GLAST - an Astro-Particle Mission to Explore the High Energy Gamma Ray Sky Ronaldo Bellazzini

1. GLAST - an Astro-Particle Mission to Explore the High Energy Gamma Ray Sky Ronaldo Bellazzini INFN - sez. Pisa XXI Symposium on Relativistic AstroPhysics Firenze, Italy, December 9-13 2002

2. Profound Connection between Astrophysics & HEP The fundamental theory ofCosmic Genesis and the questfor experimental evidencehas led to new and potential partnerships between Astrophysics and HEP. • Some Areas of Collaboration: • Origin of cosmic rays • Dark Matter Searches • CMBR • Quantum gravity • Structure Formation • Early Universe Physics • Understanding the HE Universe • Typical signatures • Ultra HE cosmic rays • gamma-rays -> GLAST • n • antimatter • extensive use of high resolution and reliable particle detectors now possible after long and successful experience in particle physics

3. 0.01 GeV 0.1 GeV 1 GeV 10 GeV 100 GeV 1 TeV Active Galactic Nuclei Solar flares Unidentified sources Cosmic ray acceleration Pulsars Dark matter Gamma Ray Bursts GLAST science - the sky above 100 MeV

4. GLAST Concept Low profile for wide f.o.v. Segmented anti-shield to minimize self-veto at high E. Finely segment calorimeter for enhanced background rejection and shower leakage correction. High-efficiency, precise track detectors located close to the conversions foils to minimize multiple-scattering errors. Modular, redundant design. No consumables. Low power consumption (580 W)  Charged particle anticoincidence shield Conversion foils Particle tracking detectors e+ e- • Calorimeter • (energy measurement) GLAST g detection technique – pair conversion telescope Pair production is the dominant photon interaction above 10MeV: E -> me+c2 + me-c2

5. Tracker Grid Thermal Blanket ACD DAQ Electronics Calorimeter GLAST Instrument: the Large Area Telescope (LAT) • Array of 16 identical “Tower” Modules, each with a tracker (Si strips) and a calorimeter (CsI with PIN diode readout) and DAQ module. • Surrounded by finely segmented ACD (plastic scintillator with PMT readout). • Aluminum strong-back “Grid,” with heat pipes for transport of heat to the instrument sides.

6. LAT Instrument Performance Including all Background & Track Quality Cuts

7. TheGLASTParticipating Institutions American Team Institutions SU - Stanford University, Physics Department and EGRET group, Hanson Experimental Physics Laboratory SU-SLACStanford Linear Accelerator Center, SLAC, Particle Astrophysics group GSFC-NASA Goddard Space Flight Center, Laboratory for High Energy Astrophysics NRL - U. S. Naval Research Laboratory, E. O. Hulburt Center for Space Research, X-ray and gamma-ray branches UCSC- University of California at Santa Cruz, Physics Department SSU- Sonoma State University, Department of Physics & Astronomy UW- University of Washington , TAMUK- Texas A&M University-Kingsville Italian Team Institutions INFN - Instituto Nazionale di Fisica Nucleare: Units of Bari, Perugia, Pisa, Rome 2, Tries ASI - Italian Space Agency IFC/CNR- Istituto di Fisica, Cosmica, CNR Japanese Team Institutions University of Tokyo ICRR - Institute for Cosmic-Ray Research ISAS- Institute for Space and Astronautical Science Hiroshima University French Team Institutions CEA/DAPNIA Commissariat à l'Energie Atomique, Département d'Astrophysique, de physique des Particules, de physique Nucliaire et de l'Instrumentation Associée, CEA, Saclay IN2P3 Institut National de Physique Nucléaire et de Physique des Particules, IN2P3 IN2P3/LPNHE-X Laboratoire de Physique Nucléaire des Hautes Energies de l'École Polytechnique IN2P3/PCC Laboratoire de Physique Corpusculaire et Cosmologie, Collège de France IN2P3/CENBG Centre d'études nucléaires de Bordeaux Gradignan Swedish Team Institutions KTHRoyal Institute of Technology Stockholms Universitet

8. GLAST Science Capability Key instrument features that enhance GLAST’s science reach: • Peak effective area: 12,900 cm2 • Precision point-spread function (<0.10° for E=10 GeV) • Excellent background rejection: better than 2.5105:1 • Good energy resolution for all photons (<10%) • Wide field of view, for lengthy viewing time of all sources and excellent transient response • Discovery reach extending to ~TeV

9. GLAST (2006 - .... ) – the future • larger effective area • larger field of view • increased sensitivity EGRET (1991-1996) – the past The Gamma-ray Sky

10. GLAST scanning mode sensitivity In scanning mode, GLAST will achieve in one day a sufficient sensitivity to detect (5) the weakest EGRET sources.

11. Broad spectral coverage is crucial for studying and understanding most astrophysical sources. GLAST and ground-based experiments cover complimentary energy ranges. The improved sensitivity of GLAST is necessary for matching the sensitivity of the next generation of ground-based detectors. GLAST goes a long ways toward filling in the energy gap between space-based and ground-based detectors—there will be overlap for the brighter sources. Covering the Gamma-Ray Spectrum Predicted sensitivities to a point source. EGRET, GLAST, and Milagro: 1-yr survey. Cherenkov telescopes: 50 hours on source. (Weekes et al., 1996, with GLAST added)

12. Predicted GLAST measurements of Crab unpulsed flux in the overlap region with ground-based atmospheric cherenkov telescopes. Overlap of GLAST with ACTs

13. Identifying Sources GLAST 95% C.L. radius on a 5 source, compared with a similar EGRET observation of 3EG 1911-2000 Unidentified Sources Counting stats not included. 170/271 3rd EGRET catalog still unidentified GLAST high resolution and sensitivity will • resolve gamma-ray point sources at arc-minute level • detect typical signatures (e.g. spectra, flares, pulsation) for identification with known source types Cygnus region (150 x 150), Eg > 1 GeV

14. Pulsar physics with GLAST known gamma-ray pulsars • direct pulsation search in the g-ray band • high time resolution • detect new gamma-ray pulsars (~250) • precise test of polar cap vs outer gap emission models • large effective area

15. AGN signature • vast amounts of energy (1049 erg/s) from a very compact central volume • large luminosity fluctuations in fractions of a day • energetic (multi-TeV), highly-collimated, relativistic particle jets • Prevailing idea: accretion onto super-massive black holes (106 - 1010 solar masses) • AGN physics to-do list • catalogue AGN classes with a large data sample (~>3000 new AGNs) • distinguish different emission models studying high statistics spectra • resolve diffuse background • study redshift dependence of spectra exploiting overlap with other wavelength observations and alert capabilities Active Galactic Nuclei • high sensitivity • large effective area • small PSF

16. Blazar physics • measure spectrum in uncovered gamma-ray energy band • identify leptonic (SSC/ESC) and hadronic (p0 decay) contributions • track flares (time scale of minutes) and correlate to other wavelengths Cosmology models Roll-offs in the g-ray spectra from AGN at large z probe the extragalactic background light (EBL) over cosmological distances and may help to distinguish models of galaxy formation Active Galactic Nuclei physics with GLAST

17. locate SNR • resolve SNR shells at 10 level • measure SNR spectra GLAST will E (MeV) Cosmic-Ray production and acceleration in SNR • SNR widely believed to be the source of CR proton acceleration after shell interaction with interstellar medium • p0 bump in the galactic spectrum detected by EGRET GLAST simulations showing SNR -Cygni spatially and spectrally resolved from the compact inner gamma-ray pulsar – a clear p0 decay signature from the shell would indicate SNR as a source of proton CR

18. Observational constraints on m and l. Bright stars: 0.5% Baryons (total): 4% ± 1% Nonbaryonic dark matter: 29% ± 4% Neutrinos: at least 0.1% (up to 5% ? ) Dark Energy: 66% ± 6% (Michael S. Turner astro-ph/0207297) A.H. Jaffe et al., Astro-ph 0007333

19. Halo WIMP annihilations X q gg or Zg q lines ~ X Example: X is c0 from Standard SUSY, annihilations to jets, producing an extra component of multi-GeV g flux that follows halo density (not isotropic) peaking at ~ 0.1 Mc0 or lines at Mc0. Background is galactic g ray diffuse. ~ ~ Good particle physics candidate for galactic halo dark matter is the LSP in R-parity conserving SUSY If true, there may well be observable halo annihilations If SUSY uncovered at accelerators, GLAST may be able to determine its cosmological significance quickly.

20. g lines 50 GeV 300 GeV Supersymmetric Cold Dark Matter searches with GLAST Total photon spectrum from galactic centre with cc annihilation contribution infinite energy resolution finite energy resolution 2-year scanning mode Bergstrom et al.

21. GLAST Expectation & Susy models A.Morselli, A.Lionetto, A.Cesarini, F.Fucito, P.Ullio, 2002 ~2 degrees around the galactic center

22. MSSM A0 = 0 > 0 mt =174 GeV tan b = 10 Estimated reaches before LHC GLAST A.Morselli et al. preliminary 0.025 <CDMh2< 1 0.1 <CDMh< 0.3 Pamela, AMS Direct search tanb=10 Km3 Fixed Halo profile, indirect limits better if halo is clumpy Excluded by chargino mass limit > 95 GeV See astro-ph 0008115

23. Gamma Ray Bursts GRBs are the most intense and most distant (z ~ 4.5) known sources of high energy g rays. With their fast temporal variability GRBs are an extremely powerful tool for probing fundamental physical processes and cosmic history. Life Extinctions by Cosmic Ray Jets - A. Dar et al. - Physical Review Letters Vol. 80, No.26, 1999

24. Simulated one-year GLAST scan, assuming a various spectral indexes. 1- localization accuracy (arc min.) Gamma-Ray Bursts • GLAST LAT will be best suited to studying the GeV tail of the gamma-ray burst spectrum. A separate instrument (GBM) on the spacecraft will cover the energy range 10 KeV – 25 MeV and will provide a hard X-ray trigger for GRB. • GLAST should detect 200 GRB per yearwith E>100 MeV, with a third of them localized to better than 10, in real time. • Excellent wide field monitor for GRB.Nearly real-time trigger for other wavelength bands, often with sufficient localization for optical follow-up. • With a 10s dead time, GLAST will see nearly all of the high-E photons. GBM LAT Energy dependent lags and the physics behind GRB temporal properties will be better studied by the broad energy coverage (10 KeV – 100 GeV) provided by GBM and LAT.

25. Gamma-Ray Bursts • transient signal, ~ 100 µs time scale • light curves vs energy • fast response/ short dead time spectral studies for • non-thermal emission model (synchrotron, ICS) • fireball baryon fraction • high energy resolution Simulated time profile of a GRB detected by the LAT and the GBM. The pulses are narrower at LAT energies. • The origin of ultra-energy cosmic rays suggested to be GRBs (Waxman 1995) • Burst of high energy g as signature of the evaporation of primordial black holes.

26. Arrival time distribution for two energy cuts 0.1 GeV and 5 GeV( cross-hatched) GRBs to probe Quantum Gravity Using only the 10 brightest bursts yr-1, GLAST would easily see the predicted energy- and distance-dependent effect.

27. One Tracker Tower Module Carbon thermal panel Electronics flex cables GLAST Tracker Design Overview • 16 “tower” modules, each with 37cm  37cm of active cross section • 83m2 of Si in all, like ATLAS • 11500 SSD, ~ 1M channels • 18 x,y planes per tower • 19 “tray” structures • 12 with 3% W on bottom (“Front”) • 4 with 18% W on bottom (“Back”) - SuperGlast • 3 with no converter foils • Every other tray is rotated by 90°, so each W foil is followed immediately by an x,y plane of detectors • 2mm gap between x and y oriented detectors • Trays stack and align at their corners • The bottom tray has a flange to mount on the grid. • Electronics on sides of trays: • Minimize gap between towers • 9 readout modules on each of 4 sides

28. Status of the Tracker construction • 140 mechanical assembled to tune production, with wafer salign ~5.5 mm • 300 flight in production for EM (1tower with 4fully operational trays, due March 2003) SSD Ladder Assembly (Italy) Tray Assembly and Test (Italy) • superGlast tray design approved • thermal and vibrational tests on prototypes • tower assembly technique and tools finalized Electronics Design, abrication & Test (UCSC, SLAC) EM prototypes production of hybrids and F.E. m s SSD Procurement, Testing (Japan, Italy, SLAC) Ileak 100nA 50nA • 4200 flight SSD produced (HPK) • 3000 tested (~35% total production) • - < 1.3% failure rate Vdep 70V 20V Cbulk 1800pF 10pF ~2mm Wafer cut ~2mm

29. Conclusions • GLAST is a partnership of HEP and Astrophysics communities sharing scientific objectives and technology expertise • GLAST will survey the sky in the 20MeV~1TeV g-ray band, where the most energetic and mysterious phenomena in nature reveal their signature • GLAST is equipped with state-of-the-art particle detectors, resulting in an order of magnitude improvement in sensitivity and resolution with respect to previous missions • the GLAST-LAT construction has started with very promising results • GLAST will therefore: • detect thousands of new and unknown g-ray sources • identify the correct emission models for known classes of sources • probe the supersymmetric phase space in search for WIMP decay and neutralino annihilation signals • provide significant data on the origin and evolution of GRBs • help building a new cosmological theory with key observation on the nature of dark matter, presence of an extra-galactic background light, quantum gravity effects ……. much anticipation awaits GLAST on its way to discoveries that will change our knowledge of the Universe