Search for $J/ψ\rightarrow K^{0}_{S}K^{0}_{S}$ and $ψ(3686)\rightarrow K^{0}_{S}K^{0}_{S}$

TL;DR

This study searches for CP-violating decays $J/\psi\rightarrow K^{0}_{S}K^{0}_{S}$ and $\psi(3686)\rightarrow K^{0}_{S}K^{0}_{S}$ using BESIII data to test Bose symmetry, CP/CPT, and EPR locality. A semiblind analysis reconstructs $K^{0}_{S}\to \pi^{+}\pi^{-}$ with vertex and 4C kinematic constraints, estimating backgrounds via large MC samples; no significant signal is observed. The 90% CL upper limits are $\mathcal{B}(J/\psi\rightarrow K^{0}_{S}K^{0}_{S})<4.7\times10^{-9}$ and $\mathcal{B}(\psi(3686)\rightarrow K^{0}_{S}K^{0}_{S})<1.1\times10^{-8}$, improving previous bounds by factors of ~3 and ~100, respectively. These results constrain CPT-violating parameters and EPR-related expectations, with $|\omega|$ limits of $|(4.91\pm0.14)\times10^{-3}|$ and $|(1.44\pm0.04)\times10^{-2}|$ for the two decays.

Abstract

Using data samples of $(10087\pm 44)\times10^{6}$ $J/ψ$ events and $(2712.4\pm 14.3)\times10^{6}$ $ψ(3686)$ events collected with the BESIII detector at the BEPCII collider, we search for the CP violating decays $J/ψ\rightarrow K^{0}_{S}K^{0}_{S}$ and $ψ(3686)\rightarrow K^{0}_{S}K^{0}_{S}$. No significant signals are observed over the expected background yields. The upper limits on their branching fractions are set as $\mathcal{B}(J/ψ\rightarrow K^{0}_{S}K^{0}_{S}) <4.7\times 10^{-9}$ and $\mathcal{B}(ψ(3686)\rightarrow K^{0}_{S}K^{0}_{S}) <1.1\times 10^{-8}$ at the 90% confidence level. These results improve the previous limits by a factor of three for $J/ψ\rightarrow K^{0}_{S} K^{0}_{S}$ and two orders of magnitude for $ψ(3686)\rightarrow K^{0}_{S} K^{0}_{S}$.

Figures (2)

• Figure 1: Two-dimensional $K^{0}_{S}$ momentum distributions for (a) $J/\psi\rightarrow K^{0}_{S}K^{0}_{S}$ and (b) $\psi(3686)\rightarrow K^{0}_{S}K^{0}_{S}$. The black and blue circles correspond to $3 \sigma$ and $5 \sigma$ determined from the individual signal MC samples, respectively.
• Figure 2: The normalized likelihood distributions for (a) $J/\psi\rightarrow K^{0}_{S}K^{0}_{S}$ and (b) $\psi(3686)\rightarrow K^{0}_{S}K^{0}_{S}$. The blue arrows indicate the 90% CL upper limits.