In Brief ...As a postdoc (Research Associate) at Princeton University I work on
the CMS (Compact Muon Solenoid) experiment at the LHC (Large Hadron
The LHC is an energy frontier particle physics experiment that is currently under construction at the CERN particle physics laboratory in Geneva. Scheduled to turn on in 2007, the accelerator will ultimately collide two proton (p) beams together at a centre of mass energy of 14 TeV. Collisions of lead (Pb) nuclei at an energy of 1150 TeV will also be studied. CMS is one of five experiments - ATLAS, ALICE, CMS, LHCb and TOTEM - that will study the products of beam collisions at the LHC.
A proton with an energy of 7 TeV will travel at approximately the speed of light (0.99999999c), taking just 89 millionths of a second to negotiate the 26.7 km LHC tunnel. The LHC accelerator has the capacity to circulate 3564 proton bunches, which at 7 TeV gives a bunch spacing of 25 nano-seconds. Of the possible 3564 bunches 2808 will be filled, each containing 1011 (about 100 billion!) protons. With 2808 filled bunches, bunch crossings will occur in the centre of the CMS detector about 32 million times every second (a rate of 32 MHz). At design luminosity this will yield roughly 800 million proton-proton scattering events in the CMS detector every second!
But why do we want to do this? The answer, in short, is that although we know more than ever about the way our universe works, our knowledge is still far from complete. In fact current models of the elementary particles, which provide an excellent description of the observed physics at low energies, leave us with many open questions. One of the most important questions to answer is: How did the particles we see today get their observed masses? Many physicists believe that the elementary particles are endowed with mass via the so-called Higgs mechanism, but this theory requires the existence of a particle (the famous Higgs boson) that has never been seen! The discovery (or NOT!) of the Higgs boson is one of the main goals of the LHC. In addition, however, physicists also have reason to believe that there should be a more fundamental "underlying" theory than the one we currently use to describe the elementary particle interactions (the "Standard Model"). Evidence points to the fact that this "new" physics should appear at around the TeV scale, hopefully within the reach of the LHC. There are many theories as to the exact form this new physics might take - supersymmetry, large extra dimensions, technicolor models, etc. As experimenters we are hoping to discover a non-standard model signature in our data that would indicate the presence of the expected new physics. If we are lucky, we might also be able to discern which (if any!) of the currently popular theories describe our discoveries.
At Princeton we are working on real time luminosity monitoring using the CMS forward hadronic calorimeters. We are also working on luminosity monitoring via W and Z counting and are responsible for monitoring the physics performance of the High Level Trigger (HLT).
Prior to commencing my postdoctoral work at Princeton, I was a graduate student at Cornell University in Ithaca, NY. I worked on the CLEO-c experiment, an electron-positron collider studying the physics of charm quark resonances. The major work of my doctoral dissertation (completed in August 2006) was a study of the exclusive semileptonic decays of D mesons to pseudoscalar pion and kaon final states. And why is that interesting? Well ... you can read my thesis to find out!