Particle properties

Mass	M
Intrinsic angular momentum	J
Size (and structure)	R
Lifetime or Width	t or G (Breit Wigner)

Interactions	Charges
Weak	weak isospin
Electromagnetic    primary force	electric charge Q (magnetic moment m)
residual forces between neutral objects e.g. Van der Waals atomic bonds	polarizability shared constituents
Strong    primary force	colour
residual forces e.g. nuclear binding	shared constituents, polarizability, isospin

Magnetic moments

Electromagnetic dipole moments are typically

For point particles, the intrinsic length is the Compton wavelength

Classically, the magnetic moment of a particle in a circular orbit with angular momentum L is

The magnetic moments of subatomic particles are usually written as

• For a classical point particle,

• For structureless spin-1/2 point fermions

• Deviations from g=2 indicate that the fermion has structure. Even point fermions turn out to have a some structure due to the constant radiation and absorption of photons.

e.g. the anomalous magnetic moment of the electron is

	a	ç=	(|g|-2)/2
	aexperiment	=	0.0011596521884(43)
	atheory	=	0.0011596522014(272)

Similarly, a structureless neutral particle must have

Particle Classifications

matter constructed from

   Quarks:

	u	c	t
	d	s	b

   Leptons:

	ne	nm	nt
	e	m	t

building

	hadrons			(from quarks and glue)
		mesons		J=0, 1, 2,…
		baryons		J=1/2, 3/2,… masses M ~ 1 GeV binding energies ÆE ~ 1 GeV
			nuclei	e.g. 1H2, 19K40, 94Pu239,… M~1-250 GeV, DE~1-200 MeV