1. Jason Koglin – ICRC – July 10, 2007 1 Antideuterons as an Indirect Dark Matter Signature: Design and Preparation for a Balloon-born GAPS Experiment

2. Jason Koglin – ICRC – July 10, 2007 2 Low-energy, neutralino-neutralino produced antideuterons are near background free & accessible by GAPS Primary component:  neutralino annihilation __ X+X → D + … Secondary component:  spallation __ p+H → p+H+D+… __ p+He → p+He+D+… GAPS is essentially a background free experiment GAPS represents a major improvement over the state of the art GAPS has outstanding discovery potential for a variety of DM models Significant antideuteron flux at the earth (with propagation & solar modulation) first pointed out by Donato et al. 2000 Kinetic Energy per Nucleon [GeV/n] 0.1110100 Secondary/Tertiary ULDB LZP (m = 40 GeV) LSP (m = 100 GeV) LKP (m = 500 GeV) GAPS LDB 10 -7 10 -5 10 -3 10 -10 10 -8 10 -6 10 -4 10 -9 Antideuteron Flux [m 2 s -1 sr -1 GeV -1 ] Signal: Baer & Profumo ’05 Back: Duperray et al. ‘05 BESS limit

3. Jason Koglin – ICRC – July 10, 2007 3 SUSY discovery potential for an antideuteron experiment is similar to direct detection methods There are over 20 current or planned direct detection experiments to probe SUSY DM A balloon GAPS antideuteron search offers SUSY parameter space complementarity to direct detection, underground searches GAPS probes an unique region of parameter space inaccessible by other methods Discovery Exploratory ULDBLDB From Baer & Profumo 2005 GAPS Both Direct LDBULDB Energy (GeV/n)0.05-0.25 Acceptance (m 2 sr GeV/n) 0.2(D),1.1(E) Observation time 60 days (3 flights) 300 days Sensitivity (m 2 sr s GeV/n) -1 3.0 x 10 -7 (E) 1.2 x 10 -6 (D) 7.5 x 10 -8 (E) 2.9 x 10 -7 (D)

4. Jason Koglin – ICRC – July 10, 2007 4 GAPS is based on radiative emission of antiparticles captured into exotic atoms _D_D Ladder Deexcitations n=1, l=1 Nuclear Annihilation         n=1 n=2 n=3 n=4 n=5 n=6 n=n K ~15 n o,l o Atomic Transitions ** ** ** Antiprotonic yields measured at KEK in 2004 & 2005 in various targets. Auger e - Refilling e - The antiparticle slows down & stops in a target material, forming an excited exotic atom with near unity probability A time of flight (TOF) system tags candidate events and records velocity Deexcitation X-rays provide signature Pions from annihilation provide added background suppression ** Plastic Scintillator TOF Si(Li) Target/Detector 44 keV 30 keV

5. Jason Koglin – ICRC – July 10, 2007 5 Si(Li) Wafers will be hexagonally packed into detector planes & surrounded by segmented Plastic TOF ~200 kg Si(Li) mass – Similar to direct detection target mass

6. Jason Koglin – ICRC – July 10, 2007 6 GAPS employs three techniques to uniquely identify antideuterons with enormous background suppression 1. Atomic X-rays 2. TOF and Depth Sensing 3. Charged Pion Multiplicity Type of Background Expected Events Basis for estimate Temporally incoherent X-rays < 0.003 Scaling from γ- ray telescopes Temporally coherent X-rays 0.001 Measured at GAPS-KEK experiment Elastic neutrons0.002 Monte-Carlo of evaporative & cascade model, KEK limits Secondary- tertiary- atmospheric antideuterons 0.006 Propagate calculated spectra through atmosphere to instrument Nuclear  -rays,  o shower photons, internal bremastrahlung negligible Data on energy & branching ratio of all possible lines; analytic calc.; GEANT4 sim. Exploration trigger0.2 (total) Analytic & Monte- Carlo Simulations Exploratory Expected Background for a 300 Day Flight

7. Jason Koglin – ICRC – July 10, 2007 7 Si(Li) Serves a Target for Stopping Antideuterons as well as an X-ray Detector & Particle Tracker Relatively low Z provides:  good compromise between X-ray escape and detection  Low internal background. Excellent timing (50 ns) & energy resolution (2 keV – much better than NaI, but modest for Si)  2 X-ray coincidence sufficient (previous designs used 3 X-rays) Relatively course pixels (8 cm 2 )  Keeps channel count low but still provides for low pileup. Dual channel electronics (5-200 keV & 0.1-200 MeV)  Good charged particle tracking Proven technology dating to 60’s We have tested a prototype detector that exceeds our requirements  Challenge is in large-scale fabrication Modular approach for ease of in-field assembly

8. Jason Koglin – ICRC – July 10, 2007 8 A Prototype Flight will Provide a Crucial Science & Engineering Demonstration Balloon Prototype Goals: Demonstrate stable, low noise operation of the Si(Li) with its polymer coating at float altitude & ambient pressure. Demonstrate the Si(Li) cooling approach & deployable sun shades. Verify thermal model. Measure incoherent background level in a flight- like configuration. 2009 Flight planned from Japan with ISIS/JAXA participation

9. Jason Koglin – ICRC – July 10, 2007 9 GAPS Development Plan Culminates in a Long-Duration Balloon (LDB) Experiment 20032004200520062007200820092010201120122013 Antarctic Science Flight Facility Design Facility Construction bGAPS Construction Japan Proto-Flight pGAPS Construction Flight Instrument Design KEK04KEK05 Data Analysis & Background Studies Si(Li) Proto Measurements Flight proposal submitted to NASA in Spring 2007 Flight of GAPS prototype from Japan in 2009 LDB GAPS flight from Antarctica in 2013 Experiment design will be ultra long duration (ULDB) capable to exploit such a launch if it becomes available; flight duration >100 days Growing collaboration & adding expertise to execute this plan NASA/ULDB

10. Jason Koglin – ICRC – July 10, 2007 10 Primary GAPS Science Goals Antideuteron Dark Matter (DM) Signature Primordial Black Holes Low-Energy Antiproton Spectroscopy Measure antideuterons from evaporating PBH’s Potentially constrain inflation temperature Execute deep searches for SUSY & UED DM Complementary with direct and other indirect measurements Measure 10 4 -10 5 antiprotons <0.3 GeV (BESS-polar measured 26 @ <0.3 GeV) Perform both DM and cosmic-ray physics From Barrau et al. 2003 From Baer & Profumo 2005