1 / 18

Flavor effects on leptogenesis

N eutrino O scillation W orkshop Conca Specchiulla, Otranto, Italy, Sep. 9-16 2006. Flavor effects on leptogenesis. Steve Blanchet Max-Planck-Institut für Physik, Munich. Based on: SB, P. Di Bari, hep-ph/0607330. September 15, 2006. Outline.

hamlin
Télécharger la présentation

Flavor effects on leptogenesis

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Neutrino Oscillation Workshop Conca Specchiulla, Otranto, Italy, Sep. 9-16 2006 Flavor effects on leptogenesis Steve Blanchet Max-Planck-Institut für Physik, Munich Based on: SB, P. Di Bari, hep-ph/0607330 September 15, 2006

  2. Outline • Review of unflavored leptogenesis and its implications • Idea of how flavor enters leptogenesis • General implications of flavor • Specific example • Non-zero Majorana phases can lead to large effects • Summary and conclusions

  3. Unflavored thermal leptogenesis • Minimal extension of the SM • The BAU can be generated because [Fukugita, Yanagida, 86] : • CP is violated in the decay of heavy neutrinos • Baryon number is violated in sphaleron processes • Decays are out of equilibrium at some point, parametrized by CP asymmetry parameter ``decay parameter´´

  4. Unflavored thermal leptogenesis • Notice how it is summed over the flavors • The fundamental Boltzmann equations are • Strong wash-out when • Weak wash-out when Sphalerons conserve B-L ! CP violation Out-of-equilibrium condition

  5. Unflavored thermal leptogenesis • It is convenient to write the solution in the form where are the final efficiency factors. • The final baryon asymmetry is given by and should be compared to the measured value [WMAP,06] • Assuming one typically has a N1-dominated scenario.

  6. WEAK WASH-OUT STRONG WASH-OUT

  7. Implications of unflavored leptogenesis • From the upper bound on the CP asymmetry[Asaka et al., 01; Davidson, Ibarra, 02] one obtains a lower bound on M1 and on the reheating temperature independent of the initial conditions[Davidson, Ibarra, 02; Buchmüller, Di Bari, Plümacher, 02] : • The suppression of the CP asymmetry for growing absolute neutrino mass scale leads to a stringent upper bound[Buchmüller, Di Bari, Plümacher, 02] :

  8. How does flavor enter leptogenesis? • Below some temperature ~109-11 GeV, the muon and tauon charged lepton interactions are in equilibrium. • These interactions are then fast enough to ‘measure’ the flavor of the state produced in the decay of the heavy neutrino; a 3-flavor basis is defined. [Barbieri, Creminelli, Strumia, Tetradis, 99 ; Endoh, Morozumi, Xiong, 03; Abada, Davidson, Josse-Michaux, Losada, Riotto, 06 ; Nardi, Nir, Racker, Roulet, 06]

  9. How does flavor enter leptogenesis? • The fundamental Boltzmann equations become Same as before! • First type of effect: the rates of decay and inverse decay in each flavor are suppressed by the projectors [Nardi et al., 06] • Second type of effect: additional contribution to the individual CP asymmetries: [Nardi et al., 06]

  10. NO FLAVOR Nj Φ L Le Lμ Ni Lτ Φ

  11. WITH FLAVOR (all projectors equal) Nj Φ Le Lμ Lτ Ni Φ

  12. General implications of flavor • There exists an upper bound on the individual CP asymmetries [Abada, et al., 06]: It does not decrease when the active neutrino mass scale increases! • Possible scenarios: • Alignment case [Nardi et al., 05] • Democratic (semi-democratic) case • One-flavor dominance and like unflavored case factor 2-3 effect and potentially big effect!

  13. General implications of flavor semi-democratic alignment • Lower bounds democratic 3x109 The lowest bounds independent of the initial conditions (K*) do not change!

  14. General implications of flavor • At fixed K1, there is a relaxation of the lower bounds [Abada et al., 06] . How much? Factor 2-3 typically, but it depends on the projectors (could be much more!). • However, the region of independence of initial conditions shrinks when the flavor effects increase (small projector, i.e. one-flavor dominance)

  15. Specific example • Let us now study a specific case, , using the known information about the PMNS mixing matrix. • For a fully hierarchical light neutrino spectrum one obtains a semi-democratic situation where • For a real UPMNS and purely imaginary Semi-democratic

  16. Specific example: Majorana phase effects • With ~ Semi-democratic • With One-flavor dominance

  17. Specific example: Majorana phase effects • Summary of with purely imaginary • Case of real cf. talk by Petcov this morning

  18. Summary and conclusions • Flavor effects can be important, but when they are, the region of the parameter space where leptogenesis does not depend on the initial conditions shrinks. • The lower bounds on M1 and Treh in the strong wash-out are not relaxed, but the bounds at fixed K are. The upper limit on m1 seems to disappear when M1<1012 GeV. • Quantitatively, flavor effects yield O(1) modification of the usual results, except either when there is one-flavor dominance or when the total CP asymmetry vanishes. In both cases, Majorana phases play an important role. • The one-flavor dominance seems to occur mainly when light neutrinos are quasi-degenerate. • In conclusion, leptogenesis provides another phenomenology where Majorana phases matter.

More Related