James Rohlf

James Rohlf

Office: PRB, Room 475. 617-353-6035
Lab: PRB, Room 459. 617-353-5635


Research Interests:

Particle Physics at the Energy Frontier

My research is in particle physics at the energy frontier. My PhD thesis, “Observation of Jets and Tests of Quantum Chromodynamics”, was the first experiment to trigger on and detect quarks scattered from proton collisions at FNAL. The innovative analysis techniques developed for that project laid the foundation for more sophisticated simulation techniques, which would become a standard in the field. After that, I went to CERN to work on the discovery of the W and Z bosons, in which I played an integral and pioneering role, especially in the identification of the first events and measurements of mass and spin. Since 1993, I have worked on the CMS experiment at CERN, where I have helped develop cutting-edge digital electronics for the detector readout, and participated in numerous physics analyses, including the discovery of the Higgs boson

Selected Publications:

“Combined Measurement of the Higgs Boson Mass in pp collisions at sqrt(s) = 7 and 8 TeV with the ATLAS and CMS Experiments,” G. Aad et al., Phys. Rev. Lets. 114, 191803 (2015).

“Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC,” S. Chatrchyan et al., Phys. Lett. B716, 3061 (2012).

“Experimental Observation of Lepton Pairs of Invariant Mass Around 95- GeV/c2 at the CERN SPS Collider,” G. Arnison et al., Phys. Lett. B126, 398 (1983).

“Experimental Observation of Isolated Large Transverse Energy Electrons With Associated Missing Energy at sqrt(s) = 540 GeV,” G. Arnison et al., Phys. Lett. B122, 103 (1983).

“Observation of Jets of Particles at High Transverse Momentum and Comparison With Inclusive Single Particle Reactions,” C. Bromberg et al., Phys. Rev. Lett. 38, 1447 (1977).

For a full list of publications, please see the attached CV.


  • Ph.D. Physics, Caltech (1980)
  • M.S. Physics, UCLA (1975)
  • B.A. Physics and B.S. Mathematics, University of Minnesota (1973)


publications: inspire

citations summary

Modern Physics Book

As a graduate student I worked on the first experiment to trigger on hadron jets with a calorimeter, Fermilab E260. My thesis used the model of Field and Feynman to compare our observed jets from hadron collisions to that from electron-positon collisions and made detailed acceptance corrections to arrive at first the measurement of quark-quark scattering cross sections. My thesis is published in Nuclear Physics B171 (1980) 1. Thesis committee:  G. C. Fox (advisor), C. Barnes, R. P. Feynman, R. Gomez

At the Cornell Electron Storage Rings, I worked on the discovery of the Upsilon (4S) resonance and using novel event shape variables developed by Steven Wolfram and my thesis advisor, Geoffrey Fox. i performed particle identification of kaons and charmed mesons to establish the quark decay sequence, b --> c.

At CERN  worked on the discovery of the W and Z bosons and measurement of their properties.

Presently, I am working on the Compact Muon Solenoid (CMS) experiment at the CERN Large Hadron Collider (LHC) which is searching for the origin of electroweak symmetry breaking.



In the news:

Research Descriptions:

Higgs Detection at The Compact Muon Solenoid Detector at the Large Hadron Collider


The Compact Muon Solenoid (CMS) is a 14 kiloton detector designed to search for new physics at an unprecedented distance scale of 10-19 m at the CERN Large Hadron Collider (LHC). The detector consists of 220 square meters of silicon pixels and strips (80 million channels) for precision charged particle tracking, 75k lead-tungsten crystals for precision electron and photon measurements, a highly segmented 1000-ton brass hadron-calorimeter plus a quartz-fiber forward calorimeter to measure jets from quark and gluon scattering and energy balance, all surrounded by precision muon chambers embedded in the return yoke of the magnet. Overall, the detector features nearly complete solid-angle coverage and can precisely measure electrons, photons, muons, jets and missing energy over a large range of particle energies. These broad capabilities of the CMS detector allow the exploration of electroweak symmetry breaking and will enable the potential discovery of physics beyond the Standard Model.

The CMS trigger and data acquisition systems are responsible for ensuring that physics-enriched data samples with potentially interesting events are recorded with high efficiency and good quality. The experiment has a two-level trigger system, unlike most other hadron collider experiments that have more traditional three-level systems. The first physical level is hardware-based and is called the “Level-1 Trigger” (L1) while the second physical level is software-based and is called the “High-Level Trigger” (HLT). L1 uses information from the calorimeters and muon detectors and is designed to select, in less than 1 ms, the most interesting events starting from a total input (collision) rate of about 40 MHz. The HLT processor farm further decreases the event rate from around 100 kHz to around 400 Hz, before data storage. The trigger system, therefore, has to provide a high selectivity of ~10-5 with respect to the active LHC bunch crossings while ensuring that the ability to select rare, exotic events is preserved. Boston University has played a leading role in the coordination of the CMS Trigger effort with Bose serving as the CMS Trigger Coordinator (2014-2016) and as the CMS Deputy Trigger Coordinator (2011-2013). Group members were involved in the design and commissioning of the CMS HLT and continued to spearhead the effor thereaftert.  Many of the BU personnel resident at CERN served as HLT on-call experts during the LHC Run 1 (Avetisyan, Carerra, Fantasia and Sperka) and Run 2 (Avetisyan, Rankin, Richardson).

The collision rate at the LHC also presents enormous technical challenges on the design of readout electronics due to the intense radiation environment and the high speed at which millions of channels of data must be processed. The Boston University group has a leadership role in calorimeter electronics and related software (Rohlf and Sulak). The group has designed and built the data concentrator, a sophisticated piece of digital electronics based on modern field programmable gate arrays (FPGAs) to read out the hadron calorimeter. Group members have also led the custom design of the 18-channel hybrid photo-diode used to convert scintillation light from the calorimeter into electrical signals. We have also designed the electronics to feed calorimeter signals into the muon trigger to greatly reduce the backgrounds in the online event selection. Members of the BU CMS team have also helped design the two hadronic forward calorimeters which are positioned at either end of the CMS detector, to pick up the myriad particles coming out of the collision region at shallow angles relative to the beam line. Group members also play a key role in the day-to-day operation of the calorimeter.

The Boston University collaborators (Bose, Rohlf, and Sulak, their postdocs Girgis and Pinna, and their grad students, with their engineers Eric Hazen and Shouxiang Wu) are reaping the physics benefits of our investment in detector hardware, trigger and algorithm development. Group members are making significant contributions to physics analyses involving searches for new particles and the hunt for the Higgs Boson. These analyses include (among many others) searches for heavy gauge bosons and exotic WZ resonances.  We are also playing a leading role in the study of diboson production; the latter is critical for increasing the sensitivity of our Higgs searches and thereby help understand the mechanism of electroweak symmetry breaking.

Bose has served as the co-convener of the Electroweak Diboson group (2011), co-convener of the Resonances group within the Beyond Two Generations physics group (2012-2014), and co-convener of the Beyond Two Generations group (2016-2017). She is currently serving a two-year term as CMS Physics Co-coordinator (2017-2019). Sulak serves on the Advisory Board of the Hadron Calorimeter, and manages some 15 undergraduates as Director of the BU/CERN/DOE Internship Program.