1. The Physics program of the Gamma-Ray Large Area Space Telescope
Luca Latronico
on behalf of the LAT collaboration
7th UCLA Symposium
Sources and Detection of Dark Matter and Dark Energy in the Universe
Marina del Rey – 23 February 2006

2. The GLAST observatory The GLAST instruments LAT: 20MeV – >300GeV
Large Area Telescope (LAT)
Gamma Ray Burst Monitor (GBM)
Spacecraft
The GLAST instruments
LAT: 20MeV – >300GeV
PI: P. Michelson (SU)
GBM: 10KeV – 30MeV
PI: C. Meegan (UofA, Huntsville)
Launch Vehicle Delta II – H
Launch Location Kennedy Space Center
Orbit Altitude 575 Km
Orbit Inclination 28.5 degrees
Orbit Period 95 Minutes
Orientation +X to the Sun
Launch Date August 2007
LAT mass 3000Kg
LAT power 650W
Gamma-rays as probes of the universe
travel undeviated by EM fields
emitted by most energetic process
Can go down to z ~700
Satellite to go below ~30GeV atmosphere cutoff

3. The LAT Collaboration total Collaboration members: 161 Members: 77
United States
California State University at Sonoma (SSU)
University of California at Santa Cruz - Santa Cruz Institute of Particle Physics (UCSC/SCIPP)
Goddard Space Flight Center – Laboratory for High Energy Astrophysics (NASA/GSFC/LHEA)
Naval Research Laboratory (NRL)
Ohio State University
Stanford University – Hanson Experimental Physics Laboratory (SU-HEPL)
Stanford University - Stanford Linear Accelerator Center (SU-SLAC)
Texas A&M University – Kingsville (TAMUK)
University of Washington (UW)
Washington University, St. Louis (WUStL)
International multi-agency mission
France
Centre National de la Recherche Scientifique / Institut National de Physique Nucléaire et de Physique des Particules (CNRS/IN2P3)
Commissariat à l'Energie Atomique / Direction des Sciences de la Matière/ Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée (CEA/DSM/DAPNIA)
Italy
Agenzia Spaziale Italiana (ASI)
Istituto di Astrofisica Spaziale (IASF, CNR)
Istituto Nazionale di Fisica Nucleare (INFN)
Japan GLAST Collaboration (JGC)
Hiroshima University
Institute for Space and Astronautical Science (ISAS)
RIKEN
Swedish GLAST Consortium (SGC)
Royal Institute of Technology (KTH)
Stockholm University
total
Collaboration members: 161
Members: 77
Affiliated Sci. 67
Postdocs: 17

4. GLAST will be a reference gamma-ray observatory:
Physics program - the sky above 20 MeV
GLAST will be a reference gamma-ray observatory:
5 years life requirement – 10 years goal
will provide high energy g data (public) for the first time with unprecedented resolution/statistics
vast, interdisciplinary physics program and scientific community (astro-particle and traditional astrophysics)
multi-wavelength campaigns (AGNs)
networked to other space/ground facilities for alert (bursts and transients)
sky map
unidentified sources
pulsar
GRB
from EGRET
solar flares
Aeff  x7 (~1m2)
FOV  x5 (2.4sr)
Max En.  > x30 (>300GeV)
Deadtime  x310-4 (26ms)
AGN
SNR and CR acceleration
Goal: measure direction, arrival time and energy of incoming photons
Constraints: mass, power, consumables, reliability, redundancy typical of use in space
to GLAST
point source sensitivity (>100MeV)
> x30 (3x10-9cm-2s-1)
dark matter
0.01 GeV GeV GeV GeV GeV TeV

5. Some possible Dark Matter Searches
Morselli et al astro/ph
Hunter et al (1997)
WIMP annihilation in galactic centre or galactic halos
talk by L.Wai
Extragalactic WIMP annihilation relic
SUSY dark matter
Kaluza Klein dark matter
talk by A. Lionetto
Active DM and New Physics working group (46 members)
Elsasser Manheimm astro/ph
this science require large sensitivity on a broad energy range, localization power, energy resolution, time resolution for variability search … key elements for the whole GLAST physics program

6. The LAT instrument: how we built it
Overall modular design:
4x4 array of identical towers - each one including a Tracker, a Calorimeter and an Electronics Module.
Surrounded by an Anti-Coincidence shield (not shown in the picture). g e+ e-
Tracker/Converter (TKR):
Silicon strip detectors (single sided, each layer is rotated by 90 degrees with respect to the previous one)
W conversion foils
~80 m2 of silicon
~106 electronics chans
fully digital electronics
High precision tracking, small dead time
Anti-Coincidence (ACD):
Segmented (89 tiles)
high energy limited
detection efficiency (overall)
Calorimeter (CAL):
1536 CsI crystals
Analog 4 range readout
8.5 X0
Hodoscopic
Shower profile reconstruction (leakage correction)

7. Ground Cosmic Rays muons in the full LAT

8. Technology impact – angular resolution
EGRET
( )
Phases 1-5
Spark chamber
sense electrode spacing ~mm
sensitive layer depth ~cm
up to 28 hit over >1m
LAT
(2007- >2012)
1-yr simulation
Si-strip detectors
sense electrode spacing ~0.2mm
better single hit resolution
sensitive layer depth ~0.4mm
up to 36 hit over 0.8m
converter proximity to minimize MCS
Cygnus region (150 x 150), Eg > 1 GeV

9. Active Galactic Nuclei
AGNs major component of EG g-rays:
vast amount of energy from a very compact central volume
large fluctuations in the luminosity
energetic, highly collimated, relativistic particle jets
prevailing idea: accretion onto super-massive black holes (106 – 1010 solar masses)
AGN physics
Catalogue AGN classes from a large sample (thousands new sources expected at our sensitivity)
measure spectrum in uncovered gamma-ray energy band
identify leptonic (SSC/ESC) and hadronic (p0 decay) contributions
track flares (down to mins) and correlate to other wavelengths
EBL search from spectra roll-off at large z

10. Dark Matter Spectroscopy
g lines
50 GeV
300 GeV
EM Calorimeter technology impact
hodoscopic, granular for shower imaging
large electronics dynamic range
specific energy dependent recon strategies
correct TKR loss at low E
correct shower leakage at high E
large energy coverage crucial to provide overlap with ground ACT
absolute CAL calibration
m + beam test on ground
heavy ions on orbit
cross-calibration with ACT on known bright sources (e.g. Crab)
confirm LAT on orbit calibration
help reduce systematics at ACT
DE/E(10GeV on-axis) 8%
DE/E(10-300GeV on-axis)
<15%
DE/E(10-300GeV off-axis, >600)
<4.5%

11. Gamma Ray Bursts GRBs phenomenology:
Dramatic variations in the light curve on a very short time scale
Isotropic distribution in the sky (basically from BATSE, on board CGRO, but little energies > 50 MeV)
Non repeating (as far as we can tell…)
Spectacular energies (~ 1051 – 1052 erg)
GRBs physics:
GLAST should detect ~ 200 GRBs/year above 100 MeV (a good fraction of them localized to better than 10’ in real time)
10 keV-300 GeV coverage from GBM+LAT: spectroscopy and timing studies to identify acceleration mechanism
Quantum gravity effects from time dispersion of light curve vs Z
large energy lever arm
minimal dead time
Simulated GRB spectrum
GBM
NaI
GBM
BGO
LAT
10KeV
100MeV
100GeV

12. LAT status Current status:
Integration of Detectors and Electronics complete
Flight software test in progress
(SPACECRAFT INTERFACE)
(EVENT PROCESSING)
Coming milestones:
LAT environmental tests at NRL - april
Calibration Unit Beam test at CERN August/September
Integration with the spacecraft
Launch – august 2007
(TRIGGER)
Trigger
Power
(POWER)
bottom view of the LAT and associated electronics

13. GLAST launch – 8/2007
GLAST is the next generation satellite g-ray observatory
prime physics on a wide range of topics, including DM and new physics searches, is expected (10 active science working groups) thanks to excellent instrument performance
GLAST put together the HEP and astrophysics communities to build a high performance detector for a first rank physics program – hopefully the shared scientific interest on the nature of Dark Matter will see revolutionary discoveries
animation by P. Michelson – LAT PI

14. Pulsars detect new gamma-ray pulsars (~250)
large effective area
direct pulsation search in the g-ray band
high time resolution + absolute time recording (2ms with GPS)
precise test of polar cap vs outer gap emission models
energy resolution

15. Resolution and sensitivity for CR physics
SNR widely believed to be the source of CR proton acceleration after shell interaction with interstellar medium
the p0 bump again from NN interaction
GLAST has the capability to
identify many SNR
resolve SNR shells from core neutron star
measure SNR spectra
E (MeV)
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

16. Technology impact – sensitivity
HEP detectors and electronics for
low aspect ratio for enhanced FOV
low noise detectors for self-trigger capability and high data rate - L0T ~10KHz
highly efficient ACD and on-board computing power for background reduction - up to ~104
fast detectors and electronics for reduced dead time - ~26ms
Integral Flux (E>100 MeV) cm-2s-1
EGRET - 5 years map
GLAST 1 year
sky-survey
simulation
Populate large catalog of sources to subtract from residual background
 particularly relevant for extra-galactic DM search

17. Resolving the background
With a best PSF ~arcmin new can
complete EGRET catalog (unidentified sources)
build a LAT catalog
resolve diffuse into sources
identify new classes of sources and possibly DM sources (NO radio partner)
AO PSF vs Energy
Improvements expected and under evaluation due to converter reduction