ATLAS-SCT : Off-Detector Stat

Jonathan Butterworth

University College London

14th June 2006

High Energy Collisions and Fundamental Physics
or
Why the proton is like a TARDIS

Experimental High Energy Physics

Very large accelerators to collide the particles

LEP & LHC at CERN, Geneva ~ 27 km

HERA at DESY, Hamburg ~ 7 km

Very large collaborations of physicists and engineers needed to build them, run them and analyse the data.

ZEUS (HERA)~400 physicists

ATLAS (LHC) ~ 2500 physicists

Large numbers of countries needed to be able to afford them!

Experimental High Energy Physics

A relevant example – Hadron-Electron Ring Anlage (HERA) Hamburg.

Collaborations

These are not “general user” experiments, but general purpose.

Everyone needs all the data

Always a “headline” physics program to which everyone contributes.

Always room to make a difference, either by finding smart ways to do this better, or by finding new things to do.

Serendipitous science as well as the things they are built for.

Stamp collecting

SM particles and forces

Some quantum mechanics

Feynman diagrams and virtual particles.

Splitting of particles, resolution, wavelength and energy.

Photons and protons at HERA

ZEUS, CTD wiring etc etc.

DIS – what it was built for

Photons from electrons

Jets

Photons and hadrons

Photon fundamental, hadron a bunch of quarks

Why the photon sometimes looks like a hadron

Two components – resolved and direct.

xgamma

angular distribution.

Massive particles “inside” light ones

Photon is massless, quarks are not

In fact, can even contain heavy quarks (charm and beauty)

Mass means smaller fluctuations

Resolution gives you the ability to probe very small fluctuations and create very massive (virtual or real) particles.

Charm, Beauty in Protons and Photons

the tardis

The weak force

W, Z reprise

DIS, unification.

W, Z being heavy explains the different strengths of the forces.

Why are the W and Z so heavy when the photon is light?

Large Hadron Collider and ATLAS

Picture of CERN

Picture of ATLAS

First machine to operate at sufficiently high energies that we are guaranteed to get information on how the W,Z and photon symmetry is broken.

Higgs or what?

In the standard model, the Higgs explains this.

Is it right?

Not at liberty to just invent stuff. Standard Model hangs together very beautifully.

e.g....

W, Z inside the proton

More tardis stuff

WW scattering.

No prediction without the Higgs contributions.

LHC will be able to measure this for the first time.

So watch out in 2007...

2005-12-12T09:36:11