2025/12/10 by R. Aaij, A. S. W. Abdelmotteleb, Aaij, R. +2357 · 2 voices
Physics and Astronomy · #FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #hep-ex
paper · pdf · doi:10.48550/arxiv.2512.09288
arxiv published 2025/12/10 · arxiv updated 2026/04/23
The decay B± → K0S π±, with a CP asymmetry expected to be close to zero in the Standard Model, is theoretically clean and sensitive to potential new physics. An analysis of the decays B± → K0S π± and B± → K0S K± is performed using proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb-1. The \CP asymmetries are determined to be \cal ACP(B± → K0S π±)=-0.028± 0.009± 0.009 and \cal ACP(B± → K0S K±)=0.118± 0.062 ± 0.031, and the branching fraction ratio is measured to be \cal B(B± → K0S K±)/\cal B(B± → K0S π±)=0.055± 0.004 ± 0.002, where the first uncertainties are statistical and the second are systematic. These results are the most precise measurements of these quantities to date. A search for the rare decay Bc± → K0S K± is also performed. No significant signal is observed, and the upper limit on the product of the branching fraction ratio \cal B(Bc± → K0S K±)/\cal B(B± → K0S π±) and the fragmentation-fraction ratio fc/fu is set to be 0.015 (0.016) at the 90% (95%) confidence level.