Perturbative QCD correction to the B → π transition form factor

Abstract

We report on the perturbative O(α s ) correction to the light-cone QCD sum rule for the B → π transition form factor f + . The correction to the product f B f + in leading twist approximation is found to be about 30%, that is similar in magnitude to the corresponding O(α s ) correction in the two-point sum rule for f B . The resulting cancellation of large QCD corrections in f + eliminates one important uncertainty in the sum-rule prediction for this form factor.

$$B-S$$ B - S transition form-factors with the light-cone QCD sum rules

“…[9][10][11][12], the B − S form-factors are calculated with the LCSR in the leading order approximation, the perturbative O(α s ) corrections are neglected. Due to the lengthy calculations, only perturbative O(α s ) corrections to the twist-2 and twist-3 terms in the LCSR for the B − P, V form-factors [18][19][20][21][22][23][24][25][26] and perturbative O(α 2 s ) corrections to the twist-2 terms in the LCSR for the B − π form-factor [27] are studied up to now, where the P and V denote the light pseudoscalar and vector mesons, respectively. In this article, we study the B − S form-factors by taking into account the perturbative O(α s ) corrections to the twist-2 terms using the LCSR.…”

Perturbative QCD correction to the light-cone sum rule for the and couplings

“…It is well known, however, that in heavylight systems next-to-leading order (NLO) effects can be essential. An important example is provided by the heavy-to-light form factors [2,3,4,5]. This calls for a NLO analysis of g B * Bπ and g D * Dπ .…”

“…The O(α s ) term T 1 has recently been calculated [2,3] in the context of the LCSR determination of the B → π form factor f + (p 2 ). For brevity, we do not repeat the explicit expressions here.…”

“…For brevity, we do not repeat the explicit expressions here. They can be found in [2] together with a detailed discussion of the treatment of ultraviolet and collinear divergences.…”

“…Therefore, Im s 2 T 1 contains both δ-and θ-functions in s 2 . In the following, we use the explicit form given in [2]. To obtain the O(α s ) correction ρ 1 (s 1 , s 2 ) one has to convolute Im s 2 T 1 with the products ϕ as π C 3/2 2n .…”