In their namesake “puzzle,” these particles have a higher-than-expected detection rate in the LHC Forward experiment. The Higgs boson was discovered by both the ATLAS collaboration and the Compact Solenoid detector named for these particles. (-5[1])An inconsistency in the Standard Model is the 3.5-standard-deviation discrepancy between this particle’s measured and predicted g-factor. By increasing the reduced mass of hydrogen, these particles are hypothesized to catalyze a type of cold fusion. (10[1])The Rossi–Hall experiment showed time dilation by observing discrepancies in the 2.2-microsecond decay time of these particles after they were produced in the atmosphere by cosmic rays. (10[1])For 10 points, name this unstable lepton with a mass between that of the tauon and electron. ■END■