Search for heavy neutral lepton production in K+ decays

A search for heavy neutral lepton production in K + decays using a data sample collected with a minimum bias trigger by the NA62 experiment at CERN in 2015 is reported. Upper limits at the 10−7 to 10−6 level are established on the elements of the extended neutrino mixing matrix |Ue4| 2 and |Uμ4| 2 for heavy neutral lepton mass in the ranges 170–448 MeV/c2 and 250–373 MeV/c2, respectively. This improves on the previous limits from HNL production searches over the whole mass range considered for |Ue4|2 and above 300 MeV/c2 for |Uμ4|2

Determination of the ππ scattering lenghts from K^± -->π^±π⁰π⁰ decays

The NA48/2 experiment at the CERN SPS has collected more than 100 million fully reconstructed K±-->π±π0π0 decays. The preliminary analysis of a third of the data shows a sudden change of slope of the π0π0 invariant mass distribution in the region around 2m, where m is the mass of the charged pion. This anomaly, which was never observed before, is interpreted as a cusp-like effect resulting mainly from the contribution of the K±-->π±π0π0 decay amplitude through π+π- -->π0π0 charge exchange. The study of this phenomenon is a new and potentially more accurate method to measure a0-a2, the difference of the I = 0 and I = 2 S-wave scattering lengths. The colloquium will consist of two parts: the experiment, given by Italo Mannelli, and the theory by Nicola Cabibbo. Organiser(s): Luis Alvarez-Gaume / PH-THNote: * Tea & coffee will be served at 16.00 hrs.</i

Festkolloquium for Heinrich Wahl

Heinrich Wahl's scientific contribution will be celebrated at CERN

Search for heavy neutrinos in K+→μ+νμK^+ \rightarrow \mu^+ \nu_{\mu} decays

International audienceThe NA62 experiment recorded a large sample of K+→μ+νμ decays in 2007. A peak search has been performed in the reconstructed missing mass spectrum. In the absence of a signal, limits in the range 2×10−6 to 10−5 have been set on the squared mixing matrix element |Uμ4|2 between muon and heavy neutrino states, for heavy neutrino masses in the range 300–375 MeV/ c2 . The result extends the range of masses for which upper limits have been set on the value of |Uμ4|2 in previous production search experiments

Measurement of the polarization of the Xi0 (anti-Xi0) hyperon beam by the NA48/1 experiment

A total of 368415 Xi(0) --> Lambda Xi(0) and 31 171 (Xi(0)) over bar --> (Lambda) over bar pi(0) were selected from data recorded in the NA48/1 experiment during 2002 data taking. From this sample, the polarization of Xi(0) and (Xi(0)) over bar hyperons was measured to be P(Xi 0) = -0.102 +/- 0.012(stat) +/- 0.008(syst) and P((Xi 0) over bar) = -0.01 +/- 0.04(stat) 0.008(syst). The dependence of P(Xi 0) on the Xi(0) transverse momentum with respect to the primary proton beam is also presented. With the same data sample. the ratio of (Xi(0)) over bar and Xi(0) fluxes in proton collisions at 400 GeV/c oil a beryllium target was measure

Determination of the relative decay rate KS -> πeν / KL -> πeν

The decay rate of K-S -> pi ev relative to the rate of K-L -> pi rev has been measured by the NA48 Collaboration in a neutral kaon beam originating from 400 GeV proton-Be interactions at the CERN SPS. The result is 0.993 +/- 0.026(stat) +/- 0.022(syst), compatible with I in agreement with the Standard Model prediction at tree level. It implies B R (K-S -> pi ev) = (7.05 +/- 0.18(stat) +/- 0.16(syst)) X 10(-4)