LHCb

Abstract:

The production of the f⁰ (1270) has been studied in the reaction π^-p → π⁺π^-n at 12 and 15 GeV/c in the momentum transfer range 0.02 to 0.80 GeV². Differential and total cross sections for the reaction π^-p → f⁰n have been determined. The f⁰ decay density matrix elements have been evaluated requiring all the matrix eigenvalues to be non-negative. The relative unnatural and natural parity exchange contributions to the f⁰ production have been studied. The results are compared with a Regge exchange model formulated in terms of the pion and A2 exchanges including cut contributions. © 1977.

Abstract:

As measurements of the CKM angle $\gamma$ in decays of $b$-hadrons become increasingly precise, it is important to consider the impact of processes that affect secondary and tertiary decay products and can contribute to the observed CP violation. The golden decay mode used to measure $\gamma$ is $B^\pm\to DK^\pm$, where $D\to K_\text{S}^0\pi^+\pi^-$. Due to the presence of a $K_\text{S}^0$ meson in the final state, $\gamma$ measurements based on this mode are affected by neutral kaon CP violation and matter regeneration, and this study examines the potential size of the impact. Previous studies determine the impact of kaon CP violation to be a few degrees in size, but make simplifying assumptions about how experimental measurements are implemented. These assumptions are lifted in the present study, and the matter regeneration effect is included for the first time. The results are presented within the context of $\gamma$ measurements to be made using the LHCb and Belle II II detectors. It is found that the expected biases due to ignoring the effects of CP violation and matter regeneration in neutral kaons is small and less than $0.5^\circ$ degrees in all experimental scenarios considered.

Abstract:

This thesis presents a measurement of CP-violation in partially reconstructed B±→D*K± and B±→D*π± decays, where the neutral pion and photon from the D*→Dπ0 and D*→Dγ decays are not reconstructed. The D meson is subsequently reconstructed in the D→KS0π+π− or D→KS0K+K− final state. The measurement of CP-violation is performed by analysing the distribution of the signal yields over the D-decay phase space, without relying on a D-decay amplitude model. Instead, inputs for strong phase-related parameters measured at CLEO and BESIII are used. The measurement is performed using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8, and 13 TeV, with a total integrated luminosity of approximately 9 fb−1. The work in this thesis measures CP-violating observables using partially reconstructed B±→D*K± and B±→D*π± decays at LHCb. These observables are interpreted in terms of physical parameters, including the Cabibbo-Kobayashi-Maskawa angle, γ, a fundamental Standard Model parameter. This is found to be γ = (92 +21 -17)◦, where the total uncertainty includes the statistical and all systematic uncertainties.