Search for the doubly Cabibbo-suppressed decays and
arXiv:2609.08266
Abstract
We present the first search for the doubly Cabibbo-suppressed decays and using an collision data sample corresponding to an integrated luminosity of 20.3 fb, collected at a center-of-mass energy of 3.773 GeV with the Beijing Spectrometer III (BESIII) detector at the Beijing Electron-Positron Collider II (BEPCII). No significant signals are observed, and the upper limits on their decay branching fractions are set to be and at the 90% confidence level, respectively. By combining these results with the world-average branching fractions of the corresponding Cabibbo-favored decays, upper limits at the 90% confidence level are obtained on the ratios of doubly Cabibbo-suppressed to Cabibbo-favored branching fractions. The limits are determined to be and for and , respectively, where denotes the Cabibbo mixing angle.
12 pages, 5 figures