Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://nuclphys.sinp.msu.ru/conf/lpp14/210809/Di%20Bari.pdf Äàòà èçìåíåíèÿ: Wed Sep 16 16:30:23 2009 Äàòà èíäåêñèðîâàíèÿ: Tue Oct 2 00:42:46 2012 Êîäèðîâêà: Ïîèñêîâûå ñëîâà: universe

Fourteenth Lomonosov Conference Moscow, August 19-25, 2009

Leptogenesis
Pasquale Di Bari
(University of Southampton & INFN-Padova)


Cosmological observations
CMBR anisotropies COBE WMAP Clusters of galaxies Large Scale Structure SLOAN DIGITAL SKY SURVEY Supernovae type Ia

+ many others (weak lensing, BAO, Ly-, ........)


CDM: a cosmological SM ?


Thermal history of the Universe


Puzzles of Modern Cosmology
1. 2. 3. 4.

Dark matter Matter - antimatter asymmetry Inflation Accelerating Universe
Leptogenesis

Î clash between the SM and LCDM !


Matter-antimatter asymmetry of the Universe
· Symmetric Universe with matter- anti matter domains ? Excluded by CMB + cosmic rays (Cohen, De Rujula, Glashow `96)



B

CMB

= (6.2 ± 0.15) x 10

-10

>>

B

(barring the possibility of anti-matter "hidden" in compact objects: talk by Dolgov)

· Pre-existing ? It conflicts with inflation ! (Dolgov `97)

dynamical generation · A Standard Model Solution ?

(baryogenesis)
by far too low !

(Sakharov '67)

New Physics is needed!


Models of Baryogenesis
· From phase transitions: · From Black Hole evaporation
-Ele

ctroweak Baryogenesis: * in the SM * in the MSSM * ................

· Spontaneous Baryogenesis · .......................................

· Affleck-Dine:
at preheating Q-balls ..........

· From heavy particle decays: - GUT Baryogenesis - LEPTOGENESIS


Neutrino masses: m1 < m2 < m

3

Tritium b decay :me<2.3 eV (Mainz 95% CL) bb0n:mbb< 0.3 ­ 1.0 eV (Heidelberg-Moscow 90% CL, similar result by CUORICINO ) using the flat prior (W0=1): CMB+BAO : S mi < 0.61 eV (WMAP5+SDSS) CMB+LSS + Lya :S mi <0.17 eV (Seljak et al.)


Neutrinos are much lighter than all other fermions !


A minimal extension of the SM

mD


The see-saw orthogonal matrix


"Vanilla" Leptogenesis
(Fukugita,Yanagida '86)

Let us start 1) Flavor

from the effects

simplest scenario (,,vanilla" leptogenesis) are neglected

Total CP asymmetries If i 0 a lepton asymmetry is generated from Ni decays and partly converted into a baryon asymmetry by sphaleron processes if Treh t 100 GeV ! (Kuzmin,Rubakov,Shaposhnikov, '85)

efficiency factors > # of Ni decaying out-of-equilibrium


Total CP asymmetries
(Flanz,Paschos,Sarkar'95; Covi,Roulet,Vissani'96; BuchmÝller,PlÝmacher'98)

It does not depend on the leptonic mixing matrix U !


2) Hierarchical heavy RH neutrino spectrum
(Blanchet,PDB '06)

3) N3 does not interfere with N2-decays:
(PDB '05)

Under the last two assumptions In the end an unflavored N1-dominated scenario holds:

It does not depend on the leptonic mixing matrix U !


4) Semi-hierarchical heavy neutrino spectrum

Upper bound on 1
(Davidson, Ibarra '02;BuchmÝller,PDB,PlÝmacher'03;Hambye et al '04;PDB'05 )


Main lessons from vanilla leptogenesis
1) The early Universe seems to ,,know" neutrino masses with leptogenesis: a first interesting concordance decay parameter (BuchmÝller,PDB,PlÝmacher '04)

The measured neutrino mass scales in neutrino oscillations are such that the wash-out is strong enough to guarantee independence of the initial conditions ..........


Main lessons from vanilla leptogenesis
2) Neutrino mass bounds ...but not too strong to prevent successful leptogenesis !

Upper bound on m1 :

m1 d 0.12 eV

(BuchmÝller,PDB,PlÝmacher '03; Giudice, Raidal, Strumia,Riotto '04)

Lower bound on M1 : M1 t 3x 109 GeV
(Davidson,Ibarra; BuchmÝller,PDB,PlÝmacher '02)

Lower bound on Treh : Treh t 109 GeV
(BuchmÝller,PDB,PlÝmacher '04)


3) A second interesting concordance
matm = 10 -5 eV

matm = 0.05 eV

matm = 10 eV

Neutrino oscillations data represent a strong positive test for leptogenesis not only in a qualitative way but also quantitavely !


A very hot Universe for leptogenesis ?


Beyond vanilla leptogenesis
beyond the hierarchical limit adding flavor to vanilla leptogenesis N2 - leptogenesis


Beyond the hierarchical limit
(Blanchet,PDB `06)

For example: · partial hierarchy: M3 >> M2 , M
1

M 3M 3 2

3 Effects play simultaneously a role for d2 ý 1 :

1. Asymmetries add up

M 2 M 1

}

2

M- M 1 2 M 1

2. Wash-out effects add up as well 3. CP asymmetries get enhanced: |1,2| µ 1/2
For d2 d 0.01 (degenerate limit) the first two effects saturate:


Flavor effects
(Nardi,Nir,Roulet,Racker '06;Abada,Davidson,Losada,Josse-Michaux,Riotto'06)

Flavor composition:

It does not play any ole only for but for M1 d 10
12

GeV Î t-Yukawa interactions

are fast enough to break the coherent evolution of and and Î ,,tend" to be projected on a 2-flavor basis: along the t and a coherent over-position of m+e
For M1d 109 GeV the m-Yukawas are also in equilibriumÍ3-flavor regime

heavy neutrino flavor index

lepton flavor index


1) Low energy phases can be the only source of CP violation!
(Blanchet,PDB, '06; Pascoli, Petcov, Riotto, '08; Anisimov, Blanchet, PDB '08)

Assume that all CP violation stems from low energy phases:

This implies that the total CP asymmetries vanish and :

Assume that even the Majorana phases vanish Î possible source of CP violation for leptogenesis is same we could observe in neutrino oscillations and described by sin 13 sin : would such a source be have successful leptogenesis ? YES ! (though with restrictions on the RH neutrino mass spectrum)

the only then the that is sufficient to severe

NOTE: (un-)discovery of CP violation in neutrino oscillations would not (dis-)prove leptogenesis but it would however certainly represent an additional strong experimental support (or a missed opportunity) !


(Blanchet,PDB '08)

2) The lower bounds on M1 and on Tr

eh

get relaxed:

It dominates for |Wij|d1 but is upper bounded because of W orthogonality:

It is usually neglected but since it is not upper bounded by orthogonality, for |Wij|t1 it can be important

The usual lower bound gets relaxed


N2-dominated scenario
(PDB'05) For a special choice of W=R
23

3 things happen simultaneously:

fl

The lower bound on M1 disappears and is replaced by a lower bound on M2 ... that however still implies a lower bound on Treh !

Thanks to flavor effects the domain of applicability extends much beyond the particular choice W=R23 !
( Vives '05; Blanchet, PDB '06; Nardi,Nir '07; Blanchet, PDB '08)


N2-flavored leptogenesis
( Vives '05; Blanchet, PDB '06; Nardi,Nir '07; Blanchet, PDB '08)

Thanks to flavor effects the domain of applicability extends much beyond the particular choice W=R23 !

Wash-out is neglected Wash-out and flavor effects are both taken into account

Unflavored case


Testing Models of New Physics with Leptogenesis
2 examples:
1. 2.

GUT 's Flavor symmetries


(Steve King at Neutrino Telescopes ´09)


(Steve King at Neutrino Telescopes ´09)


Leptogenesis and SO(10) models
Using the parameterization:
(PDB, Riotto '08)

and assuming `SO(10)-inspired relations´: VL=1 and Î Î the asymmetry produced from the lightest RH neutrino is negligible and the N2-dominated scenario is realized ! The green points correspond to
16 14 12

at 2:
10
10° 8° 6° 4° 2° 0°
-4

10

-3

10

-2

10

-1

16 14 12 10 8 6 4

a2=5
13

10

-3

10

-2

10

-1

10

0

10° 8° 6° 4° 2° 0°
-4

Log(Mi /GeV)

10 8 6 4

10

-3

10

-2

10

-1

10

10

-3

10

-2

10

-1

10

0

m1 (eV)

m1 (eV)


Flavor Symmetries
Some basic features · Assume that the theory is invariant under transformations of a flavour symmetry group G (discrete or continuous) · ...and that this is spontaneously broken to a subgroup H through the VEV `s of a set of scalar fields (flavons) · = <>/ << 1 · flavor symmetries can well embed the see-saw mechanism ! · In this case the matrices M and mD become functions of and in the limit ü 0 they have special forms enforced by the symmetry. For example defining one has:

Example: A4-symmetry Î approximate tri-bimaximal mixing after symmetry breaking (Ma `04)


A popular example: A4 x Z3 x U(1)
(Altarelli, Feruglio '05; Bertuzzo, Di Bari, Feruglio, Nardi `09)
10 GeV M1/y 10 GeV 10 GeV M3/y 10 GeV 10 GeV
13 14 2 15 16 2 2 17

FN

NORMAL HIERARCHY
10 GeV M3/y 10 GeV 10 GeV 10 GeV
m
sol

17

INVERTED HIERARCHY
2

M2/y

16

15

M2/y

2

14

M1/y

2

m

atm

10 GeV

13

m

sol

m

atm

10 eV

0

10 eV

0

10 eV

0

10 eV

0

10 eV
m
atm

-1

10 eV

-1

10 eV
m
atm

-1

m3 m
2

10 eV

-1

m

3

10 em V

-2

m

2

10 eV

-2

10 eV m1

-2

10 eV

-2

sol

m

1

10 eV

-3

m
-3 -2

sol

m

atm

10 eV

10 eV

10 eV

-1

10 eV 0 10 eV

-3

10 eV -3 10 eV

-3

m

sol

m

atm

10 eV

-3

10 eV

-2

m1

m1

10 eV

-1

10 eV

0


Leptogenesis in A4 x Z3 x U(1)
(Manohar, Jenkins ´08; Bertuzzo, Di Bari, Feruglio, Nardi '09; Hagedorn, Molinaro, Petcov ´09)

FN

NORMAL ORDERING

INVERTED ORDERING Y=2



Y=4

{
Y=0.1 Y=0.5



Optimal range

m1 (eV)
Successful leptogenesis is realized for the natural values of the parameters without any tuning + the scale of masses (and of Treh) can be lowered (lowering y)

m1 (eV)
Some tuning is needed and the scale of masses (and of Treh) is necessarily very high


Beyond the minimal scenario?
Many extensions have been explored that can potentially produce signals at colliders, in cosmic rays, ...... · Non-thermal leptogenesis · Supersymmetric Î LFV, EDM`s get enhanced and give additional constraints · type I+type II (or type III) see-saw · extra-gauge interactions
Î TeV RH neutrinos get produced (and detected) more efficiently

· light (KeV) RH neutrinos
Î can explain DM, X-ray background, pulsars kicks

· .............................................. ...on the other hand in all these extensions of the minimal seesaw the nice matching between observed neutrino masses and matter-antimatter asymmetry is spoiled to some extent


Final remarks
· current information on neutrino masses is in very nice agreement with leptogenesis expectations ! Wish list for leptogenesis : · definitive exclusion of quasi-degenerate light neutrinos · discovery of CP violation in neutrino oscillations · discovery of 00nú · emergence of correlations among different data that can be explained by leptogenesis + some model of new physics · discovery of heavy neutrinos ? dangers : · quasi-degenerate light neutrinos · viable electroweak barogenesis · Treh d 100 GeV