Searches for Lepton Number Violation and Resonances in K±→πμμ Decays

Batley, NA48/2 collaboration: J. R.; Kalmus, G.; Lazzeroni, C.; Munday, D. J.; Slater, M. W.; Wotton, S. A.; Arcidiacono, R.; Bocquet, G.; Cabibbo, N.; Ceccucci, A.; Cundy, D.; Falaleev, V.; Fidecaro, M.; Gatignon, L.; Gonidec, A.; Kubischta, W.; Maier, A.; Massri, K.; Norton, A.; Patel, M.; Peters, A.; Balev, S.; Frabetti, P. L.; Gersabeck, E.; Goudzovski, E.; Hristov, P.; Kekelidze, V.; Kozhuharov, V.; Litov, L.; Madigozhin, D.; Molokanova, N.; Polenkevich, I.; Potrebenikov, Y. u.; Stoynev, S.; Zinchenko, A.; Monnier, E.; Swallow, E.; Winston, R.; Rubin, P.; Walker, A.; Baldini, W.; Cotta Ramusino, A.; Dalpiaz, P.; Damiani, C.; Fiorini, M.; Gianoli, A.; Martini, M.; Petrucci, F.; Savrié, M.; Scarpa, M.; Wahl, H.; Bizzeti, A.; Lenti, M.; Veltri, M.; Calvetti, M.; Celeghini, E.; Iacopini, E.; Ruggiero, G.; Behler, M.; Eppard, K.; Kleinknecht, K.; Marouelli, P.; Masetti, L.; Moosbrugger, U.; Morales Morales, C.; Renk, B.; Wache, M.; Wanke, R.; Winhart, A.; Coward, D.; Dabrowski, A.; Fonseca Martin, T.; Shieh, M.; Szleper, M.; Velasco, M.; Wood, M. D.; Cenci, P.; Pepe, M.; Petrucci, M. C.; Anzivino, G.; Imbergamo, E.; Nappi, A.; Piccini, M.; Raggi, M.; Valdata Nappi, M.; Fantechi, R.; Collazuol, G.; Dilella, L.; Lamanna, Gianluca; Mannelli, I.; Michetti, A.; Costantini, Flavio; Doble, N.; Fiorini, L.; Giudici, Sergio; Pierazzini, G.; Sozzi, MARCO STANISLAO; Venditti, S.; Bloch Devaux, B.; Cheshkov, C.; Chèze, J. B.; De Beer, M.; Derré, J.; Marel, G.; Mazzucato, E.; Peyaud, B.; Vallage, B.; Holder, M.; Ziolkowski, M.; Biino, C.; Cartiglia, N.; Marchetto, F.; Bifani, S.; Clemencic, M.; Goy Lopez, S.; Dibon, H.; Jeitler, M.; Markytan, M.; Mikulec, I.; Neuhofer, G.; Widhalm, L.

doi:10.1016/j.physletb.2017.03.029

The NA48/2 experiment at CERN collected a large sample of charged kaon decays to final states with multiple charged particles in 2003--2004. A new upper limit on the rate of the lepton number violating decay $K^pm opi^mpmu^pmmu^pm$ is reported: $mathcalB(K^pm opi^mpmu^pmmu^pm)<8.6 imes 10^-11$ at 90% CL. Searches for two-body resonances $X$ in $K^pm opimumu$ decays (such as heavy neutral leptons $N_4$ and inflatons $chi$) are also presented. In the absence of signals, upper limits are set on the products of branching fractions $mathcalB(K^pm omu^pmN_4)mathcalB(N_4 opimu)$ and $mathcalB(K^pm opi^pmX)mathcalB(X omu^+mu^-)$ for ranges of assumed resonance masses and lifetimes. The limits are in the $(10^-11,10^-9)$ range for resonance lifetimes below 100 ps.