Measurement of ∆ACP using semileptonic charm baryons decays at LHCb

In this thesis work it is calculated the difference between the CP asymmetries in the decay channels Λ+ c → p + K+ + K− and Λ+ c → p +π+ +π− of the charmed baryon Λ+ c. The presented analysis uses Run 2 data, collected by the LHCb experiment in 2016, obtained from proton-proton collisions at center-of-mass energies of √s = 13 TeV, with an integrated luminosity of 0.82 fb−1 and magnet down polarity. This analysis was already performed during Run 1 and has measured ∆Awgt CP = (0.30 ±0.91 ±0.61)%. This work aims to futher study this decays with the higher statistics of Run 2. From the data sample the two raw asymmetries Araw(pK+K−) and Araw(pπ+π−) are measured. However, nuisance asymmetries, such as the production asymmetry of the charm baryon Λ+ c and the detection asymmetry of the proton can bias the raw asymmetry. The events referring to Λ+ c → p+π++π− channel are weighted so that the kinematics of Λ+ c and p match the kinematics of the same particles in the other channel, Λ+ c → p+K++K−. The following results are obtained, Araw(pK+K−)=(2.4±0.8)\%, Awgt raw(pπ+π−)=(2.6±0.5)\%. The weighting procedure ensures that nuisance asymmetries contained in Araw(pK+K−) and Awgt raw(pπ+π−) can be assumed equal. They cancel out when the difference Araw(pK+K−)−Awgt raw(pπ+π−) is calculated, so that it corresponds to the difference between the two CP asymmetries in the decay, i.e. Araw(pK+K−)−Awgt ACP(pK+K−)−Awgt CP(pπ+π−) ≡ ∆Awgt CP. The estimated value is ∆Awgt CP =(−0.2±0.9)%, The results are compatible with the hypothesis of CP conservation.