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GLAST:Gamma Ray Large Area Telescope. The GLAST Mission and its Physics reach R.Bellazzini INFN - sez. Pisa. Nature\'s Highest Energy Particle Accelerators . OUTLINE Introduction Pair-Conversions Telescopes The LAT Design LAT Performance GLAST Science Topics Conclusions .

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slide1

GLAST:Gamma Ray Large Area Telescope

The GLAST Mission

and its Physics reach

R.Bellazzini

INFN - sez. Pisa

slide2

Nature\'s Highest Energy Particle Accelerators

OUTLINE

Introduction

Pair-Conversions Telescopes

The LAT Design

LAT Performance

GLAST Science Topics

Conclusions

slide3

Polarization of cosmic

microwave background

Large scale structure

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

This quest is changing the face of both fields.

slide4

Sources in Third EGRET Catalog

First Came EGRET

Raised many interesting issues andquestions which can be addressed by a NASA mid-class mission (Delta II).

Launched in April 1991

  • Observed over 60 AGN in > 100 MeV gammas.
  • About 1/2 dozen GRB at
  • high energy.
  • Measurement of diffuse
  • gamma ray background to
  • over 10 GeV.
  • One hundred and seventy
  • unidentified sources in 3rd
  • EGRET catalog. Mystery of
  • unidentifieds since 1970s
slide5

0.01 GeV 0.1 GeV 1 GeV 10 GeV 100 GeV 1 TeV

4

3

2

10

10

10

GLAST

discovery reach

Area (square cm)

EGRET

0.01 0.1 1 10 100 1000

Energy (GeV)

GLAST Science

Map the High-Energy Universe

Supernova Remnants

AGN

  • 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 universe.
  • Physics of gamma-ray bursts at cosmological distances.
  • Probe the nature of particle dark matter: e.g., wimps, 5-10 eV neutrino.
  • Decay of relics from the Big Bang.
  • 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.
pair conversion telescope
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)

Pair-Conversion Telescope

Charged particle anticoincidence shield

Conversion foils

Particle tracking detectors

e+

e-

  • Calorimeter
  • (energy measurement)

Photons materialize into matter-antimatter pairs:

E -> me+c2 + me-c2

the large area telescope lat
The Large Area Telescope (LAT)

Tracker

Grid

Thermal Blanket

ACD

DAQ Electronics

Calorimeter

  • 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.
slide9

Tray assembling

  • Trays are C-composite panels (Al hexcel core)
  • Carbon-fiber walls provide stiffness and the thermal
  • pathway from electronics to the grid.
glast tracker design overview
GLAST Tracker Design Overview

One Tracker Tower Module

Carbon thermal panel

Electronics flex cables

  • 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% 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
      • 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
slide11

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)

international collaboration
International Collaboration
  • Organizations with LAT Hardware Involvement
      • 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 (IN2P3):
      • 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

TKR

CAL

ACD

CAL

TKR

TKR

CAL

  • expertise in each science topic (theory + obs.)
  • experience in high-energy and space instrumentation
  • access to X-ray, MeV, and TeV observatories by collaboration

for multi-wavelength observations

  • ‘mirror’ data site in Europe

~ 100 collaborators

from 28 institutions

slide13

Calendar Years

2010

2003

2000

2005

2002

2004

2001

Launch

Inst. Delivery

SRR

I-CDR

M-CDR

I-PDR

NAR

M-PDR

Implementation

Ops.

Formulation

Inst.

I&T

Inst.-S/C

I&T

Build & Test

Flight Units

Build & Test

Engineering Models

Schedule

Reserve

Project schedule

SSD Procurement

Ladder Production

Tray Assembly

lat instrument performance
LAT Instrument Performance

Including all Background & Track Quality Cuts

glast science capability
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
covering the gamma ray spectrum
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)

overlap of glast with acts
Predicted GLAST measurements of Crab unpulsed flux in the overlap region with ground-based atmospheric cherenkov telescopes.Overlap of GLAST with ACTs
snr and cosmic ray production
SNR and Cosmic-Ray Production

EGRET View of the Galactic Anti-center

GLAST Simulation of the Galactic Anti-center

So far, no conclusive results on SNR from EGRET.

Theoretical models and indirect observational evidence support the idea that Galactic CRs are accelerated in the shocks of SNRs.

p0 bump direct evidence of CR nucleai in the Milky Way

IC 443

Crab

cosmic ray acceleration
Cosmic-Ray Acceleration

GLAST simulations showing SNR -Cygni spatially and spectrally resolved.

Energy (MeV)

slide20

Faint source

EGRET data

Cosmic-Ray Acceleration

Model g-ray spectrum for SNR IC 443 adapted from Baring et al. (1999) illustrating how GLAST can detect even a faint p0-decay component. ( 1 year sky survey with 1 s error bars)

slide21

HST Image of M87 (1994)

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.

Models include emission of energetic (multi-TeV), highly-collimated, relativistic particle jets. High energy g-rays emitted within a few degrees of jet axis.

active galactic nuclei
Active Galactic Nuclei

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.

Simulation of a 1-year all-sky survey by EGRET.

Simulation of a 1-year all-sky survey by GLAST.

E>1 GeV!

measurement of agn spectra
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

blazar cosmology
Blazar Cosmology

Roll-offs in the g-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, MacMinn, Primack, 1998)

identifying sources
Identifying Sources

GLAST 95% C.L. radius on a 5 source, compared with a similar EGRET observation of 3EG 1911-2000

EGRET Unidentified Sources

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 GeV

detection of transients
Detection of Transients

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

gamma ray bursts
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

gamma ray bursts28
Gamma-Ray Bursts

Simulated one-year GLAST scan, assuming a various spectral indexes.

1- localization accuracy (arc min.)

  • GLAST will be best suited to studying the GeV tail of the gamma-ray burst spectrum.
  • 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.
slide29

Gamma-Ray Bursts

A separate instrument (NASA-MSFC) on the spacecraft will cover the energy range 10 KeV – 25 MeV 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 KeV – 100 GeV) provided by GBM and LAT.

  • 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.
slide30

GRBs and Quantum Gravity

GRB ms pulse structure at GeV energies + Gigaparsec distances may constrain

EQuantumGravity ~ 1019 GeV

See: G. Amelino-Camelia, John Ellis, D.V. Nanopoulos 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,

dNg/dEg ~ 1/Eg2

For certain string formulations photon propagation velocity in vacuum appears increased or decreased as energy increases (granularity of space-time)

vg= c(1 ± Eg/EQG+ O[(Eg /EQG)2])

Dt ~ a E/EQG D/c ~ 10 ms GeV-1 Gpc-1 (if EQG ~ 1019 GeV)

slide31

Arrival time distribution for two energy cuts 0.1 GeV and 5 GeV( cross-hatched)

Test of Quantum Gravity

Using only the 10 brightest bursts yr-1, GLAST would easily see the predicted energy- and distance-dependent effect.

dark matter problem
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 :

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

M(R) = v2R/G

slide33

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.

halo wimp annihilations
Halo WIMP annihilations

Infinite energy resolution

g lines

50 GeV

With finite energy resolution

300 GeV

GLAST two-year scanning mode

Total photon spectrum from the galactic center from cc ann.

dark matter searches neutralino
Dark Matter Searches: Neutralino

X

q

gg or Zg

q

lines

X

GLASTsE/E ~3%

q > 50o

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.

The GLAST CsI calorimeter will be the largest such device ever put into space. It is only 10 X0 viewed from the front, but from the sides it is up to 1.5 m “thick” and well suited for precision measurements of very high-energy photons.

slide36

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 g-ray from extragalactic sources
    • GRB physics at high energy.

More information on GLAST at http://www.pi.infn.it/glast

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