GLAST Gamma Ray Large Area Telescope The GLAST

GLAST: Gamma Ray Large Area Telescope The GLAST Mission and its Physics reach R. Bellazzini INFN - sez. Pisa GLAST 1 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

Nature's Highest Energy Particle Accelerators OUTLINE Introduction Pair-Conversions Telescopes The LAT Design LAT Performance GLAST Science Topics Conclusions GLAST 2 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

Profound Connection between Astrophysics & HEP The fundamental theory of Cosmic Genesis and the quest for experimental evidence has 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 Polarization of cosmic microwave background Large scale structure This quest is changing the face of both fields. 3 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 GLAST R. Bellazini – INFN Pisa

First Came EGRET Launched in April 1991 • Observed over 60 AGN in > 100 Me. V gammas. Raised many interesting issues and questions which can be addressed by a NASA mid-class mission (Delta II). Sources in Third EGRET Catalog • About 1/2 dozen GRB at high energy. • Measurement of diffuse gamma ray background to over 10 Ge. V. • One hundred and seventy unidentified sources in 3 rd EGRET catalog. Mystery of unidentifieds since 1970 s GLAST 4 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

GLAST Science 0. 01 Ge. V 0. 1 Ge. V Supernova Remnants 1 Ge. V Map the High-Energy Universe 100 Ge. V 1 Te. V AGN Area (square cm) • Physics in regions of strong gravity, huge electric & magnetic fields: e. g. particle production & acceleration near the event horizon of a black hole. • Use gamma-rays from AGNs to study evolution of the early 4 10 universe. GLAST ch • Physics of gamma-ray bursts at ea r 3 cosmological distances. 10 ry ve • Probe the nature of particle dark co is matter: e. g. , wimps, 5 -10 e. V d EGRET 2 10 neutrino. 0. 01 0. 1 1 10 1000 • Decay of relics R. Bellazini – INFN Pisa from the Big Bang. Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 • GLAST pulsar survey: provide a new window on the galactic neutron star population. • “Map” the pulsar magnetosphere and understand the physics of pulsar emission. • Origin of cosmic-rays: characterize extended supernovae sources. • Determine the origin of the isotropic diffuse gamma-ray background. 5 10 Ge. V GLAST Energy (Ge. V)

Pair-Conversion Telescope Photons materialize into matter-antimatter pairs: E -> me+c 2 + me-c 2 Charged particle anticoincidence shield GLAST Concept • • Conversion foils • • Particle tracking detectors e+ Calorimeter (energy measurement) e- • • 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. GLAST 6 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

The Large Area Telescope (LAT) Tracker • Array of 16 identical “Tower” Modules, each with a tracker (Si strips) and a calorimeter (Cs. I with PIN diode readout) and DAQ module. • Surrounded by finely segmented ACD (plastic scintillator with PMT readout). Grid DAQ Electronics 7 ACD Thermal Blanket • Aluminum strong-back “Grid, ” with heat pipes for transport of heat to the instrument sides. Calorimeter Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 GLAST R. Bellazini – INFN Pisa

The LAT Hardware GLAST 8 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

Tray assembling • Trays are C-composite panels (Al hexcel core) • Carbon-fiber walls provide stiffness and thermal pathway from electronics to the grid. GLAST 9 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

GLAST Tracker Design Overview • 16 “tower” modules, each with 37 cm of One Tracker Tower Module active cross section • 83 m 2 of Si in all, like ATLAS • 11500 SSD, ~ 1 M channels • 18 x, y planes per tower – 19 “tray” structures • 12 with 3% Pb or W on bottom (“Front”) • 4 with 18% Pb or W on bottom (“Back”) • 2 with no converter foils – Every other tray is rotated by 90°, so each Pb foil is followed immediately by an x, y plane of detectors Carbon • 2 mm gap between x and y oriented thermal detectors panel • Trays stack and align at their corners • The bottom tray has a flange to mount on the grid. • Electronics on sides of trays: Electronics – Minimize gap between towers flex cables – 9 readout modules on each of 4 sides GLAST 10 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

Prototyping of the GLAST SSD Preserie HPK detector on 6’’ wafer Gained experience with a large number of SSD (~5% of GLAST needs) Additional Prototypes: Micron (UK), STM (Italy), CSEM (Switzerland) GLAST 11 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

Production schedule Calendar Years 2000 SRR 2003 2002 2001 I-PDR NAR M-PDR I-CDR M-CDR Inst. Delivery Launch Implementation Formulation Build & Test Engineering Models Build & Test Flight Units 2010 2005 2004 Ops. Inst. I&T Inst. -S/C I&T SSD Procurement Ladder Production Schedule Reserve Tray Assembly GLAST 12 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

International Collaboration • • expertise in each science topic (theory + obs. ) experience in high-energy and space instrumentation access to X-ray, Me. V, and Te. V observatories by collaboration for multi-wavelength observations ‘mirror’ data site in Europe ~ 100 collaborators from 28 institutions Organizations with LAT Hardware Involvement TKR CAL ACD CAL TKR Stanford University & Stanford Linear Accelerator Center NASA Goddard Space Flight Center Naval Research Laboratory University of California at Santa Cruz University of Washington Commissariat a l’Energie Atomique, Departement d’Astrophysique (CEA) Institut National de Physique Nuclearie et de Physique des Particules (IN 2 P 3): Ecole Polytechnique, College de France, CENBG (Bordeaux) Hiroshima University Institute of Space and Astronautical Science, Tokyo RIKEN Tokyo Institute of Technology Istituto Nazionale di Fisica Nucleare (INFN): Pisa, Trieste, Bari, Udine, Perugia, Roma Royal Institute of Technology (KTH), Stockholm CAL 13 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 GLAST R. Bellazini – INFN Pisa

LAT Instrument Performance Including all Background & Track Quality Cuts GLAST 14 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

GLAST Science Capability Key instrument features that enhance GLAST’s science reach: • • • Peak effective area: 12, 900 cm 2 Precision point-spread function (<0. 10° for E=10 Ge. V) 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 ~Te. V GLAST 15 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

Covering the Gamma-Ray Spectrum • • 16 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 groundbased 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. Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 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) GLAST R. Bellazini – INFN Pisa

Overlap of GLAST with ACTs Predicted GLAST measurements of Crab unpulsed flux in the overlap region with ground-based atmospheric cherenkov telescopes. GLAST 17 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

SNR and Cosmic-Ray Production EGRET View of the Galactic Anti-center Geminga GLAST Simulation of the Galactic Anti-center IC 443 Crab So far, no conclusive results on SNR from EGRET. GLAST will provide • detailed maps of the galactic diffuse gamma-ray emission. • measurements of SNR spectra. • resolved SNR shells at 10 level. • detailed maps of emission from galactic molecular clouds. In order to • locate SNR in the galactic plane. • determine whether SNR could be the source of cosmic rays. • map the distribution of cosmic rays in the galaxy. GLAST 18 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

Cosmic-Ray Acceleration Energy (Me. V) GLAST simulations showing SNR -Cygni spatially and spectrally resolved. GLAST 19 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

Cosmic-Ray Acceleration Faint source EGRET data Model -ray spectrum for SNR IC 443 adapted from Baring et al. (1999) illustrating how GLAST can detect even a faint p 0 -decay component. ( 1 year sky survey with 1 error bars) GLAST 20 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

Active Galactic Nuclei (AGN) Active galaxies produce vast amounts of energy (1049 erg/s) from a very compact central volume. Prevailing idea: powered by accretion onto super-massive black holes (106 - 1010 solar masses). Highly variable objects with large fluctuations in luminosity in fractions of a day. HST Image of M 87 (1994) Models include emission of energetic (multi-Te. V), highly-collimated, relativistic particle jets. High energy -rays emitted within a few degrees of jet axis. GLAST 21 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

Active Galactic Nuclei Simulation of a 1 -year all-sky survey by EGRET. E>1 Ge. V! Simulation of a 1 -year all-sky survey by GLAST. A simple extrapolation from EGRET data suggests that GLAST will detect >5000 AGN, in addition to providing far more detailed data on the known sources. GLAST 22 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

Measurement of AGN Spectra GLAST will measure blazar quiescent emission and spectral transitions to flaring states. GLAST should readily detect low-state emission from Mrk 501 GLAST 23 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

Blazar Cosmology Roll-offs in the -ray spectra from AGN at large z probe the extragalactic background light (EBL) over cosmological distances. A dominant factor in EBL models is the era of galaxy formation: AGN roll-off may help to distinguish models of galaxy formation, e. g. , Cold Dark Matter vs. Hot Dark Matter, neutrino mass contribution, … Broad spectral coverage and observations of numerous sources will be necessary to reap solid scientific results map of the correlation between Ecut-off and Z! The gamma-ray attenuation factor for CDM models using Scalo and Salpeter models. (Bullock, Somerville, Mac. Minn, Primack, 1998) GLAST 24 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

Identifying Sources GLAST 95% C. L. radius on a 5 source, compared with a similar EGRET observation of 3 EG 1911 -2000 Counting stats not included. GLAST will make great improvements in our ability to resolve gamma-ray point sources in the galactic plane and to measure the diffuse background. Cygnus region (150 x 150), Eg > 1 Ge. V GLAST 25 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

Detection of Transients In scanning mode, GLAST will achieve in one day a sufficient sensitivity to detect (5 ) the weakest EGRET sources. GLAST 26 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

Gamma Ray Burst GRBs are the most intense and most distant (z ~ 4. 5) with fast temporal variability known sources of high energy rays. They are an extremely powerful tool for probing fundamental physical processes and cosmic history. Life Extinctions by Cosmic Ray Jets - Physical Review Letter Vol. 80, No. 26 27 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 GLAST R. Bellazini – INFN Pisa

Gamma-Ray Bursts • • GLAST will be best suited to studying the Ge. V tail of the gamma-ray burst spectrum. GLAST should detect 200 GRB per year with E>100 Me. V, 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. Simulated one-year GLAST scan, assuming a various spectral indexes. 1 - localization accuracy (arc min. ) GLAST 28 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

Gamma-Ray Bursts A separate instrument (NASAMSFC) on the spacecraft will cover the energy range 10 Ke. V – 25 Me. V and will provide a hard x-ray trigger for GRB. Energy dependent lags and the physics behind GRB temporal properties will be better studied by the broad energy coverage (10 Ke. V – 100 Ge. V) provided by GBM and LAT. • The origin of ultra-energy cosmic rays suggested to be GRBS (Waxman 1995) • Burst of high energy as signature of the evaporation of primordial black holes. GLAST 29 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

GRBs and Quantum Gravity GRB ms pulse structure at Ge. V energies + Gigaparsec distances may constrain EQuantum Gravity ~ 1019 Ge. V See: G. Amelino-Camelia, John Ellis et al. , Nature 393 (1998) 763 -765 Using GLAST, search for possible in vacuo velocity dispersion, dv ~ E/EQG of gamma rays from gamma ray bursts at cosmological distances. For many GRB (EGRET) current best estimate is, d. N /d. E ~ 1/E 2 For certain string formulations photon propagation velocity in vacuum appears increased or decreased as energy increases (granularity of space-time) v = c(1 ± E /EQG+ O[(E /EQG)2]) Dt ~ a E/EQG D/c ~ 10 ms Ge. V-1 Gpc-1 (if EQG ~ 1019 Ge. V) GLAST 30 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

Test of Quantum Gravity Using only the 10 brightest bursts yr-1, GLAST would easily see the predicted energy- and distance-dependent effect. Arrival time distribution for two energy cuts 0. 1 Ge. V and 5 Ge. V( cross-hatched) GLAST 31 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

Dark Matter Problem Experimentally, in spiral galaxies the ratio between the matter density and the Critical density W is : Wlum ≤ 0. 01 but from rotation curves must exist a galactic dark halo of mass at least: Whalo ≥ 0. 03 ÷ 0. 1 from gravitational behavior of the galaxies in clusters the Universal mass density is : M(R) = v 2 R/G Whalo @ 0. 1 ÷ 0. 3 from structure formation theories: Whalo ≥ 0. 3 but from big bang nucleosinthesis the Barionic matter cannot be more then: WB ≤ 0. 1 GLAST 32 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

Halo WIMP annihilations 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 X X q or Z q lines ~ Example: X is c 0 from Standard SUSY, annihilations to jets, producing an extra component of multi-Ge. V flux that follows halo density (not isotropic) peaking at ~ 0. 1 M ~ 0 c or lines at M ~0. Background is galactic ray diffuse. c If SUSY uncovered at accelerators, GLAST may be able to determine its cosmological significance quickly. GLAST 33 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

Halo WIMP annihilations Total photon spectrum from the galactic center from cc ann. Infinite energy resolution With finite energy resolution lines GLAST two-year scanning mode 50 Ge. V 300 Ge. V GLAST 34 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

Dark Matter Searches: Neutralino X X q or Z q lines The GLAST Cs. I calorimeter will be the largest such device ever put into space. It is only 10 X 0 viewed from the front, but from the sides it is up to 1. 5 m “thick” and well suited for precision measurements of very highenergy photons. GLAST E/E ~3% q > 50 o GLAST monoenergetic line sensitivity (95% C. L. upper limit) vs. E. Colored areas are a range of MSSMs within a restricted parameter space from standard assumptions and thermal relic abundance calculations. GLAST 35 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa

Conclusions • GLAST is a partnership of HEP and Astrophysics science communities. Forging partnerships between disciplines expands opportunities for doing exciting physics and maximizes the possibility of discoveries. • With its large improvement in sensitivity GLAST will allow to observe sources with greater precision and higher statistics – – increase by orders of magnitude the numbers of visible sources see deeper into the universe monitor continuously the complete, rapidly-changing high-energy gamma-ray sky explore a good portion of the supersymetric parameter space and study the Cold and Hot Dark Matter contribution through the IR absorptionof -ray from extragalactic sources – GRB physics at high energy. More information on GLAST at http: //www. pi. infn. it/glast GLAST 36 Les Rencontres de Physique de la Vallee d’Aoste – La Thuile 2001 R. Bellazini – INFN Pisa