Michael John Murtagh, chair of the Brookhaven National Laboratory’s physics department, a world authority on neutrino interactions, and a leader of the particle and nuclear physics communities at BNL, died on 12 July 2001 in Stony Brook, New York, from a heart attack.
Murtagh was born in Armagh, Northern Ireland, on 27 July 1943. In 1964, he completed his undergraduate studies in physics and mathematics at St. Patrick’s College, National University of Ireland, and earned a master of science degree in physics in 1965 at University College, Dublin. He received his PhD in particle physics from Harvard University in 1974; his adviser was Richard Wilson. Murtagh’s thesis explored the properties of hadrons produced in deeply inelastic muon-proton collisions, a study that evolved into a career-long focus on the physics of lepton-hadron collisions and their underlying electroweak interactions.
Even as a student, Murtagh began to distinguish himself as an independent and insightful thinker. He played a primary role in the design (in 1970) of the recoil hadron measurement apparatus for his thesis experiment. This was a significant achievement for a graduate student since experimental high-energy physics collaborations had already begun to grow and the ability of a student to have a direct impact began to diminish.
Immediately after completing his PhD, Murtagh moved to BNL, where he rose through the ranks from his initial appointment as a research associate to his final rank as a senior scientist and chair of the physics department. At BNL, he joined the neutrino group on a series of experiments using the seven-foot bubble chamber. He was a master of many trades, exhibiting prowess in hard-ware and software development as well as in data analysis. He played a crucial role in unearthing much of the physics derived from the study of neutrino interactions. This effort involved the important discovery in 1975 of the first charmed baryon and detailed studies of neutrino proton and neutron interactions at energies of a few GeV. This experiment yielded precise values for neutrino cross sections, a measurement of the axial vector form factor in quasi-elastic reactions and observation of neutral currents.
In 1975, at Fermilab, the BNL group collaborated on another series of experiments with the 15-foot bubble chamber filled with neon and hydrogen. Murtagh was a lead member of the BNL group that confirmed, in 1977, charm baryon production in neutrino interactions via the analysis of dilepton events. In 1979, the same collaborators examined the nonleptonic events, thus also confirming the existence of the first charmed baryons with a precise measurement of their mass. Murtagh also led the analysis of neutrino-electron elastic scattering events, resulting in one of the first measurements of the electroweak mixing angle , which was in good agreement with the Weinberg-Salam model. He headed the analysis of neutral correct events, and, in the same experiment, also led the search for neutrino oscillations. His result was the standard for more than two decades.
Murtagh’s experimental interest then turned to using electronic techniques to explore some of these same issues. From 1978 to 1989, at BNL, he played a significant role in the design, construction, and use of a 100-ton neutrino detector at the Alternating Gradient Synchrotron. The detector yielded large amounts of data on both neutrino-electron and neutrino-proton elastic scattering. A precise value was derived for the Weinberg angle, which was important for verifying electroweak unification. A by-product was a limit on neutrino oscillations for the small mixing-angle solution. Murtagh also contributed to the physics case for building the Colliding Beam Accelerator at BNL and the US Department of Energy’s Superconducting Super Collider.
After actively pursuing an innovative, long-baseline neutrino oscillation experiment at BNL, Murtagh joined the MINOS experiment at Fermilab in 1999. Shortly before his death, he had become actively interested in how best to measure the critical unknown parameters in the neutrino sector.
Murtagh liked three things: soccer, physics, and people. In 1997, when he assumed the chair of the BNL physics department, he won enthusiastic respect for his inclusive style. He made certain that voices were heard before decisions were made and encouraged people to reach their full potential. Murtagh never distinguished physics from personalities. To him, any new idea in physics was an extension of the proponent’s character. He used this principle for mentoring people and found this approach greatly satisfying. He was straightforward in manner and critical in his judgment, but considerate of people’s feelings, and he delivered on his promises. Murtagh was held in the highest regard by his BNL colleagues for his achievements and contributions in many scientific and administrative areas. All who had the pleasure of knowing him will miss him.
