108 research outputs found
Precision Measurement of the Ratio of the Charged Kaon Leptonic Decay Rates
A precision measurement of the ratio RK of the rates of kaon leptonic decays
K+- --> e nu and K+- --> mu nu with the full data sample collected by the NA62
experiment at CERN in 2007-2008 is reported. The result, obtained by analysing
~150000 reconstructed K+- --> e nu candidates with 11% background
contamination, is RK = (2.488+-0.010)*10^{-5}, in agreement with the Standard
Model expectation.Comment: Accepted for publication in Physics Letters B (18 January 2013). 18
pages, 6 figure
Improved calorimetric particle identification in NA62 using machine learning techniques
Measurement of the ultra-rare decay at the NA62
experiment at CERN requires high-performance particle identification to
distinguish muons from pions. Calorimetric identification currently in use,
based on a boosted decision tree algorithm, achieves a muon misidentification
probability of for a pion identification efficiency of 75%
in the momentum range of 15-40 GeV/. In this work, calorimetric
identification performance is improved by developing an algorithm based on a
convolutional neural network classifier augmented by a filter. Muon
misidentification probability is reduced by a factor of six with respect to the
current value for a fixed pion-identification efficiency of 75%. Alternatively,
pion identification efficiency is improved from 72% to 91% for a fixed muon
misidentification probability of
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.Comment: Submitted to Phys.Lett.
A study of the decay
A 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 dark photon decays to at NA62
The 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.Comment: 23 pages, 16 figures, final version, accepted for publication in JHE
KTAG: The Kaon Identification Detector for CERN experiment NA62
In the study of ultra-rare kaon decays, CERN experiment NA62 exploits an unseparated monochromatic (75 GeV/ c ) beam of charged particles of flux 800 MHz, of which 50 MHz are K+ . Kaons are identified with more than 95% efficiency, a time resolution of better than 100 ps, and misidentification of less than 10 −4 using KTAG, a differential, ring-focussed, Cherenkov detector. KTAG utilises 8 sets of 48 Hamamatsu PMTs, of which 32 are of type 9880 and 16 of type 7400, with signals fed directly to the differential inputs of NINO front-end boards and then to TDC cards within the TEL62 system. Leading and trailing edges of the PMT signal are digitised, enabling slewing corrections to be made, and a mean hit rate of 5 MHz per PMT is supported. The electronics is housed within a cooled and insulated Faraday cage with environmental monitoring capabilities
Improved calorimetric particle identification in NA62 using machine learning techniques
Measurement of the ultra-rare decay at the NA62
experiment at CERN requires high-performance particle identification to
distinguish muons from pions. Calorimetric identification currently in use,
based on a boosted decision tree algorithm, achieves a muon misidentification
probability of for a pion identification efficiency of 75%
in the momentum range of 15-40 GeV/. In this work, calorimetric
identification performance is improved by developing an algorithm based on a
convolutional neural network classifier augmented by a filter. Muon
misidentification probability is reduced by a factor of six with respect to the
current value for a fixed pion-identification efficiency of 75%. Alternatively,
pion identification efficiency is improved from 72% to 91% for a fixed muon
misidentification probability of
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