Abstract
A first search for CP violation in the Cabibbo-suppressed {{{varXi }} ^+_{c}} rightarrow {p} {{K} ^-} {{pi } ^+} decay is performed using both a binned and an unbinned model-independent technique in the Dalitz plot. The studies are based on a sample of proton-proton collision data, corresponding to an integrated luminosity of 3.0,text {fb} ^{-1} , and collected by the LHCb experiment at centre-of-mass energies of 7 and 8,text {TeV} . The data are consistent with the hypothesis of no CP violation.
Highlights
The non-invariance of fundamental interactions under the combination of charge conjugation and parity transformation, known as CP violation (CP V ), is a key requirement for the generation of the baryon–antibaryon asymmetry in the early Universe [1,2,3]
The statistical powers of the two methods are found to be comparable. Both methods are sensitive to a 5% CP asymmetry in the K ∗(892) and Δ(1232) resonance regions with 3 and 5 sigma significances that would be observed in 69% and 10% of the cases for the k-nearest neighbour method (kNN) method and 17% and 10% of the cases for the SCP method, respectively
The measured p-values using a χ 2 test are larger than 32%, consistent with no evidence for CP V
Summary
The non-invariance of fundamental interactions under the combination of charge conjugation and parity transformation, known as CP violation (CP V ), is a key requirement for the generation of the baryon–antibaryon asymmetry in the early Universe [1,2,3]. In contrast to SCS decays, in Cabibbo-favoured (CF) charm-quark transitions, such as Λ+c → pK −π + decays, there is only one dominant amplitude in the SM, resulting in no CP-violating effects. There is presently no successful method for computing decay amplitudes in multi-body charm decays, which could provide reliable predictions on how the CP asymmetries vary over the phase space of the decay. This situation favours a model-independent approach, which looks for differences between multivariate density distributions for baryons and antibaryons. In this article searches for CP V are performed through a direct comparison between the Dalitz plots of Ξc+ and Ξc− decays using a binned significance (SCP ) method [37] and an unbinned k-nearest neighbour method (kNN) [38,39,40,41], both of which are model independent
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