GLAST

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GLAST

• Alessandro de Angelis
• Università di Udine, INFN Trieste
• and Instituto Superior Técnico Lisboa

• Introduction
• The instrument
• Key physics objectives
• Work in progress

New Worlds in Astroparticle Physics Faro,
September 2000
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Exchange between laboratory physics and
astrophysics an idea which works...

• Michelson Morley 1887 key experiment on the
  propagation of light

• Michelson 1920 first measurement of the diameter
  of a star (Betelgeuse) using interferometry,
  opening a new field

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GLAST a detector for cosmic g raysin the range
20 MeV - 300 GeV
Si tracker

• g telescope
• hybrid tracker calorimeter
• International collaboration US-France-Italy-Japan-
  Sweden
• Broad experience in high-energy astrophysics and
  particle physics (science instrumentation)
• Timescale 2005-2010 (-gt2015)
• Wide range of physics objectives
• Gamma astrophysics
• Fundamental physics

Calorimeter
A HEP / astrophysics partnership...
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GLAST in space

• To be launched in 2005
• 1 year in survey mode, then pointing
• by a Delta 2 vector
• Constraint on size weight
• Orbit at 550 Km
• T 1.6 h
• Full sky coverage in 3 orbits
• Data rate 0.3 Mb/s -gt 1 Mb/s

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Why g rays ?

• Probe the most energetic phenomena occurring in
  nature
• No deflection from magnetic fields, point to
  the sources
• Clear signatures from new physics
• Large mean free path
• Good detection efficiency

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Why in the range 20 MeV - 300 GeV ?

• Flux of diffuse extra-galactic photons

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The legacy from EGRET

• High Energy g detector
• 20 MeV-20 GeV
• on the CGRO (1990s)
• Scientific success
• Increased number of identified sources
• AGN
• GRB
• Solar flares

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GLAST the instrument

• Tracker
• Si strips converter
• Calorimeter
• CsI with diode readout
• (a classic for HEP)
• 1.7 x 1.7 m2 x 0.8 m
• height/width 0.4 ? large field of view
• 16 towers ? modularity

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The tracker

• Si strips converter
• High signal/noise
• Rad-hard
• Low power
• 4x4 towers, of 37 cm ? 37 cm of Si
• 18 x,y planes per tower
• 19 tray structures
• 12 with 2.5 Pb on bottom
• 4 with 25 Pb on bottom
• 2 with no converter
• Electronics on the sides of trays
• Minimize gap between towers
• Carbon-fiber walls to provide stiffness

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The calorimeter
CsI with diode readout

• Good E resolution
• High signal/noise
• Hodoscope good position determination leakage
  correction
• 4x4 arrays of CsI (Tl) crystals
• Thickness of 10 X0

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Performance (compared to EGRET)
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Sensitivity compared topresent future detectors

• Complementary to ground-based
• GLAST is a key element of the g astrophysics
  program
• Large area
• Low deadtime (20 ms)
• Energy range to gt300 GeV
• Large FOV

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Key Science Objectives

• Resolving the g ray sky AGN, diffuse emission
  unidentified sources
• Particle acceleration mechanisms
• High energy behavior of g ray bursts transients
• Dark matter probing WIMPs
• Solar flares
• New fundamental physics (the unexpected)
• Make happy both the HEP and the astrophysics
  community...

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Key Science ObjectiveActive Galactic Nuclei

• EGRET has discovered 80 AGN at g ray energies,
  GLAST will discover several thousands
• The g part of the spectrum could be dominant
• The variability in time of the sources will
  provide important information

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Key Science ObjectiveDiffuse background
radiation...

• Is it really diffuse (lt- produced at a very early
  epoch) or a flux from unresolved sources ?
• GLAST improves the angular resolution the
  sensitivity to weak sources...

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Key Science Objectiveand unidentified sources

• gt 1/2 of the EGRET sources are unidentified.
• Determining the type of objects and the
  mechanisms for g ray emission is a high priority
  for GLAST

• A key the precise measurement of position
  (relation with supernova remnants and other
  candidates)

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Key Science ObjectiveAcceleration mechanisms of
Cosmic Rays

• Acceleration mechanisms of CR (Fermi 1949 -gt) ?
• EGRET signature of p0 decays (from NN
  interactions)

• Angular resolution of GLAST will allow to
  determine if such sources are associated with SNRs

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Key Science ObjectiveGamma-ray bursts

• EGRET high energy afterglows can last for gt 1h
• GLAST can provide measurements over a new energy
  range
• 50-100 GRB/year compared to 1 for EGRET
• Notification of GRB from earth and by an on-board
  trigger (Gamma-Ray Burst Monitor)

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Key Science ObjectiveProbing dark matter WIMPs
Some dark matter candidates (e.g. SUSY particles)
would lead to mono-energetic g lines through
annihilation
Good energy resolution in the few range is
needed
GLAST has good sensitivity for a variety of SUSY
models in the 30-100 GeV range
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Key Science ObjectiveNew physics (the
unexpected)

• Quantum gravity (Amelino-Camelia et al., Ellis et
  al.)
• V c (1 - e E/EQG)
• Effects on GRB could be O(100 ms) in GRB

• Exotic objects produced in the early universe
• Last but not least, the totally unexpected could
  come from the newly opened exploration regimes...

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Beam tests 1997 calorimeter prototype
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Beam tests 1999/2000 at SLACElectrons, photons,
hadrons

• Incident g

• Low noise
• Minimum ionizing interacting hadrons easily
  rejected
• Cosmic ray rejection of 1051 with 80 efficiency
  for g

Diffuse High Latitude gamma-ray flux
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Software

• Modern data handling technologies
• Well advanced software for simulation and
  reconstruction
• Close collaboration with the CERN Geant4
  development team (lt- ESA)

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Summary

• GLAST an important step in g astronomy (a factor
  of 100 in sensitivity above EGRET)
• A partnership between High Energy Physics and g
  Astrophysics
• Expected to be ready by 2005 beam tests and sw
  development well on the way
• Wide range of possible answers/discoveries

Credits G. Barbiellini, R. Giannitrapani, I.
Grenier, F. Longo, A. Morselli, R. Pain, S. Ritz