Optimization of track-to-jet association for b-tagging algorithms

At the LHC, the identification of jets originating from b quarks is important for searches for new physics and for measurements of standard model processes.The properties of the bottom hadrons can be used to identify the hadronic jets into which b quarks fragment. These hadrons have relatively large masses, long lifetimes and daughter particles with hard momentum spectra. Several algorithms have been developed and used in the CMS experiment, and exploit these properties to achieve the identification of b quarks. In this project, some modifications to the way tracks are associated to the jets have been implemented in order to improve the performance of those algorithms for jets of high $p_T$ and events with high pile-up. In first place, we used the tracks explicitly associated to the jet by the Particle Flow algorithm. In second place, we optimized the track selection for high $p_T$ exploiting the larger $p_T^{Rel}$ values of tracks coming from b-hadrons. In both cases, a similar improvement of the performance is achieved for high b-tagging purity.