John Butler

John Butler

Office: PRB, Room 377. 617-353-8931
Lab: PRB, Room 366. 617-353-6043


Research Interests:

My research is in the field of experimental high-energy physics (HEP). The goal of HEP is to uncover the basic building blocks of nature and the forces between them. In our current understanding of nature, called the “standard model”, the building blocks are quarks and leptons, while the forces are mediated by gauge bosons. The different masses of the building blocks tell us that electroweak symmetry is broken. In the standard model, the symmetry is broken by the Higgs mechanism. The Higgs boson is a physical manifestation of the Higgs mechanism and is the only particle in the standard model that has not been observed. The focus of my current research is the ATLAS experiment at the CERN Large Hadron Collider (LHC). If the Higgs boson exists, it will certainly be found at the LHC. Most physicists in HEP believe that the standard model is an incomplete, low energy approximation of a more fundamental theory of nature. If true, ATLAS will be in an excellent position to discover particles, forces, and perhaps even dimensions of space that are entirely new and beyond the standard model. For nearly twenty years I worked on the DØ experiment at the Fermilab Tevatron accelerator. DØ produced a wealth of physics results but the highlight was the discovery of the top quark ("Observation of the Top Quark," Phys. Rev. Letters 74, 2632 (1995)). With a mass nearly that of an entire gold atom, the top quark is by far the heaviest elementary particle ever seen. Before DØ, I searched for exotic particles called “glueballs” as a member of the ASTERIX collaboration at CERN. I also measured the lifetimes of particles containing a charm quark at SLAC for my dissertation at Stanford. Looking forward, I am involved in the development of novel instrumentation for experiments at the proposed International Linear Collider (ILC). As a member of the CALICE collaboration, I work on building a device called a “digital calorimeter” which has the unprecedented performance required to meet the physics goals of the ILC.


University of Notre Dame, BS in physics, 1980 Stanford University, PhD in physics, 1986


1986-1988   European Laboratory for Particle Physics (CERN) Fellowship

1997           Department of Energy Outstanding Junior Investigator Award



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Research Descriptions:

The ATLAS Experiment at CERN


The ATLAS experiment is a large detector system developed by a collaboration of physicists from around the world to study very-high-energy proton-proton interactions at the Large Hadron Collider (LHC) at CERN, a laboratory for high energy physics near Geneva, Switzerland. This experiment will probe the origins of electroweak symmetry breaking and the particles associated with the new physics (such as the hypothetical Higgs Boson) that must appear at energies at the symmetry breaking scale. Boston University personnel were involved in the construction and installation of the muon detectors for ATLAS. The detectors occupy a region the size of a five-story building and will measure the trajectories of muons in a magnetic field with a precision of better than 1/10 of a millimeter. This permits the determination of the muon momentum, which will be an important ingredient in searches for new phenomena at the LHC's energy scale, which will be an order of magnitude greater than currently available. Boston University also played a leading role in the development of computing and analysis tools that have been crucial since the experiment's inception. It is expected that many important discoveries in particle physics will be made at the LHC in the coming decade. These discoveries will improve our understanding of the fundamental particles and their interactions, and also of the nature of the early universe. One important goal of the LHC is to search for particles that may be responsible for the so-called "dark matter" of the universe. Possible candidates for this mysterious phenomenon are the particles associated with supersymmetry theories.

The DØ Experiment


The DØ experiment studies proton-antiproton collisions at the world’s highest energy accelerator, the Fermilab Tevatron. These collisions release energy equivalent to 2000 times the proton mass. The DØ detector is a large, highly sophisticated instrument that measures the fragments of these collisions and allows scientists to study the structure of matter at these high energies. According to our current understanding, the basic constituents of matter are quarks and leptons. All the matter surrounding us is made of the lightest quarks, called up and down, and the lightest leptons, the electron and its neutrino. However there exist two additional families of quarks and leptons with identical properties, except much larger masses. The heaviest of the quarks, the "top" quark, was discovered in 1995 by the DØ and CDF collaborations at Fermilab. The top quark turned out to have an extraordinarily large mass, approximately the same as an entire gold atom. Particle physicists believe that its further study will provide clues to the origins of mass. The members of the Boston University DØ group were actively involved in the discovery of the top quark and the study of the carrier of the weak force, the "W boson". The group is now participating in the second data-taking run which began in 2001 and will continue until 2009. During this run, thousands of top quarks will be created, allowing a detailed study of the properties of this intriguing particle. The data from the Fermilab Tevatron will also provide the best opportunity until the LHC begins operation to find the Higgs boson and new physics beyond the standard model. The Boston University group has taken leadership roles in the construction of the muon detector system and the silicon microstrip tracker, the development of algorithms to identify bottom quarks and muons, and the "Top and Higgs Physics" analysis group. The group has designed and built a significant fraction of the electronics for the muon system trigger, the silicon track trigger, and the central fiber tracker trigger. The group’s physics interests center on the top quark and the search for new particles and forces beyond the standard model.