Observation of B+ → pΛ-bar π+π−, B+ → pΛ-bar ρ and B− → p-bar ΛD0 at Belle, and Detector Simulation of the Electromagnetic Calorimeter at Belle II

• Main Authors: Po-Yuan Chen, 陳柏元
• Other Authors: Min-Zu Wang
• Format: Others
• Language: en_US
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/54147065190901221747

博士 === 國立臺灣大學 === 物理研究所 === 99 === In this thesis, there are three major topics to be addressed. Two physics analyses on the searches for the baryonic B decays at Belle. The other is the ECL upgrade study for BelleII. The first data analysis is to search for the charmless baryonic B de- cay with final state of pΛπ+π−. The second analysis is a search for the charmful baryonic B decay of B− → pΛD(∗)0. For both analyses, I use a 605fb−1 data sample collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider. In the charmless baryonic study, the first four-body charmless baryonic decay B+ → pΛ-barπ+π− is observed with a branching fraction (5.92+0.88-0.84(stat.) ± 0.69(syst.)) × 10−6 and a significance of 9.1 standard deviations (σ). We also observe the intermediate three-body decay B+ → pΛρ0 with a branching fraction of (4.78+0.67-0.64(stat.) ± 0.60(syst.)) × 10−6 and a significance of 9.5 σ, and find a hint of B+ → pΛ-bar f2(1270). No other intermediate three-body decay is found in B− → pΛ-bar π+π− final state study. In the charmful baryonic analysis, we study B− → p-bar ΛD(∗)0. The observed branching fraction for B− → p-bar ΛD0 is (1.43+0.28-0.25(stat.) ± 0.18(syst.)) × 10−5 with a significance of 8.1σ. No significant signal is found for B− → p-barΛD∗0 and the corresponding upper limit on branching fraction is 4.8 × 10−5 at the 90% confidence level. The com- mon feature of threshold enhancement in baryonic B decays is still observed in both of the modes that most of the signal events are found with the pΛ ̄ invariant mass peaking near threshold. The NTUHEP group is responsible for the software of ECL upgrade at Belle II. We provide not only the performance simulation for upgrade options of BelleII based on the Geant3 package which was well tested and calibrated in the present operating conditions of KEKB and Belle, but also the software implementation for BelleII. The software implementation for ECL upgrade consists of detector geometry description, detector simulation and data reconstruction. The simulation package is changed to Geant4.