(Richtmyer) The average sea level muon flux is about 1 muon per square centimeter per minute. Muons make up more than half of the cosmic radiation at sea level, the remainder being mostly electrons, positrons and photons from cascade events. Measuring the flux of muons of cosmic ray origin at different heights above the earth is an important time dilation experiment in relativity. The muon is produced in the upper atmosphere by the decay of pions produced by cosmic rays: The lifetime of the muon is 2.20 microseconds. The fact that the above decay is a three-particle decay is an example of the conservation of lepton number there must be one electron neutrino and one muon neutrino or antineutrino in the decay. The muon is a lepton which decays to form an electron or positron. What evidence suggests that the electron is a fundamental particle? Associated with the electron is the electron neutrino. On the other hand, one of the mechanisms for the interaction of radiation with matter is the pair production of an electron-positron pair. If an electron and a positron encounter each other, they will annihilate with the production of two gamma-rays. The electron's antiparticle, the positron, is identical in mass but has a positive charge. It is a fermion of spin 1/2 and therefore constrained by the Pauli exclusion principle, a fact that has key implications for the building up of the periodic table of elements. Table of lepton propertiesĪs one of the leptons, the electron is viewed as one of the fundamental particles. The observed abundance agrees with three types of neutrinos. When the process of nucleosynthesis from the big bang is modeled, the number of types of neutrinos affects the abundance of helium. One of the pieces of experimental evidence for that is the measured hydrogen/helium abundance ratio in the universe. The present standard model assumes that there are no more than three generations. Now that we have experimental evidence for six leptons, a relevant question is "Are there more?". Important principles for all particle interactions are the conservation of lepton number and the conservation of baryon number. The different varieties of the elementary particles are commonly called "flavors", and the neutrinos here are considered to have distinctly different flavor. There are six leptons in the present structure, the electron, muon, and tau particles and their associated neutrinos. Session DE: New Results in Fundamental SymmetriesĬhair: Martin Cooper, Los Alamos National LaboratoryĭE.00001: New Results from the emiT Experiment: A Search for Time Reversal Invariance Violation in Neuron DecayĭE.Leptons and quarks are the basic building blocks of matter, i.e., they are seen as the "elementary particles". MurakamiĭD.00008: SAMURAI-TPC: Field Cage Design and Prototypingį. SobotkaĭC.00009: Towards quantum transport for central collisions of nuclei and of clouds of ultracold quantum gasesīrent Barker, Arnau Rios, Pawel DanielewiczĭD.00001: Performance Characteristics of the Next Generation Solid-State PhotomultipliersĮrik Bjorn Johnson, Christopher Stapels, Xiao Jie Chen, Chad Whitney, Mark Hammig, Joe Campbell, James ChristianĭD.00002: Timing Resolution tests of Silicon Photomultipliers for use at the Jefferson LabĭD.00003: The NIFFTE Data Acquisition SystemĭD.00004: Implementation of Environmental Monitors for NIFFTE and SeaQuest ExperimentsĭD.00005: Analysis Techniques for the Neutron Induced Fission Fragment Tracking Experiment (NIFFTE)ĭD.00006: Progress on Data Collection and Analysis with the NIFFTE TPCĭD.00007: SAMURAI-TPC: A Time Projection Chamber for Constraining the Asymmetry Energy at High DensityĪ.B. el HoussienyĭC.00008: Probing the dynamics of heavy ion collisions via two-particle correlations Sylvie Hudan, Romualdo de Souza, Alan McIntoshĭC.00007: Precision Measurement of Isospin Diffusion SobotkaĭC.00006: Isotopic trends in dynamical breakup SfientiĭC.00005: Isospin Observables from Fragment Energy Spectra SfientiĭC.00004: Measurement of emitted neutrons and protons from 112,124Sn + 112,124Sn at Ebeam = 50 MeV/nucleon and 120 MeV/nucleonĭ.D.S. Kris Hagel, Marina Barbui, Joseph Natowitz, Marcia Rodrigues, Kasia Schmidt, Roy Wada, Zbig Majka, Hua ZhengĭC.00002: Isospin Dependence of Nucleon Exchange in 78,86Kr + 40,48Ca Reactions at E/A = 10 MeVĮric Henry, Wolf-Udo Schroder, Jan Toke, Michael Quinlan, Hardev SinghĭC.00003: Measurement of emitted tritons and 3Helium from 112,124Sn+112,124Sn collisions at Ebeam=50 MeV/ nucleon and 120 MeV/nucleon Session Index Session DA: Ultrarelativistic Heavy Ions IĭA.00001: Chiral and deconfinement transition in QCDĭA.00002: Hadron Production and Freeze-Out Dynamics in $\sqrt$Th Collisions near the Coulomb Barrier Please enable JavaScript in your browser. 2011 Fall Meeting of the APS Division of Nuclear Physics
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