Kaon experiments at CERN: recent results and prospects

Abstract

The NA48/2 and NA62-$R_K$ experiments at the CERN SPS collected large samples of charged kaon decays in flight in 2003--07. The data analysis is still on-going (with over 20 publications produced so far); the recent results from these experiments are presented. A new upper limit on the rate of a lepton number violating decay $K^{\pm }\to {\pi }^{\mp }{\mu }^{\pm }{\mu }^{\pm }$ is reported: $\mathcal{B}<8.6\times 10^{-11}$ at 90\% CL. Searches for heavy sterile neutrino $N_4$ and neutral scalar resonances ($\chi$) in $K^{\pm }\to \pi \mu \mu$ decays are reported. Upper limits on the products $\mathcal{B}(K^{\pm }\to {\mu }^{\pm }{N}_4)\mathcal{B}(N_4\to {\pi }^{\mp }{\mu }^{\pm })$ and $\mathcal{B}(K^{\pm }\to {\pi }^{\pm }\chi )\mathcal{B}(\chi \to {\mu }^{+}{\mu }^{-})$ are set in the range $10^{-10}$ to $10^{-9}$ for resonance lifetimes up to 100~ps. A preliminary measurement of the electromagnetic transition form factor slope of the ${\pi }^0$ from $1.05\times 10^6$ fully reconstructed ${\pi }^0\to \gamma e^{+}{e}^{-}$ decays is presented: the obtained result $a=(3.70\pm 0.53_{\text{stat}}\pm 0.36_{\text{syst}})\times 10^{-2}$ represents the first observation of a non-zero slope in the time-like region of momentum transfer.

Contribution to proceedings of MESON 2016 conference (Krakow, 2-6 June 2016)

References in corpus (2)

• Search for direct CP violating charge asymmetries in $K^{\pm }\to {\pi }^{\pm }{\pi }^{+}{\pi }^{-}$ and $K^{\pm }\to {\pi }^{\pm }{\pi }^0{\pi }^0$ decays
• New measurement of the K+- --> pi+-mu+mu- decay

Cited by in corpus (1)

• Measurement of the pi^0 -> e^+e^-gamma Dalitz decay at the Mainz Microtron