Why is there something rather than nothing?

Baryogenesis and leptogenesis

Krzysztof TurzyńskiInstitute of Theoretical Physics

Faculty of Physics, University of Warsaw

Early natural philosophy

Leibniz, 1697

Swinburne

Nothingness is spontaneous, while an existing Universe must have required work to form.

Nothingness is uniquely natural, because simpler than anything else.

Outline1. Rudiments2. Electroweak baryogenesis3. Baryogenesis through leptogenesis4. Leptogenesis vs neutrino and other experiments

M. Olechowski, S. Pokorski, K. Turzyński, J.D. Wells, “Reheating Temperature in Gauge Mediated Models of Supersymmetry Breaking”, JHEP 0912 (2009)

The paradigmobservations consistent with hot Biga Bang

• nucleosynthesis (T1MeV)ligt element abundances

• decoupling of radiation (T1eV) power spectrum of the cosmic microwave background

details of both processes depend on relatice densities of baryons and photons

The number

• corresponds to 20 000 000 001 quarks vs 20 000 000 000 antiquarks – small !

after Davidson et al., 0802.2962

WMAP+BAO+SNe

BBN

The number

• too big for a fluctuation in the matter-antimatter symmetric Universe

after Davidson et al., 0802.2962

WMAP+BAO+SNe

• corresponds to 20 000 000 001 quarks vs 20 000 000 000 antiquarks – small !

A few equationsmetrics of the Universe

Friedmann equation

continuity equation

equation of state

input from particle physics

History of a particle species

Photons of avg energy T cannot create efficiently create particles of mass >T

Universe too rarefied for the massive particles to meet at all

1

interaction rate > expansion rate

expansion rate

interaction rate

Sakharov conditions

Conditions necessary for dynamical generation of a nonzero baryon number in

the initially matter-antimatter symmetric Universe.

1 B violation

2 C and CP violation

3 departure from thermal equilibrium

Sakharov conditionsRemark 1. Any quantum number will do

L, B – L, B + L ...

Remark 2. If B violating interactions are even back to equilibrium, they completely wash out previously generated asymmetry.

CP in the Standard Model

daL

ubL

W–

C

CP

daL

ubL

W+ ig2Vab

daR

ubR

W– ig2Vab

daR

ubR

W– ig2Vab*

Sphalerons

Tunelling between vacua in equilibrium for 1012GeV > T > Tew

-1

1

-5 5

V

Sphaleron field configurations locally maximizing

energy

B=3L=3

B – L conserved

B + L violated

V

Electroweak phase transistion

T<<Tc

T>>TcV

T>>Tc

T<<Tc

V

A bubble of broken phase forms. It expands rapidly, coallescing with other bubbles.

Eventually the entire Universe sits inside a bubble of broken phase.

Remaining antiquarks are destroyed in

sphaleron transitions

Bubble wall allows more quarks than antiquarks inside

phase of broken symmetry

phase of unbroken symmetry

You are here

B

LB+L=0

B–L=const

Sphalerons

Sphaleron transitions • conserve B–L• wash B+L out

L asymmetry is reprocessed into B asymmetry

Neutrino masses1. Oscillations

2. Tritium decay

3. Cosmology (CMB vs LSS)

WMAP

WMAP+BAO+SNe

WMAP+BAO+Sne+HST+MegaZ

after Thomas et al, 0911.5291

Neutrino massesFermion interacting with a spinless particle changes

helicity. L R

Interactions with a constant vacuum expectation value of a scalar field => mass: Higgs mechanism

Neutrino massestwo possibilities

L R R= RL

R – new state – sterile neutrino (not interacting with W,Z0)

Dirac particle

only SM states – but lepton number broken

(so what?)

Majorana particle

Neutrino massesseesaw mechanism – 2 possibilities in 1

L R= R

NR NL= NL

m= (MEW)2 / MBig

MN = MBig

N: singlet of SU(2), fermion (Type I)triplet of SU(2), skalar (Type II)triplet of SU(2), fermion (Type III)

Generating L asymmetrygeneratione

washout

genation

washout

Generating L asymmetryCP violation

Generating L asymmetryEquilibrium (in N production)

>

Fast production processes => equilibrium distribution for RH neutrinos

Strong washout:

Generating L asymmetryOut of equlibrium (N decay)

Generowanie asymetrii w L

Summary IThe origin of the baryon asymmetry of the Universe remains a mystery. Different options are still possible, but some have already been ruled out.

Leptogenesis appears a reasonably natural option

Leptogenesis vs low-energy CP violation

Neutrino Yukawa couplings

CP asymmetry relevant for leptogenesis

CP asymmetry potentially observable in terrestrial experiments

?

CP violation:from low to high energies

Branco, Gonzalez Felipe & Joaquim, 2006

There are only low-energy (Dirac and Majorana) phases

CP violation:from low to high energies

Joaquim, Masina & Riotto, 2006

SUSY enters the game:in mSUGRA models additional constraints from LFV processes and electron EDM

CP violation:from high to low energies

Davidson, Garayoa, Palorini & Rius, 2008Markov chain Monte Carlo analysis

Does successful leptogenesis prefer any values of the low-energy CP phases in the neutrino sector?

phase 1

phas

e 2

Summary IIThe origin of the baryon asymmetry of the Universe remains a mystery. Different options are still possible, but some have already been ruled out.

Leptogenesis appears a reasonably natural option

Alas, not testable!

Generically requires T>109 GeV. In SUSY models this leads to overproduction of gravitinos, ruining nucleosynthesis