Neutrino masses. Universe

Transcription

1 Università di Padova,, 8 May, 2008 Neutrino masses and the matter-antimatter antimatter asymmetry of the Universe (new results in collaboration with Steve Blanchet to appear soon) Pasquale Di Bari (INFN, Padova)

2 Outline Puzzles of Modern Cosmology A basic picture of leptogenesis Beyond vanilla leptogenesis

3 Puzzles of Modern Cosmology

4 WMAP 5 years data

5 CMB alone is not enough!

6 Large Scale Structure The Universe observed: Sloan Digital Sky Survey The Universe simulated : Open problems: cusps (too much Dark Matter in halo centers?) Halo substructure issues (too many satellite galaxies?) Halo and galaxy merging (too much galaxy merging?)

7 ΛCDM: a cosmological SM?

8 The Universe is accelerating! q = 0 (Ω Λ, Ω M ) = (0.7, 0.3) (Ω Λ, Ω M ) = (0, 0.3) (Ω Λ, Ω M ) = (0, 1) Hubble diagram: High-redshift type Ia supernovae probe the expansion history and reveal accelerated expansion

9 A direct evidence for Dark Matter: the bullet cluster Hot gas from X-ray observations Dark Matter from gravitational lensing

10 Cosmological Concordance Clusters of galaxies are a laboratory for studying and measuring Dark Matter in a variety of ways: gravitational lensing effects, x-ray, radio, optical.

11 Thermal history of the Universe

12 The Mass-Energy budget today

13 Cosmological puzzles 1. Dark matter 2. Matter - antimatter asymmetry 3. Inflation 4. Accelerating Universe clash between the SM and ΛCDM!

14 Matter-antimatter asymmetry Symmetric Universe with matter- anti matter domains? Excluded by CMB + cosmic rays η Β = (6.2± 0.15) x >> η Β Pre-existing? It conflicts with inflation! (Dolgov 97) dynamical generation (baryogenesis) (Sakharov 67) WMAP5 A Standard Model Solution? η Β η Β : too low! SM CMB New Physics is needed!

15 Models of Baryogenesis From phase transitions: -Electroweak Baryogenesis: * in the SM * in the MSSM *. Affleck-Dine: - at preheating - Q-balls -. From Black Hole evaporation Spontaneous Baryogenesis From heavy particle decays: - GUT Baryogenesis - LEPTOGENESIS Leptogenesis has today the big advantage to be the unique model of Baryogenesis to rely on an ingredient beyond the SM that has been already observed: Neutrino Masses!

16 Neutrino masses: m 1 < m 2 < m 3 Tritium b decay : m e < 2.3 ev (Mainz 95% CL) bb0n : m bb < ev (Heidelberg-Moscow 90% CL, similar result by CUORICINO ) using the flat prior (W 0 =1): CMB+BAO : S m i < 0.61 ev (WMAP5+SDSS) CMB+LSS + Lya : S m i < 0.17 ev (Seljak et al.)

17 The basic picture of Leptogenesis ( Vanilla Leptogenesis) 1) Minimal see-saw mechanism 2) Unflavored 3) Semi-hierarchical right-handed neutrino..mass spectrum 4) Lightest RH neutrino dominance

18 1) Minimal see-saw mechanism 3 limiting cases : pure Dirac: M R = 0 pseudo-dirac : M R << m D see-saw limit: M R >> m D

19 3 light LH neutrinos: Nr2 heavy RH neutrinos: N 1, N 2, m ν m SEE-SAW M - the `see-saw pivot scale m is then an important quantity to understand the role of RH neutrinos in cosmology

20 m * ~ 1 GeV m> m* ï high pivot see-saw scale ï `heavy RH neutrinos m< m* ï low pivot see-saw scale ï `light RH neutrinos

21 The see-saw orthogonal matrix

22 2) Unflavoured leptogenesis (Fukugita,Yanagida 86) m D is complex in general ï natural source of CP violation Total CP asymmetries If ε i 0ïa lepton asymmetry is generated from N i decays and partly converted into a baryon asymmetry by sphaleron processes if T reh t 100 GeV (Kuzmin,Rubakov,Shaposhnikov, 85) efficiency factors > # of N i decaying out-of of-equilibrium

23 Total CP asymmetries (Flanz,Paschos,Sarkar 95; Covi,Roulet,Vissani 96; Buchmüller,Plümacher 98) It does not depend on U!

24 3) Semi-hierarchical heavy neutrino spectrum Upper bound on the CP asymmetry of the lightest RH neutrino (Davidson, Ibarra 02; Buchmüller,PDB,Plümacher 03;Hambye et al 04;PDB 05 )

25 4) N 1 -dominated scenario N 2 does not couple with N 3 : It does not depend on U!

26 NO FLAVOR (Blanchet,, PDB 06) N 1 Φ l 1 Φ

27 Efficiency factor decay parameter 1

28 z M 1 / T K 1 t U (T=M 1 )/τ 1 WEAK WASH-OUT STRONG WASH-OUT 0.07 z d 0.35 z B (0) K= K=10 (d Κ f /dz) z z (d Κ f /dz) z z z=20 z=30 z=10 z=0.1 z=0.2 z=0.3 z=0.4 z=0.5 z=4 z=5 z=7 z=8 z=9 z=6 z=1.5 z=0.7 z=1.2 z=3.5 z=0.6 z=0.8 z=1.7 z= z z B 10 z 1 1 N N1 K= K= N eq N 1 N N1 N eq N Κ f Κ f 1 10 z=m 1 /T z=m 1 /T

29 Dependence on the initial conditions weak wash-out strong wash-out N in N 1 = κ fin no dependence on the initial abundance N in N 1 =0 dependence on the initial abundance m 1` m sol M 1`10 14 GeV K Neutrino mixing data favor the strong wash-out regime!

30 A first interesting coincidence!

31 Neutrino mass bounds ~ 10-6 ( M 1 / GeV) Lower bound on M 1 (Davidson, Ibarra 02; Buchmüller, PDB, Plümacher 02) 3x10 9 GeV M 1 (GeV) Upper bound on the absolute neutrino mass scale (Buchmüller, PDB, Plümacher 02) N in N 1 = ev N in = 1 m N 1 1 (ev) Lower bound on T reh : T reh t 1.5 x 10 9 GeV (Buchmüller, PDB, Plümacher 04; Giudice,Notari,Raidal,Riotto,Strumia 04) The lower bounds on M 1 and T reh becomes more stringent when m 1 increases (PDB 04)

32 A second interesting coincidence m atm = 10 5 ev m atm = 0.05 ev =10 ev m atm

33 A very hot Universe for leptogenesis?

34 Beyond vanilla leptogenesis 1) Evading the CP asymmetry bound 2) N 2 -dominated scenario 3) Beyond the hierarchical limit 4) Flavor effects

35 Beyond Vanilla heavy neutrino flavor index lepton flavor index CP asmmetry enhancement for degenerate RH neutrinos Vanilla leptogenesis FLAVOR EFFECTS Contribution from heavier RH neutrinos Extra-term violating the usual CP asymmetry upper bound

36 CP asymmetry bound revisited If M 3 M 2 t 3M 1 : (Hambye,Notari,Papucci,Strumia 03; PDB 05; Blanchet, PDB 06 )

37 W = R 12 (w 12 ) R 13 (w 13 )R 23 (w 23 ) M 3 >> M 2 = 3 M 1 w ij <1 w 23 <50 If R 23 is switched off the extra-term does not help to relax the bounds!

38 Beyond the hierarchical limit (Pilaftsis 97, Hambye et al 03, Blanchet,PDB 06) Different possibilities, for example: partial hierarchy: M 3 >> M 2, M 1 M 3 3 M 2 M 3 >> GeV : ï M 2 M 1 } δ M - M M 1

39 3 Effects play simultaneously a role for d 2 Ü 1 : 1. Asymmetries add up 2. Wash-out effects add up as well 3. CP asymmetries get enhanced For d 2 d 0.01 (degenerate limit) the first two effects saturate and:

40 N 2 -dominated scenario (PDB 05) For a special choice of W=R 23 Four things happen simultaneously: fl Equivalent to assume: The lower bound on M 1 disappears and is replaced by a lower bound on M 2 that however still implies a lower bound on T reh!

41 Flavor effects (Nardi,Roulet 06;Abada, Davidson, Josse-Michaux, Losada, Riotto 06) Flavour composition: Does it play any role? but, for lower values of M 1, t-yukawa interactions, (Blanchet,PDB, Raffelt 06) are fast enough to break the coherent evolution of the and quantum states projecting them on the flavour basis within the horizon î potentially a fully flavored regime holds!

42 FULLY FLAVORED REGIME (Blanchet,, PDB 06) Lµ Lτ t R Φ l 1 Φ N1

43 Fully flavoured regime Let us introduce the projectors (Barbieri,Creminelli,Strumia,Tetradis 01) : These 2 terms correspond to 2 different flavour effects : 1. In each inverse decay the Higgs interacts now with incoherent flavour eigenstates! ï the wash-out is reduced and 2. In general and this produces an additional CP violating contribution to the flavoured CP asymmetries: Interestingly one has that now this additional contribution depends on U!

44 In pictures: 1) N 1 2) N 1 t t m m

45 General scenarios (K 1 >> 1) Alignment case and Democratic (semi-democratic) case One-flavor dominance and Remember that: big effect! ï the one-flavor dominance scenario can be realized only if the DP 1 a term dominates!

46 Do flavour effects relax the bounds on neutrino masses? For an arbitrary W and m 1 = 0 : (Blanchet,PDB 06) Flavor effects do not relax the lower bound on M 1 and T reh!

47 Arbitrary W W = R 13 PMNS phases off Red: Green: Blue :

48

49 Neutrino mass bounds (Abada,Davidson, Losada,, Riotto 06; Blanchet,, PDB 06)? 0.12 ev M 1 (GeV) EXCLUDED Condition of validity of a classic description in the fully flavored regime FULLY FLAVORED REGIME EXCLUDED EXCLUDED m 1 (ev) Is the fully flavoured regime suitable to answer the question? No! There is an intermediate regime where a full quantum kinetic description is necessary! (Blanchet,PDB,Raffelt 06) INTERMEDIATE REGIME

50 Red: Green: Blue :

51 Leptogenesis from low energy phases? (Blanchet,, PDB 06) Let us now further impose W real setting Im(w 13 )=0ï 1 = 0 M 1 min Majorana phases Dirac phase F 1 = -p/2 F 2 = 0 d = 0 traditional unflavored case The lower bound gets more stringent but still successful leptogenesis is possible just with CP violation from low energy phases that can be tested in bb0n decay (Majorana phases) ( difficult) and more realistically in neutrino mixing (Dirac phase)

52 Dirac phase leptogenesis (Anisimov, Blanchet,, PDB, arxiv ) In the hierarchical limit (M 3 >> M 2 >> M 1 ): M 1 (GeV) sinq 13 =0.20 F 1 = 0 F 2 = 0 d = -p/2 In this region the results from the full flavored regime are expected to undergo severe corrections that tend to reduce the allowed region Here some minor corrections are also expected d-leptogenesis represents another important motivation for a full Quantum Kinetic description!

53 Full degenerate limit: M 1 > M 2 > M 3 The maximum enhancement of the CP asymmetries is obtained in so called resonant leptogenesis: ï lower bound on sin q 13 and upper bound on m 1

54 Some remarks on d-leptogenesis : there is no theoretical motivation however, within a generic model where all 6 phases are present, it could be regarded as an approximate scenario if the contribution from d dominatesïit is interesting to know that something we could discover in neutrino mixing experiments is sufficient to explain (in principle) a global property of the Universe On the other hand notice that: if we do not discover CP violation in neutrino mixing it does not dis prove leptogenesis

55 Unflavored vs. flavored leptogenesis Unflavored Flavored Lowest bounds on M 1 and T reh Upper bound on m 1 N 2 - dominated scenario Leptogenesis from low energy phases ~ 10 9 GeV 0.12 ev for W ~ R 23 Non-viable Unchanged? (QKE needed!) Domain is enlarged but no drastic changes Viable only marginally in the HL ï DL is needed (QKE needed!)

56 Can we detect RH neutrinos at LHC? Typically lowering the RH neutrino scale at TeV, the RH neutrinos decouple and they cannot be efficiently produced in colliders Different claimed possibilities to circumvent the problem: t - resonant leptogenesis (Pilaftsis, Underwood 05) additional gauged U(1) B-L (King,Yanagida 04) Going beyond the usual type I see-saw : leptogenesis with Higgs triplet (Ma,Sarkar 00 ; Hambye,Senjanovic 03; Rodejohann 04; Hambye,Strumia 05) leptogenesis with three body decays (Hambye 01) see-saw with vector fields (Aristizabal,Losada,Nardi 07)..

57 A wish list for future

58 EWBG versus Leptogenesis Two experimental facts gave a (strong but still partial!) advantage to Leptogenesis: Discovery of Neutrino Masses The stringent Higgs Mass lower bound from LEP2 An easy game (thanks SPIRES) : Find title Leptogenesis EWBG Baryogenesis date < 2000 date > BACK!

59 A relevant specific case Consider: (Blanchet,PDB 06) The projectors and the flavored asymmetries depend also on U î one has to plug the information from neutrino mixing experiments For m 1 =0 (fully hierarchical light neutrinos) ï î Semi-democratic case Flavor effects represent just a correction in this case!

60 Do flavour effects relax the bounds on neutrino masses? Hierarchical limit (M 3 >> M 2 >> M 1 ) M 1 min (GeV) The usual lowest bounds are not relaxed! f 1 = f 2 = d = 0 f 1 = -p m 1 =m atm > 0.05 ev K 1