Measurement of the branching fraction and search for CP violation in $D^0\rightarrow K^0_S\,K^0_S\,\pi^+\pi^-$ decays at Belle

TL;DR

This study measures the decay rate and searches for CP violation in a specific D0 meson decay mode using Belle data, finding no significant CP violation but providing precise branching fraction measurement.

Contribution

First measurement of the branching fraction and CP asymmetries in D0→K0S K0S π+π− decays at Belle, with improved precision and no evidence of CP violation.

Findings

Branching fraction measured as (4.79 ± 0.08 (stat) ± 0.10 (syst) ± 0.31 (norm))×10^{-4}

CP asymmetry A_CP found to be approximately -2.51% with uncertainties

No evidence of CP violation observed in the decay channel.

Abstract

We measure the branching fraction for the Cabibbo-suppressed decay $D^0\rightarrow K^0_S\,K^0_S\,\pi^+\pi^-$ and search for $CP$ violation via a measurement of the $CP$ asymmetry $A_{\rm CP}$ as well as the $T$-odd triple-product asymmetry $a^T_{\rm CP}$. We use 922 fb$^{-1}$ of data recorded by the Belle experiment, which ran at the KEKB asymmetric-energy $e^+e^-$ collider. The branching fraction is measured relative to the Cabibbo-favored normalization channel $D^0\rightarrow K^0_S\,\pi^+\pi^-$; the result is $\mathcal{B}(D^0\rightarrow K^0_S\,K^0_S\,\pi^+\pi^-) = [4.79 \pm 0.08\,({\rm stat}) \pm 0.10\,({\rm syst}) \pm 0.31\,({\rm norm})]\times 10^{-4}$, where the first uncertainty is statistical, the second is systematic, and the third is from uncertainty in the normalization channel. We also measure $A_{\rm CP} = [-2.51\,\pm 1.44\,({\rm stat})\,^{+0.11}_{-0.10}\,({\rm syst})]\%$, and $a^T_{\rm CP} = [-1.95\,\pm 1.42\,({\rm stat})\,^{+0.14}_{-0.12}\,({\rm syst})]\%$. These results show no evidence of CP violation.