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T: Fachverband Teilchenphysik
T 43: Flavourphysik 2 (CP Verletzung)
T 43.8: Talk
Monday, March 24, 2014, 18:30–18:45, GFH 01-701
Measurement of ACP in fully inclusive B→ Xs+dγ decays using a leptonic tag at BelleMeasurement of ACP in fully inclusive B→ Xs+dγ decays using a leptonic tag at Belle — •Luis Pesantez1, Jochen Dingfelder1, and Phillip Urquijo1,2 for the Belle collaboration — 1Physikalisches Institut, Universität Bonn — 2University of Melbourne
The Belle detector at the KEKB e+e− collider recorded 770×106 BB pairs produced at the Υ(4S) resonance. The decay B→ Xs+dγ occurs through a flavor changing neutral current, which is forbidden at tree level in the Standard Model (SM), it includes all hadronic final states with an s or d quark. The CP asymmetry, ACPB→ Xs+d γ, is predicted to be zero with very small theoretical uncertainty, this provides a stringent test of the SM and the possibility to search for New Physics with new CP-violating phases.
The asymmetry ACPB→ Xs+d γ is measured using a semileptonic tag of the second B meson in the event to determine its flavor. The suppression of the dominant continuum background (e+e−→ qq, q = u,d,s,c ), is based on multivariate analysis techniques. A potential bias on the asymmetry due to detector effects, lepton identification and tracking, as well as the calibration of all background sources, are evaluated with data. The optimized selection and the use of the full Belle data set lead to an improved statistical uncertainty compared to previous measurements at the B-factories.