Kaluza-Klein (KK) Dark Matter

1. Kaluza-Klein (KK) Dark Matter Torsten Bringmann, SISSA ENTApP Visitor Program and Workshop on Dark Matter, SISSA, Trieste, 12-21 Oct 05

2. Universal extra dimensions (UED) The lightest Kaluza-Klein particle (LKP): Indirect detection properties Direct detection Summary and conclusions Torsten Bringmann 2/19 Kaluza Klein Dark Matter Outline a viable dark matter candidate - the positron peak - the gamma-ray spectrum - antiprotons

3. Universal extra dimensions (UED) The lightest Kaluza-Klein particle (LKP): a viable dark matter candidate Indirect detection properties - the positron peak - the gamma-ray spectrum - antiprotons Direct detection Summary and conclusions Torsten Bringmann 2/19 Kaluza Klein Dark Matter Outline Why should we be interested in this particular dark matter candidate?

4. . For large distances (low energies), ordinary 4D physics is recovered. In the effective 4D theory, there appears a Kaluza-Klein tower of new, very massive states. . M . n = 3 n = 2 1/R n = 1 n = 0 Torsten Bringmann 3/19 Kaluza Klein Dark Matter Extra dimensions: the basic idea Compactify extra dimensions on some small scale R : 2 R Fig.: Greene ‘00

5. All standard model fields are allowed to propagate in the extra dimensions. Compactification on an orbifold: 0 0 y | | Impose symmetry under R y - y | | R R This is needed in order to get rid of unwanted degrees of freedom at the zero mode level. (Fields can transform even, , or odd, , under orbifold transformations. The latter have no zero modes.) Torsten Bringmann 4/19 Kaluza Klein Dark Matter Universal Extra dimensions (UED) Appelquist, Cheng & Dobrescu, PRD ‘01

6. physical scalars Goldstones two fermions for each SM fermion Torsten Bringmann 5/19 Kaluza Klein Dark Matter The field content in 4D At the first KK level, one finds the following mass eigenstates: Vector bosons: Scalars: Ghosts: Fermions:

7. 0 Compactification on an orbifold | translational invariance broken 5D momentum (and thus KK number) no longer conserved | R ... but KK parity still is a conserved quantity! The lightest KK particle (LKP) is stable and cannot decay into standard model particles Torsten Bringmann 6/19 Kaluza Klein Dark Matter The lightest Kaluza-Klein particle Does this give a viable dark matter candidate?

8. Including radiative corrections, this becomes electroweak contribution bulk contribution Contribution from orbifold fixpoints (depends on cutoff ) Mass spectrum at first KK level Torsten Bringmann 7/19 Kaluza Klein Dark Matter What is the LKP? Cheng, Matchev & Schmaltz, PRD ‘02 At tree level, the mass of the KK modes is given by: The LKP is given by the B(1)

9. The thermal relic density of the B(1) has by now been determined in great detail. - Servant & Tait, NPB ‘03 (Including coannihilations, second KK level resonances,...) - Kakizaki, Matsumoto, Sato & Senami, PRD ‘05 - Kakizaki, Matsumoto, Sato & Senami, hep-ph/0508283 - Burnell & Kribs, hep-ph/0509118 - Kong & Matchev, hep-ph/0509119 h² = 0.1 500 GeV  R-1  600 GeV (in the minimal scheme) KMSS KM Torsten Bringmann 8/19 Kaluza Klein Dark Matter The LKP as a dark matter particle The WMAP bound translates into

10. Current bounds LHC reach: R-1  700 GeV R-1  250 GeV Flacke, Hooper & March-Russell, hep-ph 0509352 Appelquist, Cheng & Dobrescu, PRD ‘01 Appelquist & Yee, PRD ‘03 R-1  3 TeV Rizzo, PRD ‘01 Macesanu, McMullen & Nandi, PRD ‘02 Torsten Bringmann 9/19 Kaluza Klein Dark Matter Collider bounds - Direct non-detection: R-1  300 GeV Appelquist, Cheng & Dobrescu, PRD ‘01 Agashe, Deshpande & Wu, PL B ‘01 - Electroweak precision tests:

11. Indirect detection methods making use of the high branching ratio into leptons are very promising. Can even be used to discriminate between the LKP and a Majorana dark matter candidate! Torsten Bringmann 10/19 Kaluza Klein Dark Matter Indirect detection B(1)B(1) annihilation ratios at tree level: - 59% into leptons Compare to SUSY! - 35% into quarks - 4% into neutrinos - 2% into gauge and Higgs bosons

12. Cheng, Feng & Matchev, PRL ‘02 Hooper & Kribs, PRD ‘04 Hooper & Silk, PRD ‘05 For high masses, however, this cannot be discriminated against the background... CFM A clumpy halo distribution can boost the positron flux. KK DM - With a boostfactor of 5, AMS will be able to see a peak up to mB~ 1 TeV. - background To explain the HEAT data, a BF of several 100 would be needed (for mB= 600 GeV). Torsten Bringmann 11/19 Kaluza Klein Dark Matter The positron peak Appearance of a smoking gun signature in the spectrum. HK

13. total spectrum only quark fragmentation added tau fragmentation Torsten Bringmann 12/19 Kaluza Klein Dark Matter The gamma-ray spectrum Bergström, T.B., Eriksson & Gustafsson, PRD ‘05 At high energies, the gamma-ray spectrum is dominated by internal bremsstrahlung from final state leptons: This gives a nice signature to look for.

14. ~ 0.13 (NFW,  = 10-5) Cesarini et al., AP ‘04  100 - 1000 due to baryonic compression Blumenthal et al., ApJ ‘86 Prada et al., astro-ph/0401512 Edsjö, Schelke & Ullio, JCAP ‘05 b ~ 100 b ~ 1000 Bertone & Merritt., astro-ph/0501555 New data: New data: Power law and thus astrophysical explanation more likely... Power law and thus astrophysical explanation for the bulk effect more likely... Torsten Bringmann 13/19 Kaluza Klein Dark Matter The H.E.S.S. data Expected gamma-ray flux from the galactic center:

15. 0.25 % detector resolutions 0.5 % 1 % continuous signal For comparison: HESS has an energy resolution of only 15 % ... Torsten Bringmann 14/19 Kaluza Klein Dark Matter Can one see the photon peak? Bergström, T.B., Eriksson & Gustafsson, JCAP ‘05 As for SUSY, direct annihilation into or Zis loop-suppressed.

16. T.B., JCAP ‘05 Barrau et al., PRD ‘05 background flux Contribution from LKP decay for various dark matter profiles T.B. Torsten Bringmann 15/19 Kaluza Klein Dark Matter Antiprotons from KK dark matter Expected fluxes are in general too low to be seen

17. T.B., JCAP ‘05 Barrau et al., PRD ‘05 In that case, there must appear a positron peak as well. Possible discrimination against SUSY! Torsten Bringmann 15/19 Kaluza Klein Dark Matter Antiprotons from KK dark matter Expected fluxes are in general too low to be seen Allowing for clumpy halo distributions, however, PAMELA and AMS will be able to see a characteristic distortion in the spectrum. mB(1) = 800 GeV, boost-factor: 100 T.B. ‘05

18. Cheng, Feng & Matchev, PRL ‘02 Hooper & Kribs, PRD ‘03 Equilibrium reached between annihilation and capture rate in the sun (but not in the earth). For a 1 km² telescope and an LKP mass of 600-800 GeV: a few to tens of events per year LKP annihilations in the galactic center NFW with adiabatic compression and an LKP mass of 800 GeV: a few events per year and km² Bertone, Servant & Sigl, PRD ‘03 Bergström, T.B., Eriksson & Gustafsson, PRL ‘05 Torsten Bringmann 16/19 Kaluza Klein Dark Matter Neutrinos In contrast to SUSY, neutrinos are directly produced in LKP annihilations (branching ratio ~ 4%).

19. spin-dependent best prospects for spin-independent experiments with heavy target nuclei spin-independent Cheng, Feng & Matchev, PRL ‘02 Torsten Bringmann 17/19 Kaluza Klein Dark Matter Direct detection Single nucleon cross sections: spin-independent/spin-dependent ~mp/mB(1) Detection rates: spin-independent/spin-dependent ~A²

20. Promising prospects for a direct detection in the future Torsten Bringmann 18/19 Kaluza Klein Dark Matter Upcoming direct-detection experiments Servant & Tait, NJP ‘02 Ge detectors Xe detectors

21. UEDs provide a useful ‘playground’ for extra-dimensional dark matter scenarios Interesting phenomenology for a massive vector dark matter particle. Observational prospects are promising: - no helicity suppression - TeV scale masses - hard spectra - good signal/noise - distinctive spectral shapes for , e+ (and ) - s-channel resonance - enhanced direct detection rates The LHC will probe practically the whole UED parameter space. Torsten Bringmann 19/19 Kaluza Klein Dark Matter Conclusions The LKP appears as a natural dark matter candidate in the UED model