Radiative Decays of the B Meson
The radiative decays of the B meson to the final states K *(892){gamma} and {rho}(770){gamma} proceed through virtual effective flavor-changing neutral current processes which are sensitive to contributions from high mass scales from within the Standard Model of particle interactions and from possible new physics. In the context of the Standard Model, these transitions are of interest in probing the weak interaction behavior of the top quark. In particular, the ratio of branching fractions for the two processes can be used to extract the ratio of Cabibbo-Kobayashi-Maskawa matrix elements |V{sub td}/V{sub ts}|. Potential new physics contributions in these virtual transitions may induce new sources of direct CP violation and enhancement or suppression of the rate of these processes. The B {yields} K*{gamma} is a manifestation of the b {yields} s{gamma} radiative transition. This process has been previously observed by the CLEO collaboration and its branching fraction measured. While the theoretical prediction for the inclusive rate of b {yields} s{gamma} transitions is more robust than that of the exclusive B {yields} K*{gamma}, the prospects for precise measurements of {Beta}[B {yields} K*{gamma}] and direct CP violation in this channel has attracted considerable attention. The analysis described here represents an improved measurement of the B {yields} K*{gamma} branching factions and a more sensitive search for direct CP violation. In 22.7 x 10{sup 6} B{bar B} events collected by the BABAR detector in 1999-2000, we measure: {Beta}[B{sup 0} {yields} K*{sup 0}{gamma}] = 4.23 {+-} 0.40(stat.) {+-} 0.22(syst.) x 10{sup -5} and {Beta}[B{sup +} {yields} K*{sup +}{gamma}] = 3.83 {+-} 0.62(stat.) {+-} 0.22(syst.) x 10{sup -5}. We find no evidence for direct CP violation in the decays and constrain -0.170 < A{sub CP} < 0.082 at 90% Confidence Level. The B {yields} {rho}{gamma} proceeds through the analogous b {yields} d{gamma} radiative transition. As such, its rate is suppressed by a factor of |V{sub td}/V{sub ts}|{sup 2} {approx} {Omicron}(50) relative to B {yields} K*{gamma} and remains unobserved. Current limits on the branching fractions of B {yields} {rho}{gamma} are still an order of magnitude above the theoretical predictions. While the uncertainty in the theoretical predictions for the branching fraction of this mode are large, it may be possible to reduce these uncertainties by considering the ratio of the branching fractions for B {yields} {rho}{gamma} and B {yields} K*{gamma} which would lead to a measurement of |V{sub td}/V{sub ts}|. The analysis presented here represents a search with nearly an order of magnitude more data and new analysis techniques. In a sample of 61 .7 x 10{sup 6} B{bar B} events, we find no significant evidence for the decay B {yields} {rho}{gamma} is and establish the following 90% Confidence Level upper limits on the branching fraction: {Beta}[B{sup 0} {yields} {rho}{sup 0}{gamma}] < 1.5 x 10{sup -6} and {Beta}[B{sup +} {yields} {rho}{sup +}{gamma}] < 2.8 x 10{sup -6}.
- Research Organization:
- SLAC National Accelerator Lab., Menlo Park, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (US)
- DOE Contract Number:
- AC03-76SF00515
- OSTI ID:
- 815633
- Report Number(s):
- SLAC-R-604; TRN: US0304744
- Resource Relation:
- Other Information: PBD: 23 Sep 2003
- Country of Publication:
- United States
- Language:
- English
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