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Register a new userSearch for $C!P$ violation in $Lambda^0_b to p K^-$ and $Lambda^0_b to p pi^-$ decays
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A search for $C!P$ violation in $Lambda^0_b to p K^-$ and $Lambda^0_b to p pi^-$ decays is presented using a sample of $pp$ collisions collected with the LHCb detector and corresponding to an integrated luminosity of 3.0 fb$^{-1}$. The $C!P$-violating asymmetries are measured to be $A_{mathrm{CP}}^{pK^-} = -0.020 pm 0.013pm 0.019$ and $A_{mathrm{CP}}^{ppi^-} = -0.035 pm 0.017 pm 0.020 $, and their difference $A_{mathrm{CP}}^{pK^-}-A_{mathrm{CP}}^{ppi^-} = 0.014 pm 0.022 pm 0.010$, where the first uncertainties are statistical and the second systematic. These are the most precise measurements of such asymmetries to date.
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A search for $C!P$ violation in the decay $Lambda^0_b to p K^- mu^+ mu^-$ is presented. This decay is mediated by flavour-changing neutral-current transitions in the Standard Model and is potentially sensitive to new sources of $C!P$ violation. The study is based on a data sample of proton-proton collisions recorded with the LHCb experiment, corresponding to an integrated luminosity of $3$ $mathrm{fb}^{-1}$. The $Lambda^0_b to p K^- mu^+ mu^-$ decay is observed for the first time, and two observables that are sensitive to different manifestations of $C!P$ violation are measured, $Deltamathcal{A}_{C!P} equiv mathcal{A}_{C!P}(Lambda^0_b to p K^- mu^+ mu^-)-mathcal{A}_{C!P}(Lambda^0_bto pK^- J/psi)$ and $a_{C!P}^{widehat{T}-odd}$, where the latter is based on asymmetries in the angle between the $mu^+mu^-$ and $p K^-$ decay planes. These are measured to be $Deltamathcal{A}_{C!P} = (-3.5 pm 5.0(stat) pm 0.2(syst))times 10^{-2}$, $a_{C!P}^{widehat{T}-odd} = (1.2 pm 5.0(stat) pm 0.7(syst))times 10^{-2}$, and no evidence for $C!P$ violation is found.
A search for $C!P$ violation in the $Lambda_b^0 to p pi^- pi^+ pi^-$ decay is performed using LHCb data corresponding to an integrated luminosity of 6.6$,fb^{-1}$ collected in $pp$ collisions at centre-of-mass energies of 7, 8 and 13$,Tekern -0.1em V$. The analysis uses both triple product asymmetries and the unbinned energy test method. The highest significances of $C!P$ asymmetry are 2.9 standard deviations from triple product asymmetries and 3.0 standard deviations for the energy test method. Once the global $p$-value is considered, all results are consistent with no $C!P$ violation. Parity violation is observed at a significance of $5.5$ standard deviations for the triple product asymmetry method and $5.3$ standard deviations for the energy test method.
Using $pp$ collisions corresponding to 3$,text{fb}^{-1}$ integrated luminosity, recorded by the LHCb experiment at centre-of-mass energies of 7 and 8$,text{TeV}$, the ratio of branching fractions begin{align*} mathcal{B}(Lambda^0_b!topsi(2S) Lambda )/mathcal{B}(Lambda^0_b!to J/psi Lambda)= 0.513 pm 0.023, (text{stat}) pm 0.016 , (text{syst}) pm 0.011, (mathcal{B}) end{align*} is determined. The first uncertainty is statistical, the second is systematic and the third is due to the external branching fractions used.
Three-body $B^+to p overline p K^+$ and $B^+to p overline p pi^+$ decays are studied using a data sample corresponding to an integrated luminosity of 3.0 $fb^{-1}$ collected by the LHCb experiment in proton-proton collisions at center-of-mass energies of $7$ and $8$ TeV. Evidence of CP violation in the $B^+to p overline p K^+$ decay is found in regions of the phase space, representing the first measurement of this kind for a final state containing baryons. Measurements of the forward-backward asymmetry of the light meson in the $poverline p$ rest frame yield $A_{mathrm{FB}}(p overline p K^+,~m_{poverline p}<2.85mathrm{,Gekern -0.1em V!/}c^2)=0.495pm0.012~(mathrm{stat})pm0.007~(mathrm{syst})$ and $A_{mathrm{FB}}(poverline p pi^+,~m_{poverline p}<2.85mathrm{,Gekern -0.1em V!/}c^2)=-0.409pm0.033~(mathrm{stat})pm0.006~(mathrm{syst})$. In addition, the branching fraction of the decay $B^+tokern 0.1emoverline{kern -0.1emLambda}(1520)p$ is measured to be $mathcal{B}(B^+ to kern 0.1emoverline{kern -0.1emLambda}(1520)p)=(3.15pm0.48~(mathrm{stat})pm0.07~(mathrm{syst})pm0.26~(mathrm{BF}))times 10^{-7}$, where BF denotes the uncertainty on secondary branching fractions.
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