Semileptonic and exclusive rare B decays

• Published in: Physics letters. B 1994-04, Vol.325 (1), p.219-226
• Main Authors: O'Donnell, Patrick J., Xu, Q.P.
• Format: Article
• Language: English
• Subjects: Bottom mesons; Decays of bottom mesons; Exact sciences and technology; Leptonic and semileptonic decays of mesons; Mesons; Physics; Properties of specific particles; Specific reactions and phenomenology; The physics of elementary particles and fields
• ISSN: 0370-2693; 1873-2445
• DOI: 10.1016/0370-2693(94)90095-7

The exclusive rare decay B→K ∗γ takes place in a region of maximum recoil, q 2=0, posing a problem for nonrelativistic quark models which are usually thought to be most reliable at zero recoil. The Bauer-Stech-Wirbel (BSW) model, formulated in the infinite-momentum-frame (IMF) formalism, is designed to work at q 2=0. We show in this model that the ratio relating the decay B→K ∗γ and the q 2-spectrum of the semileptonic decay B→ϱe ν , becomes independent of the wave function in the SU(3) flavor symmetry limit. We show that this feature is also true in relativistic quark models formulated in the IMF or light-cone formalism, if the b quark is infinitely heavy. In fact, these relativistic models, which have a different spin structure from the BSW case, reduce to the BSW model in the heavy b-quark limit. A direct measurement of the q 2-spectrum of the semileptonic decay cam therefore provide accurate information for the exclusive rare decay.