New measurement of the K+- -> pi+- mu+ mu- decay

Batley, 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.; Norton, A.; Maier, A.; Patel, M.; Peters, A.; Balev, S.; Frabetti, P. L.; Goudzovski, E.; Hristov, P.; Kekelidze, V.; Kozhuharov, V.; Litov, L.; Madigozhin, D.; Marinova, E.; 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, Andrea; 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.; Cerri, C.; Fantechi, R.; Collazuol, G.; Dilella, L.; Lamanna, G.; Mannelli, I.; Michetti, A.; Costantini, F.; Doble, N.; Fiorini, L.; Giudici, S.; Pierazzini, G.; Sozzi, M.; 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.2011.01.042

A sample of 3120 K ± → π ± μ+ μ− decay candidates with (3.3 ± 0.7)% background contamination has been collected by the NA48/2 experiment at the CERN SPS, allowing a detailed study of the decay properties. The branching ratio was measured to be BR = (9.62 ± 0.25) × 10−8 . The form factor W(z), where z = ( M(μμ) / M(K) )^2 , was parameterized according to several models. In particular, the slope of the linear form factor W(z) = W0 (1 + δ z) was measured to be δ = 3.11 ± 0.57. Upper limits of 2.9 × 10^-2 and 2.3 × 10^-2 on possible charge asymmetry and forward-backward asymmetry were established at 90% CL. An upper limit BR( K ± → π ∓ μ± μ± ) < 1.1 × 10^-9 was established at 90% CL for the rate of the lepton number violating decay.

New measurement of the K+- -> pi+- mu+ mu- decay / J. R., B., G., K., C., L., D. J., M., M. W., S., S. A., W., R., A., G., B., N., C., A., C., D., C., V., F., M., F., L., G., A., G., W., K., A., N., A., M., M., P., A., P., et al.. - In: PHYSICS LETTERS. SECTION B. - ISSN 0370-2693. - STAMPA. - 697:2(2011), pp. 107-115. [10.1016/j.physletb.2011.01.042]