292 research outputs found
Study of timing characteristics of a 3 m long plastic scintillator counter using waveform digitizers
No full textA plastic scintillator bar with dimensions 300 cm x 2.5 cm x 11 cm was exposed to a focused muon beam to study its light yield and timing characteristics as a function of position and angle of incidence. The scintillating light was read out at both ends by photomultiplier tubes whose pulse shapes were recorded by waveform digitizers. Results obtained with the WAVECATCHER and SAMPIC digitizers are analyzed and compared. A discussion of the various factors affecting the timing resolution is presented. Prospects for applications of plastic scintillator technology in large-scale particle physics detectors with timing resolution around 100 ps are provided in light of the results.A plastic scintillator bar with dimensions 300 cm × 2.5 cm × 11 cm was exposed to a focused muon beam to study its light yield and timing characteristics as a function of position and angle of incidence. The scintillating light was read out at both ends by photomultiplier tubes whose pulse shapes were recorded by waveform digitizers. Results obtained with the WAVECATCHER and SAMPIC digitizers are analyzed and compared. A discussion of the various factors affecting the timing resolution is presented. Prospects for applications of plastic scintillator technology in large-scale particle physics detectors with timing resolution around 100 ps are provided in light of the results
Search for a feebly interacting particle X in the decay K + → π + X
No full textA search for the K+ → π+X decay, where X is a long-lived feebly interacting particle, is performed through an interpretation of the K+ → π+νν ̄ analysis of data collected in 2017 by the NA62 experiment at CERN. Two ranges of X masses, 0–110 MeV/c2 and 154–260 MeV/c2, and lifetimes above 100 ps are considered. The limits set on the branching ratio, BR(K+ → π+X), are competitive with previously reported searches in the first mass range, and improve on current limits in the second mass range by more than an order of magnitude
Improved calorimetric particle identification in NA62 using machine learning techniques
No full textMeasurement of the ultra-rare K+→ π+νν ̄ 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 1.2 × 10 −5 for a pion identification efficiency of 75% in the momentum range of 15–40 GeV/c. 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 10 −5
Search for dark photon decays to μ + μ − at NA62
No full textThe NA62 experiment at CERN, designed to study the ultra-rare decay K + → π + νν ̄ , 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 μ + μ − pairs is reported, based on a sample of 1.4 × 1017 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/c 2
In-flight search for K+ → π+νν: First NA62 results
No full textNA62 has searched for the K+ → π+νν decay using a new kaon decay in-flight technique. One candidate event, compatible with the Standard Model prediction, has been observed from a sample of 1.2 ×1011 decays. Assuming that the event is background, an upper limit of 1.4 ×10−9 (95% CL) has been placed. Prospects for further improvements of the measurement are given
Searches for lepton number violating K+→π− (π0)e+e+ decays
No full textSearches for lepton number violating K+ -> pi(-)e(+)e(+) and K+ -> pi(-)pi(0)e(+)e(+) decays have been performed using the complete dataset collected by the NA62 experiment at CERN in 2016-2018. Upper limits of 5.3 x 10(-11 )and 8.5 x 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+ -> pi(-)pi(0)e(+)e(+) decay rate. (C) 2022 The Author. Published by Elsevier B.V
Searches for lepton flavour and lepton number violation in K+ decays
No full textThe NA62 experiment at the CERN SPS is designed to conduct precision tests of the Standard Model by studying rare decays of charged kaons. NA62 took data in 2016-2018 and collected a large sample of charged kaon decays into final states with multiple charged particles. The sensitivity to a range of lepton flavour and lepton number violating kaon decays provided by this data set is improved over the previously reported measurements. Results from the searches of K+→ π-l+l+ decays with a partial NA62 data sample are presented
New measurement of the radiative decay Ke3γ at the NA62 experiment at CERN
No full textThe NA62 experiment at CERN reports new results from the study of the radiative kaon decay K+ → π0e+νγ (Ke3γ), using a data sample recorded in 2017 and 2018. Preliminary results with the most precise measurement of the Ke3γ branching ratio, and a T-asymmetry measurement in the Ke3γ decay, are presented
Recent results in kaon physics
No full textA review of the present experimental status of the K → πνν (Kπνν) and other kaon decay analyses at experiments NA62 (CERN) and KOTO (J-PARC) is given. The Kπνν decay is one of the best candidates among the rare meson decays for indirect searches for new physics in the mass ranges complementary to those accessible by current accelerators. The Standard Model (SM) prediction of the branching fraction (B) of the Kπνν decay is lower than 10−10 in both neutral and charged modes. The NA62 experiment aims to measure the B of the charged mode with better than 10% precision. Three candidate events, compatible with the SM prediction, have been observed from a sample of 2.12×1012 K+ decays collected in 2016 and 2017 by NA62. More than twice the statistics is available in the 2018 dataset currently being analysed. The KOTO experiment in Japan aims to measure B(KL → π0νν) using a technique similar to NA62, but with much lower momentum. In the first dataset taken in 2015 zero signal candidate events were observed. The current status of the analysis of the 2016-2018 dataset with 1.4 times more data is presented. Finally, the most recent results of other physics analyses at the NA62 experiment are summarised
Search for heavy neutral lepton production in K+ decays at NA62
No full textLarge samples of charged kaon decays have been collected by the NA62-RK (2007) and the NA62 (2015) experiments at CERN SPS. This proceedings summarizes upper limits on heavy neutrino production measured by these experiments
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