New Tagging Method of B Flavor of Neutral B Meson in CP Violation Measurement in Asymmetric B-Factory Experiment

In CP violation measurements in asymmetric B-factory experiments, a determination of the B flavor of the neutral B mesons is necessary. A new method to this purpose using only three vectors of charged particles has been developed. This method (weighted charge method) does not require either lepton identification or charged-kaon identification. The tagging efficiency, probability for incorrect tagging, and effective tagging efficiency of this method are 43.1, 18.3, and 17.3%, respectively. Asymmetric B-factories are being constructed to measure CP violation parameters in the B system[1, 2]. In such measurements, for example, B 0 (B 0) → ψKs decay must be identified by a full reconstruction. One should thus identify the B flavor of the other B 0 (B 0) meson [B 0 (B 0)-tagging] in order to determine the CP eigenstate at its decay timing. Hereafter, the description of B 0 includes its charge conjugation, i.e., B 0. The typical methods of B 0-tagging are lepton and charged-kaon tagging[3]. The effective tagging efficiency is written as ǫeff = ǫ(1 − 2w) 2, where ǫ and w are tagging efficiency and the probability for incorrect tagging, respectively. A typical value is ǫeff=0.28[1]. However, these methods require expensive devices, such as a CsI calorimeter