Indirect Detection Of Dark Matter D.T. Cumberbatch

Motivation for Dark Matter Rotation Curves of spiral galaxies: M/L ratio Abell 1689, HST Galaxy clusters: Proper motion X-ray emissions from hot gas Gravitational lensing Large-scale structure 2dFGRS WMAP Anisotropies in the CMB

What is the Dark Matter made of? Weakly Interacting Massive Particles (WIMPS) Lightest Neutralino Stable LSP of SUSY models which conserve R-Parity characteristic of EW interactions … AND MANY MORE!!! (e.g. LDM, Gravitinos, Axions, KK bosons, …)

DM Detection Methods Two Complementary Methods: Direct Detection Measure phonon, charge or light signals produced from elastic scattering of WIMPS with a nuclear target DAMA, CDMS, EDELWEISS, ZEPLIN, CRESST Indirect Detection Measure excess in diffuse antiparticle flux from DM annihilations HEAT, HESS, EGRET, BESS

A Positron Excess Astrophysical sources are insufficient!!! Background (Protheroe, 1984) EXCESS! Astrophysical Sources? Supernovae Type 1a Massive Wolf-Rayet stars Astrophysical sources are insufficient!!!

Positron Production from annihilation Continuum positrons from cascades involving and Final injection spectrum depends on mass and decay modes: For , (solid) dominates and (dotted) less so For : (dashed) occur, producing a more complicated spectrum

annihilation within a smooth halo Positrons Antiprotons (Baltz et al. 2001) Annihilation Rate We require Substructure!!!

DM Substructure Standard model assumes that structure originated from quantum fluctuations during inflation “Bottom-up” hierarchical structure formation Subhalo Population = (Constructive Merging) + (Tidal Destruction) Total flux from DMCs strongly depends upon and (Diemand et al. Nature, 433, 389 (2005)) Assuming that the DMC distribution traces the halo density with a halo-to-halo scatter of 4

DM Substructure But the simulation was terminated at z=26 We must account for subsequent tidal stripping by stellar encounters during orbits (Zhao et al. 2005) We assume that all clumps will currently possess a fraction f (0< f <1) of its mass at z=26, since We adopt NFW profiles for the DMCs (~consistent with simulation data) The amplification of the antiparticle flux from clumps is then:

Cosmic Ray Propagation Charged particles diffuse through ISM Scattering off galactic B-field, CMB radiation and starlight result in energy losses Diffusion can be well-approximated to a random walk Diffusion Constant Energy loss rate Assuming a constant B-field: Source Term Proportional to halo annihilation rate per unit vol.

Cosmic Ray Propagation We solve for the steady-state solution Manipulate into an inhomogeneous ( “heat” ) equation (Baltz et al. 1998) We can solve for by constructing the Green’s function

Cosmic Ray Propagation We solve the inhomogeneous equation, using method of Fourier Transforms, for a mono-energetic, point source (of energy and position ): Boundary Conditions? z Assume uniform cylindrical diffusion zone: 2L Diffusion Zone Free Escape Zone BCs require at (Webber et al. 1971) Using principle of superposition (Baltz et al. 1998):

Cosmic Ray Propagation Finally, the solution for the local differential flux (z=0, r=8 kpc) is Calculate PF using for 4 benchmark MSSM models Calculate PF for and 1.6 or 3 left as a free parameter

Positron Fraction

Positron Fraction We require: (for up to 90% stripping) Canonical value: Profumo indicates how canonical value can be grossly violated with at possible However these models require co-annihilations and resonant annihilations making them more contrived

Conclusion + Further Work Considering the errors in the halo DMC abundance, some models are clearly permitted, with preferential selection towards lighter LSPs, even when considering the effects of tidal destruction To improve our analysis we can select LSPs based on a more stringent scan of the entire MSSM parameter space Cross-reference results on PF with an analysis of cosmic antiprotons, antideuterons, gamma rays, etc.