Infoscience

Thesis

# Determination of the polarization amplitudes and CP asymmetries in B⁰ → φK*(892)⁰ at LHCb

The LHCb experiment is one of the large experiments installed around the LHC collider. Its aim is the study of CP violation and rare b-hadrons decays. This thesis addresses these two objectives. CP violation was found in 1964 in the decays of neutral kaons by J. H. Christenson, J. W. Cronin, V. L. Fitch, and R. Turlay. It was reconfirmed in 2001 in B meson systems by BaBar and Belle experiments. CP violation can be explained in SM using CKM matrix with three quark generations. The B0->PhiK*(892)0 is a rare flavour changing neutral decay which processes via the gluonic penguin diagram (b -> s transition). In SM, the predicted CP asymmetry is so small for this decay channel and any deviation from the SM value would signal New Physics". This decay is a pseudo-scalar decaying to vector mesons with spin-1. Conservation of angular momentum leads to three possible helicity states of the vector mesons which reflects into three amplitudes: these will be unravelled by an angular analysis of the final-state particles, Phi->KK and K* -> Kpi. An angular analysis of the decay B0->PhiK*(892)0 is reported based on data of pp collision at a centre-of-mass energy of 8 TeV and corresponding to an integrated luminosity of 2.0 fb^{-1}, with the LHCb detector. The analysis includes both the contribution of Kpi and KK S-waves and a significant contribution from them is found. The measurements of P-wave amplitudes and phases is consistent with the one of BaBar and Belle experiments, but are much more precise. The longitudinal polarization fraction f_L for the P-wave is measured to be 0.499 +- 0.011 +- 0.010. The differences between the polarization amplitudes and phases of the B0->PhiK*(892)0 and bar{B0}->Phibar{K}*(892)0 decays have been derived as well as the triple-product asymmetries. The results show no evidence for direct CP violation.

Thèse École polytechnique fédérale de Lausanne EPFL, n° 6725 (2015)
Programme doctoral Physique
Faculté des sciences de base
Institut de physique de l'énergie et des particules
Laboratoire de physique des hautes énergies 1
Jury: Prof. Vincenzo Savona (président) ; Dr Minh Tâm Tran, Prof. Aurelio Bay (directeurs) ; Prof. Minh Quang Tran, Dr Greig Cowan, Prof. Mau-Chung Nguyen (rapporteurs)

Public defense: 2015-10-23

#### Reference

Record created on 2015-10-13, modified on 2016-08-09