Brown University

The Brown faculty on CMS. Images Courtesy of Brown University

The Brown University High Energy Physics group has been a part of the Compact Muon Solenoid (CMS) experiment at the LHC since 2004. Presently, we have three faculty (Profs. Dave Cutts, Greg Landsberg, and Meenakshi Narain), five research associates, and four graduate students working on CMS, as well as a number of undergraduate students contributing to this exciting project. Our group helped to build a part of the CMS Silicon Tracker—a special detector, made out of silicon wafers, just like the ones used to manufacture integrated circuits—which helps us to measure the trajectories of charged particles coming out of the LHC collisions. We have also contributed to several aspects of the CMS trigger, a sophisticated system, which decides in a split second whether a particular collision is interesting enough to retain it for further investigation, or if it is due to well-known “bread-and-butter” physics and thus not worth keeping. Since we can only afford to keep one or two collisions out of a million (still about 100 collisions recorded every second!), this is a very important and challenging project, as we have to make sure that all potentially interesting collisions are kept and only really “dull” ones are being ignored.

The Brown students and research assistants on CMS. Images Courtesy of Brown University

Our group has previously focused on research at a different collider: the Fermilab Tevatron, where we gained significant experience in dealing with complex “events” resulting from colliding beams. Members of our team made major contribution to the discovery of the heaviest known elementary particle—the top quark—about a decade ago, and have conducted many searches for new particles and even new spatial dimensions. While none of these new phenomena have been found yet, the hopes are very high that the LHC will open a new era of discoveries. Our team plans to play a major role in this quest for the unknown. We will be looking for new dimensions in space, new particles, such as those predicted by supersymmetry theory, and black holes possibly produced at the LHC. While searches for new physics are one of the most exciting parts of LHC research, there are still many things not known about the top quark. The LHC will be a true top-quark “factory” with about a dozen of these particles produced every second. We will be using these events to better understand various properties of the top quark and also to calibrate the CMS detector: yesterday's discovery will quickly become an important tool for future ones!

We have also contributed and plan to continue contributing in many different ways to the development and tuning of numerous tools required to analyze the LHC data. Among these tools are the ones used to measure the energy of “jets,” narrow beams of particles that indicate if a quark or a gluon has been emitted from the collision. Some of these jets are due to the little brother of the top quark, the so-called bottom quark. We are developing techniques to distinguish bottom jets from those caused by other particles. Finally, we are working on better determination of “missing” energy in events, which could indicate the presence of new particles produced in collisions escaping the CMS detector unnoticed, such as dark matter particles. Discovery of these particles would turn the LHC from the best microscope ever built into a great telescope as well!