Lee Roberts

Lee Roberts

Office: PRB, Room 373. 617-353-2187
Lab: PRB, Room 270. 617-353-9453


Research Interests:

Properties of Subatomic Particles

Much of my research career has been centered on properties of subatomic particles, their interactions and the fundamental symmetries which govern these interactions. From 1989 until its completion in 2004 I served as Co-Spokesman for the muon (g-2) experiment at Brookhaven National Laboratory (E821). We measured the anomalous magnetic moment of the muon to a relative precision of 0.54 ppm (parts per million). At present there is a 3.4 standard-deviation difference between the experimental value and the standard-model value, which could be an indication of new physics such as supersymmetry. I am now co-leading E989, a new experiment at Fermilab which will increase the precision to 0.14 ppm in order to confirm whether there is such a discrepancy. The superconducting storage ring has been moved from Brookhaven to Fermilab and is being installed in a new building. We expect to take first beam in 2016. I am also a member of the Mu2e Collaboration that Professor Miller is leading. For more information, please go to my research website.

Selected Publications:

“First Direct Observation of Time Reversal Noninvariance in the Neutral Kaon System”, A. Angelopoulos et al., (CPLEAR Collaboration), Phys. Lett. B 444 43 (1998)

“Final Report of the Muon E821 Anomalous Magnetic Moment Measurement at BNL”, G. Bennett, et al., (Muon (g 2) Collaboration), Phys. Rev. D 73, 072003 (2006)

“Muon (g 2): experiment and theory”, James P. Miller, Eduardo de Rafael and B. Lee Roberts, Rept. Prog. Phys. 70, 795-881, 2007, (293 citations).

“Physics at a future Neutrino Factory and super-beam facility”, A. Bandyopandhyay, et al. (The ISS Physics Working Group) Editors: S.F. King, K. Long, Y. Nagashima, B.L. Roberts and O. Yasuda, Rep. Prog. Phys. 72 (2009) 106201 (185pp),

“The Muon (g 2) Theory Value: Present and Future” T. Blum, A. Denig, I. Logashenko, E. de Rafael, B.L. Roberts, T. Teubner and G. Venanzoni, arXiv:1311.2198v1 [hep-ph] 9 Nov 2013

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



  • Fellow, American Physical Society

In the news:

Research Descriptions:


Our muon lifetime experiment (MuLan Collaboration),  at the Paul Scherrer Institut,  which grew out of Brookhaven E821, has published a 1 ppm measurement of the muon lifetime in Physical Review Letters, which improves the precision of the Fermi constant for muon decay. See Phys. Rev. Lett. 106, 041803 (2011), and Phys.Rev. D 87, 052003 (2013)

Muon (g-2) project at Fermilab

This experiment will upgrade of BNL E821. Boston University physicists are playing a leading role. The goal is a factor of four improvement on the precision on the muon anomalous magnetic moment, which will require 21 times the data, approximately 200 million analyzed events, and a factor of three improvement in the systematic errors. The goal is to clarify whether the evidence obtained at Brookhaven is a signal of New Physics entering at the loop level, or a statistical fluctuation.


Neutrinoless Muon to Electron Conversion

The goal of the Mu2e experiment (pronounced 'mew to ee') is to measure the rate of a muon converting into an electron with no accompanying neutrinos to a precision 10000 times better than previous experiments. Such a violation of charged lepton flavor conservation has never been seen by charged leptons such as muons and electrons. It has already been seen for neutral leptons, neutrinos, in the form of neutrino oscillations. A positive signal is a sure sign of new physics. Mu2e is one of the flagship experiments in the future Fermilab program. It currently has CD0 level (initial) approval at the DOE and is in the process of obtaining CD1 status (funding for a full detailed engineering design).