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PoS(HQL 2016)033

Recent results from NA48/2 and NA62 Experiments at CERN

N. Lurkin, 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, M. De Beer, H. Danielsson, G. Dellacasa, J. Derré, D. Di Filippo, H. Dibon, L. DiLella, N. Doble, V. Duk, J. Engelfried, K. Eppard, V. Falaleev, R. Fantechi, M. Fidecaro, L. Fiorini, T. Fonseca Martin, M. Fiorini, 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, Y. 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, on behalf of the NA48/2 Collaboration, on behalf of the NA62 Collaboration

in XIII International Conference on Heavy Quarks and Leptons

Contribution: pdf

Abstract

The NA48/2 and \nark experiments at the CERN SPS collected a large sample of charged kaon decays in
flight. \nark was running in 2007--08 with a highly efficient minimum bias trigger for decays into electrons. A
preliminary measurement of the electromagnetic transition form factor slope of the \(\pi^0\) from \(1.05\times 10^6} fully
reconstructed \(\pi^0\) Dalitz decays is presented. The obtained value \(a = (3.70 \pm 0.53_\text{stat} \pm
0.36_\text{syst})\times 10^{-2}\) represents a \(5.8\sigma\) observation of a non-zero slope in the time-like
region of momentum transfer.
An upper limit on the rate of a lepton number violating decay \(K^\pm\to\pi^\mp\mu^\pm\mu^\pm\) is
reported from \(\sim 1.6\times 10^11 K^\pm\) decays at NA48/2 in 2003--04: \(\mathcal{B} < 8.6\times 10^{-11}\) at \(90\%\) CL.
Searches for heavy sterile neutrino \(N_4\) and inflaton \(\chi\) resonances in \(K^\pm\to\pi\mu\mu\) decays are
reported. No signal is observed and 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 \(\left(10^{-10}-10^{-9}\right)\) for resonance lifetimes up to \(100 \text{ps}\).
The result of a search for dark photon with the same sample of decays is also reported. In the absence of observed
signal, the limits on the mixing parameter \(\varepsilon^2\) in the range \(\left(9-70\right) \text{MeV}/c^2\) are improved.