Kaon experiments at CERN: recent results and prospects


The NA48/2 and NA62-RKR_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±πμ±μ±K^\pm\to\pi^\mp\mu^\pm\mu^\pm is reported: B<8.6×1011\mathcal{B} < 8.6\times 10^{-11} at 90\% CL. Searches for heavy sterile neutrino N4N_4 and neutral scalar resonances (χ\chi) in K±πμμK^\pm\to\pi\mu\mu decays are reported. Upper limits on the products B(K±μ±N4)B(N4πμ±)\mathcal{B}(K^\pm\to\mu^\pm N_4)\mathcal{B}(N_4\to\pi^\mp\mu^\pm) and B(K±π±χ)B(χμ+μ)\mathcal{B}(K^\pm\to\pi^\pm \chi)\mathcal{B}(\chi\to\mu^+\mu^-) are set in the range 101010^{-10} to 10910^{-9} for resonance lifetimes up to 100~ps. A preliminary measurement of the electromagnetic transition form factor slope of the π0\pi^0 from 1.05×1061.05\times 10^6 fully reconstructed π0γe+e\pi^0\to\gamma e^+e^- decays is presented: the obtained result a=(3.70±0.53stat±0.36syst)×102a = (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.Comment: Contribution to proceedings of MESON 2016 conference (Krakow, 2-6 June 2016

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