Indirect detection of dark matter Larry Wai SLAC

Indirect detection of dark matter Larry Wai SLAC July 21, 2006 - VLCW 06 Cosmology Session Larry Wai / SLAC

Indirect detection – a complementary way to observe dark matter signals! DM Experiment Class Dark matter source location Dark matter interaction Direct Detection Earth’s Surface WIMP-nucleus scattering Particle Beam Collider Irrelevant WIMP pair production Indirect Detection Earth, Sun, Galaxy, extragalactic July 21, 2006 - VLCW 06 Cosmology Session Larry Wai / SLAC WIMP pair annihilation 2

Particles used for indirect detection of dark matter WIMP pair annihilation hadronic final states time c c W-/Z/q _ W+/Z /q p 0 } nm p+ p- nm ne m+ nm m- e+ nm ne e+ a few p/p, d/d July 21, 2006 - VLCW 06 Cosmology Session Larry Wai / SLAC 3

Particles used for indirect detection of dark matter WIMP pair annihilation leptonic final states c c time n/e-/m-/t- n/e+/m+/t+ July 21, 2006 - VLCW 06 Cosmology Session } m/t- p 0 nm/tne e- or t- nt p- m/t+ nm/tne nm nm ne m- e- e+ Larry Wai / SLAC 4

Particle yields & spectra Gamma ray yield per final state bb WIMP pair annihilation gamma spectrum July 21, 2006 - VLCW 06 Cosmology Session MWIMP Total# >100 Me. V >1 Ge. V >10 Ge. V 10 Ge. V 17. 3 12. 6 1. 0 0 100 Ge. V 24. 5 22. 5 12. 4 1. 0 1 Te. V 31. 0 29. 3 22. 4 12. 3 200 Ge. V mass WIMP Larry Wai / SLAC 5

Spectral lines time Ø For lines, energy = WIMP mass; branching fraction is suppressed c Ø e+e-, nn lines are possible at tree level (especially for Dirac fermion or boson WIMPs) c Ø For WIMP masses > MZ /2 can also have Z 0 line , e+, n ? , e-, n γ c ? Ø Measurement of line branching fractions would constrain particle theory July 21, 2006 - VLCW 06 Cosmology Session Larry Wai / SLAC c Z 0 6

Annihilation flux spectrum ∫(∑id. N/d. E Bi)d. E (particle physics) x x 2 number density 2 2 2 4 p ∫r (r)r dr / M WIMP (astrophysics) x x ann. cross-section <sn> / 2 (cosmology, particle physics) x x 1/4 pd 2 distance-2 July 21, 2006 - VLCW 06 Cosmology Session Larry Wai / SLAC 7

Where should we look for indirect signals? • • • Galactic satellites Galactic halo Extra-galactic Galactic center Stars July 21, 2006 - VLCW 06 Cosmology Session Larry Wai / SLAC 8

Current experiments Gamma ray detectors • Space (20 Me. V-300 Ge. V) Ø GLAST Neutrino detectors • Underground (>5 Me. V) Ø Super-Kamiokande • Undersea / ice (>5 Ge. V) • Ground (>100 Ge. V) Ø VERITAS Ø HESS Ø MAGIC July 21, 2006 - VLCW 06 Cosmology Session Ø AMANDA/ ICECUBE Ø ANTARES Anti-Matter detectors • Space Ø PAMELA Ø AMS Larry Wai / SLAC 9

~ 10 km 1. 8 m Particle Shower effective area ~ 4 x 105 m 2 field of view~0. 01 sq. rad. particle bkgd<100 Ge. V s. E~15% 1. 0 m e+ e– 565 km altitude effective area ~ 1 m 2 field of view~2. 5 sq. rad. particle bkgd<100 Me. V s. E~10% (E>100 Me. V) ~ 100 m July 21, 2006 - VLCW 06 Cosmology Session Larry Wai / SLAC 10

Gamma Ray Detectors MAGIC GLAST Ship to SASS in Sept. 2006 Launch in Sept. 2007! 2 nd large telescope in late 2007 VERITAS HESS 5 th telescope in early 2008 4 telescopes in 2007 July 21, 2006 - VLCW 06 Cosmology Session Larry Wai / SLAC 11

Diffuse gamma ray background EGRET E >1 Ge. V, point-source subtracted, Cillis & Hartman (2005) Modeling with GALPROP Inputs include matter distribution July 21, 2006 - VLCW 06 Cosmology Session Larry Wai / SLAC 12

Example A. dark matter satellite 55 -days GLAST in-orbit counts map (E>1 Ge. V) Galactic Center Optimistic case: 70 counts signal, 43 counts background within 1. 5 deg of clump center July 21, 2006 - VLCW 06 Cosmology Session 30 -deg latitude Larry Wai / SLAC 13

Dark matter source spectrum GLAST 55 days (10 -sigma) Dark matter spectrum Diffuse background E-2. 6 spectrum July 21, 2006 - VLCW 06 Cosmology Session Larry Wai / SLAC 14

How many observable dark matter sources? LSP WIMP (SUSY) GLAST 5 -yrs LCC 2 LCC 4 July 21, 2006 - VLCW 06 Cosmology Session Larry Wai / SLAC Simulation of Milky Way dark matter satellites from Taylor & Babul (2004, 2005) SUSY model definitions from Baltz, et. al. (2006); LCC 2 and LCC 4 are favorable to GLAST compared to LCC 1 and LCC 3. 15

Example: GLAST-IACT search strategy • Assume GLAST finds some high latitude dark matter point sources consistent with WIMP mass ~100 Ge. V • Assume IACTs learn how to eliminate all of the charged particle background <150 Ge. V while retaining 20% gamma efficiency Ø Example: 10 -sigma high latitude GLAST WIMP source (5 -yr exposure) would have ~100 counts background (0. 5 -deg radius circle, E>1 Ge. V), ~100 counts signal; follow-up by IACT would have ~40 line gammas for a line branching fraction ~. 003. The IACT extragalactic gamma background would be ~60 (100 Ge. V mass WIMP). July 21, 2006 - VLCW 06 Cosmology Session Larry Wai / SLAC 16

Example B. Milky Way dark matter halo EGRET E >1 Ge. V, point-source subtracted, Cillis & Hartman (2005) High latitude Region Disk Region Center Region Disk Region High latitude Region July 21, 2006 - VLCW 06 Cosmology Session Larry Wai / SLAC WIMP search “sweet spot” (Stoehr et. al. 2004) 17

EGRET diffuse “Ge. V excess” -still up for grabs! Hunter et al (1997); similar “Ge. V excess” in all sky regions EGRET Instrumental effects |b|<10 deg, |l|<60 deg ØNeed to include diffractive pp->p 0 cross-section; Kamae (2005) ØCan be explained with astrophysical mechanisms; i. e. SMR (2004) ØDe Boer has claimed WIMP annihilation; i. e. De Boer, et. al. (2005) ØScenarios can be tested with anti-matter fluxes; i. e. Edsjo (2006) July 21, 2006 - VLCW 06 Cosmology Session Larry Wai / SLAC 18

Back-of-the-envelope line significance • Consider high latitude region |b|>10 deg (|b|>30 deg for |l|<30 deg), 5 years GLAST on -orbit • line background is flux within DE/E=0. 235 at MWIMP, Z line Ø Assume WIMP continuum is 30% of galactic diffuse flux for E>. 01 MWIMP Ø Assume 0. 1% branching fraction to line Ø # sigma is no. line counts/sqrt(no. bkgd counts) July 21, 2006 - VLCW 06 Cosmology Session Larry Wai / SLAC line Z line 19

Example C: Galactic Center EGRET GLAST Mayer-Hasselwander (1998) - EGRET point source Spatial analysis • 100 Me. V-300 Me. V (l ~ -0. 75 deg) HESS Cesarini, (2004)Fucito, Lionetto, Morselli, Ullio (2003) • 300 Me. V-1 Ge. V (l ~ -0. 30 deg) • > 1 Ge. V (l ~ 0. 05 deg) 95% CL CL • > 5 Ge. V (l ~ 0. 20 deg) Hooper & Dingus (2004) x New diffuse component in the galactic center region, HESS (2006) Galactic Center Hooper and Dingus (2002) July 21, 2006 - VLCW 06 Cosmology Session Larry Wai / SLAC Mayer-Hasselwander et. al. (1998) 20

Galactic center m. SUGRA sensitivity: small tan(b) regime (5 s) Ø Ø July 21, 2006 - VLCW 06 Cosmology Session See Baltz, et. al. (2006) for definition of LCC 2. Note: position of this point is very sensitive to mt and this placement estimates the equivalent LCC 2. Accelerator limits are from H. Baer, et al. (2004) Larry Wai / SLAC 21

Galactic center m. SUGRA sensitivity: large tan(b) regime Ø (5 s) July 21, 2006 - VLCW 06 Cosmology Session Ø See Baltz, et. al. (2006) for definition of LCC 4. Note: position of this point is very sensitive to mt and this placement estimates the equivalent LCC 4. Accelerator limits are from H. Baer, et al. (2004) Larry Wai / SLAC 22

Dark matter neutrino detection technique July 21, 2006 - VLCW 06 Cosmology Session Larry Wai / SLAC 23

Neutrino detectors Super-Kamiokande Feb. 2006 9 strings (80 by 2011) July 21, 2006 - VLCW 06 Cosmology Session Larry Wai / SLAC ANTARES Feb. 2006 – 1 line (12 lines by 2007) 24

Solar WIMP sensitivity July 21, 2006 - VLCW 06 Cosmology Session Larry Wai / SLAC 25

dark matter anti-matter sources Galactic Center / Halo Dark matter source Earth anti-proton, positron ~3 kpc galactic magnetic field scale height July 21, 2006 - VLCW 06 Cosmology Session Larry Wai / SLAC 8. 5 kpc 26

Anti-matter detectors PAMELA July 21, 2006 - VLCW 06 Cosmology Session Larry Wai / SLAC AMS-1 27

Dark matter anti-matter spectra 336 Ge. V mass WIMP July 21, 2006 - VLCW 06 Cosmology Session Larry Wai / SLAC GALPROP background estimate 28

Future of indirect detection Impact of new information • Direct detection results on cross-section will impact expected neutrino flux from solar WIMP accumulation • WIMP mass measurements (from direct, LHC, GLAST? ) will impact expected annihilation spectrum; i. e. what threshold do we need for IACT line measurements? • Location of WIMP annihilation sources by GLAST would dramatically alter the landscape; i. e. tell IACTs where to look! July 21, 2006 - VLCW 06 Cosmology Session Indirect experiments • ICECUBE, PAMELA, AMS-2 – discovery potential for large mass, large lepton branching fraction scenarios • GLAST, IACTs, & Beyond VERITAS – accurate line branching fraction measurements would constrain particle theory Larry Wai / SLAC 29

Indirect detection summary Search regions: Øgalactic center Øgalactic satellites Øgalactic halo Øextragalactic Øthe sun, earth July 21, 2006 - VLCW 06 Cosmology Session Goals: Ø Observe particle nature of dark matter Ø Measure WIMP mass Ø Constrain leptonic branching fractions Ø Measure line branching fractions Larry Wai / SLAC 30