{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Class27HO - Class 27 The Standard Model and General...

Info iconThis preview shows pages 1–21. Sign up to view the full content.

View Full Document Right Arrow Icon
Class 27 The Standard Model and General Relativity Physics 106 Fall 2011 Press CTRL-L to view as a slide show.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Last Time Last time we discussed: I Elementary Particles I Fundamental Interactions I Feynman Diagrams I New Particles
Background image of page 2
Learning Outcomes Today we will discuss: I Feynman Diagrams I Particle Families I The Eight-fold Way I Quarks and the Standard Model I Cosmology and General Relativity
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Conservation Laws
Background image of page 4
Conservation Laws I Conservation of baryon number I Conservation of lepton number and three separate types of lepton numbers: I Conservation of electron number I Conservation of muon number I Conservation of tau number I Conservation of strangeness
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Conservation of Baryon Number I Assigning baryon number: I B = 1 for baryons I B = - 1 for antibaryons I B = 0 for all other particles I Whenever a baryon is created an antibaryon is also created
Background image of page 6
Conservation of Electron Number I Assigning electron number: I L e = 1 for the e - and the electron neutrino, ν e I L e = - 1 for the e + and the electron antineutrino, ¯ ν e I L e = 0 for all other particles
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Conservation of Muon Number I Assigning muon number: I L μ = 1 for the μ - and the muon neutrino, ν μ I L μ = - 1 for the μ + and the muon antineutrino ¯ ν μ I L μ = 0 for all other particles I Tau numbers are assigned similarly I Lepton number is the sum of electron, muon, and tau numbers
Background image of page 8
Strange Particles I Discovered in the 1950s I Produced in strong interaction I Decayed by weak interaction (long-lived) I Called " strange particles "
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Conservation of Strangeness I New quantum number, S I Strange particles have integral strangeness ( ± 1 , ± 2 , ± 3) I An antiparticle has strangeness opposite that of the particle I Strangeness is conserved in strong and electromagnetic interactions (when strange particles are produced) I Strangeness can change by one unit in weak interactions (when strange particles decay)
Background image of page 10
Bubble Chamber Example I The dashed lines represent neutral particles I At the bottom, π + + p Λ 0 ( S = - 1 ) + K 0 ( S = + 1 ) I Then Λ 0 π - ( S = 0 ) + p ( S = 0 ) K 0 π - + μ - ( S = 0 ) + ν μ ( S = 0 )
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
The Standard Model
Background image of page 12
The Eightfold Way
Background image of page 13

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Murray Gell-Mann I b. 1929 I Worked on theoretical studies of subatomic particles I Nobel Prize in 1969
Background image of page 14
The Eightfold Way I The eightfold wayis a symmetric pattern proposed by Gell-Mann and Ne’eman I These schemes are based on spin, baryon number, strangeness, etc.
Background image of page 15

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
An Eightfold Way for Baryons I Eight spin 1/2 baryons I Strangeness vs. charge is plotted on a sloping coordinate system I Two particles are at the center I There is a similar pattern for antibaryons
Background image of page 16
An Eightfold Way for Mesons I Nine spins 0 mesons I Plot strangeness vs. charge I The particles and their antiparticles are on opposite sides of the hexagon I The remaining three mesons at the center are their own antiparticles
Background image of page 17

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Quarks
Background image of page 18
The Eightfold Way and Quarks I This pattern can be understood in terms of quarks I Three types make up most matter I u - up I d - down I s - strange
Background image of page 19

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Quark Model I Quarks have fractional electrical charges I q u = + 2 / 3 e I q d = - 1 / 3 e I q s = - 1 / 3 e I Quarks have baryon number of 1/3 I The strange quark has a strangeness of - 1, others are 0
Background image of page 20
Image of page 21
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}