Eduardo do Couto e Silva - ATC/LM Colloquium, June 2004 1 How many neutralinos are there? Expansion...

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Eduardo do Couto e Silva - ATC/LM Colloquium, June 2004

How many neutralinos are there?

])()[(vH3 22 eqxx nnn

dt

dn

Expansion of universe

Depletion of neutralinos

Creation of neutralinos

Negligible at late times

Negligible at earlier times

To determine the current number of neutralinos (relic abundances), we need to solve the Boltzmann equation for early and late times

Hubble Constant

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Why are we so excited about GLAST?

• GLAST will – Study gamma radiation from Universe with a

lot more details than previous missions – explore regions never explored before in space– gives us insight in how the Universe evolved

• The GLAST Project allows us to – develop a successful partnership between DOE

and NASA

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Gamma ray Large Area Space Telescope

GLAST will measure the direction, energy and arrival time of rays

LAT: main instrument

GBM: smaller instrument catching bursts of radiation

Orbit

575 km, circular

Inclination

28.5o

Lifetime

5 years (min)

Launch Date2007

Launch VehicleDelta 2920H-10

Launch Site Kennedy Space

Center

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2007 GLAST

2001 LATBalloon Flight

Why do we need a satellite ?

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Why rays ?

satellite

~ 500 km

center of galaxiesradiate gamma rays

• Universe is transparent to rays • not affected by magnetic fields• probes early times of the Universe

Gamma rays: most violent energy processes found in Nature

Gamma rays: similar to visible light but with higher frequency

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Light – a Fingerprint of the Universe

The electromagnetic spectrum carries a lot of information about the evolution of the Universe

Optical

Rays

Credit; Lund Observatory Credit: COBE Team

Infrared

Credit: COBE Team

Microwave

Credit: WMAP Team

Microwave

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EGRET found 300 objects in 10 yrsLAT: LAT: expects to find expects to find 300 objects in 2 days300 objects in 2 days

LAT : expects to find 10,000 objects in 2 yrsLAT : expects to find 10,000 objects in 2 yrs

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Gamma-Ray Bursts

• Last from milliseconds to ~ 100 seconds• Brightest phenomenon in Universe• Several bursts expected daily • Do not know what causes them !

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galaxies radiate gamma rays

(very powerful)

Where does the energy come from?

Black holes inside the galaxy??

AGN - Supermassive Black Holes ?

Extragalactic Jet

Accretion disk

Black Hole

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Dark Matter

How is matter measured in the galaxy?

1. By calculating how fast stars go around the center of the galaxy

2. By measuring light from the galaxy and using results in an equation to

obtain amount of matter

1 and 2 give different results !!!!

Strong Evidence that Dark Matter exists

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Simulations of Local Group

Dark Matter Simulations

We do not know what dark matter is but we can guess

We use simulations to indicate how dark matter is

formed

GLAST could measure dark matter and explain its origins

Credit: B. Moore, www.nbody.net

z = 20Past

z = 5z = 10

Todayz = 1

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GLAST LAT Overview

e+ e–

Tracker

Grid (& Thermal Radiators)

Calorimeter

ACD

~150 collaborators

Measuresdirection

MeasuresEnergy

Get rid ofbackground

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How do we see gamma rays?

E --> me+c2 + me-c2

electron positron

LAT detects the gamma ray indirectly

through pair conversions

(into charged particles)

Charged particles create current in each

detector

There are 100,000 charged particles

external to the LAT for every gamma ray

in space

The unwanted charged particle background is

REJECTED by the outermost detector

( in green)

Charged particle background

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Two Tower Integration

Installation of Tower A in Single bay

Tower A in Grid. Tower B being installed in grid.

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Hole to accommodate Solar Array mast

Overview of LAT Mechanical Systems

LAT in the Delta-II fairing

Radiator

Cut-outs for possible S.A. launch locks

VCHP reservoirs

Radiator Mount Bracket at 4 corners of Grid

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GLAST Feb 2007 launch

Eduardo do Couto e Silva - ATC/LM Colloquium, June 2004 1 How many neutralinos are there? Expansion...

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