Leptogenesis: Origin of Matter and Dark Matter, and Direct Detection

1. Leptogenesis as a common origin for matter and dark matter, and direct detection Haipeng An, University of Maryland In collaboration with Shaolong Chen, R. N. Mohapatra, S. Nussinov, and Yue Zhang. Talk given at Pheno10. arXiv:0911.4463 [hep-ph] arXiv:1004.3296 [hep-ph]

2. Motivation • Dark matter particle is heavy and stable. The only known particle which is heavy and stable is proton; • The relic density of dark matter is five times of the relic density of baryon; • If these two relic densities were generated from the common mechanism, it could be a major step to understand that they are of the same order of magnitude. • An elegant way to generate baryon number is though leptogenesis in the framework of seesaw mechanism.

3. Framework of the model Fukugita, T. Yanagida (1986) Sphaleron process Kuzmin, Rubakov, Shaposhnikov (1985) NR is a singlet of SM, therefore one field can serve the roles of both NR and N’R .

4. Framework of the model Mirror Symmetry Softly breaking of the mirror symmetry Hodges (1993), Mohapatra, Teplitz (1999, 2000) Berezhiniani, Comelli, Villante (2001)

5. Framework of the model

6. Mass of dark matter Trace anomaly Masses of quarks m’n and m’p are mainly contributed by mirror quark masses.

7. Mass of dark matter • For the sake of the constraint from dark matter self-interaction, we want to mirror neutron to be the dark matter. • Two-higgs-doublet model is invoked in both the sectors so that • In the SM sector, tanβ = 50; in the mirror sector Randall et al. (2007)

8. Neutrino masses • In the basis the neutrino mass matrix can be written as • Add triplets in both the two sectors • The triplet is also used to break U(1)’EM in the mirror sector. Rank = 2

9. Neutrino masses • In the case the SM neutrino mass lies in the type II + inverse seesaw regime, whereas the mirror neutrino mass lies in the type I seesaw regime. • In this regime the triplet conducted leptogenesis is negligible, so that we can keep the relation R. N. Mohapatra, (1986) T. Hambye, G. Senjanovic (2004), S. Antusch, S.F.King (2004)

10. Constraints Resonant leptogenesis is needed. Pilaftsis, Underwood (2004, 2005) • Leptogenesis; • Big bang nuclear synthesis; • Neutrinoless doubless double beta decay; • Self-interaction cross section of dark matter.

11. Direct detection • The kinetic mixing between photon and mirror photon induces a interaction between nucleons and the mirror neutron. • c1 can be seen as the magnetic moment of the mirror neutron, c1 and c2 are determined by the strong dynamics of the mirror QCD.

12. Direct detection SI SD • The amplitude depends on the momentum of initial and final states. • Enhancement for detectors made of light elements. • The cross section is different from the usual SI or SD interactions. And the SI part will be increased by Z2 instead of A2 in the usual case. An, Chen, Mohapatra, Nossinov, Zhang (2010) Chang, Pierce, Weiner (2009), Chang, Liu, Pierce, Weiner, Yavin (2010)

13. Direct detection MD, SI MD, SD MI, SI MI, SD

14. Conclusion • In this model the SM sector and the mirror sector share the common right-handed neutrinos. • The number density of the dark matter is approximately equal to the number density of nucleons. • The direct detection cross section is momentum-dependent.

15. Constraint from dark matter self-interaction • The self-interaction can be conducted by strong scattering. • The cross section between neutron and proton by exchanging a charged pion is about 10-24 cm2. In the mirror sector, the mass of the pion is about 10 times larger, therefore the cross section of dark matter self-interaction is about 10-28 cm2. • The current astronomical bound from bulletin cluster is

16. Constraint from neutrinoless double beta decay • The mixing between the mirror neutrino and the SM neutrino contributes to the neutrinoless double beta decay. • The contribution to the neutrinoless double beta decay is proportional to • Due to the mirror symmetry the masses of the light SM neutrinos are given by • Therefore the neutrinoless double beta decay constraint can be avoided by fine-tune the e’e’-component of the mirror neutrino mass matrix.

17. Constraint from leptogenesis • After leptogenesis, this scattering may be still in equilibrium, and can wash out the lepton number in the two sectors. • For the decay of the right handed neutrino to generate enough lepton numbers, the washout factor. • From the BBN constraint, the mirror neutrino should decay before BBN. The decay • Resonant leptogenesis is needed.

18. Constraint from leptogenesis and BBN To generate enough lepton number Resonant leptogenesis is needed. Pilaftsis, Underwood (2004, 2005)

19. Constraint from leptogenesis and BBN • At T ~ 1 MeV, the d.o.f of sterile neutrinos should be smaller than 1.44 at 95% CL. • The electrons, neutrinos, photons, and protons have to decay before BBN, therefore their lifetimes should be smaller than 1 second. Cyburt, Fields, Olive (2005) Muon anomalous magnetic moment Pospelov (2009)

20. Outline • Motivation; • Framework of the model; • Mass of dark matter and neutrinos • Constraints; • Direct detection; • Conclusion.