Radiative B to axial-vector meson decays at NLO in soft-collinear effective theory

Abstract

The rare decay B → Aγ, with A representing axial-vector mesons such as K 1(1270), K 1(1400), b 1(1300), a 1(1260), is studied at next-to-leading order (NLO) in soft collinear effective theory (SCET). The large outgoing meson energy encourages the study of the decay with an appropriate factorization scheme that separates the factorizable and non-factorizable parts systematically. We have analyzed the leading-power and O ( α s ) diagrams that contribute to matching to SCETI. The new intermediate theory is matched onto SCETII and the running of SCETI operators is performed to sum large perturbative logarithms. The values of soft-overlap function ζ ⊥ for K 1(1270, 1400), a 1 and b 1 mesons are estimated from the light cone-sum-rules, and later using it the corresponding branching fractions for B → K 1 ( 1270 , 1400 ) , a 1 , b 1 γ decays are calculated. We find that in case of B → K 1(1270, 1400)γ decays the results are in good agreement with their experimental measurements. Also the estimated values of the branching ratios of the B → (b 1, a 1)γ decays are potentially large to be measured at the LHCb and future B-factories.

Radiative B to tensor meson decays at NLO in SCET

“…To start with, let us define the gauge-invariant fields required for SCET II , i.e. Reproduced from [8]. © IOP Publishing Ltd. All rights reserved.…”

“…© IOP Publishing Ltd. All rights reserved. Reproduced from [8]. © IOP Publishing Ltd. All rights reserved.…”

“…Similar decay involving axial-vector meson in the final state, i.e. B → Aγ is calculated in the context of large-energy-effective theory (LEET) [7] and using soft-collinear effective theory (SCET) [8]. The radiative…”

“…The introduction of these SCET operators makes the resummation of the large logarithms possible. During this process, the resummation of C i I is avoided because of the hard scale, however, for the C i II it is performed due to the lower value of the intermediate scale (for details: see [8]).…”

“…Later, using the calculation of SCET form factor for B → K * γ, its branching ratio is estimated [21]. [8] discussed similar calculations for the radiative B → Aγ, where A is representing an axial-vector meson. In [23], the authors carried out a study for the semileptonic B → K * decay, i.e.…”