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Статья

A new algorithm for identifying the flavour of $B_s^0$ mesons at LHCb

Journal of Instrumentation. 2016. Vol. 11.
Ustyuzhanin A., Likhomanenko T., Derkach D., Rogozhnikov A., Borisyak M. A., LHCb c.

A new algorithm for the determination of the initial flavour of B0 s mesons is presented. The algorithm is based on two neural networks and exploits the b hadron production mechanism at a hadron collider. The first network is trained to select charged kaons produced in association with the B0 s meson. The second network combines the kaon charges to assign the B0 s flavour and estimates the probability of a wrong assignment. The algorithm is calibrated using data corresponding to an integrated luminosity of 3 fb−1 collected by the LHCb experiment in proton-proton collisions at 7 and 8 TeV centre-of-mass energies. The calibration is performed in two ways: by resolving the B0 s -B0 s flavour oscillations in B0 s → D− s π + decays, and by analysing flavour-specific B∗ s2 (5840)0→ B+K− decays. The tagging power measured in B0 s → D− s π + decays is found to be (1.80 ± 0.19 (stat) ± 0.18 (syst))%, which is an improvement of about 50% compared to a similar algorithm previously used in the LHCb experiment.