Hysics 2 - Lecture 12: Elementary Particles - Huynh Quang Linh

Nội dung text: Hysics 2 - Lecture 12: Elementary Particles - Huynh Quang Linh

1. ELEMENTARY PARTICLES Tran Thi Ngoc Dung – Huynh Quang Linh – Physics A2 HCMUT 2016
2. HISTORY • In 1930 the known elementary particles were the proton, the electron, and the photon. • Thomson identified the electron in 1897, and Einstein defined the photon in 1905. The proton is the nucleus of the hydrogen atom. • 1932, Chadwick proved the existence of the neutron, and Carl Anderson identified the positron in cosmic rays.
3. Elementary particles Fundamental Bosons Fundamental fermions (force particles) (MATTER - ANTIMATTER that mediate interaction PARTICLES) between fermions QUARKS - ANTIQUARKS GAUGE BOSONS LEPTONS-ANTILEPTONS and HIGGS BOSONS
4. MATTER PARTICLES QUARKS LEPTONS HADRONS MESONS BARYONS NUCLEI ATOMS MOLECULES
5. Cosmic rays • Cosmic rays are highly energetic particles, mostly protons, that cross interstellar space and enter the Earth’s atmosphere, where their interaction with particles creates cosmic “showers” of many distinct particles.
6. MESONS : are particles mades up of 1quark and 1 antiquarks. Mesons are bosons, while the baryons are fermions. Rest Anti- Make Lifetim Decay Particle Symbol mass S C B particle up e Modes MeV/c2 2.60 Pion π+ π- ud 139.6 0 0 0 μ+ν x10-8 μ 0.83 Pion π0 Self 135.0 0 0 0 2γ x10-16 1.24 μ+ν , Kaon K+ K- us 493.7 +1 0 0 μ x10-8 π+π0 - - -
7. Each baryon is composed of three quarks (qqq) each antibaryon of three antiquarks (qqq); Each meson is composed of ( q,q) The corresponding antiquarks have opposite values of charge Q, , B and S. Each quark also has a fractional value 1/3 for its baryon number and each antiquark has a baryon- number value -1/3. In a meson, a quark and antiquark combine with net baryon number 0 and can have their spin angular momentum components parallel to form a spin-1 meson or antiparallel to form a spin -0 meson. Similarly, the three quarks in a baryon combine with net baryon number 1 and can form a spin 1/2 baryon or a 3/2 baryon.
8. Lepton number In all interactions, each lepton number is separately conserved. For example
9. 4 Fundamental Interactions Interaction Strength Range Mediating particle Name Mass Charge Spin Strong 1 Short (1fm) Gluon 0 0 1 Electromagnetic 1/137 Long (1/r2) Photon 0 0 1 Weak 10-4 short W+, W-, Zo 80, 90 e,0 1 GeV/c2 0.001fm Gravitational 10-38 long (1/r2) Graviton 0 0 2