UCSD Seminar Feb14, 2006
Gamma Ray Large Area
Space Telescope
Eduardo do Couto e Silva
SLAC/KIPAC
UCSD Astrophysics Seminar – Feb 14, 2006
E. do Couto e Silva SLAC/KIPAC
UCSD Seminar Feb14, 2006
Outline

Overview of the GLAST Observatory
• Current status of two instruments (GBM and LAT)

GLAST Science
• Highlights of Instrument Capabilities
• Selected Physics Topics
• Gamma Ray Bursts
• Particle Acceleration


Active Galactic Nuclei
Supernova Remnants
• Diffuse g Ray Emission
• Dark Matter Searches and New Physics

Timeline
E. do Couto e Silva SLAC/KIPAC
UCSD Seminar Feb14, 2006
GLAST Observatory : Overview
GLAST will measure the direction, energy and arrival time of celestial g rays
Principal Investigator: Peter Michelson
LAT
will record gamma-rays
in the energy range
~ 20 MeV to >300 GeV
Orbit
565 km, circular
GBM
will provide correlative
observations of transient
events in the energy
range
~10 keV – 25 MeV
Observing modes
All sky survey
Pointed observations
Re-pointing Capabilities
Autonomous
Rapid slew speed
(75° in < 10 minutes)
E. do Couto e Silva SLAC/KIPAC
Inclination
28.5o
Lifetime
5 years (min)
Will follow on the measurements by its predecessor
(EGRET) with unprecedented capabilities
Launch Date
Sep 2007
Launch Vehicle
Delta 2920H-10
Launch Site
Kennedy Space
Center
UCSD Seminar Feb14, 2006
GLAST Burst Monitor: Overview
NaI and BGO counters exposed to the entire sky
Principal Investigator: Charles Meegan
NaI crystals (12)
low-energy spectral coverage
~10 keV to ~1 MeV
rough burst locations
BGO crystals (2)
high-energy spectral coverage
~150 keV to ~30 MeV
GBM
10 keV to ~ 25 MeV
Correlative observations
of transient phenomena
E. do Couto e Silva SLAC/KIPAC
Spectral Measurements
measures spectra for bursts
connects with LAT measurements
Afterglows in Gamma Ray Bursts
Wide Sky Coverage (8 sr)
autonomous repoint for exceptionally bright bursts
that occur outside LAT field of view
Connections to the Ground Network of Telescopes
burst alerts to the LAT and ground telescopes within seconds
UCSD Seminar Feb14, 2006
Current Status of GBM Assembly
12 NaI modules
E. do Couto e Silva SLAC/KIPAC
2 BGO modules
Environmental Tests
at Max Planck Institute
UCSD Seminar Feb14, 2006
Large Area Telescope: Overview
Principal Investigator: Peter Michelson
The LAT is a pair-conversion telescope
of 16 towers surrounded by plastic scintillators
g
Silicon Microstrip Tracker
~ 80 m2 of silicon
8.8 x 105 readout channels
Strip pitch = 228 µm
xy layers interleaved with
W converters
~1.5 X0
Calorimeter
Hodoscopic array
Array of 1536 CsI(Tl)
crystals in 8 layers
~8.5 X0
Anti-Coincidence Detector
89 scintillator tiles
Segmented design
E. do Couto e Silva SLAC/KIPAC
Silicon Microstrip Tracker
Measures g direction
g identification
Calorimeter
Measures g energy
Shower imaging
e+
e–
LAT
3000 kg, 650 W (allocation)
1.8 m  1.8 m  1.0 m
20 MeV – 300 GeV
Currently there is no other telescope
covering this energy range
Anti-Coincidence Detector
Rejects background of
charged cosmic rays
segmentation removes selfveto effects at high energy
UCSD Seminar Feb14, 2006
LAT Integration @ SLAC
Calorimeter module
Tracker module
LAT Integration & Test Team
Anti Coincidence Detector being integrated
with 16 towers
E. do Couto e Silva SLAC/KIPAC
UCSD Seminar Feb14, 2006
LAT Data from Tests at SLAC
From A. Borgland
Muon candidates
Most of the 500 Hz of triggers
recorded are muons
Photon Candidates?
~20% of cosmic ray showers
are not muons
E. do Couto e Silva SLAC/KIPAC
UCSD Seminar Feb14, 2006
Science with GLAST
I will cover only
few selected topics

High Energy Sky Survey :
•
Unidentified EGRET sources and GLAST Source Catalog
•
•
Population Studies
•
•
AGN jets
energy conversion
shocks in SNRs
role of hadrons in radiation processes
High-energy behavior of transients :
•
•

Galactic and Extragalactic
Physics of particle acceleration
•
•
•
•

To avoid peculiarities of individual sources (AGN, Pulsars, SNR…)
Diffuse Gamma ray emission
•
•
unresolved point sources
Gamma Ray Bursts
Solar Flares
LAT strengths:
All-sky monitoring
Broad range of time scales
Energy range
Discovery Potential:
•
•
•
•
New classes of astrophysical objects
Origin of Extragalactic Background
Searches for Dark Matter and Extra Dimensions
Tests of Lorentz Invariance
E. do Couto e Silva SLAC/KIPAC
UCSD Seminar Feb14, 2006
LAT will Rediscover the g Ray Sky
GLAST 1 year
all sky survey
E. do Couto e Silva SLAC/KIPAC
Source class
Seen by
EGRET
Predicted
with
GLAST
Unidentified sources
170
?
Rotation powered
pulsars
3-6
100-500
AGN (mostly blazars)
50-80
>2000
Normal galaxies
2
4-5
Gamma ray bursts
5
>500
Supernova
Remnants/plerions
1-5
>10
Radio galaxies
1-1
?
X ray
binaries/microquasars
1-1
?
Starburst galaxies
0
?
Cluster of galaxies
0
?
UCSD Seminar Feb14, 2006
3rd
Comparison of Instrument Performance
EGRET Catalog
LAT Simulation
EGRET
LAT
E > 100 MeV
E > 100 MeV
Pointing
1991-2001
All sky
2007 - ?
5 yr operation
requirement
10 yr operation
goal
Improvement
Energy
30 MeV - 30 GeV
Peak effective area
1500 cm²
Field of view
Sensitivity (1yr)
0.5 sr
~ 10-7 g cm-2 s-1
Localization (bright source)
Deadtime
E. do Couto e Silva SLAC/KIPAC
15 ’
100 ms
20 MeV - 300 GeV
> 8000 cm²
>5
> 2.0 sr
>4
< 6 10-9 g cm-2 s-1
> 20
< 0.5 ’
> 30
< 30 ms
> 1000
Large area
Low instrumental background
UCSD Seminar Feb14, 2006
All Sky Monitoring with Improved Sensitivity
All-sky survey:
sensitivity after O(1)
day to detect the
weakest EGRET
sources at (5s) level !
100 sec
Fraction of the
g ray
sky
100
sec
observed
within 2 min
- GRB940217 (100sec)
- PKS 1622-287 flare
- 3C279 flare
- Vela Pulsar
1 orbit ~ 90 min
- Crab Pulsar
- 3EG 2020+40 (SNR g Cygni?)
zenith-pointed
- 3EG 1835+59
- 3C279 lowest 5s detection
- 3EG 1911-2000 (AGN)
- Mrk 421
- Weakest 5s EGRET source
1 day
1~day
EGRET
Flux
rocking” all-sky scan: alternating orbits
point above/below the orbit plane
E. do Couto e Silva SLAC/KIPAC
UCSD Seminar Feb14, 2006
GLAST/LAT
performance
Thin
Thick
Intrinsic resolution of the tracker
Slide from N. Omodei
Energy Resolution: ~10% (~5% off-axis)
PSF (68%) at 100 MeV ~ 5o
PSF (68%) at 10 GeV ~ 0.1o
Field Of View: 2.4 sr
Point Source sens. (>100 MeV): 3x10-9 cm-2 s-1
Thin
converters
(3%)
Thin
Thick
Full Tkr
E. do Couto e Silva SLAC/KIPAC
Thick
converters
(18%)
No
converters
F.o.V.: 2.4 sr
UCSD Seminar Feb14, 2006
Gamma Ray Bursts: GBM and LAT

GBM
• Huge field of view (8sr)
• Measure spectra for bursts
from 10 keV to 30 MeV

LAT
• Wide field of view (>2sr)
• Extends spectral coverage to
higher energies
GLAST
Can be re-pointed to
catch exceptionally bright
bursts that occur outside
the LAT field of view
GLAST all-sky monitoring will be
follow transient phenomena to a wide
range of time scales
from ~ 30 µs (GRB, solar flares) to
hours or longer (AGN)
E. do Couto e Silva SLAC/KIPAC
+
Simulated GBM and LAT
response to timeintegrated flux from
bright GRB 940217
Spectral model parameters
from CGRO wide-band fit
1 NaI (14 º) and 1 BGO (30 º)
NaI
BGO
LAT
UCSD Seminar Feb14, 2006
Some GRB Experimental Facts

Intensity, location, rate
•
Typical fluences

•
Cosmological distances

•
1 /Myrs/galaxy
940217
(Hurley 1994)
Energy Spectrum
•
Non-thermal emission


z~1
Rate


10-4 to -7 ergs cm-2
up to g rays (3 GeV)
Temporal properties
•
Rapid flux variations

•
miliseconds
Range of burst durations

few seconds to hours
E. do Couto e Silva SLAC/KIPAC
Transients
are hard to catch!
UCSD Seminar Feb14, 2006
High Energy Emission in GRB 941017
Compare data from EGRET and BATSE:
high-energy component has different time behavior than sub–MeV component!
Low Energy < 3 MeV
Epeak ~ 0.5 MeV
Duration ~ 100s
Where is the
high-energy
peak? Is there
a cut-off?
internal or
external
shocks?
High Energy > 3 MeV
dN/dE ~ E-1
Duration ~ 200s
hadrons or
electrons?
Is the spectral
index timedependent ?
How common
is this GRB ?
-18 to 14 s
14 to 47 s
high energy component
start to develop
47 to 80 s
80 to 113 s
113 to 211 s
BASTE-LAD
Gonzalez et al 2003
E. do Couto e Silva SLAC/KIPAC
Need GLAST
data!!
EGRET-TASC
UCSD Seminar Feb14, 2006
Fireball Model
Kobayashi, Piran & Sari 1999
z=43
E=1052 ergs
h=50
R =3×1010 cm
UInt to UKin

External Shock
Plethora of models
• Shells

HOT
HOT
COLD
Reverse Forward
Relativistic or Newtonian
• External Medium

COLD
thin or thick
• Shocks

Ukin to UISM
ISM or wind like
E. do Couto e Silva SLAC/KIPAC
shock
Fireball
shock
ISM
ISM
UCSD Seminar Feb14, 2006
High Energy Emission Models
Leptonic
Models

No definitive
answer yet…

Hard to model IC
Hadronic
models
(Pe’er Waxman 2005)
•
•
•
Shocks:
Internal/
External?
Forward/
Reverse?
IC
Synchroton
E. do Couto e Silva SLAC/KIPAC
KN regime
HE EM cascades
Large t from e+-
Proton
Synchrotron
pp, pn , pg

UCSD Seminar Feb14, 2006
Modeling High Energy Emission for GRB941017
Two models used
• External shock (Pe’er
&Waxmann 2004)


e- accelerated in
FS IC scatter g from
RS
SSA is important
• Internal Shock (Granot
& Guetta 2003)




e- in FS IC scatter g
whlle RS is going
on
SSC from RS
(depends on
spectal index)
eB ~ 10-7
Dt = 10-5
E. do Couto e Silva SLAC/KIPAC
High Energy data constrains
Total energy, Lorentz factor and ambient density
Pe’er & Waxman 2004
E = 3 × 1054 ergs, n = 0.10 cm-3, G i = 300, eB,r = 10-1, eB,f= 10-6, z = 0.10
E = 1 × 1055 ergs, n = 0.10 cm-3, G i = 200, eB,r = 10-3, eB,f= 10-5, z = 0.10
E = 1 × 1054 ergs, n = 0.03 cm-3, G i = 220, eB,r = 0.2, eB,f= 10-6, z = 0.06
E = 3 × 1052 ergs, n = 0.10 cm-3, G i = 1500, eB,r = 10-7, eB,f= 10-7, z = 0.15
Flux between
100 and 200 s
after the burst
Data from Gonzalez et al 2003
GRB941017
GBM
LAT
Dt = 10-5
UCSD Seminar Feb14, 2006
Shock Plasma Parameters

Luminosity of the Source
•
L ~ 1052 ergs s-1


Lorentz Factor of Bulk Plasma
•
G ~ 102 to 103


DT ~ 10-4 to 10-3 s

eB ~ 1 to 10-5

Ratio of peaks in SED (GLAST + X ray Detector?)
Fraction of Thermal Electron Energy Density behind the shock
•
ee ~ 1 to 10-5


~30 ms deadtime with GLAST (EGRET was 100 ms)
Fraction of Magnetic Energy Density behind the shock
•

cut-offs at the energy spectrum (GLAST + IACT?)
Time Variability
•

GLAST may measure Epeak
Can we use GLAST
measurements to
help constrain these
parameters?
Ratio of peaks in SED (GLAST + X ray Detector?)
Energy distribution of accelerated electrons
•
p (power law index) ~ 2 to 3

SED fits (GLAST + X ray Detector?)
E. do Couto e Silva SLAC/KIPAC
Are p, eB ee time
independent?
(Paitanescu and Kumar 2001)
UCSD Seminar Feb14, 2006
Multiwavelength Observations to Constrain Models



Model
•
Prompt emission from
internal shocks

in relativistic wind
Pe’er & Wazman 2004
•
Spectra as high as 10
GeV


Flux has a strong
dependence on G
Measure cut-offs with
GLAST!
Ratio of peaks in kev/GeV
can be used to constrain
ratio of eB / ee


LAT + GBM?
Swift + GLAST?
Caveat:
•
single shell collisions
E. do Couto e Silva SLAC/KIPAC
100 keV
eB = 0.33
eB = 0.01
eB = 0.0001
1 GeV
l’ < 10
G = 600
Dt = 10-4



UCSD Seminar Feb14, 2006
Which model should we choose?
Region I
• Proton synchroton

hard with GLAST

large eB
Region II
• Inverse Compton



good for GLAST
denser medium helps
Typical from afterglows
(Painatescu & Kumar 2001)
(Painatescu & Kumar 2002)
small eB :internal
shocks
Region III
• Electron synchroton

not in GLAST range
E. do Couto e Silva SLAC/KIPAC
Zhang
&&
Meszaros
2001
Zhang
Meszaros
2001



UCSD Seminar Feb14, 2006
We need DATA !
Region I
Zhang & Meszaros 2001
z = 0.1
z=1
• Proton synchroton

hard with GLAST

large eB
Region II
• Inverse Compton


good for GLAST
denser medium helps
Region III
• Electron synchroton

not in GLAST range
E. do Couto e Silva SLAC/KIPAC
eB = 10-4
ee = 0.5
GRB 940217
(Hurley 1994)
UCSD Seminar Feb14, 2006
Delayed High Energy Emission in GRB940217

LAT
• Large effective Area (can probe
smaller fluxes)
• Extends spectral coverage to
higher energies

GBM will cover down to few keV
E. do Couto e Silva SLAC/KIPAC
GRB 940217
(Hurley 1994)


UCSD Seminar Feb14, 2006
Can we constrain p and G from GRB940217?
Guetta & Granot 2003
Model
•
Prompt emission from internal
shocks

•
G = 600
G = 350
G = 200
300 keV
1 GeV
in relativistic wind
SSC dominates above 100 MeV


Power law index > 2
GLAST can constrain p
30 MeV
Parameters
•
•
G= 600, Dt = 0.1 ms, Ep = 200 KeV
Should we expect variability
smaller that 0.1 ms?
E. do Couto e Silva SLAC/KIPAC
Dt = 10 ms
Dt = 1 ms
Dt = 0.1 ms
UCSD Seminar Feb14, 2006
SNR: Sites of Hadronic Acceleration?

Supernova Remnants: sites of galactic cosmic ray
acceleration
•
•
Non-thermal emission (X-rays)
Signs of g-ray activity
•
•

Question:
•

EGRET: GeV activity near SNR (3EG J1714-3837)
HESS: Recent detection of TeV g-rays
Do g rays originate from hadronic or leptonic processes?
Measurements in the range of 100MeV-100GeV
•
essential ingredient to resolve the origin (p vs e+/-) Uchiyama (2003)
Supernova remnant RX J1713.7-3946
HESS (color) + ASCA (contours)
Adapted from Aharonian’s talk at the
Texas Symposium 2004
HESS data
astro-ph/0511678
p0
model
GLAST
E. do Couto e Silva SLAC/KIPAC
e+/model
UCSD Seminar Feb14, 2006
AGN (Blazars): Emission Mechanisms
Adapted from P. Coppi

Most of the EGRET AGNs were
blazars
•
•

Radiation is produced by one or
more of the following processes
•
•
•
•

(Buckley, Science, 1998)
E. do Couto e Silva SLAC/KIPAC
Variability: relativistic jets
Jets point towards us !
Synchrotron Self Compton
External Compton
Proton Induced Cascades
Proton Synchrotron
Key issues to be addressed
•
•
•
•
•
Energetics of the source
jet formation
jet collimation
nature of the plasma
particle acceleration
UCSD Seminar Feb14, 2006
Time lags: hadronic or leptonic model in
AGNs?
Credit: EGRET Team

Leptonic processes are
“preferred” by
theorists
g rays
• Hadronic models have
not yet been
excluded!

Time lags between
AGN flares may
suggest dominance of
hadronic processes
X rays
Changes in Luminosity in a fraction of a day !
Variability constrains the size of the emitting source
E. do Couto e Silva SLAC/KIPAC
UCSD Seminar Feb14, 2006
Multiwavelength Observations

Contemporaneous observations with other wavelengths
• disentangle effects from state changes within individual sources

GLAST will provide “continuous” baseline in GeV
• helpful to ground based TeV g-ray telescopes
Blazar PKS 2155-304
3rd EGRET
Catalog
~103 g cm-2
leptonic model
common origin optical/Xray
g
High g-ray state
(Verstrand et al. 1995)
~30 km
Aharonian et al. (2005)
Atmosphere:
For Eg > ~ O(100) GeV,
must measure light
emitted at the
atmosphere (Cerenkov)
leptonic
model
E. do Couto e Silva SLAC/KIPAC
hadronic
model
GeV-TeV campaigns will
complement GLAST science!
Multiwavelength
planning in progress:
http://glast.gsfc.nasa.gov/science/multi
UCSD Seminar Feb14, 2006
AGN: Extragalactic Background Light

High Energy photons (e.g. from AGN) can be absorbed via pair production
•
•

GeV (TeV) photons interact with intergalactic photons UV(IR)
strong dependence on the distance from the source (inferred from redshift)
GLAST will see thousands of AGN
•
•
look for systematic effects vs redshift
key energy range for cosmological distances
effect is model-dependent (this is good!!):
Salamon & Stecker, ApJ 493, 547 (1998)
opaque
source
No EBL
Salamon & Stecker
source
Eg
lower
No significant attenuation
below 10 GeV
Primack &
Bullock
E. do Couto e Silva SLAC/KIPAC
A dominant factor in EBL models is
the era of galaxy formation
AGN roll-offs may help distinguish
models of galaxy formation
Chen, Reyes, and Ritz, ApJ 2004

UCSD Seminar Feb14, 2006
Gamma Ray Background Radiation

Extragalactic Emission
•
Higher latitudes
•
EGRET Gamma Ray Emissions > 100 MeV

Galactic Emission
•
•
|b| <
|b| > 10 0
falls rapidly at higher latitudes
gas density concentrated in the plane
100
cosmic rays
(from SNR?)
p
p
g
ISM
0
g
g
Galactic plane
• Contains about 90% of the g ray emission
• Mostly high energy cosmic ray interactions with the interstellar medium (ISM)
E. do Couto e Silva SLAC/KIPAC
e-
UCSD Seminar Feb14, 2006
Origin of Extragalactic g-Ray Background

GLAST can shed light in one of the longstanding problems in high energy astrophysics
• The origin of the extragalactic background
Original EGRET spectrum
Galactic Diffuse g ray is
subtracted
Reanalysis using slightly
modified e- spectrum with
respect to the local injected
spectrum
Strong, Moskalenko, Reimer (2004)
What is it made of?
•
Blazars
•
•
New physics
•
•
E. do Couto e Silva SLAC/KIPAC
we can probe…
Primordial diffuse
•
LAT
we expect…
If else fails…
UCSD Seminar Feb14, 2006
Galactic Diffuse Gamma Ray Emission
The g ray sky is dominated by diffuse emission
Accurate modelling is essential
EGRET
GLAST
Many more point sources
Background determination for energy above 10 GeV
Sharper definition of the diffuse background
(smaller bins in the sky)
E. do Couto e Silva SLAC/KIPAC
UCSD Seminar Feb14, 2006
EGRET DATA: “g-ray excess” is controversial

After diffuse background subtraction there was an excess of g in the
EGRET Data
•
Revisited pp cross section: accounts for a fraction of the GeV excess
EGRET DATA
New Model
Old pp interaction models
 Constant inelastic cross-section
 Feynman scaling
 No diffraction dissociation
-2.5
-2.7
Old Model
New pp interaction model
 Rising cross-sections
 Scaling violation
 Diffraction dissociation
Kamae et al. 05, Kamae, Karlsson, Mizuno et al. 05, Kamae, Karlsson, Cohen-Tanugi Mizuno et al.05
E. do Couto e Silva SLAC/KIPAC
UCSD Seminar Feb14, 2006
Dark Matter
NGC3198
Strong Evidence that Dark Matter
exists comes from
Taga et al 1994
Rotational curves
Clusters of galaxies
Cosmological fits to data
Extracted from Peter Watson’s website http://www.physics.carleton.ca/~watson/
E. do Couto e Silva SLAC/KIPAC
GMm mv2

r2
r
GM
v
r
UCSD Seminar Feb14, 2006
Dark Matter Candidate: Neutralino
If true, there may well be
observable halo annihilations

~
~3
~0
~0
  a11B  a12W  a13H1  a14 H 2
0
1
Good particle physics candidate for galactic halo dark matter
• Lightest Supersymmetric Particle in R-parity conserving SUSY


q

g
q

g
continuum
energy spectrum
Higher statistics…
but higher background
E. do Couto e Silva SLAC/KIPAC
Distinct signature
a “peak” in the energy spectrum !!
Lower background…
but lower statistics
UCSD Seminar Feb14, 2006
Can WIMPs be the source of Dark Matter?

Weakly Interacting Massive Particles (WIMP)
Direct searches:
• scattering of WIMPS with nucleons in the detector
• DAMA, CDMS, EDELWEISS, etc.

Indirect Searches:
• WIMP annihilations into other particles
• GLAST, ICECUBE, ANTARES, GENIUS, HEAT, AMS, etc
Galactic
Earth
neutrinos
Sun
neutrinos
Extragalactic
Galactic Halo
antideuterons
positrons
antiprotons
photons
positrons
E. do Couto e Silva SLAC/KIPAC
Galactic Center
photons
photons
UCSD Seminar Feb14, 2006
Flux of Photons from Neutralino Annihilations
Where High Energy Particle and Astrophysics meet…
Particle Physics
Astrophysics
F  sv J (nˆ )
J (nˆ ) 
Choose a SUSY model
Calculate masses and spectrum
Select cosmologically relevant relic density
E. do Couto e Silva SLAC/KIPAC
1
R 2

2
(l )dl (nˆ )
line- of - sight
Choose a HALO model
Integrate along the line of sight
UCSD Seminar Feb14, 2006
Dark Matter from SUSY: g line and continuum
g lines
Large uncertainties in the
Particle spectrum
Halo model
Background estimation
Detection rates can
increase if halo is clumpy
Dark matter halo
Milky Way
E. do Couto e Silva SLAC/KIPAC
N-body simulations from Calcáneo-Roldan and Moore, Phys. Rev. D62 (2000) 23005.
UCSD Seminar Feb14, 2006
Halo Dark Matter Searches with GLAST

WIMP Annihilations in halo Clumps (b >|10| 0):
• continuum g from p0 @ ~100 MeV
• lines (2 g, g) (Bergstrom et al)
• Depends on models of clumps


see previous slide
IC from secondary electrons (Baltz & Wai 04)
• >GeV IC from e + starlight
• near galactic plane < 300 (trapping by B field)

KK DM Scenario – electron “line” (20% Br) smeared
into a sharp edge via mainly IC
• >500 GeV: ~ 100 e± /year edge height
• all-sky signature!

E. do Couto e Silva SLAC/KIPAC
see next slide
UCSD Seminar Feb14, 2006
Dark Matter: SUSY or Extra Dimensions?

KK Dark Matter?
SUSY
Baltz and Hooper, JCAP07(2005)001
• Lightest Supersymmetric
Particle
• Neutralino
• Accelerator bounds
• M 0 > tens of GeV
• Search for photons

Extra Dimensions
• Lightest Kaluza-Klein
Particle
• B1
• Accelerator bounds
• M B1 > 300 GeV
• Search for photons and
leptons
• Charged leptons are not
helicity suppressed
• 59% charged leptons
• 35% quarks
E. do Couto e Silva SLAC/KIPAC
endpoint spectral feature !!!
Limited statistics with GLAST.
HARD to measure
but very interesting…!
UCSD Seminar Feb14, 2006
Extra Dimensions: Possible GLAST Signatures?
Large Extra Dimensions
Universal Extra Dimensions


Thermal graviton emission (how
much energy went into the bulk
without affecting cosmological
evolution?) (Perez-Lorenzana 2005)
•
•


•
•
•
•
•
• not on SM particles only
E. do Couto e Silva SLAC/KIPAC
Limited statistics and maybe DE/E
Low Energy Signal ( < 100 MeV)
•

Photons from qq and synchroton
High Energy Signal (hundreds of GeV)
•

Bremstrahlung of charged leptons
Secondary gamma rays
•

59% charged leptons
35% quarks
4% neutrinos
1% charged gauge bosons
0.5 % neutral gauge bosons
0.5 % Higgs bosons
Primary gamma rays
•
NS shines because gravitons are
gravitationally trapped
Excess in diffuse gamma ray
emission around 30 MeV
Gamma ray emission from NS in the
galactic bulge
Problem: heavy KK can decay into
more lighter KK modes
Charged lepton production is not
helicity suppressed
•
•
•
•
•
•
SN (Hannestad 2003)
Massive Graviton decays into gg
continuously emitted by the
Universe (less robust)
Two photons via loop diagrams
(Servant and Tait)
B1B1 annihilation in Galactic Center
•
BBN (Hannestad 2004)
For n=2 there would be many KK
Modes which would release too
much energy into gravitons


•
Gravitons emitted by stellar objects
take away energy
•
B1B1 annihilation in Galactic Center
Uncertainties in the background
Can theorists give us a signal between
10 and 100 GeV?
•
LZP (Agashe and Servant hep-ph 0403143)
GLAST MISSION ELEMENTS
UCSD Seminar Feb14, 2006
GLAST MISSION ELEMENTS
Large Area Telescope
& GBM
GPS
TLM: S-band @ 1,2,4,8 kbps
TLM: Ku-band @ 40 Mbps (13
- GB/day average)
• Telemetry
1 kbps
CMD: S-band @ .25, 4 kbps
GLAST Spacecraft
DELTA
7920H
•
TDRSS SN
S & Ku
•
•
S
•
40 Mbps
GN
•
Internet 2
Schedules
Mission Operations
Center (MOC)
GRB
Coordinates Network
GLAST Science
Support Center
Schedules
Alerts
Data, Command Loads
E. do Couto e Silva SLAC/KIPAC
LAT Instrument
Operations Center
Archive
GBM Instrument
Operations Center
White Sands
HEASARC
GSFC
UCSD Seminar Feb14, 2006
Operation Phases

First year of science operations
•
initial on-orbit checkout, verification, and calibrations, followed by an allsky survey
•
•
•
key projects needed by the community
•
•
limited first-year guest observer program
extraordinary Targets of Opportunities supported.
workshops for guest observers on science tools and mission
characteristics for proposal preparation
Observing plan in subsequent years
•

data on transients will be released, with caveats.
repoints for bright bursts and burst alerts enabled.
First Year Guest Observer Program
•
•
•

source catalog, diffuse background models, etc.
Transients
•
•

detailed instrument characterization
refinement of the alignment
driven by guest observer proposal selections by peer review.
All data released through the GLAST Science Support Center (GSSC).
E. do Couto e Silva SLAC/KIPAC
UCSD Seminar Feb14, 2006
The Look Ahead
Fabrication
Instrument & Spacecraft I&T

The GLAST mission is
2005
Observatory I&T
2006
• completing the fabrication phase and
• is well into integration.

LAT, GBM, and spacecraft assembly
• complete by early 2006.

Delivery of the LAT and GBM instruments
• for observatory integration in spring 2006.

Observatory integration and test
• spring 2006 through summer CY07.

Major scientific conference,
• the First GLAST Symposium, being planned for early 2007.
E. do Couto e Silva SLAC/KIPAC
2007
Launch
UCSD Seminar Feb14, 2006
GLAST
E. do Couto e Silva SLAC/KIPAC
September 2007 launch
Back up slides
Page Number
UCSD Seminar Feb14, 2006
GBM Performance
The GLAST Burst Monitor for GLAST, A. von Kienlin et al., in Proc of the SPIE-Conference, Glasgow 2004



•compare count rates for 2 of the modules
GBM NaI Location
• 6 in the equatorial plane
• 4 at 45o
• 2 at 20o
GBM BGO Location
• 2 in opposite sides of the
spacecaft
GBM Trigger
same as BATSE


GBM Trigger Sensitivity
•< 1 ph cm-2s-1
BATSE: 0.2 ph cm-2s-1 (5s)


GBM Burst Localization
•< 15o within 1.8s (on board)
can be used as a LAT trigger
if outside LAT FOV

•possible to repoint to catch delayed emissions
•< 5o within 5s (ground)
E. do Couto e Silva SLAC/KIPAC
< 3o within 1 day (ground)

UCSD Seminar Feb14, 2006
GLAST and GRBs


Full sky survey every 3 hours
Number of Bursts
• GBM ~ 200 bursts/yr
• > 60 bursts within FoV of the LAT


1 burst/month ~ 100 photons
Alert and Localization
• Alert to GCN ~ 10 s
• GBM < 150 initially, update 50
• LAT > 10 arcmin depending on the burst

Downlink and Communications
• near real-time (TDRSS)
• full science data ~ 6-8 times a day

Downlink and Communications
• Intense burst: GLAST can repoint


keep LAT in the FoV
Dwell time: 5 hr (adjustable)
E. do Couto e Silva SLAC/KIPAC
Slide from N. Omodei
(GLAST GRB SWG)
UCSD Seminar Feb14, 2006
GLAST and SWIFT era

•
Swift can point for follow on observations.


Precise measurements of the position will be given by Swift!
GLAST will frequently scan the position of the bursts hours after the Swift
alerts
•
•

Slide from N. Omodei
(GLAST GRB SWG)
GLAST can provide alerts to GRBs
monitoring for High energy emission.
In these cases, we will have a broad spectral coverage of the GRB spectrum (from 0.1
keV to hundreds of GeV > 9 decades!!).
Swift is seeing 100 bursts per yr: ~ 20/yr will be in the LAT FoV
~2020
GBM
LAT
2007
XRT
BAT
2005
E. do Couto e Silva SLAC/KIPAC
0.1 keV
10 keV 100 KeV
1 MeV
30 MeV
300 GeV
UCSD Seminar Feb14, 2006
Duration of GRBs
160
(e.g stellar mass BH
accreting from a
massive disk,
rotating NS driving
Poynting flux)
120
NUMBER OF BURSTS
If there is a compact
object at the inner
engine, the source must
also be active for a long
time
Long
Compact
Mergers?
(ISM)
Collapsar
Model ?
(wind)
1 cm-3
103-4 cm-3
80
40
0
0.01
E. do Couto e Silva SLAC/KIPAC
Short
0.1
1
10
DURATION, SECONDS
100
1000
UCSD Seminar Feb14, 2006
X ray Flares

Giant X-ray Flare
• 500 times higher amplitude
GRB050502b
Falcone 2005
E. do Couto e Silva SLAC/KIPAC

Can we detect IC from X ray
flares?
UCSD Seminar Feb14, 2006
RX J1713.7-3946
E. do Couto e Silva SLAC/KIPAC
UCSD Seminar Feb14, 2006
Complex Modeling of Particle Transport
Courtesy of I. Moskalenko
Sources of CR:
SNRs, Shocks,
Superbubbles
Particle acceleration
Photon emission
X
+
e-
Chandra
B
P
diffusion
He
energy losses
CNO
reacceleration
convection e +etc.
+
π_
P
Halo
gas
p
solar
modulation
disk
BESS
E. do Couto e Silva SLAC/KIPAC
ISM
IC
ISRF
gas
π0
LiBeB
He
CNO
AMS
Charged particle measurements will provide
consistency checks for g ray models
GLAST
Need to model
•Number density of primary nuclei
•Production cross section
•Gas distribution and composition
ACE
UCSD Seminar Feb14, 2006
SUperSYmmetry - New Particles
A model of supersymmetric particles can be built to explain
why “forces meet” at about 1016 GeV
For each particle there will be
a supersymmetric partner
quark
squark
The lightest SUSY particle (STABLE) in most theories is the
NEUTRALINO
E. do Couto e Silva SLAC/KIPAC
UCSD Seminar Feb14, 2006
Dark Matter
1

Energy matter density/critical density
Contributions from
0.3
0.7
 = M + 
M matter
 cosmological constant
B baryonic matter
B + NB
NB non-baryonic matter
Ordinary matter
0.05
0.25
Dark matter?
0.25/0.3 ~ 90% of matter in the universe is non luminous, hence Dark Matter
What is the origin of Dark Matter?
Could it be an exotic Particle?
If it is why haven’t we seen it?
E. do Couto e Silva SLAC/KIPAC
UCSD Seminar Feb14, 2006
How many neutralinos are there?
To determine the current number of neutralinos (relic abundances),
we need to solve the Boltzmann equation for early and late times
Hubble
Constant
Negligible at
earlier times
dn
dt
Negligible at late times
 3Hn  - s xx v [( n ) - (n ) ]
Expansion of
universe
E. do Couto e Silva SLAC/KIPAC
2
Depletion of
neutralinos
eq 2
Creation of
neutralinos
UCSD Seminar Feb14, 2006
n /s
Neutralino: a Dark matter Candidate?
Approximate solution to Boltzmann equation leads to
Early Universe
 h 
2
m n 
c
3.10 -27 cm -3 s -1

s  v
Later…
s  v 
2
100GeV 
2
 10 - 25 cm -3 s -1
100 GeV neutralino can explain
Dark matter with  = 0.3
Adapted from Bernheuter astro-ph/0205729
1 /T
Neutralino is a good particle physics candidate for galactic halo dark matter
E. do Couto e Silva SLAC/KIPAC
UCSD Seminar Feb14, 2006
Models for Distribution in the Halo
: astro-ph/0207125
The Dark Matter
distribution in the
galactic halo is not
well known !
 (r) 
0
 r r0 1  r r0 
2
0 ~ 0.3 – 05 GeV/cm3
r0 = 8.5 kpc
E. do Couto e Silva SLAC/KIPAC
Galactic
Center
UCSD Seminar Feb14, 2006
Dark Matter Detection with GLAST
GLAST
sensitivity
curve
Not too
many
photons
There is no obvious
choice for “the”
model!
With 2 years of data is
harder for GLAST to
detect neutralinos if the
model is below the
curve
Each point corresponds to one possible model
All models assume the same Dark Matter distribution in the halo
E. do Couto e Silva SLAC/KIPAC
Bergström, Ullio & Buckley, ’97
UCSD Seminar Feb14, 2006
Dark Matter Simulations
Credit: B. Moore, www.nbody.net
z = 50
z = 20
z = 10
z=5
z=1
z=0
Simulations indicate that dark
matter haloes are formed in a
hierarchical structure where
smaller haloes form first
2 Mpc
Simulations of Local Group
E. do Couto e Silva SLAC/KIPAC
UCSD Seminar Feb14, 2006
Kaluza Klein Equations



2
 2   - 2  xm , x5   0
 x


t
 5

2
2
 2pnx5 
 xm , x5    xm cos

 R 
 2  2  2pn  2 
 - 2 - 
 xm   0




t
R





Kaluza Klein equation
•
•
•

Boundary conditions
•

R=radius of compactification
Effective mass term in 4D
(tower)
•
•
•
E. do Couto e Silva SLAC/KIPAC
Scalar field in 5d
Extra d is compactified
Radius is order of Planck
Scale
Each SM field n=0 has an
infinite number of KK partners
n>0
Lightest KK mode n=1
R ~ TeV, cosmologically
relevant
UCSD Seminar Feb14, 2006
Gravitational Effects through Compactification

The theory from Arkani-Hamed et al (ADD)
•
•
gravitational effects can be enhanced by winding modes of graviton.
Every time it winds around a compactified dimension
•
•

It is a periodic coordinate from 0 to 2p
It gives rise to additional gravitational force
What determines the number of revolutions ?
Along this axis
Extra dimensions are compactified with a radius of curvature of about 10-30 cm or less.
If we walk in this direction we always come back to the same point.
R
Along this axis
4D
space
E. do Couto e Silva SLAC/KIPAC
Extra dimensions are flat
(assume it is infinity)
Compactification in circles
creates massless states, if
we do in orbifolds get rid
of these states
Search for Extra Dimensions with the
LAT
UCSD Seminar Feb14, 2006

The experimental signatures for Extra Dimensions with the LAT
are challenging and probably at the limit of the instrument
capabilities
• As experimentalists we will search and
• work harder to improve the LAT performance

There are two main ranges of interest
• Low energies (< 100 MeV)
• Large extra dimensions (see Andrea Lionetto’s talk)

Graviton decays
• limited by the knowledge of the background
• Higher energies (>300 GeV)
• Universal extra dimensions

Annihilation of KK states
• Statistics limited
• May require further improvements in the energy resolution

Will systematic uncertainties play a role in the measurements?
E. do Couto e Silva SLAC/KIPAC
UCSD Seminar Feb14, 2006
Experimental Bounds on KK
Appelquist et al PRD 64, 035002 (2001)

SM in UED models lead to
contributions to EW observables
first at the one-loop level
(Appelquist et al 2001)
•

Splitting in the W and Z masses is
sensitive to physics beyond SM
Depends on
•
•
•
•

The lower bound on 1/R
depends on the cut-off scale
(Ms )
The example here is for d = 2
Higgs mass (Mh)
Compactification radius (R)
Cutoff-scale (Ms)
Number of extra-dimensions (d)
Non-observation of KK pair
production at LEP/SLC implies in
•
1/R > 300 GeV
•
Via T parameter that depends on
Mw,Mz,mt,
Above here
Calculations become
non-perturbative and
contributions to one-loop
level are no longer
reliable
Less model dependent than SUSY
E. do Couto e Silva SLAC/KIPAC
UCSD Seminar Feb14, 2006
Bounds on UED from Searches at the Tevatron
Applequist et al PRD 64 035002 (2001)

IF KK parity is not violated KK
must be produced in pairs
• KK to quarks and gluons

Run I: Search for heavy stable
quarks
• Mass > 195 GeV (charge 1/3)
• Mass > 220 GeV, (charge 2/3)
• Use this and look at production
cross-section

1/R > 300-350 GeV


Applequist 2001 estimated
Run II data will
• either discover an UED or
• significantly increase the lower
bound on R
E. do Couto e Silva SLAC/KIPAC

Sorry I had no time to get
the plots !
UCSD Seminar Feb14, 2006
Kaluza-klein as a DM Candidate
Servant and Tait Nucl.Phys. B 650 (2003) 391

B1 as the LKP
• first partner of
hypercharge gauge
boson

Prediction of the
relic density as
function of LKP
mass
• Varies with model
E. do Couto e Silva SLAC/KIPAC
UCSD Seminar Feb14, 2006
B1 annihilations into photons
Bergstrom et al JCAP 04 (2005)
Fermion box contributions

Assumptions
•
•
•
•
Halo profile: NFW (r-1)
Boost: 100
D = 10--5
B1 = 800GeV
Total spectrum: line + continuum

4
3
•
0.5 %
1%
•
Strong dependence on the
details of the galactic halo
profile
Will we have enough events
at this energy with the LAT?
•
2%

2
Problems
Homework…
•
Extrapolate to ~ 300 GeV
•
•
1
New hadronization
shape?
More channles open up?

Photon Energy (GeV)
E. do Couto e Silva SLAC/KIPAC
Clumpy halo helps
See E. Nuss talk
tomorrow
UCSD Seminar Feb14, 2006
B1 annihilations into photons
B1 B1
l +l - g
Bergstrom et al PRL 94, 131301 (2005)

Assumptions
• Halo profile: NFW (r-1)
• Boost: 100
• Vary from 1 to 1000
•
D = 10—5
• LAT is larger
HESS data compared to 2 UED models
• B1 = 800GeV
10—7
• Could be lower

10—8
800 GeV with
b ~ 200
10 TeV with
b ~ 1000
10—9
Problems
• Strong dependence on
the details of the galactic
halo profile
• Will we have enough
events at this energy
with the LAT?
• Clumpy halo helps
Photon Energy (TeV)
b parameterizes uncertainty in halo models
E. do Couto e Silva SLAC/KIPAC
<JGC>D D = 0.13 b
UCSD Seminar Feb14, 2006
Lower Bounds on B1 mass from gamma rays
Value of average J required to produce gamma ray flux
observable as function of B1 mass

Bertoni et al PRD 68, 044008 (2003)
Assumptions
• Halo profile: NFW (r-1)
• Boost: 100
• Vary from 1 to 1000
• D = 10—3
• B1 = 800GeV
• Could be lower

Problems
• Strong dependence on
the details of the galactic
halo profile
• Will we have enough
events at this energy
with the LAT?
For a Moore profile masses below 1.2 TeV are excluded if
LAT does not observe any radiation from the GC
E. do Couto e Silva SLAC/KIPAC
• Cumpy halo helps
Integrated gamma ray flux as a function of B1
mass Bertoni et al PRD 68, 044008 (2003)
UCSD Seminar Feb14, 2006
Gamma ray excesses are detectable for
masses < 600 GeV

Assumptions
• Halo profile: NFW (r-1)
• J average: 500
• D = 10—3

Problems
• Strong dependence on
the details of the galactic
halo profile
• Will we have enough
events at this energy
with the LAT?
• Cumpy halo helps
E. do Couto e Silva SLAC/KIPAC
UCSD Seminar Feb14, 2006
SUSY vs UED
Cheng et al PRL 89, 211301 (2002)
Battaglia al hep-ph/0502041

Nontrivial to disentangle both
in hadron colliders
•
Masses are model dependent
•
•
KK towers of states
•
•
•
•
Not robust
Spin is different !
•

Can’t reconstruct them or
see resonances
Contrib\ution to cross
section is small
SUSY one extra particle
Additional Higgs states in
SUSY
•
•
so does not help
Hard to measure in hadron
machines
Radiative corrections make
UED and SUSY more similar
experimentally
E. do Couto e Silva SLAC/KIPAC

A peak in positron spectrum
will be
•
•
Smoking gun for DM
exclude neutralino as a source
UCSD Seminar Feb14, 2006
SUSY vs UED : Linear Collider
E. do Couto e Silva SLAC/KIPAC
UCSD Seminar Feb14, 2006
Tevatron Searches
E. do Couto e Silva SLAC/KIPAC
UCSD Seminar Feb14, 2006
Direct Detection of B1
E. do Couto e Silva SLAC/KIPAC
Pulsar physics with GLAST
UCSD Seminar Feb14, 2006
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
E. do Couto e Silva SLAC/KIPAC
UCSD Seminar Feb14, 2006
1 GeV = 1,000,000,000 eV
Unification of Forces
10-13 GeV
102 GeV
1016 GeV
1019 GeV
PARTICLE ENERGY
Gravitational
Electromagnetic
T
O
D
A
Y
W, Z, g
Weak Nuclear
?
Electroweak
Supersymmetric
Particles?
B
A
N
G
?
Strong Nuclear
TIME AFTER THE BIG BANG
17 s
~10
E. do Couto e Silva
SLAC/KIPAC
~10-10 s
10-35 s
B
I
G
10-43 s