33 research outputs found
The kaon identification system in the NA62 experiment at CERN SPS
The main goal of the NA62 experiment at the CERN SPS accelerator is to measure the branching fraction of the ultra-rare decay K(+)→π(+)νbar nu with 10% accuracy. Key aspects of the detector configuration are described, with emphasis on tagging and timestamping the minority kaons in the high intensity, unseparated, charged-particle beam using KTAG, an upgraded version of a CEDAR differential Cherenkov detector. Data are presented showing that KTAG was successfully commissioned at CERN in November 2012
Measurement of the W+- boson cross section in the electron decay channel at [square root] s=7 TeV with the ATLAS detector
At the LHC, the process pp -+ W± X followed by the leptonic decays W- -+ e-v and W+ -+ e+lI is investigated to test the Standard Model in a completely new kinematic range. This thesis describes W± cross-section measurements using pp collisions recorded by the ATLAS detector in 2010. The charge dependence is measured both integrated and differentially in lepton pseudorapidity 'f); and analysis of the systematic uncertainties is presented. The results are compared with a recent publication by ATLAS which uses different reconstruction and background estimations. The cross-sections are also compared with theoretical predictions based on recent P DF sets determined recently by the CTEQ, MSTW, ABKM, HERAPDF and JR groups. The values of the W± cross-sections and their respective uncertainties, for 35.1 pb-1 at 7 TeV centre of mass energy, determined by this analysis, are: δfid/w+ x BR(W -+ e+ve) = 2.907 ± 0.015(stat.) ± 0.113(syst.) ± 0.099(lumi.) [nb] δfid/w+ x BR(W -+ e+ve) = 1.913 ± 0.012(stat.) ± 0.077(syst.) ± 0.065(lumi.) [nb]EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Comparison of one- And two-dimensional dielectric reflector geometries for high-energy laser pulse compression
The NA62 experiment at CERN aims to make a precision measurement of the
ultra-rare decay , and relies on a
differential Cherenkov detector (KTAG) to identify charged kaons at an average
rate of 50 MHz in a 750 MHz unseparated hadron beam. The experimental
sensitivity of NA62 to K-decay branching ratios (BR) of requires a
time resolution for the KTAG of better than 100 ps, an efficiency better than
95% and a contamination of the kaon sample that is smaller than . A
prototype version of the detector was tested in 2012, during the first NA62
technical run, in which the required resolution of 100 ps was achieved and the
necessary functionality of the light collection system and electronics was
demonstrated
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
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
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
Measurement of the very rare decay
The NA62 experiment reports the branching ratio measurement BR at 68% CL, based on the observation of 20 signal candidates with an expected background of 7.0 events from the total data sample collected at the CERN SPS during 2016-2018. This provides evidence for the very rare decay, observed with a significance of 3.4. The experiment achieves a single event sensitivity of , corresponding to 10.0 events assuming the Standard Model branching ratio of . This measurement is also used to set limits on BR(), where is a scalar or pseudo-scalar particle. Details are given of the analysis of the 2018 data sample, which corresponds to about 80% of the total data sample