Soft-QCD effects in B double right arrow gamma gamma decay: quark level form factors

摘要

Soft-QCD effects of quark-level form factors in gamma gamma decay of B-s-mesons via D (D) over bar intermediate states, suggested by Ellis et al., are examined in the "Salpeter" model reinterpreted in terms of the Markov-Yukawa Transversality Principle (MYTP) when formulated on a covariant light front (null-plane). The gluonic kernel in the infrared regime which generates the constituent mass via standard DB chi S, is calibrated to both q (q) over bar and qqq spectra, meson mass splittings, pion form factor, and other parameters. With this check, an exact evaluation of the D (D) over bar gamma vertex form factor F(alpha) (normalized to F(0) = 1), gives a multiplicative effect of F-2(alpha) On the B-s --> gamma gamma amplitude via D-meson triangle loop, where alpha = (p(2) + M-2)/M-2 is the off-shellness parameter of the exchanged D-meson of mass M and 4-momentum p(mu), and is a variables of the (internal) loop integration. Unfortunately, the F-2(alpha) effect decreases the loop amplitude by a factor of 30 w.r.t. the point hadron value, resulting in a reduction of 3 orders of magnitude in long distance (hadronic) contributions to the B-s --> gamma gamma decay rate, thus greatly impairing the visibility of such modes. (C) 2000 Published by Elsevier Science B.V. All rights reserved. References: 40