Search for CP violation in Ds+→KS0K−π+π+ decays using triple and quadruple products

Abstract

We perform the first search for CP violation in $D_{\left(s\right)}^{+}\to K_S^0{K}^{-}{\pi }^{+}{\pi }^{+}$ decays. We use a combined data set from the Belle and Belle II experiments, which study e⁺e⁻ collisions at center-of-mass energies at or near the Υ(4S) resonance. We use 980 fb⁻¹ of data from Belle and 428 fb⁻¹ of data from Belle II. We measure six CP-violating asymmetries that are based on triple products and quadruple products of the momenta of final-state particles, and also the particles’ helicity angles. We obtain a precision at the level of 0.5% for $D^{+}\to K_S^0{K}^{-}{\pi }^{+}{\pi }^{+}$ decays, and better than 0.3% for $D_s^{+}\to K_S^0{K}^{-}{\pi }^{+}{\pi }^{+}$ decays. No evidence of CP violation is found. Our results for the triple-product asymmetries are the most precise to date for singly-Cabibbo-suppressed D⁺ decays. Our results for the other asymmetries are the first such measurements performed for charm decays.