Measurement of the Direct CP Asymmetry in over-bar & RARR; gamma; Decays with a Lepton Tag
L Pesantez, P Urquijo, J Dingfelder, A Abdesselam, I Adachi, K Adamczyk, H Aihara, S Al Said, K Arinstein, DM Asner, V Aulchenko, T Aushev, R Ayad, S Bahinipati, AM Bakich, V Bansal, E Barberio, V Bhardwaj, B Bhuyan, A Bobrov Show all
PHYSICAL REVIEW LETTERS | AMER PHYSICAL SOC | Published : 2015
We report the measurement of the direct CP asymmetry in the radiative B¯→X(s+dγ) decay using a data sample of (772 ± 11)×10(6) BB[over ¯] pairs collected at the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. The CP asymmetry is measured as a function of the photon energy threshold. For Eγ*≥2.1 GeV, where Eγ* is the photon energy in the center-of-mass frame, we obtain A(CP)(B¯→X(s+dγ))=(2.2±3.9±0.9)%, consistent with the standard model prediction.
Awarded by Science and Technology Facilities Council
We thank the KEKB group for excellent operation of the accelerator; the KEK cryogenics group for efficient solenoid operations; and the KEK computer group, the NII, and PNNL/EMSL for valuable computing and SINET4 network support. We acknowledge support from MEXT, JSPS, and Nagoya's TLPRC (Japan); ARC (Australia); FWF (Austria); NSFC (China); MSMT (Czechia); CZF, DFG, and VS (Germany); DST (India); INFN (Italy); MOE, MSIP, NRF, GSDC of KISTI, and BK21Plus (Korea); MNiSW and NCN (Poland); MES and RFAAE (Russia); ARRS (Slovenia); IKERBASQUE and UPV/EHU (Spain); SNSF (Switzerland); NSC and MOE (Taiwan); and DOE and NSF (USA).