Elementary particles - Tran Thi Ngoc Dung

Nội dung text: Elementary particles - Tran Thi Ngoc Dung

1. ELEMENTARY PARTICLES Tran Thi Ngoc Dung – Huynh Quang Linh – Physics A2 HCMUT 2016
2. SOME OF BASIC QUESTIONS ABOUT NATURE • What are the basic building blocks of matter? • What is inside the nucleus? • What are the forces that hold matter together? • How did the universe begin? • Will the universe end, and if so, how and when?
3. 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.
4. Fundamental particles • An elementary particle or fundamental particle is a particle whose substructure is unknown, thus it is unknown whether it is composed of other particles.[ Known elementary particles include • fundamental fermions (quarks, leptons, antiquarks, and antileptons), which generally are "matter particles" and "antimatter particles", • And the fundamental bosons (gauge bosons and the Higgs boson), which generally are "force particles" that mediate interactions among fermions.
5. 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
6. 6 QUARKS, 6 LEPTONS and their antiparticles
7. MATTER PARTICLES QUARKS LEPTONS HADRONS MESONS BARYONS NUCLEI ATOMS MOLECULES
8. PROPERTIES 1. Mass 2. Charge 3. Spin 4. Baryon number 5. Strange number 6. Lepton number ANTI-PARTCLES Have the same mass and lifetime as their associated particles Have the same magnitude but are opposite in sign for such physical quantities as electric charge and various quantum numbers All particles, even neutral ones (with some notable exceptions like the neutral pion), have antiparticles.
9. 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.
10. Baryons are massive particles which are made up of three quarks Rest Lifetime Decay Particle Symbol Makeup mass Spin B S (second Modes MeV/c2 s> Proton p uud 938.3 1/2 +1 0 Stable - Neutron n ddu 939.6 1/2 +1 0 920 pe νe 2.6 Lambda Λ0 uds 1115.6 1/2 +1 -1 pπ-, nπ0 x10-10 0.8 Sigma Σ+ uus 1189.4 1/2 +1 -1 pπ0, nπ+ x10-10 Sigma Σ0 uds 1192.5 1/2 +1 -1 6x10-20 Λ0γ 1.5 Sigma Σ- dds 1197.3 1/2 +1 -1 nπ- x10-10 0.6 Delta Δ++ uuu 1232 3/2 +1 0 pπ+ x10-23 / -
11. 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 - - -
12. p uud n udd
13. 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.
14. Lepton number In all interactions, each lepton number is separately conserved. For example
15. In all interactions, the total baryon number is conserved. strangeness is conserved in strong interactions but it can change by zero or one unit in weak interactions Each baryon is composed of three quarks (qqq) each antibaryon of three antiquarks (qqq); Each meson is composed of ( q,q)
16. 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
17. 44.4. quark–antiquark pair annihilation • A proton and an antiproton annihilate, producing two photons. Find the energy, frequency, and wavelength of each photon (a) if the p and p are initially at rest and (b) if the p and p collide head-on, each with an initial kinetic energy of 830 MeV. a) p p 2 b) Consevation of Energy : 2 2E 2 2mpc 2  Eo EK 939.4MeV 830MeV 1769.4MeV 2 1.24  m c2 1.67 10 27 3 108 (m) p 6 10 1769.4 10 eV 1.503 10 J 939.4MeV  7.008 10 16 m 1.24 (m) f c /  4.28 1023 Hz 939.4 106 (eV)  1.32 10 15 m f c /  2.27 1023 Hz