Two-loop corrections to the B → π form factor from QCD sum rules on the light-cone and |Vub|

Self Cite

521

775

We present B q → ρ, B q → ω, B q → K * , B s → K * and B s → φ form factors from light-cone sum rules (LCSR) at O(α s ) for twist-2 and 3 and O(α 0 s ) for twist-4 with updated hadronic input parameters. Three asymptotic light-cone distribution amplitudes of twist-4 (and 5) are determined, necessary for the form factors to obey the equations of motion. It is argued that the latter constrain the uncertainty of tensor-to-vector form factor ratios thereby improving the prediction of zeros of helicity amplitudes of major importance for B → K * angular observables. We provide easy-to-use fits to the LCSR results, including the full error correlation matrix, in all modes at low q 2 as well as combined fits to LCSR and lattice results covering the entire kinematic range for B q → K * , B s → K * and B s → φ. The error correlation matrix avoids the problem of overestimating the uncertainty in phenomenological applications. Using the new form factors and recent computations of non-factorisable contributions we provide Standard Model predictions for B → K * γ as well as B → K * + − and B s → φµ + µ − at low dilepton invariant mass. Employing our B → (ρ, ω) form factor results we extract the CKM element |V ub | from the semileptonic decays B → (ρ, ω) ν and find good agreement with other exclusive determinations.

Section: A5 Scheme Dependence Of the Form Factorsmentioning

confidence: 99%

“…SR only increases by 2% [53]. Therefore we make use of the QCD sum rules result at O(α s ) [54,55] for f B .…”

Section: Input Parameters and Uncertaintiesmentioning

confidence: 99%

B →Vℓ+ℓ− in the Standard Model from light-cone sum rules

Bharucha

Straub

Zwicky

2016

Self Cite

521

775

“…We use the expressions for OPE derived in [7] extending them to the B → K and B s → K cases (see also [18]). We do not include the O(β 0 ) estimate of the twist-2 O(α 2 s ) contribution to the twist-2 hard-scattering amplitude calculated in [44], since the resulting effect in LSCR is very small and does not yet represent a complete NNLO computation of T (2) 1 . The analytic result for 2 ) is matched to the hadronic dispersion relation for the correlation function (A.1) in the variable (p + q) 2 .…”

Section: Jhep08(2017)112mentioning

confidence: 99%

B s → Kℓν ℓ and B (s) → π(K)ℓ + ℓ − decays at large recoil and CKM matrix elements

Khodjamirian

Rusov

2017

We provide hadronic input for the B-meson semileptonic transitions to a light pseudoscalar meson at large recoil. The B s → K form factor calculated from QCD lightcone sum rule is updated, to be used for a |V ub | determination from the B s → K ν width. Furthermore, we calculate the hadronic input for the binned observables of B → π + − and B → K + − . In addition to the form factors, the nonlocal hadronic matrix elements are obtained, combining QCD factorization and light-cone sum rules with hadronic dispersion relations. We emphasize that, due to nonlocal effects, the ratio of branching fractions of these decays is not sufficient for an accurate extraction of the |V td /V ts | ratio. Instead, we suggest to determine the Wolfenstein parameters A, ρ, η of the CKM matrix, combining the branching fractions of B → K + − and B → π + − with the direct CP -asymmetry in the latter decay. We also obtain the hadronic matrix elements for a yet unexplored channel B s → K + − .

“…For our analysis, we take the results from light cone QCD sum rules (LCSR), which are typically calculated at q 2 = 0. The relevant form factors are f + B→π (0) = 0.252 +0.019 −0.028 [36], f + B→K (0) = 0.34 +0.05 −0.02 [37] and f + Bs→K (0) = 0.30 +0.04 −0.03 [38], where the first two describe transitions for both the B 0 d and the B + mesons. The q 2 dependence of these form factors is parametrised by means of the BGL method described in ref.…”

Section: Jhep03(2015)145mentioning

confidence: 99%

A roadmap to control penguin effects in B d 0 → J/ψK S 0 and B s 0 → J/ψϕ

Bruyn

Fleischer

2015

The theoretical interpretation of the corresponding observables is limited by uncertainties from doubly Cabibbo-suppressed penguin topologies. With continuously increasing experimental precision, it is mandatory to get a handle on these contributions, which cannot be calculated reliably in QCD. In the case of the measurement of sin 2β from B 0 d → J/ψK 0 S , the U -spinrelated decay B 0 s → J/ψK 0 S offers a tool to control the penguin effects. As the required measurements are not yet available, we use data for decays with similar dynamics and the SU(3) flavour symmetry to constrain the size of the expected penguin corrections. We predict the CP asymmetries of B 0 s → J/ψK 0 S and present a scenario to fully exploit the physics potential of this decay, emphasising also the determination of hadronic parameters and their comparison with theory. In the case of the benchmark mode B 0 s → J/ψφ used to determine the B 0 s -B 0 s mixing phase φ s the penguin effects can be controlled through B 0 d → J/ψρ 0 and B 0 s → J/ψK * 0 decays. The LHCb collaboration has recently presented pioneering results on this topic. We analyse their implications and present a roadmap for controlling the penguin effects.