Princeton University

The goal of high energy physics is the understanding of the elementary particles that are the fundamental constituents of matter. The fabulous success of the Standard Model has given us a framework for interpretation of most particle interactions, but it has also created a foundation from which we can begin to explore a deeper level of issues such as the origin of mass, the preponderance of matter over antimatter in the Universe, the identity of "dark matter," the physics of the Big Bang, and the microscopic structure of space-time. The most direct experimental path to the understanding of such issues uses particles of the highest achievable energies, as available at the Large Hadron Collider at CERN (Switzerland).

The Princeton group joined the CMS experiment at the LHC in 1994 when our effort mostly concentrated on the Electromagnetic Calorimeter (ECAL) and Software reconstruction. Since then our activity in CMS has grown considerably. 

At present the group consists of 5 Faculty members, 3 Senior Physicists, 3 Post-docs, 4 Engineers, and 6 Graduate Students. We are heavily involved in the following activities:

  • LHC Physics Center:  Princeton is responsible for co-leading the LHC Physics Center at Fermilab.  Several faculty members are involved in coordinating the US physics effort and maintain a strong collaboration with other US groups.
  • Hadron Calorimeter (HCAL):  The Princeton group designed and built the calorimeter trigger timing distribution boards, used for HCAL and ECAL.  Our group continues to be a strong component of the commissioning effort.  Princeton co-leads the HCAL Detector Performance Group culminating in strong contributions to the global testing of the CMS detector under run conditions.  The group is also making dedicated lifetime tests of the HPD photodetector in a 4-Tesla magnet at Princeton.
  • Luminosity measurements (Lumi): The Princeton group is responsible for measuring, monitoring, and reporting the luminosity delivered to CMS by the LHC.   Luminosity information is fundamental to almost every measurement that will be made by CMS.  We pursuing a number of different approaches to measuring the luminosity.  One technique uses signals from the forward hadronic calorimeter (HF), while another is based on a proposed device known as the Pixel Luminosity Telescope (PLT). 
  • Beam Radiation Monitoring (BRM): The Princeton group is involved in measuring the amount of radiation entering the CMS detector.   The beams of the LHC are capable of causing radiation doses that could do serious damage to the components of the CMS detector in a very short time.   It is therefore essential to monitor the beams closely so as to obtain an early warning of abnormal beam conditions.
  • Investigation of flavor physics: Princeton is leading the CMS group devoted to the study of bottom and charm quarks, which will be key elements in the study of quark “flavor” at unprecedented center of mass energies when the LHC turns on.  One of the primary goals of the B Physics Group will be to search in first-year data for extremely rare decays of the B meson that might show hints of physics beyond the Standard Model; an approach that will complement direct searches for new particles with masses near one trillion electron volts. 
  • Computing and Software (Soft): Princeton is involved in the development of the computing and software used to store, process and analyze the data from the detector and accompanying simulations. The unprecedented data rates from the LHC and the globally distributed nature of the available computing resources are significant challenges along the path to extracting physics results from CMS. Group members hold key roles in the development of the data and workflow management system, the calibrations software, the core application framework, and the integration of the offline software.