Service WorkIn large collaborations such as CMS, all scientists are expected to contribute to the operation of the detector. These contributions are needed to ensure that the data from CMS are reliable, well calibrated, and easy to access.
Among other things, the Princeton group leads in the measurement of luminosity in CMS. Luminosity is a basic measure of accelerator performance, indicating how many collisions have occurred in a particular data sample. It is used in essentially all physics analyses.
Luminosity is measured in a variety of ways and a major part of the luminosity effort involves cross checks among the different methods. Most methods are calibrated using a technique called the Van der Meer scan.
Analysis of luminosity data offers an excellent way for students new to CMS to get involved in data analysis. For experienced analysts, it offers a change of pace and a unique set of challenges that differ from those in many physics analyses.
One of the detectors used to measure the luminosity online is the Pixel Luminosity Telescope (PLT). This detector was built by a Princeton-Rutgers-Tennessee-CERN collaboration.
Physics AnalysisCMS offers a staggering array of physics opportunities. Recent projects in our group include searches for displaced di-jets and searches for di-Higgs production using the final state H-->gamma gamma b b.
The displaced di-jet analysis , which was the first of its type in CMS, was led by former graduate student Andrzej Zuranski. Current graduate students Jinyu Luo is working an application of this analysis to the Run 2 data.
Former graduate student Phil Hebda participated in the di-Higgs analysis , which will soon be submitted for journal publication. This analysis will continue to be of interest throughout Run 2 as the data samples grow in size. Although observation at the standard model rate will likely remain somewhat beyond the reach of the LHC, numerous models predict enhancements and the experience gained in searching will be useful in the ultimate observation of this important process.
Finally, we emphasize that there are many topics of potential interest
and students in the group are encouraged to pursue their interests.
High-Luminosity LHC Detector UpgradeThe Princeton group has a long history of detector hardware development, which will continue into the foreseeable future. One area of active involvement is the CMS Outer Tracker upgrade. Princeton has excellent micro-electronics fabrication facilities, including the use of three automatic wirebonders, two of which are owned by the Princeton HEP group. One of the bonders is located in the HEP group's microelectronics lab, which is shown in the photo below.
A second, recently acquired bonder, which has a large (12" x 12") work table, and is thus particularly useful for the fabrication of detectors, is located in a nearby room. As a prelude to detector production, the group is engaged in R&D, an activity that is especially ripe for student involvement. The detector R&D thus far has taken advantage of our close connection to the Princeton Institute for the Science and Technology of Materials .
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