CMS progress report
Lothar Bauerdick, head of the CMS Center at Fermilab, wrote this week's column.
I spent last week at the CMS Physics Meeting in Bodrum, Turkey. The meeting focused on the progress of reconstructing physics objects in the detector, such as leptons, jets and missing transverse energy that allow physicists to identify and measure collisions containing heavy quarks, massive vector bosons like the Z and the W, and possibly other heavy, undiscovered objects.
As the results presented at the summer conferences have shown, CMS is doing impressively well regarding operational efficiencies and detector performance and is also progressing quickly in understanding the complex detector. Physicists are processing the newly arriving data very quickly, and the results look clean and remarkably similar to our Monte Carlo simulations. This includes even the particularly difficult measurement of missing energy, which is simulated over many orders of magnitude. CMS physicists are readying the tools that they will use to discover signatures of new physics.
Physics results are coming in quick succession. We showed the first measurements of Standard Model processes, such as W and Z boson observations; established the top quark signal, and already provided first limits on physics beyond the Standard Model by looking for anomalies in very high energy particle jets.
CMS has been able to observe top candidate events with luminosities of only a few 100 inverse nanobarns. By November, we expect to have about 1,000 top quark events, which is a good fraction of the size of the total top quark sample the Tevatron experiments have collected so far.
CMS is also looking at intermediate energies where we have seen a first unexpected result in analyzing correlations between particles in high-multiplicity events.
In previous months LHC luminosity has grown exponentially. Filling 100 billion protons per bunch after just a few months of running was an important milestone on the way to achieving an integrated luminosity of one inverse femtobarn by the end of next year.
CMS has now collected a luminosity of 3.3 inverse picobarns, already a factor of 10 above what was available for the summer conferences. This week the machine started again after a technical stop. The plan is to increase luminosity by creating bunch trains. Each train has several bunches following one another closely. The trains initially will have four bunches and then increase to eight and then 12.
It has been an amazing summer for CMS and the LHC, and the fall promises to be even more exciting.