Decaying Gravitino Dark Matter

1. Decaying Gravitino Dark Matter Are Raklev University of Cambridge In collaboration with Deirdre Black (Cambridge), Nils-Erik Bomark (Bergen), Magda Lola (Patras), Emanuel Malek (Cambridge), Per Osland (Bergen) and Helen Vryonidou (Cambridge) Based on Lola, Osland, ARR, arXiv:0707.2510 Lola, Osland, ARR, arXiv:0811.2969 and various papers in preparation. TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.: AAAAAAAA

2. Main Points • Motivation: Dark Matter & SUSY • The necessity of R-parity? • Decaying Dark Matter: The gravitino case • Some calculations on gravitino decays • Cosmological (and other) model constraints • (If time) some LHC phenomenology • Conclusions, hopes & dreams Decaying Gravitino Dark Matter

3. There is more than one ingredient in this pie:CMB, 2dFGRS,Lya-forest, SN1a LCDM The WMAP pie Decaying Gravitino Dark Matter

4. Why do we like SUSY? SUSY MSSM GMSB CMSSM NMSSM Split SUSY AMSB Full of (more or less) good Dark Matter candidates Decaying Gravitino Dark Matter

5. WIMPs au naturel? Astrophysics measurements have pinned down the DM density The relic density of a Weakly Interacting Massive Particle (WIMP) c is suggestive The lightest neutralino of the MSSM seems to be a good candidate. Decaying Gravitino Dark Matter

6. WIMPs au naturel? CMSSM/mSUGRA for generic values of No EWSB Tend to overproduce neutralinos, they’re a bit on the heavy side... Stau LSP [Battaglia et al., hep-ph/0106204] Decaying Gravitino Dark Matter

7. WIMPs au naturel? Astrophysics measurements have pinned down the DM density However, the WIMPs are just a special case, more generically we get We may well have DM in a Hidden Valley. [Feng, Kumar, Phys.Rev.Lett.101(2008)] Decaying Gravitino Dark Matter

8. The DM needs to stick around Need mechanism to keep DM (almost) stable! • Need a lifetime of tDMtuniverse13.7£ 109 y • A symmetry is usually introduced: • R-parity in SUSY • T-parity in Little Higgs • KK-parity in UED • ... in your own favourite model • What about (super-)weak coupling?Seems to require intolerable fine-tuning. Decaying Gravitino Dark Matter

9. R-parity and all that jazz • Conservation of R-parity • Sparticles decay into sparticles. • Sparticles produced in pairs. • Lightest sparticle (LSP) is anatural DM candidate if weakly interacting. collidercascade decays Decaying Gravitino Dark Matter

10. R-parity and all that jazz • Conservation of R-parity • A priori, R-parity violating (RPV) terms are allowed in the MSSM superpotential. Decaying Gravitino Dark Matter

11. R-parity violation • The R-parity violating terms are problematic: • Violate lepton and baryon number. • Can lead to rapid proton decay. • No SUSY Dark Matter candidate? Decaying Gravitino Dark Matter

12. R-parity violation • Conservation of R-parity • Prevents rapid proton decay and other unwanted lepton and baryon number violating processes. • However, dimension-5 operators can still contribute to proton decay. • Saving the proton can be done by introducing a baryon or lepton triality(Z3) instead. • We now look at a possibility for SUSYDM even if there are non-zero RPV couplings! [Ibanez, Ross, Nucl.Phys.B368, 3-37 (1992)] Decaying Gravitino Dark Matter

13. Gravitino Dark Matter • Gravity is a natural choice for giving asuper-weak coupling. • Since gravitino interactions are suppressed by the Planck mass, Mp~1018 GeV, with a gravitino LSP the DM lifetime goes aseasily far above the age of the universe! [Berezinsky, Phys.Lett.B261, 71-75,1991] [Takayama, Yamaguchi, hep-ph/0005214] [Moreau, Chemtob, hep-ph/0107286] Decaying Gravitino Dark Matter

14. Gravitino Dark Matter • The idea has been around for some time – but not recieved much attention until recently: • Most work has centered on bilinear RPV. (neutrino-neutralino mixing decays gravitino) [W. Buchmuller et al., hep-ph/0702184] [H. Yuksel, M.D. Kistler, arXiv:0711.2906] [Lola, Osland, ARR, arXiv:0707.2510] [M. Taoso et al., arXiv:0711.4996] [G. Bertone et al., arXiv:0709.2299] [A. Ibarra, D. Tran, arXiv:0804.4596] [W. Buchmuller et al., arXiv:0809.4667] [K. Ishiwata et al., arXiv:0805.1133] [L. Covi et al., arXiv:0809.5030] [A. Ibarra, D. Tran, arXiv:0811.1555] [Lola, Osland, ARR, arXiv:0811.2969] [F. Takahashi et al., arXiv:0901.21.68] Decaying Gravitino Dark Matter

15. Gravitino Dark Matter For trilinear RPV the three-body gravitino decays were calculated in Decays suppressed by • Planck mass • R-violating coupling • Three-body phase space • Sfermion mass • Fermion final state mass [Moreau, Chemtob, hep-ph/0107286] Decaying Gravitino Dark Matter

16. Gravitino Dark Matter We have calculated the radiative gravitino decay Decays suppressed by • Planck mass • R-violating coupling • Loop factors [Lola, Osland, ARR, arXiv:0707.2510] Decaying Gravitino Dark Matter

17. Radiative decay calculation We use the Rarita-Schwinger formalism for spin-3/2 particles with gravitino vertices: This is a low-energy effective theory. [See e.g. Moroi, hep-ph/9503210] Decaying Gravitino Dark Matter

18. Radiative decay calculation The resulting total width is where Decaying Gravitino Dark Matter

19. Three-body vs. Radiative decay Radiative decay dominates for low gravitino masses: [Lola, Osland, ARR, arXiv:0803.0547] Decaying Gravitino Dark Matter

20. Insensitivity to sfermion mass Gravitino-sfermion-fermion vertex: depends on loop 4-momentum [Lola, Osland, ARR, arXiv:0707.2510] Decaying Gravitino Dark Matter

21. An aside on gravitino masses What is a ”natural” gravitino mass? • Really depends on you favouritemethod for SUSY breaking. • Gravity mediated • Simplest models (Polonyi, dilaton) suggest • Gauge mediation • Light gravitino masses generic. • Could be down below keV scale. Decaying Gravitino Dark Matter

22. Constraints on GDM • Dark Matter density • The thermal production of gravitinos after inflation depends on re-heating temperature TR. • Can well be in correct range. [M. Bolz, W. Buchmüller, M. Plümacher, hep-ph/0012052] Decaying Gravitino Dark Matter

23. Constraints on GDM • Dark Matter density • Big Bang Nucleosynthesis • Long lived NLSP problem avoided by RPV. Decaying Gravitino Dark Matter

24. Constraints on GDM • Dark Matter density • Big Bang Nucleosynthesis • Genesis • Baryo-/Leptogenesis may be washed out if RPV strong enough at electroweak phase transition. • Flavour effects may help. Decaying Gravitino Dark Matter

25. Constraints on GDM • Dark Matter density • Big Bang Nucleosynthesis • Genesis • Neutrino masses • RPV couplings can give rise to neutrino masses. • Gives restrictions on RPV couplings. • May explain measured masses. Decaying Gravitino Dark Matter

26. Constraints on GDM • Dark Matter density • Big Bang Nucleosynthesis • Genesis • Neutrino masses • Photon flux (!) • Measurement of galactic and diffuse extra-galactic gamma ray flux constrains RPV-couplings. • Perhaps also interesting to look at PAMELAs positrons and/or neutrinos? Decaying Gravitino Dark Matter

27. Constraints on GDM Photon flux taken from EGRET data [P. Sreekumar et al., astro-ph/9709257] Recent re-analysis: [A.W. Strong et al., astro-ph/0406254] [G. Bertone et al., arXiv:0709.2299] Decaying Gravitino Dark Matter

28. Constraints on GDM We set limits lmax on RPV coupling vs. gravitino mass, using photon flux taken from EGRET. Need to take into account redshift. [Lola, Osland, ARR, arXiv:0811.2969] [Bomark, Lola, Osland, ARR, in preparation] Decaying Gravitino Dark Matter

29. Constraints on GDM Due to loop-decay dependence on fermion mass,lmax is very flavour dependent. [Lola, Osland, ARR, arXiv:0811.2969] [Bomark, Lola, Osland, ARR, in preparation] Decaying Gravitino Dark Matter

30. Low mass gravitino For light gravitinos hadronization effectsare important. Two-body decays to meson+lepton dominate. [Black, Malek, ARR, Vryonidou in preparation] Decaying Gravitino Dark Matter

31. Phenomenology at the LHC Large variety of signatures depending on dominant RPV-coupling. Most NLSP/RPV-coupling combinations not fully reconstructable due to neutrinos. Decaying Gravitino Dark Matter

32. Conclusions • The gravitino is a possible Dark Matter candidate even with large RPV couplings. • For light(ish) gravitinos, radiative loop decays are important and even dominant. • Measurements of photon flux set strict upper bounds on RPV couplings in these scenarios. • We are eagerly awaiting Fermi/GLAST data to set even strickter bounds, or... Decaying Gravitino Dark Matter

33. Triality? Lepton triality, allowing bilinearRPV-coupling: Baryon triality, allowing bilinear RPV-coupling. Baryon triality, dis-allowing bilinear RPV-coupling. Decaying Gravitino Dark Matter