Semi-leptonic W decay to B meson with lepton pairs in HQET factorization upto O(αs)

Abstract

Weextend the factorization formalism for a somewhat complex process W+ → B+ℓ+ℓ− in the non-zero limit of invariant squared-mass of dilepton, q2, at the lowest order in 1/mb up to O(αs), inspired by the investigation of heavy-light meson production within the context of heavy quark effective theory (HQET) factorization. In current study, we have extended the HQET factorization formula for the decay W+ → B+ℓ+ℓ− and cal culated the form factors up to next-to-leading order (NLO) corrections in αs. We have shown that the amplitude of decay W+ → B+ℓ+ℓ− can be written into a convolution between the perturbatively calculable hard-scattering kernel and the non-perturbative light-cone distribution amplitude (LCDA) defined in HQET. The validity of HQET fac torization depends on the assumed scale hierarchy mW ∼ mb ≫ ΛQCD. We calculated the form factors associated to W+ → B+ℓ+ℓ− process in HQET factorization,revealing details on its phenomenology. Furthermore, we conduct an exploratory phenomenolog ical investigation on W+ → B+ℓ+ℓ− by using the LCDAs with an exponential model for B+ meson. According to our research, the branching ratio for W+ → B+ℓ+ℓ− is below 10−10. This channel in high luminosity LHC experiments may serve to further restrict the value of λB even when the branching ratios are small.