Szczegóły publikacji

The first observation of the decay $B^+ \to p \bar{\Lambda}$ is presented using proton-proton collision data collected by the LHCb experiment between 2016 and 2018 at a center-of-mass energy of $13\,\mathrm{TeV}$, corresponding to an integrated luminosity of $5.4\,\mathrm{fb}^{-1}$. The signal significance exceeds seven standard deviations. Using the $B^+ \to K_S^0 \pi^+$ decay as a normalization channel, the branching fraction is measured and combined with previous LHCb results based on data collected at 7 and 8\,TeV in 2011 and 2012, yielding \[ \mathcal{B}(B^+ \to p \bar{\Lambda}) = (1.24 \pm 0.17 \pm 0.05 \pm 0.03)\times 10^{-7}, \] where the first uncertainty is statistical, the second is systematic, and the third comes from the uncertainty on the branching fraction of the normalization channel. The $B^+ \to p \bar{\Lambda}$ weak decay parameter is measured to be \[ \alpha_B = 0.87^{+0.26}_{-0.29} \pm 0.09, \] indicating the presence of comparable S-wave and P-wave decay amplitudes.