Angular analysis of the decay B°→ΦK*(892)°

Abstract

The LHCb experiment is a single-arm forward spectrometer situated at the Large Hadron Collider, CERN. LHCb is optimised for the precision study of beauty and charm flavoured hadrons and in 2011 collected 1 fb-1 of proton- proton collision data at a centre-of-mass energy of 7TeV. The aim of LHCb is to search for rare decays and make precise measurements of Charge-Parity (CP) violation in the beauty and charm sectors. In the Standard Model the decay B°→ ΦK*(892)° is described by a loop mediated process, providing a sensitive test for new physics. In this decay, signs of CP violation could indicate the presence of physics beyond the Standard Model. This thesis presents a study of the flavour eigenstate B° → Φ(→ K+K-)K*(892)°(→ K+π-) and its charge conjugate -B°-decay. The decay products form an admixture of CP-even and CP-odd eigenstates, which can have longitudinal or transverse polarisation. An angular analysis is performed to disentangle these different contributions and the polarisation amplitudes and strong phases are measured. No difference is observed between B0 and -B0 amplitudes, supporting the hypothesis that CP is conserved in this decay. In addition, the Triple Product Asymmetries (TPAs) are determined from the products of the polarisation amplitudes and strong phases. True TPAs are zero in the event that CP symmetry is conserved, while fake TPAs can arise due to final-state interactions. Although the measured true TPAs are consistent with zero, several significant fake TPAs are observed.