[PDF] Search For The Lepton Flavor Violating Decay Zu2192e In Pp Collisions At S eBook
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We use the ATLAS detector at the Large Hadron Collider to search for the lepton flavor violating process Z→e? in pp collisions using 20.3 fb-1 of data collected at √s=8 TeV. An enhancement in the e? invariant mass spectrum is searched for at the Z-boson mass. The number of Z bosons produced in the data sample is estimated using events of similar topology, Z→ee and ??, significantly reducing the systematic uncertainty in the measurement. In conclusion, there is no evidence of an enhancement at the Z-boson mass, resulting in an upper limit on the branching fraction, B(Z→e?)7.5×10sup-7
The ATLAS detector at the Large Hadron Collider is used to search for the lepton flavor violating process Z -> eμ in pp collisions using 20.3 fb^(-1) of data collected at sqrt(s)= 8 TeV. An enhancement in the eμ invariant mass spectrum is searched for at the Z boson mass. The number of Z bosons produced in the data sample is estimated using events of similar topology, Z -> ee and μμ, significantly reducing the systematic uncertainty in the measurement. There is no evidence of an enhancement at the Z boson mass, resulting in an upper limit on the branching fraction, B(Z -> eμ)
Abstract: We present a search for the lepton flavor violating decay Z->eu in proton-proton collisions at a center of mass energy of 7 TeV using approximately 3.1 pb−1 of data recorded with the ATLAS detector at the CERN large hadron collider. Candidate events have two isolated high p[tau] leptons (an electron and a muon), no jets, and little missing transverse energy. We observe no events with eu invariant mass above 60 GeV/c2. This demonstrates that we can suppress the eu background to a negligible level and are sensitive to exotic eu production. We set 95% confidence upper limit on the Z->eu branching ratio of 2.0 x 10−4.
A direct search for lepton flavour violating decays of the Higgs boson (H) in the H to e tau and H to e mu channels is described. The data sample used in the search was collected in proton-proton collisions at sqrt(s)=8 TeV with the CMS detector at the LHC and corresponds to an integrated luminosity of 19.7 inverse femtobarns. No evidence is found for lepton flavour violating decays in either final state. Upper limits on the branching fractions, B(H to e tau)
A search for the lepton-flavor-violating decay of the tau into one charged lepton and two charged hadrons has been performed using 221.4 fb−1 of data collected at an ee− center-of-mass energy around 10.58 GeV with the BABAR detector at the PEP-II storage ring. In all 14 decay modes considered, the numbers of events found in data are compatible with the background expectations. Upper limits on the branching fractions are set in the range (0.7-4.8) x 10−7 at 90% confidence level. All results are preliminary.
The Standard Model (SM) is one of the most tested and verified physical theories of all time, present experimental observations are consistent with SM expectations. On the other hand SM can not explain many physical observations: the cosmological observations possibly infer the presence of dark matter which is clearly beyond the SM expectations; the SM Higgs model, while explaining the generation of fermion masses, can not explain the hierarchy problem and a non natural fine tuning of SM is needed to cancel out quadratic divergences in the Higgs boson mass. New physics (NP) beyond SM should hence be investigated: rising the energy above NP processes thresholds, and detecting new particles or new effects not predicted by the standard model directly, is one of the possible approaches; another approach is to make precision measurements of well known processes or looking for rare processes which involve higher order contribution from NP processes, this approach need higher luminosities with respect to the previous approach but lower beam energies. Search for Lepton Flavor Violation (LFV) in charged lepton decays is promising: neutrino physics provides indeed a clear and unambiguous evidence of LFV in the neutral lepton sector via mixing processes, which have been observed for the first time by the Homestake collaboration. We expect LFV in the charged sector as well, both in ? and ? sector, but current experimental searches for LFV processes did not find any evidence for those processes, and more results are expected to come from new experiments in the coming years.