Studies of b Hadron decays to Charmonium, the LHCb upgrade and operation

Abstract

Precise measurements of CP violation provide stringent tests of the Standard Model towards the search for signs of new physics. Using LHC proton-proton collision data, collected by the LHCb detector during 2015 and 2016 at the centre-of-mass energy of 13 TeV corresponding to an integrated luminosity of 1.9 fb−1 , presented is the latest measurement of the CP -violating phase, ϕs , using B 0 s → J/ψϕ decays. The machine-learning-based data selection, data-driven corrections to simulated event samples, and the control of systematic effects using dedicated samples are discussed. The values ϕs = −0.083±0.041±0.006 rad, ∆Γs = 0.077± 0.008±0.003 ps−1 (i.e. the decay width difference between the light and the heavy mass eigenstates in the B 0 s system) and Γs −Γd = −0.0041±0.0024±0.0015 ps−1 (i.e. the difference of the average B 0 s and B 0 d meson decay widths) are obtained, yielding the World’s most precise determination of these quantities 1 . Furthermore, shown are the efforts and contributions towards the LHCb Upgrade: the quality assurance and testing of the LHCb RICH Upgrade components, and the redesign and upgrade of the fully online software trigger – LHCb HLT Upgrade. Regarding the former, an original implementation of a parallelised, robust and highly available automation system is introduced. In connection to the latter, a novel neural network architecture and optimisation methods are laid out, enabling complex machine learning to be performed in a low latency high-throughput environment. Those directly influence the future deployment of the experiment and its data collecting and analysis capabilities. Thus, they are essential for future more precise and stringent research.