zero recoil.

Sterile neutrinos in leptonic and semileptonic decays

“…Indeed, the decay rates are parametrised by two form factors, F + (q 2 ) and F 0 (q 2 ). The first, F + (q 2 ), has recently been experimentally well measured [84] and the behaviour of the second, F 0 (q 2 ), with respect to the transfer momentum q 2 , has also been determined [78] (consistent with many different theoretical estimations from Lattice QCD collaborations [85,86], as well as with QCD sum rules analyses [87,88]),…”

Looking for possible new physics in B→D(*)τντ in light of recent data

“…Different experimental collaborations have already fitted the form-factor parameters [17] from the data collected for the decays B → D ( * ) ν , e.g. [18,19]. Using the present data on B → D ( * ) τ ν τ , we can check whether the fitted form-factors are in good agreement with those obtained from the decay B → D ( * ) ν .…”

“…The q 2 -distribution of the decay rate of the decays B → D ( * ) ν are obtained from equations (21) and (22) by setting C W = 0 and m τ = 0. we define our observables as given in equations (17) and (18).…”

Semileptonic B decays

“…An alternative lattice determination, currently available only in the quenched approximation, consists in calculating the form factor normalization directly at values ω > 1, avoiding the large extrapolation to ω = 1 and thus reducing the model dependence [9,10]. This approach, by using 2009 BaBar data [11], gives a slightly higher value than the lattice result (2.9), that is…”