Why is there something rather than nothing?

Why is there something rather than nothing?

Baryogenesis and leptogenesis Krzysztof Turzyński

Institute 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.

Outline

1. Rudiments

2. Electroweak baryogenesis

3. Baryogenesis through leptogenesis

4. 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 paradigm

observations consistent with hot Biga Bang

• nucleosynthesis (T1MeV) ligt element abundances

• decoupling of radiation (T1eV) 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 equations

metrics 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

2

3

Sakharov conditions

Remark 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

d^a_L

u^b_L W^–

C CP d^a_L

u^b_L

W⁺ ig₂V^ab

d^a_R

u^b_R W^– ig₂V^ab d^a_R

u^b_R W^– ig₂V^ab*



Sphalerons

Tunelling between vacua in equilibrium for

10¹²GeV > T > T_ew

-1 1

-5 5



V

Sphaleron

field configurations locally maximizing

energy

B=3

L=3

B – L conserved B + L violated

 V



Electroweak phase transistion

T<<T_c T>>T_c

V



T>>T_c

T<<T_c

 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 B+L=0 L

B–L=const

Sphalerons

Sphaleron transitions

• conserve B–L

• wash B+L out

L asymmetry is

reprocessed into B asymmetry

Neutrino masses

1. 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 masses

Fermion interacting with a spinless particle changes

helicity.





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

Neutrino masses

two possibilities









= 

_R – new state – sterile neutrino (not interacting with W^,Z⁰)

Dirac particle

only SM states – but lepton number broken

(so what?)

Majorana particle

Neutrino masses

seesaw mechanism – 2 possibilities in 1





= 

N

N

= N

m_= (M_EW)² / M_Big M_N = M_Big

N:

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

Generating L asymmetry

generatione

washout

genation

washout

Generating L asymmetry

CP violation

Generating L asymmetry

Equilibrium (in N production)

>

Fast production processes => equilibrium distribution for RH neutrinos

Strong washout:

Generating L asymmetry

Out of equlibrium (N decay)

Generowanie asymetrii w L

Summary I

The 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, 2008 Markov chain Monte Carlo analysis

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

phase 1

phase 2

Summary II

The 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