0000000000216822
AUTHOR
M. Noy
Search for heavy neutrinos at the NA48/2 and NA62 experiments at CERN
© The Authors, published by EDP Sciences. The NA48/2 experiment at CERN has collected large samples of charged kaons decaying into a pion and two muons for the search of heavy nuetrinos. In addition, its successor NA62 has set new limits on the rate of charged kaon decay into a heavy neutral lepton (HNL) and a lepton, with = e, µ, using the data collected in 2007 and 2015. New limits on heavy neutrinos from kaon decays into pions, muons and positrons are presented in this report.
Search for K+→ π+νν¯ at NA62
Flavour physics is one of the most powerful fields for the search of new physics beyond the Standard Model. The kaon sector with the rare decay K+ → π+νν̅ provides one of the cleanest and most promising channels. NA62, a fixed target experiment at the CERN SPS, aims to measure BR (K+ → π+νν̅) with 10% precision to test the Standard Model validity up to an energy scale of hundreds of TeV. NA62 had dedicated data taking for the K+ → π+νν̅ measurement in 2016 and 2017 and will continue in 2018. Here preliminary results on a fraction of 2016 dataset are presented. The analysis of the complete 2016 data sample is expected to achieve the SM sensitivity.
NA48/62 latest results
The NA62 experiment at the CERN SPS recorded in 2007 a large sample of K+ ? µ+?µ decays. A peak search in the missing mass spectrum of this decay is performed. In the absence of observed signal, the limits obtained on B(K+ ? µ+?h) and on the mixing matrix element |Uµ 4| are reported. The upgraded NA62 experiment started data taking in 2015. About 5×1011K+ decays have been recorded so far to measure the branching ratio of the K+ ? ?+?? decay. Preliminary results from the K+ ? ?+?? analysis based on about 5% of the 2016 statistics are reported.
Indication of electron neutrino appearance from an accelerator-produced off-axis muon neutrino beam
The T2K experiment observes indications of $\nu_\mu\rightarrow \nu_e$ appearance in data accumulated with $1.43\times10^{20}$ protons on target. Six events pass all selection criteria at the far detector. In a three-flavor neutrino oscillation scenario with $|\Delta m_{23}^2|=2.4\times10^{-3}$ eV$^2$, $\sin^2 2\theta_{23}=1$ and $\sin^2 2\theta_{13}=0$, the expected number of such events is 1.5$\pm$0.3(syst.). Under this hypothesis, the probability to observe six or more candidate events is 7$\times10^{-3}$, equivalent to 2.5$\sigma$ significance. At 90% C.L., the data are consistent with 0.03(0.04)$<\sin^2 2\theta_{13}<$ 0.28(0.34) for $\delta_{\rm CP}=0$ and a normal (inverted) hierarchy.
The T2K Experiment
The T2K experiment is a long-baseline neutrino oscillation experiment. Its main goal is to measure the last unknown lepton sector mixing angle {\theta}_{13} by observing {\nu}_e appearance in a {\nu}_{\mu} beam. It also aims to make a precision measurement of the known oscillation parameters, {\Delta}m^{2}_{23} and sin^{2} 2{\theta}_{23}, via {\nu}_{\mu} disappearance studies. Other goals of the experiment include various neutrino cross section measurements and sterile neutrino searches. The experiment uses an intense proton beam generated by the J-PARC accelerator in Tokai, Japan, and is composed of a neutrino beamline, a near detector complex (ND280), and a far detector (Super-Kamiokande)…