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Study of B meson decays with J/ψ　and φ in the final states Study of B meson decays with J/ψ　and φ in the final states LIU, YANG リュウ, ヤン LIU, Yang We study the decay modes of B meson decay to final states including J/ψ and Φ mesons based on a large amount of data sample at the &upsih;(4S) state collected with Belle detector in KEKB asymmetric energy e+e- collider. 　　The decay B0 → J /ψΦ is expected to involve W-exchange and final state interac- tion (FSI) processes. The mechanisms contributing to this decay can be divided into four categories: 1) The photo-production; 2) The tri-gluon fusion; 3) The rescattering effect; 4) The ω - Φ mixing. The dominant contribution is from ω- Φ mixing and the branching fraction for this decay is estimated to be (1.8 ± 0.3) × 10-7. 　　We perform a search for B0 → J /ψΦ decays using a data sample of 605 fb-1 containing 657 × 106 BBpairs. 　　We reconstruct B mesons from the decays J/ψ → l+l- (l = e,μ) and Φ → K+ K-. Events are required to pass a basic hadronic event selection. We identify B candidates using two widely used kinematic variable calculated in the center-of-mass system:the beam-energy constrained mass (Mbc &equiv; <big>√</big>E2beam　―　P2B) and the energy difference (△E &equiv; EB - Ebeam), where Ebeam is the beam energy, PB and EB are the reconstructed momentum and energy of the B0 candidate. We select B candidates within the range -0.2 GeV < △E < 0.3 GeV and 5.27 GeV / c2 ＜ Mbc < 5.29 GeV / c2 for final analysis. 　　We study reconstruction efficiency and event selection criteria using a large signal Monte Calor (MC) sample. To study the background, we use a MC sample corre- sponding to 3.86 × 106generic BB decays (59 times that of real data) that includes all known B →　J/ψX processes as well as sideband region. 　　The dominant background comes from BB events with B decays to J/ψ. We find that the dominant backgrounds come B0 → J/ψK*0(892)[→K-π+] and B0- → J/ψK1(1270)[→ K-π+π0/-]. In both cases, a pion is misidentified as a kaon, and in the latter case, the other pion is missed. The former has a peak at △E ～0.1～ GeV, while the latter has a broad peak in the negative △E region. The remaining background is due to random combinations of J/ψand Φ candidates and does not have structure in the △E distribution (referred to as combinatorial background). 　　The signal yield is extracted by performing an unbinned extended maximum- likelihood fit to the △E distribution of candidate events. The signal PDF is mod- eled by a sum of two Gaussians. The background PDFs are two Gaussians for the J/ψK1 component, a bifurcated Gaussian for the J/ψK*0 component and a second- order polynomial for combinatorial background, respectively. The parameters of these PDFs are determined from MC simulations. 　　We obtain a signal yield of 4.6+3.1-2.5 events with a statistical significance of 2.3σ. As no significant signal is found for the B0 →　J /ψΦ decay mode, we an upper limit on the yield at the 90% confidence level by a frequentist method using ensembles of pseudo-experiments. Finally an upper limit at the 90% confidence level is obtained: 　　　　　　　　　　　　　　β(B0 → J /ψΦ)< 9.4 × 10-7. 　　　　　 (1) 　　This result improves upon the previous result by about a factor of 10 and is consistent with the theory prediction. The result shows that a large enhancement from rescattering is not likely in this decay mode. To check the prediction more precisely, a larger data sample is needed. 総研大甲第1196号 eng thesis https://ir.soken.ac.jp/records/711 博士（理学） 2008-09-30 総合研究大学院大学 https://ir.soken.ac.jp/record/711/files/甲1196_要旨.pdf application/pdf 252.8 kB 2016-02-17 https://ir.soken.ac.jp/record/711/files/甲1196_本文.pdf application/pdf 23.0 MB 2016-02-17