The Cherenkov Telescope Array

Gamma-ray particle astrophysics Dark Matter Space time Cosmic rays...?

Particle Dark Matter Direct Detection Colliders Indirect Detection

Particle Dark Matter CDMS Direct Detection Colliders Indirect Detection

Where should we look? No clear prediction from theory at what particle mass or at what annihilation (or scattering) crosssection we should find dark matter WIMP miracle Predicts that annihilation crosssection is ~3x10-26 cm 3 s -1 Predicts a mass somewhere between 1 GeV and ~10 TeV

Search for Dark Matter in various places Fermi-LAT, 2 years; E > 1 GeV Extragalactic Diffuse Galaxy Clusters Galactic Halo Unidentified sources Galactic Center + spectral lines + electrons Dwarf Satellites + Local Group Galaxies

Detection Not to scale! Pair Creation in the detector ~1 m 2 area ~10 7 ev detection threshold

Detection Beamed blue Cherenkov light 10 5 m 2 light pool ns arrival times, 10 10-10 11 ev detection threshold Not to scale! Pair Creation in the detector ~1 m 2 area ~10 7 ev detection threshold

Comparison of sensitivities Complementary in many aspects, most notably: In energy range and in pointed versus all-sky

Current status: the big three Veritas MAGIC H.E.S.S.

Current status: the big three Veritas The Future: CTA MAGIC H.E.S.S.

Indirect detection of dark matter Held workshop here at SLAC to discuss the HEP-related science case for indirect detection of dark matter ~ 40 participants from various communities (observer, galaxy formation, theorists)

The situation Fermi-LAT reached below the thermal relic crosssection (3x10-26 cm 3 s -1 ) for WIMP masses of 10-25 GeV for bb-annihilation. Abdo et al. (Fermi Collaboration), PRL, 2011 With 10 years of operation (and additional dwarfs found through surveys of the southern sky) expect to rule out thermal relic crosssection from 10-100 GeV.

The situation Abramowski et al. (HESS Collaboration), PRL, 2011 H.E.S.S. GC halo observations within an order of magnitude of thermal relic crosssection for bb, and within factor two for ττ. CTA: expect factor of at least 10-20 improvement (with US contribution more like a factor of 20-40).

The situation Abazajian & Harding, 2011, http://arxiv.org/abs/1110.6151 H.E.S.S. GC halo observations within an order of magnitude of thermal relic crosssection for bb, and within factor two for ττ. CTA: expect factor of at least 10-20 improvement (with US contribution more like a factor of 20-40). So expect to get below thermal relic density for ~400 GeV to ~5 TeV for bb (and more for ττ)

Complementarity direct and indirect detection methods Direct detection (scattering) MSSM / msugra models Indirect detection (annihilation γ s)

Lots of other exciting things Fermi-Bubbles Positron Fraction Acceleration to 10 PeV Lots of other exciting discoveries, some of which might be related to dark matter annihilation

Sensitivity for next-generation instrument Aim: decrease energy threshold, improve sensitivity at midenergies, extend range to higher energies

Low-energy section energy threshold of 20-30 GeV ~24m telescopes Medium Energies: mcrab sensitivity 100 GeV 10 TeV 12m telescopes (one) possible configuration 100 M (2006 costs) High-energy section 10 km 2 area at multi-tev energies 4-6m telescopes x4 x23 x~50

CTA collaboration Merger of the big three, H.E.S.S., MAGIC, VERITAS + many others Currently ~600 physicists involved Europeans are strongest participant in terms of numbers. US, Germany, France largest single countries. Strong support by all relevant European funding agencies (ASPERA, ESFRI, AstroNet). Received 5.2 M for preparation of construction of the observatory from 2011-2013 years time.

CTA-US (former AGIS) 18 US University groups 2 National Labs 35 Physicists 15 engineers 10 technicians ~20 postdocs March 10 2010 AGIS: Presentation to the DoE & NSF F. Krennrich

Unique US design (two-mirror telescope system) Fine Pixelation: Vassiliev et al. 2007 0.28 o 0.20 o 0.07 o Main motivation: Decrease camera size (0.7x0.7m versus 3x3m) Decrease (physical and angular) pixel size Comes at the expense of light-collection area (roughly factor 2) Science goal: increase field of view and improve angular resolution 11 m primary

SC Telescopes A SC dual-mirror telescope is clearly superior to a single-mirror telescope when comparing Arrays with the same number of telescopes Of the same light collecting power Operating perfectly within specs However, we need to compare Arrays where the number of telescopes is limited by funding SC telescopes which have smaller mirrors and...... whose optical system is more complex to align

SC Telescopes In-depth R&D and prototyping required A SC dual-mirror telescope is clearly superior to a single-mirror telescope when comparing Arrays with the same number of telescopes Of the same light collecting power Operating perfectly within specs However, we need to compare Arrays where the number of telescopes is limited by funding SC telescopes which have smaller mirrors and...... whose optical system is more complex to align

Scenario proposed Assumptions: Non-US funding covers basic (LST/MST/SST) CTA array, allowing construction from ~2014-2018 US funding at full recommended level (from e.g. Astro2010, 100 M$) starting later than 2014 Proposal Seamless integration of US groups in CTA Use US resources to boost mid-energy sensitivity of CTA source Using dual-mirror SC telescopes if proven advantageous R&D work until 2015 at which time there is a decision point on which kind of telescope to build (R&D proposal for ~7M$ to construct prototype telescope)

Low-energy section energy threshold of 20-30 GeV ~24m telescopes Medium Energies: mcrab sensitivity 100 GeV 10 TeV 12m telescopes High-energy section 10 km 2 area at multi-tev energies 4-6m telescopes x4 x(23 + 36) x~50

New systems aim for contained light pool

Improving sensitivity and angular resolution Color scale: number of triggered telescopes for 500 GeV showers Addition of 36 telescopes will significantly improve performance of the array Exact layout will need to be investigated

Improve CTA in the core energy range! Sensitivity and energy coverage Design goal

The past three years at SLAC Established close collaboration between ANL, and SLAC as lead labs in CTA LDRD (~1 M$): development of fast, reliable, mass-producible γ-ray camera Goal: $20/chan (electronics) + $40/chan MAPMT), compare: current generation ~ $1000/chan. Main saving through: MAPMT Custom-designed ASIC chip (SLAC & Univ. Hawaii) Switched capacitor array with Wilkinson-type digitization + triggering capability

The past three years at SLAC Established close collaboration between ANL, and SLAC as lead labs in CTA LDRD (~1 M$): development of fast, reliable, mass-producible γ-ray camera Goal: $20/chan (electronics) + $40/chan MAPMT), compare: current generation ~ $1000/chan. Main saving through: MAPMT ~30 cm Custom-designed ASIC chip (SLAC & Univ. Hawaii) Switched capacitor array with Wilkinson-type digitization + triggering capability

Medium-sized telescope Quarter dish at ANL ANL-CEA-DESY Design

Summary DM parameter space is huge, detection requires three pieces: accelerator based searches, direct searches and indirect searches Indirect searches provide the only means of connecting any particle detected with the other two techniques to the actual distribution on the sky Fermi is now ruling out important parts of the parameter space, CTA provides one of the very few opportunities of accessing DM particles at the TeV-scale... And you can do lots of interesting physics with it. To keep us going, need modest R&D support right now!

National Planning Committees PASAG Given the great excitement in the field and the success of the technique, a more ambitious and likely very highly productive concept for the future is an array of many (~50) atmospheric Cherenkov telescopes distributed over a square kilometer. PASAG also recommends that the AGIS collaboration works expeditiously towards a merger with the CTA effort. Astro 2010 Ranked among top 4 priorities for large ground-based projects, after LSST, Mid-scale Innovation Program and the Giant Segmented Mirror Telescope An international collaboration seems necessary for the full potential of the next generation array to be realized. In addition, R&D by the U.S. group on new telescope technologies should be encouraged. The promise of this field is so high that continued involvement is strongly recommended.

Where? Current plan has northern and southern array