Search for K ⁺ → π ⁺ ννat the NA62 experiment

Looking for phenomena beyond the Standard Model (SM) in rare decays is a complementary approach to direct searches for New Physics (NP) at colliders. One of the theoretically cleanest processes is the ultra rare decay K+ → π+νν̄. The goal of the NA62 experiment at CERN SPS is to measure the branching ratio (BR) of this decay with 10% precision. The experiment has been launched in 2014. In 2015, the detector was commissioned at a low intensity beam. The experimental setup is described and performances achieved in 2015 are discussed in view of the final measurement

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

Prospects for K+→π+ννˉK+ \rightarrow \pi^+ \nu \bar{\nu} observation at CERN in NA62

The primary goal of the NA62 experiment at CERN SPS is to measure the branching ratio (BR) of the decay K+ → π+ν¯ν with ∼ 10% precision. The experimental method and detectors are described in the present paper. Selected results of the pilot run in 2014 are shown

Cosmology tests in rare kaon decays

The Standard Model (SM) of particle physics is an extremely successful theory that effectively describes strong and electroweak interactions up to the energies presently accessible. Still, the SM does not explain the observed parameters of neutrino oscillations, baryon asymmetry of the Universe and Dark Matter (DM), and contains a fine-tuning of 16 orders of magnitude (the gauge hierarchy problem). Various New Physics (NP) models beyond the SM have been developed in order to address the above limitations. This paper concentrates on several models related to cosmology and their tests in rare kaon decays. In particular, recent NA48/2 results on the search for heavy neutrinos, light in-flatons and dark photons are presented. Prospects for the ongoing NA62 experiment are discussed

First results on the K+ → π+vv¯ decay search from NA62

The precise measurement of the branching ratio of an ultrarare decay K+ → π+vv¯ (~10-10 according to the calculation within the Standard Model) allows to probe New Physics via indirect effects at mass scales higher than those accessible at the LHC. The NA62 experiment at the CERN SPS is aimed at measuring this branching ratio with the 10% precision. To achieve such level of precision, a novel decay-in-flight technique is used. The statistics collected during the first NA62 physics run in 2016 allowed to demonstrate the proof of the experimental method and obtain O(10-10) single event sensitivity. The preliminary results based on the 2016 data set are described

Recent Results From NA62

The NA62 experiment at CERN SPS is aimed at collecting O(100) events of the ultrarare decay with the background ∼10%. The data taking is supposed to start in 2014. In 2012 a part of the setup was commissioned during the Technical Run (TR). In this paper the experimental setup and selected results of the TR are briefly discussed

The RICH detector of the NA62 experiment

The NA62 experiment at CERN is aimed at measuring the ultra-rare decay K+→π+νν with 10% accuracy. One of the detectors that is crucial for the rejection of background events is the RICH detector: a gas based detector aimed at π/μ separation in the 15–35 GeV/c momentum range with an inefficiency of less than 1%. The RICH must also provide a very precise time measurement (with the time resolution ∼100 ps) to correctly associate the π+ with the parent K+ particle measured by an upstream detector. This paper contains the detailed description of the RICH detector, its readout, and the results of the commissioning run at CERN in 2014