Exclusive b → sγ decays at Belle

4th Symposium on Prospects in the Physics of Discrete Symmetries

Dutta, D.^1 ; Bhuyan, B.^1

Indian Institute of Technology Guwahati, Assam, India^1

关键词: Asymmetric energy;    Belle detectors;    Branching fractions;    Confidence levels;    Gammagamma;    The standard model;    Upper limits;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/631/1/012038/pdf
DOI  :  10.1088/1742-6596/631/1/012038

来源: IOP

【 摘 要 】

We report results on two exclusive b → sγ decays, namely B0s→ Øγ and B0s→ γγ at Belle. For this study, we have used 121.4 fb-1of Υ(5S) data collected with the Belle detector at the KEKB asymmetric-energy e+e-collider. Calculations within the Standard Model framework predict the B0s→ Øγ branching fraction to be in the range (3.9 - 4.3) x 10-5and the B0s→ γγ branching fraction to be in the range (0.18 - 2.45) x 10-6. The B0s→ Øγ branching fraction is measured as (3.6 ± 0.5 ± 0.3 ± 0.6) x 10-5, where the first uncertainty is statistical, the second is systematic and the last one is due to the uncertainty in the fraction of events. This result agrees with the theoretical predictions and other experimental results. We observe no statistically significant signal for B0s→ γγ and have thus set a 90% confidence-level upper limit on its branching fraction at 3.1 x 10-6. This improves on the previous result by a factor of about 3 and is the most stringent limit till date.