33 research outputs found
Measurement of the very rare decay
The decay K+→π+νν¯
, with a very precisely predicted branching ratio of less than 10−10
,
is among the best processes to reveal indirect effects of new physics.
The NA62 experiment at CERN SPS is designed to study the K+→π+νν¯
decay and to measure its branching ratio using a decay-in-flight technique.
NA62 took data in 2016, 2017 and 2018, reaching the sensitivity of the Standard Model
for the K+→π+νν¯
decay by the analysis of the 2016 and 2017 data,
and providing the most precise measurement of the branching ratio to date
by the analysis of the 2018 data.
This measurement is also used to set limits on BR(K+→π+X
), where X
is a scalar
or pseudo-scalar particle.
The final result of the BR(K+→π+νν¯
) measurement and its interpretation in terms
of the K+→π+X
decay from the analysis of the full 2016-2018 data set is presented, and future plans and prospects are reviewed
Analysis of the rare decay
The main goal of the NA62 experiment at CERN is a study of the ultra rare decay . The collected statistics allows to analyse other rare decays, in particular, . Rare decays make it possible to experimentally investigate one of the aspects of the Standard Model, the chiral perturbative theory (ChPT). ChPT predicts decay probability of . This decay channel is also of great interest due to the fact, that it was not experimentally observed, there is only an upper limit x CL 90%. We present the research methodology, the first results of signal selection and the study of the background sources for the decay
Search for leptonic decays of the dark photon at NA62
The 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.The 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
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 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
A search for the decay
A search for the decay, forbidden within the Standard Model by either lepton number or lepton flavour conservation depending on the flavour of the emitted neutrino, has been performed using the dataset collected by the NA62 experiment at CERN in 2016--2018. An upper limit of is obtained for the decay branching fraction at 90% CL, improving by a factor of 250 over the previous search
Searches for lepton number violating decays
Searches for lepton number violating and decays have been performed using the complete dataset collected by the NA62 experiment at CERN in 2016-2018. Upper limits of and are obtained on the decay branching fractions at 90% confidence level. The former result improves the limit by a factor of four over the previous best limit, while the latter result represents the first limit on the decay rate.Searches for lepton number violating K+→π−e+e+ and K+→π−π0e+e+ decays have been performed using the complete dataset collected by the NA62 experiment at CERN in 2016–2018. Upper limits of 5.3×10−11 and 8.5×10−10 are obtained on the decay branching fractions at 90% confidence level. The former result improves by a factor of four over the previous best limit, while the latter result represents the first limit on the K+→π−π0e+e+ decay rate.Searches for lepton number violating and decays have been performed using the complete dataset collected by the NA62 experiment at CERN in 2016-2018. Upper limits of and are obtained on the decay branching fractions at 90% confidence level. The former result improves by a factor of four over the previous best limit, while the latter result represents the first limit on the decay rate
Search for decays to a muon and invisible particles
The NA62 experiment at CERN reports searches for and decays, where and are massive invisible particles, using the 2016-2018 data set. The particle is assumed to be a heavy neutral lepton, and the results are expressed as upper limits of of the neutrino mixing parameter for masses in the range 200-384 MeV/ and lifetime exceeding 50 ns. The particle is considered a scalar or vector hidden sector mediator decaying to an invisible final state, and upper limits of the decay branching fraction for masses in the range 10-370 MeV/ are reported for the first time, ranging from to . An improved upper limit of is established at 90% CL on the branching fraction.The NA62 experiment at CERN reports searches for K+→μ+N and K+→μ+νX decays, where N and X are massive invisible particles, using the 2016–2018 data set. The N particle is assumed to be a heavy neutral lepton, and the results are expressed as upper limits of O(10−8) of the neutrino mixing parameter |Uμ4|2 for N masses in the range 200–384 MeV/ c2 and lifetime exceeding 50 ns. The X particle is considered a scalar or vector hidden sector mediator decaying to an invisible final state, and upper limits of the decay branching fraction for X masses in the range 10–370 MeV/ c2 are reported for the first time, ranging from O(10−5) to O(10−7) . An improved upper limit of 1.0×10−6 is established at 90% CL on the K+→μ+ννν¯ branching fraction.The NA62 experiment at CERN reports searches for and decays, where and are massive invisible particles, using the 2016-2018 data set. The particle is assumed to be a heavy neutral lepton, and the results are expressed as upper limits of of the neutrino mixing parameter for masses in the range 200-384 MeV/ and lifetime exceeding 50 ns. The particle is considered a scalar or vector hidden sector mediator decaying to an invisible final state, and upper limits of the decay branching fraction for masses in the range 10-370 MeV/ are reported for the first time, ranging from to . An improved upper limit of is established at 90% CL on the branching fraction
A search for the decay
A search for the decay, forbidden within the Standard Model by either lepton number or lepton flavour conservation depending on the flavour of the emitted neutrino, has been performed using the dataset collected by the NA62 experiment at CERN in 2016--2018. An upper limit of is obtained for the decay branching fraction at 90% CL, improving by a factor of 250 over the previous search