Search for heavy charged particles and for particles with anomalous charge in e+e− collisions at LEP (original) (raw)
Related papers
1998
A search for stable and long-lived massive particles of electric charge jQ=ej = 1 o r 2 = 3, pair-produced in e + e collisions at centre-of-mass energies from 130 to 183 GeV, is reported by the OPAL collaboration at LEP. No evidence for production of these particles was observed in a mass range between 45 and 89.5 GeV. Model-independent upper limits on the production cross-section between 0.05 and 0.19 pb have been derived for scalar and spin-1/2 particles with charge 1. Within the framework of the minimal supersymmetric model (MSSM), this implies a lower limit of 82.5 (83.5) GeV on the mass of long-lived right-(left-)handed scalar muons and scalar taus. Long-lived charged leptons and charginos are excluded for masses below 89.5 GeV. For particles with charge 2/3 the upper limits on the production cross-section vary between 0.05 and 0.2 pb. All limits, on masses and on cross-sections, are valid at the 95% condence level for particles with lifetimes longer than 10 6 s.
Search for heavy stable and long-lived particles in e+e− collisions at GeV
Physics Letters B, 2000
A search for stable and long-lived heavy charged particles was performed using the data taken by the DELPHI experiment at an energy of 189 GeV. The Cherenkov light detected in the Ring Imaging Cherenkov Detector and the ionisation loss measured in the Time Projection Chamber were used to identify heavy particles passing through the detector. No evidence for the production of such particles has been found, therefore exclusion limits at 95% confidence level were derived on the masses of left and right handed smuons and staus. The results were combined with previous DELPHI searches in this channel. Including previous DELPHI results, masses of left (right) handed stable smuons and staus can be excluded between 2 GeV/c 2 and 88 (87.5) GeV/c 2 at 95% CL.
Search for unstable heavy and excited leptons in e+ e− collisions at∝ s= 170-172 GeV
1979
We have searched for unstable neutral and charged heavy leptons, N and L ± , and for excited states of neutral and charged leptons, ν * , e * , µ * and τ * , in e + e − collisions at centre-of-mass energies of 170 and 172 GeV using the OPAL detector at LEP. No evidence for their existence was found. From the analysis of charged-current decays of pair-produced unstable heavy leptons, and of charged-current and photonic decays of pairproduced excited leptons, lower limits on their masses are derived. From the analysis of charged-current and photonic decays of singly-produced excited leptons, upper limits on the ratio of the coupling to the compositeness scale, f /Λ, are determined for masses up to the kinematic limit.
Search for heavy stable charged particles in pp collisions at root s=7 TeV
Journal of High Energy Physics, 2011
The result of a search at the LHC for heavy stable charged particles produced in pp collisions at √ s = 7 TeV is described. The data sample was collected with the CMS detector and corresponds to an integrated luminosity of 3.1 pb −1 . Momentum and ionization-energy-loss measurements in the inner tracker detector are used to identify tracks compatible with heavy slow-moving particles. Additionally, tracks passing muon identification requirements are also analyzed for the same signature. In each case, no candidate passes the selection, with an expected background of less than 0.1 events. A lower limit at the 95% confidence level on the mass of a stable gluino is set at 398 GeV/c 2 , using a conventional model of nuclear interactions that allows charged hadrons containing this particle to reach the muon detectors. A lower limit of 311 GeV/c 2 is also set for a stable gluino in a conservative scenario of complete charge suppression, where any hadron containing this particle becomes neutral before reaching the muon detectors.