The Origin of the Matter-Antimatter Asymmetry:

Will we ever know?

Michael DineSLAC Conference on Heavy Flavor Physicsat High Luminosity e+e- Colliders May, 2003

The Asymmetry

• From Nucleosynthesis: B h2 = 0.0214§ 0.002• From CMBR: Bh2 = 0.0224§ 0.0009

Sakharov Conditons

• Violation of Baryon Number at the level of the fundamental laws

• An Arrow of Time• CP Violation

u

u

d

d^c

e+

o

XX

ee++

X

XX

MMWW=g=g

MMWW=0=0

[[Cline,Joyce and Kainulainen, 1998]Cline,Joyce and Kainulainen, 1998]

N

l

NN

ll

hh

VV

Scalar in condensateScalar in condensate

PROSPECTSCosmology and Microphysics

• Nucleosynthesis: we can calculate the dark matter density from our knowledge of microphysics.

• Dark Matter: We might calculate the dark matter density in the future if supersymmetry is discovered, and the properties of superparticles measured (esp. masses – linear collider); or if we discover axions. Both scenarios require (plausible) assumptions about the early universe.

• Inflation: probably requires theoretical as well as observational input (string theory?).

Baryogenesis: we have narrowed the possibilities, but:

• With neutrino mass, we may have encountered a basic clue to the origin of the matter-antimatter asymmetry. Measurements plus theoretical developments will be necessary to a calculation of the asymmetry.

• Discovery of supersymmetry would open up new possibilities (coherent production, electroweak baryogenesis). But theory as well as experiment will be necessary.

• In either case, further theoretical progress will surely require more theoretical input on the questions of flavor and CP violation.