| Radiative decays of B-mesons are ideal laboratories for probing New Physics (NP). Since flavor-changing neutral currents are forbidden at tree-level in the Standard Model (SM), a loop diagram is necessary to facilitate the B → Xsgamma transition, where Xs represents any strange hadronic final state. New Physics particles can potentially propagate in this loop, and if the NP couplings are comparable to those of the SM, deviations from the SM prediction of the B → Xsgamma branching fraction could be observed. The current SM prediction for B (B → Xsgamma) has been obtained with good precision, requiring a precise measurement to make any definitive statement on the presence of NP.;A precision measurement of the B → Xsgamma analysis at BABAR has been performed. To compare directly with the SM prediction, the B → Xsgamma branching fraction must be measured inclusively, where all Xs final states are taken into account. This is achieved by only reconstructing the high-energy photon from the decay. Consequently, the signal is overwhelmed with backgrounds from continuum processes and non-signal B-meson decays. A series of selection criteria is imposed to suppress continuum background. The remaining continuum background is subtracted with data taken 40MeV below the Upsilon(4S) resonance. Photon backgrounds from BB¯ events primarily originate from pi0(eta) → gammagamma decays, as well as radiative decays of o and eta' mesons. Energy deposits from electrons and antineutrons also imitate photons from B → Xsgamma decays. These backgrounds are subtracted using data-corrected Monte Carlo (MC) simulation of BB¯ events.;The signal region of 1.8 < E*g < 2.8 GeV is not looked at until the selection criteria and data-corrected MC backgrounds are fixed. A set of control region checks must be satisfied before the signal region is unblinded, after which the background-subtracted photon spectrum is efficiency-corrected. After a series of corrections related to reference frame differences, photon energy extrapolation, and removal of the B → Xdgamma contribution, a total branching fraction is obtained: BB→Xsg Eg>1.6GeV =3.28+/-0.16+/-0.28+/-0.10 x10-4, where the errors are the statistical, systematic, and model-dependent uncertainties, respectively. This result is consistent with the SM and can be used to place stringent constraints on NP theories. |
