30 research outputs found
Measurement of the W+- boson cross section in the electron decay channel at [square root] s=7 TeV with the ATLAS detector
No full textAt 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
Measurement of the W+- boson cross section in the electron decay channel at [square root] s=7 TeV with the ATLAS detector
No full textA measurement of the decay
No full textA sample of 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 , 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 .A 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 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)
First search for K <sup>+</sup> →π <sup>+</sup> νν̅ using the decay-in-flight technique
No full text The NA62 experiment at the CERN SPS reports the first search for K + →π + νν̅ using the decay-in-flight technique, based on a sample of 1.21×10 11 K + decays collected in 2016. The single event sensitivity is 3.15×10 −10 , corresponding to 0.267 Standard Model events. One signal candidate is observed while the expected background is 0.152 events. This leads to an upper limit of 14×10 −10 on the K + →π + νν̅ branching ratio at 95% CL. </p
Search for production of an invisible dark photon in decays
No full textThe results of a search for π decays to a photon and an invisible massive dark photon at the NA62 experiment at the CERN SPS are reported. From a total of 4.12 × 10 tagged π mesons, no signal is observed. Assuming a kinetic-mixing interaction, limits are set on the dark photon coupling to the ordinary photon as a function of the dark photon mass, improving on previous searches in the mass range 60–110 MeV/c. The present results are interpreted in terms of an upper limit of the branching ratio of the electro-weak decay , improving the current limit by more than three orders of magnitude.The results of a search for decays to a photon and an invisible massive dark photon at the NA62 experiment at the CERN SPS are reported. From a total of tagged mesons, no signal is observed. Assuming a kinetic-mixing interaction, limits are set on the dark photon coupling to the ordinary photon as a function of the dark photon mass, improving on previous searches in the mass range 60--110 MeV/. The present results are interpreted in terms of an upper limit of the branching ratio of the electro-weak decay , improving the current limit by more than three orders of magnitude
Searches for lepton number violating decays
No full textSearches 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
A search for the decay
No full textA 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 K+→μ−νe+e+ 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 8.1×10−11 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, 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
Performance of the NA62 trigger system
No full textThe 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.The 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.The 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
Searches for lepton number violating decays
No full textThe NA62 experiment at CERN reports a search for the lepton number violating decays and using a data sample collected in 2017. No signals are observed, and upper limits on the branching fractions of these decays of and are obtained, respectively, at 90\% confidence level. These upper limits improve on previously reported measurements by factors of 3 and 2, respectively.The NA62 experiment at CERN reports a search for the lepton number violating decays K+→π−e+e+ and K+→π−μ+μ+ using a data sample collected in 2017. No signals are observed, and upper limits on the branching fractions of these decays of 2.2×10−10 and 4.2×10−11 are obtained, respectively, at 90% confidence level. These upper limits improve on previously reported measurements by factors of 3 and 2, respectively.The NA62 experiment at CERN reports a search for the lepton number violating decays and using a data sample collected in 2017. No signals are observed, and upper limits on the branching fractions of these decays of and are obtained, respectively, at 90% confidence level. These upper limits improve on previously reported measurements by factors of 3 and 2, respectively
Search for heavy neutral lepton production in K+ decays to positrons
No full textA search for heavy neutral lepton (N) production in K+→e+Ndecays using the data sample collected by the NA62 experiment at CERN in 2017–2018 is reported. Upper limits of the extended neutrino mixing matrix element |Ue4|^2 are established at the level of 10^−9 over most of the accessible heavy neutral lepton mass range 144–462 MeV/c2, with the assumption that the lifetime exceeds 50 ns. These limits improve significantly upon those of previous production and decay searches. The |Ue4|^2 range favoured by Big Bang Nucleosynthesis is excluded up to a mass of about 340 MeV/c2
