The first observation of about 2000 candidates, with a background contamination below 3%, of the rare decay K± → φ± φ0e+e- is reported by the NA48/2 experiment. The preliminary branching ratio in the full kinematic region is obtained to be: B(K± → φ±φ0e+e-) = (4.06 ± 0.17) • 10-6 by analyzing the data collected in 2003. A sample of 4.687×106 K± → φ±φ0D,decay candidates with a negligible background contamination collected in 2003-04 is analyzed to search for the dark photon (A') via the decay chain K± → φ± φ0, φ0 → γA',A'→e+e-. No signal is observed, and preliminary limits in the plane dark photon mixing parameter η2 vs. its mass mA' are reported.
NA48/2 studies of rare decays / Raggi, M., Anzivino, G., Arcidiacono, R., Baldini, W., Balev, S., Batley, J.R., Behler, M., Bifani, S., Biino, C., Bizzeti, A., Bloch-Devaux, B., Bocquet, G., Cabibbo, N., Calvetti, M., Cartiglia, N., Ceccucci, A., Cenci, P., Cerri, C., Cheshkov, C., Cheze, J.B., et al.. - In: IL NUOVO CIMENTO C. - ISSN 2037-4909. - 38:4(2015), pp. N/A-N/A. [10.1393/ncc/i2015-15132-0]
NA48/2 studies of rare decays
Bizzeti A.;
2015
Abstract
The first observation of about 2000 candidates, with a background contamination below 3%, of the rare decay K± → φ± φ0e+e- is reported by the NA48/2 experiment. The preliminary branching ratio in the full kinematic region is obtained to be: B(K± → φ±φ0e+e-) = (4.06 ± 0.17) • 10-6 by analyzing the data collected in 2003. A sample of 4.687×106 K± → φ±φ0D,decay candidates with a negligible background contamination collected in 2003-04 is analyzed to search for the dark photon (A') via the decay chain K± → φ± φ0, φ0 → γA',A'→e+e-. No signal is observed, and preliminary limits in the plane dark photon mixing parameter η2 vs. its mass mA' are reported.
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