Studies of Systematics for Dark Matter Observations John Carr 1

Objectives of Work  Identify best methods to discover dark matter in CTA  observations around Galactic Centre  Understand systematics of measuring a diffuse flux  Requirements on observational pointing strategy  Requirements on instrument calibration and monitoring  Requirements on Monte Carlo simulations Dark Matter Systematics, J. Carr2/20

Indirect Search for Dark Matter Dark Matter Systematics, J. Carr The Galactic Center -Brightest spot in the sky -Considerable astrophysical backgrounds The Galactic Halo -High statistics -Requires detailed model of galactic backgrounds Extragalactic Background -High statistics -potentially difficult to identify Individual Subhalos -Unlikely detectable -Low backgrounds

Dark Matter Systematics, J. Carr Targets for IDM Searches RICAP14, Oct /32 Milky WayLarge Magellanic Cloud “Dark Targets”: Dwarf Galaxies Clumps Studies in progress to decide best way to use observation time

Rates for DM Annihilation

Expectations for WIMP Dark Matter Many SUSY models give M  : 0.5 to 2.5 TeV with 5  to 3  cm 3 sec  1 Roszkowski et al., arXiv: , expectations for common SUSY models In thermal picture of early Universe, relic density and annihilation cross-section are inversely related: For

Dark Matter Systematics, J. Carr Existing Limits from Indirect Gamma 7/32 Fermi has best limits up to ~ 500 GeV mass “thermal” annihilation cross-section bb annihilation spectrum

Likelihood fit Dark Matter Systematics, J. Carr8/20

Morphology fit Dark Matter Systematics, J. Carr9/20 Bin data in galactic coordinates (b, l) and gamma energy E. Cut  0.3  in b to remove Galactic Ridge bb ll Signal Background Signal Background

Azimov Data Set Method Dark Matter Systematics, J. Carr10/20 Generate one data set “Azimov” with expected background and zero signal Fit with signal free to find signal value which gives Dark Matter Systematics, J. Carr10/20 5% MC <0 Simulate Toy MC With annihilation cross-section 1.7  10  26 cm 3 s  1 corresponding to limit from Azimov Data Set Method Number of MC results Mean MC 1.7  10  26 cm 3 s  1 Gives 95% confidence level exclusion for no real signal Check with Toy Monte Carlo

Dark Matter Sensitivity Predictions “thermal” annihilation cross-section

Systematic errors Dark Matter Systematics, J. Carr Following Silverwood et al. (arXiv: ), use nuisance parameters  in the likelihood to evaluate uncorrelated background systematics

Uncorrelated systematics Dark Matter Systematics, J. Carr13/20

Example of correlated systematic Dark Matter Systematics, J. Carr Variation of effective area across Filed of View (FoV) Knowledge from full Monte Carlo simulations

Different pointing configurations Dark Matter Systematics, J. Carr15/20 ll bb ll bb ll bb ll bb Optimize pointing configuration to minimize statistical and systematic errors

Toy MC Dark Matter Systematics, J. Carr16/20 Input efficiency over FoV Generated signal MC ll bb ll bb

Example Toy MC results Dark Matter Systematics, J. Carr17/20 Simulate Toy MC with 1.7  10  26 cm 3 s  1 corresponding to limit from Asimov Data Set Method Number of MC results 1.7  10  26 cm 3 s  1 Number of MC results Generate with one linear variation of efficiency over FoV Fit with different efficiency variation  (eff) =0.01 at  1.3  10  26 cm 3 s  1

Corrected systematic across FoV Dark Matter Systematics, J. Carr18/20 Different pointing configurations

Summary  Chance to discover WIMP Dark Matter in CTA  Must maintain very low systematic errors for diffuse flux measurements =Dark Matter Systematics, J. Carr19/20

March 2014Cherenkov Telescope Array, J. Carr20

mass: M(R) = v 2 R / G velocity, v radius, R observed Expected from visible stars Evidence for Dark Matter March 2014 Astroparticle Physics, J. Carr 21 “Bullet” colliding galaxies Dark matter Normal Matter Dark matter Galaxy Clusters dynamic stability and gravitational lensing Formation of large scale structure in the universe

Matter/Energy in the Universe March 2014 Astroparticle Physics, J. Carr 22    b   +  CDM   total      Matter: Cold Dark Matter :  CDM  0.23 WIMPS/neutralinos, axions, … Neutrinos:    with  eV Cold Dark Matter Dark Energy Baryonic matter :  b   stars, gas, brown dwarfs, white dwarfs baryons neutrinos cold dark matter