Subatomic World • Protons, neutrons, and electrons make up atoms. • Photons are particles that convey electromagnetic energy. • Force carrier • These make up most of the material universe.
Unstable particles can be produced. Unique mass energy Characteristic lifetime The lifetime t is related to the probability that a particle will survive a given period of time. The survival time is affected by relativity. Artificial Particles
Leptons are fundamental particles. Interact weakly – no nuclear interaction Able to exist in isolation Electrons are stable. Muons and taus are unstable. Neutrinos are stable and very low mass. Partner with charged leptons Charged leptons: electron, e-: 0.511 MeV/c2 = 1/1836 mp muon, m-: 0.1057 GeV/c2 = 1/9 mp tau, t- : 1.776 GeV/c2 = 1.9 mp Leptons
Baryons have atomic mass comparable to protons and neutrons. Conserved quantity First artificial ones were given a property of strangeness. Quantum number Later ones were given new properties. Charm, beauty, truth Baryons n p S- S0 S+ L X- X0
Some artificial particles were lower mass than baryons. No atomic mass conservation Mesons are also had same quantum properties as baryons. Strangeness conserved Mesons
Quarks are fundamental building blocks, but are not detected directly. Binding force too great Stable quarks bind to others Quarks exist in hadrons. Baryons are three quarks Mesons are a quark-anti quark pair. Some baryons proton, p: uud neutron, n: udd lambda, L0: uds lambda-b, Lb0 : udb Some mesons pi-minus, p-: ud k-plus, K+: us J/psi, Y: cc Quarks
The fundamental particles can be placed into a compact table. Standard Model Separate matter from force carriers The leptons and quarks fall into three related generations. Normal mater in first generation Standard Model next