University of California, Riverside

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Robert Clare

Robert Clare


Department of Physics & Astronomony
Physics 3032
(951) 827-5335

Research Areas

  • Experimental High Energy Physics

Professor Clare has been a leader in the studies of electroweak physics for many years. He chaired the LEP Electroweak Working Group from 1996-2001, which was responsible for combining the results of the 4 LEP experiments to obtain the best possible constraints on the Standard Model. The data led to predictions of the top quark mass before it was discovered at the Tevatron. With the latest measurements of the top quark mass at the Tevatron and W boson mass at both LEP and the Tevatron, the data have been used to predict the Higgs boson to be lighter than about 300 GeV. This is well within the discovery potential of the upcoming experiments at CERN's Large Hadron Collider (LHC).

Professor Clare and his team are now taking part in the commissioning of the Compact Muon Solenoid (CMS) facility, one of the two large detectors that will exploit the LHC. In the new energy region explored by LHC, one will hope to finally see signs of physics beyond the Standard Model, but among the prime programmatic goals of the LHC will be the search for the Higgs boson, believed to be responsible for electroweak symmetry breaking in the Standard Model. Data taking was originally scheduled to start in Fall 2008; however, because of the damage that occurred on Sept 19, 2008, during LHC commissioning, we won't see data until June 2008, at the earliest.

The ability of a detector to trigger on muons in very high energy hadron collisions is crucial to extract the physics in the LHC environment, which will be characterized by very high luminosity and very high data rates. American physicists from a number of university and national laboratory groups are responsible for muon detection in the endcap region of the CMS detector. The UCR group was involved in building and testing the "Cathode Strips Chambers" for this region. Production of the chambers has finished now, and all chambers have been installed. Commissioning work is on-going. Members of the group are playing an integral role in the development of the muon reconstruction software, as well as investigations into physics channels involving muons. Among the most exciting prospects would be the discovery of the Higgs boson. The group is responsible for the analysis of the Higgs decaying into two Z bosons, with the subsequent decay of the Z into muons (or electrons). As a large number of the decay muons will go in the forward direction, this project ties in nicely with the hardware the group has worked on. Another important source of muons will be the decay of top quarks. The study of top quark production is interesting in its own right. In addition, top quark production will be a background in the search of many new particles, including the Higgs. The group is also responsible for the development of the Detector Control System (DCS) for the end cap muon detector.

The computing resources necessary to analyze the CMS data will be enormous, as approximately one Petabyte of data will be recorded per year. UCR is involved in establishing US-based computing facilities to allow physicists to participate in the analysis from their home institutes. This requires hardware and software to work in a distributed grid of world-wide resources. Currently available at UCR is a small cluster consisting of 40 Opteron cores and about 30 TB of disk storage. The cluster is a Tier-3 center, part of the CMS world wide computing system. Professor Clare helps organize the Tier 3 computing for all of the US institutions in CMS.


Ph.D., 1982, Massachusetts Institute of Technology


  1. The CMS experiment at the CERN LHC, The CMS Collaboration, Journal of Instrumentation 3, S08004 (2008).
  2. Efficiency of finding muon track trigger primitives in CMS cathode strip chambers, R. Breedon, et al., NIM A592, 26 (2007).
  3. CMS Technical Design Report, Volume II: Physics Performance, The CMS Collaboration, Journal of Physics G 34, 995 (2007).
  4. Precision Electroweak Measurements on the Z Resonance, The ALEPH, DELPHI, L3, OPAL and SLD Collaborations, Physics Reports 427, 257 (2006) [arXiv:hep-ex/0509008].
  5. Measurement of the mass and the width of the W boson at LEP, The L3 Collaboration, Eur. Phys. J. C 45, 569 (2006) [arXiv:hep-ex/0511049].
  6. The CMS high level trigger, The CMS Collaboration, Eur. Phys. J. C 46, 605 (2006) [arXiv:hep-ex/0512077].
  7. Measurement of the cross section of W-boson pair production at LEP, The L3 Collaboration, Phys. Lett. B 600, 22 (2004)
  8. Present and future electroweak precision measurements and the indirect determination of the mass of the Higgs boson, U. Baur, et al., [arXiv:hep-ph/0202001].
  9. Measurement of the W-pair Production Cross Section and W-Decay Branching Fractions in e+e- Interactions at √s = 189 GeV, The L3 Collaboration, Phys. Lett. B 496, 19 (2000).
  10. Measurements of Cross Sections and Forward-Backward Asymmetries at the Z Resonance and Determination of Electroweak Parameters, The L3 Collaboration, Eur. Phys. Jour. C 16, 1 (2000).
  11. Measurement of the Properties of the η' and Search for Other Resonances in γ γ -> η π0 π0, The Crystal Ball Collaboration, Phys. Rev. D 36, 2633 (1987).

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University of California, Riverside
900 University Ave.
Riverside, CA 92521
Tel: (951) 827-1012

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Tel: (951) 827-5331
Fax: (951) 827-4529