Constraints on Anomalous Gauge Boson Couplings From b →

The recent results of the CLEO Collaboration on both inclusive and exclusive radiative B decays are combined with those of the UA2 Collaboration on Wγ production to highly constrain the anomalous trilinear gauge couplings of the W . The theoretical analysis of the b → sγ process employs, next-to-leading order operator coefficient evolution as well as QCD bremsstrahlung and appropriate phase space corrections. ∗Research supported by the U.S. Department of Energy, Division of High Energy Physics, Contracts W-31-109-ENG-38. The Standard Model(SM) provides an excellent description of presently available experimental data[1]. However, it is believed that the SM cannot be the whole story as it leaves too many questions unanswered. Whatever new physics actually exists beyond the SM may be more subtle in its first appearance than the production of an unexpected particle at a hadron or ee collider. Thus, one approach in looking for new physics is to probe for small deviations from the predictions of the SM either through the detailed analysis of high precision data or by looking for rare processes which are either highly suppressed or forbidden in the SM. One aspect of the SM which has only recently begun to be directly tested[2], is the trilinear gauge coupling of the photon or Z to WW. Models which introduce ‘anomalous’ couplings are convenient test beds for looking for deviations from the SM and tell us something about ‘how the SM is doing.’ There have been many discussions about such couplings in the literature[3] many of which have recently been called into question [4]. Such analyses take either one of two approaches: looking for deviations from the SM via tree-level processes, such as ee → WW at LEP II or pp̄ → Wγ at the Tevatron, or they examine the influence of the anomalous couplings on loop-order processes. The latter procedure can be particularly dangerous as in many cases, such as the g − 2 of the muon, cutoffs must be introduced to regulate loop integrals and can err in attributing a physical significance(e.g., the scale of new physics) to the cutoff. This point has recently been stressed by Burgess and London [5]. Some loop-order processes do not suffer from this difficulty, due to the cancellations provided by the GIM mechanism[6], and can yield cutoff-independent bounds on any anomalous couplings. One example of such a process is the reaction b → sγ which we will examine in the discussion below. Assuming that CP is conserved, the usual analysis of the WWγ trilinear coupling postulates the existence of only two additional parameters: κ = 1 + ∆κ