000002474 001__ 2474
000002474 005__ 20210628073450.0
000002474 037__ $$aBELLE2-PTHESIS-2021-007
000002474 041__ $$aeng
000002474 100__ $$aYo Sato
000002474 245__ $$aMeasurement of Branching Fractions of B -> Xs l+ l− Decays at the Belle II experiment
000002474 260__ $$aSendai, Miyagi$$bTohoku University$$c2021
000002474 300__ $$amult. p
000002474 500__ $$aPresented on 28 01 2021
000002474 502__ $$aPhD$$bSendai, Miyagi, Tohoku University$$c2021
000002474 520__ $$aThe inclusive B -> Xs l+ l- decays are a great probe to search for physics beyond the standard model (SM) of particle physics. The process is a flavor-changing-neutral-current (FCNC) process which proceeds via loop diagrams in the standard model and thus are strongly suppressed. Since a new heavy particle might be able to enter the loop, the FCNC is sensitive for new physics. Moreover, B -> Xs l+l- decays provide complementary information with less hadronic uncertainty to the exclusive B -> K(*) l+ l- decays in which tensions from the SM prediction have been observed. Belle II is a unique experiment to explore the process with large statistics to shed light on the anomalies. We performed the measurements of the branching fractions of B -> Xs l+ l- decay using the data set accumulated by Belle II experiment which corresponds to 37.7 million B-meson pairs. This is the first measurement on B -> Xs l+ l- at Belle II experiment. Because the statistical significance on muon modes and combined mode is less than 2-sigma level, the upper limit on the branching fraction is set for these modes. The branching fraction of B -> Xs e+ e- and B -> Xs mu+ mu- is consistent with previous measurements and the SM prediction. Result of B -> Xs l+ l- is consistent with the world average, Belle measurement and the SM prediction, while the difference from BaBar is at 1.4-sigma level. The analysis procedure of B -> Xs l+ l- decays at Belle II experiment well established and we have got ready to lead decisive conclusions regarding the anomalies which are observed in the exclusive B -> K(*) l+ l- decays with upcoming Belle II data.
000002474 8560_ $$fyosato@post.kek.jp
000002474 8564_ $$uhttps://docs.belle2.org/record/2474/files/BELLE2-PTHESIS-2021-007.pdf
000002474 980__ $$aTHESIS