Introduction to Particle Physics Thomas Gajdosik, FI & VU

VU Seminar – Introduction to Particle Physics Thomas Gajdosik, FI & VU

Taxonomie of Particles

∆++

u

uu

π+

u

d

d

us

Λ0

c

d

D+

s

u

Κ−

b

b

ϒ

d

uu

du

d

proton neutron

mesons

baryons

...

...

nucleus

He-nucleus(α-particle)

atom

matter


Bosons

Spin 0,1,2, …

Bose-Einstein statistic

Fermions

Spin ½, 1½, 2½, …

Fermi-Dirac statistic

Pauli exclusion principle

angular momentum

π+

u

d


photon

γ

neutron

ud

d

proton

ud

uelectron

e-


composite elementary

divisible into smaller parts

π+

u

d


photon

γneutron

ud

d

proton

ud

u

electron

e-

matteratom


elementary

e-

e+

Kp

p

e-

e+

K

π

it is impossible to “split” elementary particles!(i.e.: to separate and isolate the parts of an elementary particle)

if one collides elementary particles,

only elementary particles come out


extended Hadrons

but elementary particles can have a (sub)structure

π+

u

d

neutron

ud

d

proton

ud

u


fundamental ~ pointlike

leptonsτ

ντ

e

νe

µ

νµ

γvector bosons Z0W±

g

h Higgs boson (?)

b

t

s

c

d

uquarks

They appear point-like

even to our best

microscopes (which are particle accelerators)

in fundamental particles,

scientists could not find

any substructure.


Baryons

• are fermions:

Spin ½ and 1½

• made of 3 quarks

(or antiquarks)

Mesons

• are bosons:

Spin 0 (pseudoscalar)

Spin 1 (vector)

• quark and antiquark

Hadrons

neutron

ud

d

proton

ud

u

Spin 0Spin ½

∆++

uu

u

Υ(1s)

bb

π+

ud

Spin 1Spin 1½


• is a borderline case:

– large molecules behave more or less like classical objects

– small molecules, like H2 can form quantum mechanical coherent states

• H2 is a boson

• HD is a fermion


molecule

macroscopic matter

• follows the laws of classical physics:the quantum mechanical description brings understanding of the properties of the material, but is not suited to classify the macroscopic object.

• There is no Bose-Einstein or Fermi-Dirac statistics, only Maxwell-Boltzman

they are neither fundamental nor elementary!


• the nucleus is a quantum mechanical object.• it has definite spin and parity

(can be boson or fermion)

• it is extended• it can be split into nucleons protons and neutrons (a few MeV are needed)

• the atom is a quantum mechanical object.• it has definite spin and parity

(can be boson or fermion)

• it is extended• it can be split into electrons and nucleus plasma (only a few eV are needed)

they are neither fundamental nor elementary!

atom

nucleus



the electrone-

Thomson

the electron is fundamental and elementary!

Spin ½ FermionMass: 511 keVCharge: -1stable


the photonγ

Planck Einstein

Compton

e-

the photon is fundamental and elementary!

Spin 1 BosonMass: 0Charge: 0stable


the proton

e-

γ

Rutherford

p

the proton is not fundamental but elementary!

Spin ½ FermionMass: 938 MeVCharge: +1stable


Spin ½ FermionMass: 939.6 MeVCharge: 0

the neutron

e-

γ

n

p

Chadwick

the neutron is not fundamental but elementary!

τ½: 886 s “stable”


the muon

e-

γ

µ

pn

Who ordered that one?

• Hess• Anderson, Neddermeyer• Street, Stevenson

spark chamber

the muon is fundamental and elementary!

Spin ½ FermionMass: 105 MeVCharge: -1τ½: 2.2 μs unstable


the pion

e-

γ

π

pn

µ

Powell Yukawa

prediction discovery

Spin 0 BosonMass: 135 / 140 MeVCharge: 0 / ±1

the pion is not fundamental but elementary!

τ½: 8.4×10-17 s / 2.6×10-8 s unstable


the positron (anti-matter)

e-

γ

e+

pn

µπ

Anderson

Dirac

prediction

discovery

the electron is fundamental and elementary!

exactly like the electron!Spin ½ FermionMass: 511 keVCharge: +1stable


the neutrino

e-

γ

ν

pn

µπ

e+

Fermi Pauli

the neutrino is fundamental and elementary!

Spin ½ FermionMass: < 2.2 eVCharge: 0stable


strange particles

e-

γ

K

pn

µπ

e+

Rochester,Butler,...

ν

Σ

Λ

are Hadronsunstable

strange particles are not fundamental but elementary!


antiproton

e-

γp

n

µπ

e+

cosmic rays,Bevatron,PS (CERN)

ν

p_

also antiprotons!

the antiproton is not fundamental but elementary!

same as proton! Spin ½ FermionMass: 938 MeVCharge: -1stable


charm quark: J/Ψ

e-

γp

n

µπ

e+

Burt Richter (SLAC), Samuel Ting (BNL)1974

ν

c

all quarks are fundamental but not elementary!

Spin ½ FermionMass: 1.16 – 1.34 GeVCharge: + ⅔unstable


tau lepton: τ

e-

γp

n

µπ

e+Martin Perl (SLAC-LBL)1975 ν

τ

all leptons are fundamental and elementary!

Spin ½ FermionMass: 1.8 GeVCharge: -1

τ½: 2.9×10-13 s unstable


bottom quark

e-

γp

n

µπ

e+

ν

b


Spin ½ FermionMass: 4.13 – 4.37 GeVCharge: - ⅓unstable

E288 (Fermilab)1977


Gluon

e-

γp

n

µπ

e+

PETRA (DESY)1979

ν

g

the gluon is fundamental but not elementary!

Spin 1 BosonMass: 0Charge: 0stable


W- and Z-boson

e-

γp

n

µπ

e+

discovery: UA1, UA2 (CERN)1983

ν

W,Z

W- and Z-bosons are fundamental and elementary!

Z0-bosonSpin 1mZ = 91.2 GeVCharge: 0unstableΓZ = 2.5 GeV

W±-bosonsSpin 1mW = 80.4 GeVCharge: ±1unstableΓW = 2.14 GeV


top quark

e-

γp

n

µπ

e+

ν

tCDF, D0 (Fermilab)1995


Spin ½ FermionMass: ~173 GeVCharge: + ⅔unstable


Higgs particleH

ATLAS, CMS (CERN)

2012

CDF, D0 (Fermilab)?

!

?

!the SM Higgs-boson is

fundamental and elementary!

Higgs-bosonSpin 0mH = 125.9 GeVCharge: 0unstableΓH ~ 4 MeV

Documents

Introduction to Particle Physics Thomas Gajdosik, FI & VU