34 research outputs found
Search for dark photon decays to at NA62
International audienceThe NA62 experiment at CERN, designed to study the ultra-rare decay , has also collected data in beam-dump mode. In this configuration, dark photons may be produced by protons dumped on an absorber and reach a decay volume beginning 80 m downstream. A search for dark photons decaying in flight to pairs is reported, based on a sample of protons on dump collected in 2021. No evidence for a dark photon signal is observed. A region of the parameter space is excluded at 90% CL, improving on previous experimental limits for dark photon masses between 215 and 550 MeV
Search for lepton number and flavour violation in and decays
Searches for the lepton number violating decay and the lepton flavour violating and decays are reported using data collected by the NA62 experiment at CERN in 20172018. No evidence for these decays is found and upper limits of the branching ratios are obtained at 90% confidence level: B() K^{+} \rightarrow \pi^{-} \mu^{+} e^{+}K^{+} \rightarrow \pi^{+} \mu^{-} e^{+}\pi^{0} \rightarrow \mu^{-} e^{+}20172018\mathcal{B}(K^{+}\rightarrow\pi^{-}\mu^{+}e^{+})<4.2\times 10^{-11}\mathcal{B}(K^{+}\rightarrow\pi^{+}\mu^{-}e^{+})<6.6\times10^{-11}\mathcal{B}(\pi^{0}\rightarrow\mu^{-}e^{+})<3.2\times 10^{-10}$. These results improve by one order of magnitude over previous results for these decay modes
Performance of the NA62 trigger system
International audienceThe NA62 experiment at CERN targets the measurement of the ultra-rare decay, and carries out a broad physics programme that includes probes for symmetry violations and searches for exotic particles. Data were collected in 2016–2018 using a multi-level trigger system, which is described highlighting performance studies based on 2018 data
A measurement of the decay
International audienceA sample of 2.8 × 10K → πμμ candidates with negligible background was collected by the NA62 experiment at the CERN SPS in 2017–2018. The model-independent branching fraction is measured to be (9.15 ± 0.08) × 10, a factor three more precise than previous measurements. The decay form factor is presented as a function of the squared dimuon mass. A measurement of the form factor parameters and their uncertainties is performed using a description based on Chiral Perturbation Theory at (p)
A study of the decay
International audienceA sample of candidates with less than 1% background was collected by the NA62 experiment at the CERN SPS in 2017-2018. Branching fraction measurements are obtained at percent relative precision in three restricted kinematic regions, improving on existing results by a factor larger than two. An asymmetry, possibly related to T-violation, is investigated with no evidence observed within the achieved precision
Search for heavy neutral lepton production in decays
A search for heavy neutral lepton production in 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 to level are established on the elements of the extended neutrino mixing matrix () for heavy neutral lepton mass in the range . This improves on the results from previous production searches in decays, setting more stringent limits and extending the mass range.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
NA62 Technical Design
NA62 technical design repor
Search for leptonic decays of the dark photon at NA62
International audienceThe NA62 experiment at CERN, configured in beam-dump mode, has searched for dark photon decays in flight to electron-positron pairs using a sample of protons on dump collected in 2021. No evidence for a dark photon signal is observed. The combined result for dark photon searches in lepton-antilepton final states is presented and a region of the parameter space is excluded at 90% CL, improving on previous experimental limits for dark photon mass values between 50 and 600 MeV and coupling values in the range to . An interpretation of the search result in terms of the emission and decay of an axion-like particle is also presented
Search for leptonic decays of the dark photon at NA62
International audienceThe NA62 experiment at CERN, configured in beam-dump mode, has searched for dark photon decays in flight to electron-positron pairs using a sample of protons on dump collected in 2021. No evidence for a dark photon signal is observed. The combined result for dark photon searches in lepton-antilepton final states is presented and a region of the parameter space is excluded at 90% CL, improving on previous experimental limits for dark photon mass values between 50 and 600 MeV and coupling values in the range to . An interpretation of the search result in terms of the emission and decay of an axion-like particle is also presented