{"id":374,"date":"2026-08-03T15:15:52","date_gmt":"2026-08-03T19:15:52","guid":{"rendered":"https:\/\/www.bu.edu\/physics\/?post_type=profile&p=374"},"modified":"2026-08-08T13:38:04","modified_gmt":"2026-08-08T17:38:04","slug":"james-rohlf","status":"publish","type":"profile","link":"https:\/\/www.bu.edu\/physics\/profile\/james-rohlf\/","title":{"rendered":"James Rohlf"},"content":{"rendered":"

James W. Rohlf<\/a> (Jim)<\/path><\/path><\/path><\/path><\/svg><\/a>: Professor of Physics at Boston University.<\/p>\n

Experimental particle physics<\/a> and cosmology<\/a><\/h3>\n

Research pages:<\/strong> home<\/a> \u00b7 DESI \u2014 dark energy<\/a> \u00b7 CMS \u2014 calorimeter electronics, AMC13, jets<\/a> \u00b7 UA1 \u2014 W and Z discovery<\/a> \u00b7 CLEO \u2014 Upsilon(4S) discovery<\/a> \u00b7 E260 \u2014 first calorimeter jet trigger<\/a><\/p>\n

Since 2024 I have worked on the Dark Energy Spectroscopic Instrument<\/a> at Kitt Peak<\/a> National Observatory, which has built the largest three-dimensional map of the universe<\/a> ever made, from the redshifts of tens of millions of galaxies and quasars<\/a>. DESI measures the expansion history<\/a> of the universe through baryon acoustic oscillations<\/a> and the Lyman-alpha forest<\/a>, constraining the equation of state of dark energy<\/a> and the sum of the neutrino<\/a> masses. The data favor a dark energy density that evolves with time \u2014 a departure from \u039bCDM<\/a>, the standard cosmological model, which is under strain from the Hubble tension<\/a> as well.<\/p>\n

Since 1991 I have worked on the Compact Muon Solenoid<\/a> experiment at the CERN Large Hadron Collider<\/a>, having come to it by way of the Superconducting Super Collider, where I measured the radiation hardness of small drift tubes for the L* detector. My work on CMS has centered on the hadron calorimeter<\/a> and its electronics. I led the design, performance and calibration of the HCAL barrel, outer and endcap wedges, and the synchronization and timing of the calorimeter using test beam, cosmic ray and LHC beam data. I designed two generations of the HCAL Data Concentrator Card<\/a>, then the AMC13<\/a>, which provides timing, trigger and data acquisition for the experiment, and most recently the Apollo ATCA<\/a> platform for the High-Luminosity LHC upgrade. I also worked on the silicon photomultiplier<\/a> readout and the mapping of calorimeter trigger primitives. On the physics side I have measured the angular distributions of high transverse momentum jets, contributed the hadron calorimeter, jets and missing energy sections of the CMS Physics Technical Design Report<\/a> Volume 1, and participated in the analyses that discovered the Higgs boson and that established the formation of the quark-gluon plasma<\/a> in heavy-ion collisions, including the sequential suppression of the Upsilon states<\/a>.<\/p>\n

At CERN I worked on the UA1 experiment<\/a> and the discovery of the W<\/a> and Z bosons<\/a>, playing an integral role in the identification of the first events. The neutrino from a W decay leaves only missing transverse energy, which admits two kinematic solutions; with the help of Lev Okun I recognized that one solution is often kinematically forbidden while the two are otherwise nearly identical, which made the decay angle accessible and allowed the spin of the W to be measured. I reported that result<\/a> at the 12th International Conference on High-Energy Accelerators (HEACC 83) at Fermilab. I also built readout electronics for the experiment, including the transition from FASTBUS to VME<\/a>.<\/p>\n

At the Cornell Electron Storage Ring I discovered the Upsilon(4S)<\/a> resonance, using the event-shape<\/a> variables newly invented by Stephen Wolfram and my thesis advisor, Geoffrey Fox. I also performed the particle identification of kaons<\/a> and charmed<\/a> mesons that established the quark decay sequence b \u2192 c, work that set the foundation for subsequent reconstruction of exclusive B meson decays<\/a>\u00a0by CLEO<\/a>.<\/p>\n

My PhD thesis, \u201cJet Production in High-Energy Hadron-Proton Collisions<\/a>,\u201d came from Fermilab E260<\/a>, the first experiment to trigger on hadron jets with a calorimeter and therefore the first to detect quarks scattered directly out of proton collisions. Using the model<\/a> of Field and Feynman, I compared the jets we observed in hadron collisions with those seen in electron-positron collisions, and made the detailed acceptance corrections needed for the first measurement of quark-quark scattering<\/a> cross sections. The analysis techniques developed there laid the foundation for simulation methods that later became standard in the field. My thesis committee was G. C. Fox (advisor), C. Barnes, R. P. Feynman, and R. Gomez.<\/p>\n

Elsewhere:<\/strong> DESI, talks and papers<\/a> \u00b7 selected talks, 1979\u20132026<\/a> \u00b7 honors<\/a> \u00b7 INSPIRE<\/a> \u00b7 ORCID<\/a> \u00b7 BU DESI<\/a><\/p>\n

Selected papers<\/strong><\/p>\n

\u201cDESI DR2 Results IV: Alcock-Paczy\u0144ski Measurements from the Lyman-\u03b1 Forest and Cosmological Constraints,\u201d A. G. Adame et al. (DESI Collaboration), arXiv:2607.27410 (2026).<\/a><\/p>\n

\u201cDESI DR2 Results II: Measurements of Baryon Acoustic Oscillations and Cosmological Constraints,\u201d M. Abdul Karim et al. (DESI Collaboration), Phys. Rev. D 112, 083515 (2025).<\/a><\/p>\n

\u201cPositive Neutrino Masses with DESI DR2 via Matter Conversion to Dark Energy,\u201d S. P. Ahlen et al. (DESI Collaboration), Phys. Rev. Lett. 135, 081003 (2025)<\/a>.<\/p>\n

\u201cCombined Measurement of the Higgs Boson Mass in pp Collisions at sqrt(s) = 7 and 8 TeV with the ATLAS and CMS Experiments,\u201d G. Aad et al., Phys. Rev. Lett. 114, 191803 (2015)<\/a>.<\/p>\n

\u201cObservation of a New Boson at a Mass of 125 GeV with the CMS Experiment at the LHC,\u201d S. Chatrchyan et al., Phys. Lett. B 716, 30 (2012)<\/a>.<\/p>\n

\u201cExperimental Observation of Lepton Pairs of Invariant Mass Around 95 GeV\/c^2 at the CERN SPS Collider,\u201d G. Arnison et al., Phys. Lett. B 126, 398 (1983)<\/a>.<\/p>\n

\u201cExperimental Observation of Isolated Large Transverse Energy Electrons with Associated Missing Energy at sqrt(s) = 540 GeV,\u201d G. Arnison et al., Phys. Lett. B 122, 103 (1983)<\/a>.<\/p>\n

\u201cObservation of the Production of Jets of Particles at High Transverse Momentum and Comparison with Inclusive Single Particle Reactions,\u201d C. Bromberg et al., Phys. Rev. Lett. 38, 1447 (1977)<\/a>.<\/p>\n

Recent talks<\/strong><\/p>\n

\u201cResults From DESI,\u201d APS Division of Particles and Fields, Fermilab, 22 July 2026 \u2014 plenary talk, 41 slides. Conference record<\/a>.<\/p>\n

\u201cRecent Cosmological Results from DESI,\u201d PPC 2025: XVIII International Conference on Interconnections between Particle Physics and Cosmology, Deadwood, South Dakota, 23 June 2025 \u2014 plenary talk, 42 slides. Conference record<\/a>.<\/p>\n

I received a B.A. in physics and a B.S. in mathematics from the University of Minnesota in 1973, an M.S. from UCLA in 1975, and a Ph.D. from Caltech in 1980, where my advisor was Geoffrey Fox. I worked on Fermilab E260 as a graduate student, then on CLEO at the Cornell Electron Storage Ring (1980\u20131983) and UA1 at CERN (1983\u20131991). I joined the Boston University faculty in 1988, and I have been a member of CMS since 1991 and of DESI since 2024. I am the author of several physics texts, including Modern Physics from \u03b1 to Z0<\/sup><\/a><\/em>.<\/p>\n