Dark Matter Direct detection in the Galaxy
Malcolm Fairbairn
all the really good stuff is here x
you are here x Plan of Talk
• Motivation • Astrophysical uncertainties • Effect on direct detection rate for high mass particles
Latest Constraints from LHC Fine Tuning in MSSM Focus point region in MSSM leads to large cross section
Current Limits
XENON 100 result using new scintillation data 1104.2549 Question:-
How exactly do astrophysical uncertainties change this picture? Direct detection of dark matter Integral over velocity Idealised Xenon Detector (to illustrate uncertainties assumed in their paper)
Isothermal sphere with varying escape velocity Idealised Xenon Detector (to illustrate uncertainties assumed in their paper)
Isothermal sphere with varying escape velocity Spherical Sources of Astrophysical Uncertainty • Uncertain Density profile • Uncertain mass of galaxy • Spherical Baryonic contraction • Non Maxwellian Velocities • Lack of knowledge of velocity Anisotropy b(r) • Uncertain solutions to Jeans Equation
Non-Spherical Sources of Astrophysical Uncertainty • Tidal Streams • Substructure • Dark Discs (density and/or velocity) • Effect of Baryonic Disk • Effect of Spiral Arms • Lack of axial symmetry of Galaxy
Dark Matter Simulations fit Einasto Profile
Navarro et al 0810.1522 Choose a Dark Matter Halo
Duffy et al 0804.2486 Baryonic Contraction Zeldovich, Blumenthal, Primack, Gnedin
Baryons lose energy, dark matter doesn’t.
conservation of angular momentum
conservation of mass
Need to take this into account when working out the expected flux from the galactic centre However, dark matter orbits are not circular need to modify the equations…
It often works quite well.
M. Gustafsson, M.F. and J. Sommer-Larsen Solutions of Jeans Equations
Cannot observe this Can obtain this by so cannot be fitted fitting data
Tangential Velocity Dispersion
Radial Velocity Dispersion Via Lactea non-Gaussianity and anisotropy
MF and Schwetz : arXiv 0808.0704 : Velocity distributions around 8.5 kpc.
Kuhlen et al. arXiv: 0912.2358
Best fit Maxwell-Boltzmann Procedure
Take into account following uncertainties:- • Local density • Escape velocity • Velocity dispersions • Velocity Anisotropy • Non-Maxwellianity • Uncertainties in A and w parameters for baryonic contraction Velocity Anisotropy at Solar radius Rotational Velocity at Solar Radius Final Broadening including all effects Conclusions
• Well known that astrophysical uncertainties has huge implications for interpretations of direct detection experiments • In this work we have tried to quantify the uncertainty at higher energies • Very difficult to get broadening larger than a factor of a few • If you assume dark discs, substructure and tidal tails this could change but evidence for such objects limited from simulations