Dr. H. Fearn CSUF Physics 1 Lecture 3: The Standard Model The fundamental model for elementary...

Dr. H. Fearn CSUF PhysicsDr. H. Fearn CSUF Physics 11

Lecture 3: The Standard ModelLecture 3: The Standard Model

The fundamental model for elementary The fundamental model for elementary particles.particles.

Point Particles not strings !Point Particles not strings ! No gravity !No gravity ! What are the 3 families of particles?What are the 3 families of particles? What’s a Boson, Fermion, Lepton and What’s a Boson, Fermion, Lepton and

quark?quark? Is Nature Supersymmetric?Is Nature Supersymmetric? What are Higgs particles?? Monopoles???What are Higgs particles?? Monopoles???


http://particleadventure.org/particleadventure/index.htmlhttp://www2.slac.stanford.edu/vvc/theory/hadrons.html


Electrons & muons & Taus… oh my.Electrons & muons & Taus… oh my.Welcome to the particle ZOO.Welcome to the particle ZOO.

The standard model is a good theory for The standard model is a good theory for the constituents of matter.the constituents of matter.

Almost all the particles predicted have Almost all the particles predicted have been found experimentally.been found experimentally.

It is fairly simple, and explains hundreds of It is fairly simple, and explains hundreds of particles and their complex interactions particles and their complex interactions with only 6 quarks, 6 leptons and a few with only 6 quarks, 6 leptons and a few force carrying particles. (Double with force carrying particles. (Double with SUSY.)SUSY.)


What are the 3 families of particles?What are the 3 families of particles?


Details Details ??Details Details ??


Hadrons, Baryons & MesonsHadrons, Baryons & Mesonshttp://www2.slac.stanford.edu/vvc/theory/hadrons.html


Bosons and FermionsBosons and Fermions A Boson is a particle with integer spin. A A Boson is a particle with integer spin. A

photon has spin 1. So does a gluon and W, photon has spin 1. So does a gluon and W, Z particles. Do not obey the Pauli Z particles. Do not obey the Pauli exclusion principle, obey Bose-Einstein exclusion principle, obey Bose-Einstein statistics. statistics. (eg. Vector bosons are often (eg. Vector bosons are often forceforce carriers. Not carriers. Not Higgs boson though, Higgs Boson has spin =0)Higgs boson though, Higgs Boson has spin =0)

A Fermion is a particle with odd ½ integer A Fermion is a particle with odd ½ integer spin. An electron has spin ½. Also protons spin. An electron has spin ½. Also protons and neutrons… all matter particles in fact. and neutrons… all matter particles in fact. Obey Pauli exclusion principle and Fermi-Obey Pauli exclusion principle and Fermi-Dirac statistics.Dirac statistics.


Leptons and QuarksLeptons and Quarks

Leptons and quarks are supposedly Leptons and quarks are supposedly indivisible particles.indivisible particles.

LeptonsLeptons (Electrons, Muons, Taus, neutrinos (Electrons, Muons, Taus, neutrinos & their antiparticles) are stand-alone & their antiparticles) are stand-alone particles and can be observed in the wild, particles and can be observed in the wild, err… “err… “naked”.naked”.

QuarksQuarks can only be found inside other can only be found inside other particles, like Protons and Neutrons (in 3s) particles, like Protons and Neutrons (in 3s) and Mesons (in 2s, quark +anti-quark).and Mesons (in 2s, quark +anti-quark).


Quarks and Anti-QuarksQuarks and Anti-Quarks

Baryons and Mesons are colorless.Baryons and Mesons are colorless.


What are Protons and Neutrons made of ?What are Protons and Neutrons made of ?What is isotopic spin symmetry?What is isotopic spin symmetry?

Quarks have both electric and color chargeQuarks have both electric and color charge Color charges: Red, green & blue {1,2,3} Color charges: Red, green & blue {1,2,3} And Flavors: { u d c s t b } And Flavors: { u d c s t b } yummyyummy


Quantum Chromodynamics QCD.Quantum Chromodynamics QCD.Gluons have both color and anti-color, 9 varieties but 1 combination is Gluons have both color and anti-color, 9 varieties but 1 combination is

white which is not allowed which leaves 8 types of gluon.white which is not allowed which leaves 8 types of gluon.


A Physicists drawing of the same process; A Physicists drawing of the same process; using an up quark.using an up quark.


When gluons interact When gluons interact with each other…with each other…

You get a GLUEBALL !!You get a GLUEBALL !!


From QED to U(1) + SU(2) & SU(3)From QED to U(1) + SU(2) & SU(3) Extension of the local U(1) symmetry of QED to Extension of the local U(1) symmetry of QED to

include QCD SU(3), was done by Yang and Mills in include QCD SU(3), was done by Yang and Mills in 1954. Electroweak theory proven 1983.1954. Electroweak theory proven 1983.

Larger symmetries involve non-commuting Larger symmetries involve non-commuting algebra (non-Abelian, ie. Aalgebra (non-Abelian, ie. AxxB is not BB is not BxxA.) Now A.) Now called Yang-Mills theories.called Yang-Mills theories.

U(1) gauge symmetry refers to Local phase U(1) gauge symmetry refers to Local phase invariance. invariance. (A(A 1/2 wave plate in front of 1 slit, in a 2 slit 1/2 wave plate in front of 1 slit, in a 2 slit interference experiment, is like AB-effect, introduce a B-field interference experiment, is like AB-effect, introduce a B-field between the slits.)between the slits.)

U(3) refers to 3 colors, red green blue in QCD.U(3) refers to 3 colors, red green blue in QCD. Yang-Mills gauge symmetry U(2) involves isotopic Yang-Mills gauge symmetry U(2) involves isotopic

spin which is the interchange of protons and spin which is the interchange of protons and neutrons in the nucleus.neutrons in the nucleus.


Higgs BosonHiggs Boson adds particle mass adds particle mass

These spin-less force particles give These spin-less force particles give other particles their mass.other particles their mass.

The addition of the Higgs field The addition of the Higgs field (a field (a field

implies there are associated force particles)implies there are associated force particles) again helps to renormalize the again helps to renormalize the theory.. gets rid of infinities.theory.. gets rid of infinities.

Axions may represent yet another Axions may represent yet another field, with much lighter particles. field, with much lighter particles. OK OK too many details…OK OK too many details…


Renormalized electroweak theory:Renormalized electroweak theory:Weinberg-Salam-Glashow model confirmed, CERN 1983.Weinberg-Salam-Glashow model confirmed, CERN 1983.

Heavy W+ W- and Z particles foundHeavy W+ W- and Z particles found


What aboutWhat about Super-symmetry? Super-symmetry?

In order to remove infinities in the theory In order to remove infinities in the theory fermions should transform into bosons and fermions should transform into bosons and vice versa. vice versa. (This is a natural consequence of string (This is a natural consequence of string theory!!)theory!!)

Each particle is predicted to have a super-Each particle is predicted to have a super-partner called a partner called a sparticle.sparticle.

The partner for the electron (fermion) is The partner for the electron (fermion) is the selectron (boson), for photon is the selectron (boson), for photon is photino etc. Each differs from its partner photino etc. Each differs from its partner by spin ½. by spin ½. (More about this in the next lecture)(More about this in the next lecture)


Hunting for monopolesHunting for monopoles

Maxwell’s equations are more symmetric with Maxwell’s equations are more symmetric with monopoles. monopoles. (write on board)(write on board)

GUT requires their existence GUT requires their existence Monopoles have not been found yet, because Monopoles have not been found yet, because

they are very massive and rare.they are very massive and rare.


Where do we stand with the TOE?Where do we stand with the TOE?


Standard Model Draw-backsStandard Model Draw-backs

A unified theory would consist of a A unified theory would consist of a mathematical framework in which all mathematical framework in which all the forces and particles occur the forces and particles occur naturally. The masses and naturally. The masses and interaction strengths should be interaction strengths should be predicted by the theory not input as predicted by the theory not input as experimental parameters. Gravity experimental parameters. Gravity should be included, and it is NOT in should be included, and it is NOT in the standard model.the standard model.


Reading Material: for the quiz…Reading Material: for the quiz… Just kidding about the quiz!Just kidding about the quiz! http://particleadventure.org/particleadventure/index.htmlhttp://particleadventure.org/particleadventure/index.html ““Superheavy Magnetic Monopoles” Superheavy Magnetic Monopoles” Sci. AmerSci. Amer. April p.106 (1982).. April p.106 (1982). ““The search for proton decay” Sci. Amer. p.54 June (1985).The search for proton decay” Sci. Amer. p.54 June (1985). ““Is Nature Supersymmetric” Sci. Amer. p.52 June (1986)Is Nature Supersymmetric” Sci. Amer. p.52 June (1986) ““The Higgs Boson” The Higgs Boson” Scientific AmericanScientific American p.76 Nov (1986) p.76 Nov (1986) ““The theory formerly known as Strings” Sci. Amer. p.64 June The theory formerly known as Strings” Sci. Amer. p.64 June

(1998).(1998). ““Gauge theories of the forces between elementary particles”, by Gauge theories of the forces between elementary particles”, by

Gerard t’ Hooft Sci. Amer., June (1980).Gerard t’ Hooft Sci. Amer., June (1980). Particle Physics: A Los Alamos PrimerParticle Physics: A Los Alamos Primer,, Ed. by N. G. Cooper and G. Ed. by N. G. Cooper and G.

B. West, Cambrige U. Press, 1988.B. West, Cambrige U. Press, 1988. Introduction to Elementary particlesIntroduction to Elementary particles,, by David Griffiths, Wiley by David Griffiths, Wiley

1987.1987. THE 2 LAST BOOKS ARE EXCELLENT… QM and E&M by Griffiths are THE 2 LAST BOOKS ARE EXCELLENT… QM and E&M by Griffiths are

also excellent!! And I strongly recommend them to students.also excellent!! And I strongly recommend them to students.


THE ENDTHE END

See you Feb 23See you Feb 23rdrd

Lecture 4: Strings and thingsLecture 4: Strings and things

Dr. H. Fearn CSUF Physics 1 Lecture 3: The Standard Model The fundamental model for elementary...

Documents

Transcript of Dr. H. Fearn CSUF Physics 1 Lecture 3: The Standard Model The fundamental model for elementary...