Measurement of an excess of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mover accent="true"><mml:mi>B</mml:mi><mml:mo>¯</mml:mo></mml:mover><mml:mo>→</mml:mo><mml:msup><mml:mi>D</mml:mi><mml:mrow><mml:mo mathvariant="bold" stretchy="false">(</mml:mo><mml:mo>*</mml:mo><mml:mo mathvariant="bold" stretchy="false">)</mml:mo></mml:mrow></mml:msup><mml:msup><mml:mi>τ</mml:mi><mml:mo mathvariant="bold">−</mml:mo></mml:msup><mml:msub><mml:mover accent="true"><mml:mi>ν</mml:mi><mml

We compute perturbative QCD corrections to B → D form factors at leading power in Λ/m b , at large hadronic recoil, from the light-cone sum rules (LCSR) with Bmeson distribution amplitudes in HQET. QCD factorization for the vacuum-to-B-meson correlation function with an interpolating current for the D-meson is demonstrated explicitly at one loop with the power counting scheme m c ∼ O √ Λ m b . The jet functions encoding information of the hard-collinear dynamics in the above-mentioned correlation function are complicated by the appearance of an additional hard-collinear scale m c , compared to the counterparts entering the factorization formula of the vacuum-to-B-meson correction function for the construction of B → π from factors. Inspecting the next-toleading-logarithmic sum rules for the form factors of B → D ν indicates that perturbative corrections to the hard-collinear functions are more profound than that for the hard functions, with the default theory inputs, in the physical kinematic region. We further compute the subleading power correction induced by the three-particle quark-gluon distribution amplitudes of the B-meson at tree level employing the background gluon field approach. The LCSR predictions for the semileptonic B → D ν form factors are then extrapolated to the entire kinematic region with the z-series parametrization. Phenomenological implications of our determinations for the form factors f +,0 BD (q 2 ) are explored by investigating the (differential) branching fractions and the R(D) ratio of B → D ν and by determining the CKM matrix element |V cb | from the total decay rate of B → Dµν µ .

Section: Jhep06(2017)062mentioning

confidence: 72%

Perturbative corrections to B → D form factors in QCD

Wang

Wei

Shen

et al. 2017

“…In fact, BaBar excludes the latter contributions as an explanation of the deviations in R(D) and R(D * ) from their SM predictions [82]. Moreover, and as discussed in [83], the observed excess on R(D) (and R(D * )) also fails to be explained in large portions of the more general type-III 2HDM. Similarly, the authors of ref.…”

Section: Jhep02(2014)091mentioning

confidence: 99%

Sterile neutrinos in leptonic and semileptonic decays

Abada

Teixeira

Vicente

et al. 2014

113

107

Abstract:We address the impact of a modified W ℓν coupling on a wide range of observables, such as τ leptonic and mesonic decays, leptonic decays of pseudoscalar mesons, as well as semileptonic meson decays. In particular, we concentrate on deviations from lepton flavour universality, focusing on the ratios, and BR(B → τ ν). We further consider leptonic gauge boson decays, such as W → ℓν and Z → νν. For all the above observables, we provide the corresponding complete analytical expressions, derived for the case of massive neutrinos. Working in the framework of the Standard Model extended by additional sterile fermions, which mix with the active (left-handed) neutrinos, we numerically study the impact of active-sterile mixings on the above mentioned observables.

“…The combined results of BaBar [1,2], Belle [3][4][5][6] and LHCb [7] read [8] R(D) = 0.403 ± 0.047, R(D * ) = 0.310 ± 0.017, ρ = −0.23,…”

Section: Introductionmentioning

confidence: 99%

Y and ψ leptonic decays as probes of solutions to the R(D (*)) puzzle

Aloni

Efrati

Grossman

et al. 2017

Experimental measurements of the ratios R(D ( * ) ) ≡ Γ(B→D ( * ) τ ν) Γ(B→D ( * ) ν) ( = e, µ) show a 3.9σ deviation from the Standard Model prediction. In the absence of light righthanded neutrinos, a new physics contribution to b → cτ ν decays necessarily modifies also bb → τ + τ − and/or cc → τ + τ − transitions. These contributions lead to violation of lepton flavor universality in, respectively, Υ and ψ leptonic decays. We analyze the constraints resulting from measurements of the leptonic vector-meson decays on solutions to the R(D ( * ) ) puzzle. Available data from BaBar and Belle can already disfavor some of the new physics explanations of this anomaly. Further discrimination can be made by measuring Υ(1S, 2S, 3S) → τ τ in the upcoming Belle II experiment.