Results From VERITAS K. Byrum High Energy Physics (HEP) Division Argonne National Laboratory Indirect and Direct Detection of Dark Matter 6-12 Feb 2011, Aspen Colorado

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 2 Talk Outline  Introduction  VERITAS  VERITAS Results  VERITAS Upgrade  Beyond VERITAS: CTA

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 3 Very High Energy Gamma-ray Sky 1999 Crab first observed 1989 (Whipple)

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 4 Very High Energy Gamma-ray Sky 2010 >130 sources

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 5 Very High Energy Gamma-Ray Science: Astronomy, Astrophysics, Cosmology, Fundamental Physics This is a Broad Program  Search for Dark Matter & Fundamental Physics  Extragalactic Science (GRBs, Cosmology, AGNs, Starburst Galaxies)  Galactic Science (SNRs, PWNs, Binaries)

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 6 Current status: Very High Energy Gamma-ray Detectors H.E.S.S. MAGIC Milgro FGST HAWC (future) VERITAS

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 7 Talk Outline  Introduction  VERITAS  VERITAS Results  VERITAS Upgrade  Beyond VERITAS: CTA

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 8 VERITAS

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 9

10 VHE Gamma-ray Technique Multiple Telescopes:  improve angular resolution  improve energy resolution  reduce background  eliminate muons  improve stability

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 11 VERITAS is currently the most sensitive TeV Observatory in the world. Trigger & Readout: Three-level trigger  Constant fraction discriminator for each PMT  Pattern trigger on every telescope (requires hits on adjacent 3 PMTs within ~7-9ns)  Array trigger requires 2 or more telescopes 500 MS/s Flash-ADC on every ch. 8-bit dual gain

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 12

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 13

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 14 Talk Outline  Introduction  VERITAS  VERITAS Results  VERITAS Upgrade  Beyond VERITAS: CTA

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 15 VERITAS: Indirect Dark Matter Program  Dark Matter makes up ~25% of energy budget of Universe   DM h 2 = (WMAP +BAO +SN1a) ~ 23%  DM has only been inferred gravitationally by its interaction with visible matter  Well described theoretically by extensions to standard model of particle physics (MSSM, Kaluza-Klein).  Cosmological constraints: Thermal relic of early universe with weak scale cross section & mass produces present DM density (Lee & Weinberg, 1977)  ~ 50 GeV/c 2 < M WIMP < ~ 10 TeV/c 2  WIMP annihilation to  -rays:   -ray line from direct annihilation (higher order process)   -ray continuum from hadronization  Enhanced near M WIMP from internal brem

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 16 Search for Indirect Detection of Dark Matter

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 17 VERITAS Dark Matter Program Concentrate on WIMP scenario: SUSY or Kaluza-Klein particle with mass in the GeV-TeV range Assume pair annihilation giving rise to flux of  -rays w/cutoff at M wimp Expect  -ray flux proportional to squared DM density Because of large uncertainties (WIMP mass, , astrophysical flux), VERITAS observing strategy has been: “variety of targets” Target Advantages Disadvantages Galactic Center Dwarf spheroidal galaxies Globular clusters Clusters of galaxies -Closeby -Huge amount of DM -Many astrophysical backgrounds -Huge uncertainities in the DM distribution (O(10 3 )) -DM dominated -Clear of astrophysical bkgd -Very close -Huge amount of DM -May be beyond reach of current instrument sensitivity -Can be tidally disrupted: uncertainties in the DM distribution O(10)) -Not DM dominated -Astrophysical backgorund -Interplay of baryons with DM not well known -Very far -Astrophysical background

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 18 Indirect DM Search using Dwarf Spheroid 18 Recent discovery of many dSphs by SDSS; likely more discoveries in future VERITAS Dwarf Spheroid Targets: Draco, Ursa Minor, Bootes 1, Willman 1, Segue 1

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 19  Dwarf galaxy observations made since early 2007  Wobble pointing mode (0.5deg offset from camera center).  Second moment analysis (Hillas parameter of the shower image in the camera focal plane) for the selection of  -rays: cut optimized for a 3.5% Crab-like source  Reflected background model to subtract the residual background Indirect DM Search using Dwarf Spheroid Typical map of null observation

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 20 Indirect DM Search using Dwarf Spheroid No significant excess detected in any of the observations. a Significance calculated using Li & Ma method (ApJ 272, 317 eqn.17) b 95% CL upper limits using Rolke, Lopez & Conrad (arXiv: v4) bounded profile likelihood method c Above energy threshold, for a Crab-like spectrum

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 21 Indirect DM Search using Dwarf Spheroid

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 22 Indirect DM Search using Dwarf Spheroid  MSSM models from DarkSUSY within ±1 standard deviations of WMAP measured relic density.  Uncertainty ±1 order of magnitude due to systematics in halo modeling  95% CL upper limits from Reflected Region Background Model analysis and Rolke zero-bounded profile likelihood  Boost factor from substructure, internal bremsstrahlung could give × smaller Limits from VERITAS on annihilation : ~ cm -3 s -1 X 100 ApJ 2010 By Matthieu Vivier

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 23 VERITAS Future Dark Matter Analysis  Continued observations on dSphs should reduce the theoretical uncertainties on mass models.  Will target deeper exposures on select dSph targets  Stacked analysis  FERMI follow-up observations of DM source candidates  Analysis currently underway –Galactic Center –Globular clusters –Electron spectrum

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 24 Talk Outline  Introduction  VERITAS  VERITAS Results  VERITAS Upgrade  Beyond VERITAS: CTA

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 25 VERITAS Upgrade Underway Motivation  Increased effective area  Better Background Suppression  Better Angular Resolution  Lower Energy Threshold  Faster Slewing time Result is Improved Sensitivity  Faster detection for a given source strength  Detect weaker and more distant sources Components (started with T1 move in Summer 2009)  PMT replacement with higher QE PMTs  FPGA Level-2 pattern Trigger  Faster slewing for Telescopes After T1 move + mirror align 1% crab = 28 hr (already) After Trigger, High QE PMTs: 1% crab: ?

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 26 Higher QE PMTs

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 27 VERITAS FPGA Level 2 Trigger Upgrade  Meant to be a drop in replacement to current aging L2  With enhanced capabilities –Coincidence window improvement (down to 3-4ns) –Pixel timing alignment –Improved diagnostic capabilities –Reconfigurable trigger through downloadable firmware –Updates/improvements do not require access to hardware –Alternate/experimental triggers may be tested w/o access to hardware  All the hooks in place for adding a future L4 topological trigger First telescope installed parasitically Nov 2010; remaining telescopes in Summer 2011.

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 28 Talk Outline  Introduction  VERITAS  VERITAS Results  VERITAS Upgrade  Beyond VERITAS: CTA

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 29 CTA

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 30 VHE Gamma-ray Sensitivities: Present and Future FGST Energy (GeV) Space IACT EAS

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 31 Sensitivities for WIMP detection  “A significant region of parameter space could potentially be excluded (or the effort might result in a detection!) through observations of nearby dwarf galaxies. Therefore, increasing the sensitivity of atmospheric Cherenkov telescopes by another order of magnitude is our top priority for exploring the nature of dark matter” (Astro2010, Panel Report) x100 Exposure x10 Sensitivity x5 BG reduction E Threshold

Indirect and Direct Detection of Dark Matter, 6-12 Feb, 2011, K.Byrum 32 Summary  VERITAS: Broad science program (that I didn’t discuss)  Current Dark Matter program : –Observations of 5 northern dSphs, with exposures 15 hrs –No  -ray signal detected (so far) –Limits on annihilation cross-sections of order cm 3 s -1 ; competitive with limits obtained by MAGIC and with southern dSphs by HESS –Results using Draco, Ursa Minor, Willman 1 and Bootes 1 reported in ApJ –Analysis of Galactic Center and Globular clusters underway  VERITAS upgrade underway; expect improved sensitivity  Future Dark Matter observations w/VERITAS: –Upcoming observational data sets on dSphs will reduce the theoretical uncertainties on mass models and point to better dSph candidates –Will target deeper exposures on select targets –Will provided FERMI follow-up observations of DM source candidates  Future Dark Matter observations with CTA –Improved sensitivity of CTA order of magnitude beyond current instruments