Kaon experiments at CERN: recent results and prospects

School of Physics and Astronomy, University of Birmingham, B15 2TT, United Kingdom

^* For the NA48/2 and NA62 collaborations: F. Ambrosino, A. Antonelli, G. Anzivino, R. Arcidiacono,W. Baldini, S. Balev, J.R. Batley, M. Behler, S. Bifani, C. Biino, A. Bizzeti, B. Bloch-Devaux, G. Bocquet, V. Bolotov, F. Bucci, N. Cabibbo, M. Calvetti, N. Cartiglia, A. Ceccucci, P. Cenci, C. Cerri, C. Cheshkov, J.B. Chèze, M. Clemencic, G. Collazuol, F. Costantini, A. Cotta Ramusino, D. Coward, D. Cundy, A. Dabrowski, G. D’Agostini, P. Dalpiaz, C. Damiani, H. Danielsson, M. De Beer, G. Dellacasa, J. Derré, H. Dibon, D. Di Filippo, L. DiLella, N. Doble, V. Duk, J. Engelfried, K. Eppard, V. Falaleev, R. Fantechi, M. Fidecaro, L. Fiorini, M. Fiorini, T. Fonseca Martin, P.L. Frabetti, A. Fucci, S. Gallorini, L. Gatignon, E. Gersabeck, A. Gianoli, S. Giudici, A. Gonidec, E. Goudzovski, S. Goy Lopez, E. Gushchin, B. Hallgren, M. Hita-Hochgesand, M. Holder, P. Hristov, E. Iacopini, E. Imbergamo, M. Jeitler, G. Kalmus, V. Kekelidze, K. Kleinknecht, V. Kozhuharov, W. Kubischta, V. Kurshetsov, G. Lamanna, C. Lazzeroni, M. Lenti, E. Leonardi, L. Litov, D. Madigozhin, A. Maier, I. Mannelli, F. Marchetto, G. Marel, M. Markytan, P. Marouelli, M. Martini, L. Masetti, P. Massarotti, E. Mazzucato, A. Michetti, I. Mikulec, M. Misheva, N. Molokanova, E. Monnier, U. Moosbrugger, C. Morales Morales, M. Moulson, S. Movchan, D.J. Munday, M. Napolitano, A. Nappi, G. Neuhofer, A. Norton, T. Numao, V. Obraztsov, V. Palladino, M. Patel, M. Pepe, A. Peters, F. Petrucci, M.C. Petrucci, B. Peyaud, R. Piandani, M. Piccini, G. Pierazzini, I. Polenkevich, I. Popov, Yu. Potrebenikov, M. Raggi, B. Renk, F. Retière, P. Riedler, A. Romano, P. Rubin, G. Ruggiero, A. Salamon, G. Saracino, M. Savrié, M. Scarpa, V. Semenov, A. Sergi, M. Serra, M. Shieh, S. Shkarovskiy, M.W. Slater, M. Sozzi, T. Spadaro, S. Stoynev, E. Swallow, M. Szleper, M. Valdata-Nappi, P. Valente, B. Vallage, M. Velasco, M. Veltri, S. Venditti, M. Wache, H. Wahl, A. Walker, R. Wanke, L. Widhalm, A. Winhart, R. Winston, M.D. Wood, S.A. Wotton, O. Yushchenko, A. Zinchenko, M. Ziolkowski. Email: eg@hep.ph.bham.ac.uk; supported by ERC Starting Grant 336581.

Published online: 29 November 2016

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^± →π^∓μ^±μ^± is reported: B< 8.6×10⁻¹¹ at 90% CL. Searches for heavy sterile neutrino N₄ and neutral scalar resonances (χ) in K^± → πμμ decays are reported. Upper limits on the products B(K^± → μ^±N₄)B(N₄ → π^∓μ^±) and B(K^± → π^±χ)B(χ → μ⁺μ⁻) 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 π⁰ from 1.05 × 10⁶ fully reconstructed π⁰ → γe⁺e⁻ decays is presented: the obtained result a = (3:70 ± 0:53_stat ± 0:36_syst) × 10⁻² represents the first observation of a non-zero slope in the time-like region of momentum transfer.