Indirect dark matter searches with the Cherenkov Telescope Array

Indirect dark matter searches with the Cherenkov Telescope Array Jennifer Gaskins GRAPPA, University of Amsterdam for the CTA Consortium For more details, please see: arxiv:1508.06128 Carr et al. 2015 [CTA Consortium] (ICRC proceedings) https://portal.cta-observatory.org/cta_observatory/performance/sitepages/home.aspx C. Balazs, T. Bringmann T. Buanes, J. Carr, M. K. Daniel, M. Doro, C. Farnier, M. Fornasa,, G. A. Gomez-Vargas, M. Hayashida, K. Kohri, V. Lefranc, A. Morselli, E. Moulin, N. Mirabal, J. Rico, T. Saito, M.A. Sánchez-Conde, M. Wilkinson, M. Wood, G. Zaharijas, H.-S. Zechlin

Atmospheric Cherenkov Telescopes pair-production detector: detects charged particle events as well as gamma rays can identify cosmic-ray electron and positron events; in general cannot determine charge on an event-by-event basis* Image credit: H.E.S.S. Collaboration 2

The Cherenkov Telescope Array next-generation gamma-ray observatory with > 100 telescopes open observatory designed to operate for 30 years Northern and Southern sites Southern: in Chile, near Paranal Northern: La Palma, Canary Islands, Spain 31 nations, ~ 297M (construction costs) Image credit: CTA Collaboration 3

The Cherenkov Telescope Array Image credit: CTA Collaboration Array configuration assumed for results shown here: CTA Southern Site (area covered by the array of telescopes: ~4 km 2 ): 4 large-size telescopes 24 medium-size telescopes 72 small-size telescopes CTA Northern Site (area covered by the array of telescopes: ~0.4 km 2 ): 4 large-size telescopes 15 medium-size telescopes detailed expected performance information at https://portal.cta-observatory.org/cta_observatory/performance/sitepages/home.aspx 4

Current and future capabilities angular resolution (80% containment radius) Angular Resolution ( ) 0.25 0.2 0.15 0.1 0.05 CTA South MAGIC HAWC VERITAS Fermi LAT Pass 8 www.cta-observatory.org (2015-05-11) 0 10 2 1 10 1 10 10 Energy E (TeV) R 2 Courtesy of CTA Consortium 2015 5

Current and future capabilities sensitivity vs energy -2 s -1 ) x Flux Sensitivity (erg cm 2 E 11 10 12 10 13 10 MAGIC 50 h VERITAS 50 h Differential sensitivity (5 bins per decade in energy) HAWC 1 year HAWC 5 year CTA North 50 h CTA South 50 h www.cta-observatory.org (2015-05-11) 2 10 1 10 1 10 10 Energy E 2 R (TeV) Courtesy of CTA Consortium 2015 6

IACTs vs Fermi LAT IACTs have a large irreducible cosmic-ray background whereas the LAT can reject charged CRs at high efficiency this is a major challenge for searches for extended signals, such as dark matter annihilation in the Inner Galaxy 7

Anomalies! Credit: Jester @ http://resonaances.blogspot.com 8

Anomalies! Credit: Jester @ http://resonaances.blogspot.com indirect detection 8

Anomalies! Credit: Jester @ http://resonaances.blogspot.com indirect detection CTA 8

Dark matter search targets for CTA -14-9 -12-7 The Galactic halo Image credit: JG 2008 Milky Way satellites Draco. Image credit: J. Moore et al. 2012 The Large Magellanic Cloud Image credit: NASA 9

Galactic halo projected sensitivity 500h, Einasto, different channels 500h, bb, different profiles (statistical errors only) Carr et al. 2015 (CTA Consortium) 10

LMC projected sensitivity 340h 200 GeV threshold different profiles and channels (statistical errors only) C 2015 Courtesy of CTA Consortium 2015 11

Satellites projected sensitivity 500h, Sculptor, different channels 500h, bb, different dsph (statistical errors only) Carr et al. 2015 (CTA Consortium) 12

Comparison of targets 500h, WW / bb, different targets CTA Halo/Sculptor: 30 GeV threshold HESS (bb) CTA LMC: 200 GeV threshold (statistical errors only) SYSTEMATICS MUST BE CONTROLLED EXTREMELY WELL TO ACHIEVE STATISTICALLY-POSSIBLE SENSITIVITY Fermi (bb) CTA (WW) Carr et al. 2015 (CTA Consortium) 13

Spectral information using full spectral information in analysis improves sensitivity at moderate/high dark matter masses (now included in recent CTA projections shown here) h vi 3 1 10 23 10 24 10 25 10 26 Galactic halo, 500h, NFW profile b b + µ + µ 10 27 10 2 10 3 m Pierre, JG, & Scott, 2014 14

Morphological information Galactic halo, 100h, comparison of analyses using full morphological information (as opposed to simple ON-OFF techniques) in analysis improves sensitivity (under study for implementation in future CTA analyses) Self-annihilation cross-section h vi [cm 3 s 1 ] 10 21 10 22 10 23 10 24 10 25 10 26 3% 1% 0.3% CTA Ring method CTA Morph. analysis CTA Morph. analysis (3% syst.) CTA Morph. analysis (0.3% syst.) b b, 100 hours HESS GC Fermi-LAT dsph Doro et al. 2013, CTA Wood et al. 2013, CTA Pierre et al. 2014, CTA 10 2 10 3 10 4 DM particle mass m [GeV] Silverwood et al. 2014 see also Lefranc et al. 2015 for impact of spectral and morphological analysis 15

Summary CTA will improve dramatically on existing sensitivity to DM annihilation for a range of interesting DM masses for many annihilation channels CTA will test the canonical thermal relic annihilation cross section if the Galactic halo density profile is NFW/Einasto while less promising, the LMC and Milky Way satellite galaxies are complementary targets with different uncertainties understanding and controlling systematics will be key for interpreting a possible detection or placing constraints using any targets 16

Additional slides 17

Calculating indirect signals (for particles that propagate directly to the observer without deflection, attenuation, or secondary production) differential intensity = particle physics term K astrophysics term J ANNIHILATION: K ann = dn de h vi 2m 2 J ann ( ) = 1 4 Z los ds 2 (s, ) DECAY: K decay = dn de 1 m J decay ( ) = 1 4 Z los ds (s, ) 18

Calculating indirect signals (for particles that propagate directly to the observer without deflection, attenuation, or secondary production) differential intensity = particle physics term K astrophysics term J ANNIHILATION: K ann = dn de h vi 2m 2 J ann ( ) = 1 4 Z los ds 2 (s, ) spectrum of particles produced DECAY: K decay = dn de 1 m J decay ( ) = 1 4 Z los ds (s, ) 18

Calculating indirect signals (for particles that propagate directly to the observer without deflection, attenuation, or secondary production) differential intensity = particle physics term K astrophysics term J ANNIHILATION: K ann = dn de h vi 2m 2 J ann ( ) = 1 4 Z los average of pair annihilation cross section times relative velocity ds 2 (s, ) DECAY: K decay = dn de 1 m J decay ( ) = 1 4 Z los ds (s, ) 18

Calculating indirect signals (for particles that propagate directly to the observer without deflection, attenuation, or secondary production) differential intensity = particle physics term K astrophysics term J ANNIHILATION: K ann = dn de h vi 2m 2 J ann ( ) = 1 4 Z los ds 2 (s, ) dark matter density DECAY: K decay = dn de 1 m J decay ( ) = 1 4 Z los ds (s, ) 18

The multi-wavelength Inner Galaxy VLA @ 330 MHz HESS > 380 GeV Aharonian et al. 2006 19

Sensitivity to gamma-ray lines energy resolution vs energy Courtesy of CTA consortium 2015 20

Sensitivity to gamma-ray lines CTA: 500h, 1 deg around GC, Einasto -26 10 CTA w/ Burkert H.E.S.S s -1 ] Fermi 3 < v> [cm -27 10-28 10-29 10-1 10 1 10 m DM [TeV] CTA diff. sensitivity CTA unbinned likelihood Courtesy of CTA consortium 2015 21

Proposed search strategy Year 1 2 3 4 5 6 7 8 9 10 Galactic halo 175 h 175 h 175 h Segue 1 (or best) dsph 100 h 100 h 100 h in case of detection at GC, large v Segue 1 (or best) dsph 150 h 150 h 150 h 150 h 150 h 150 h 150 h Galactic halo 100 h 100 h 100 h 100 h 100 h 100 h 100 h in case of detection at GC, small v Galactic halo 100 h 100 h 100 h 100 h 100 h 100 h 100 h in case of no detection at GC Best Target 100 h 100 h 100 h 100 h 100 h 100 h 100 h Courtesy of CTA consortium 2015 22