Professor Riles carries out research into the fundamental forces of nature, working in both elementary particle physics and gravitational wave physics. Riles is a member of the LIGO Scientific Collaboration (LSC), searching for gravitational waves from astrophysical sources. This $300 million project, led by Caltech and MIT, involves three km-scale Michelson laser interferometers at sites in Washington and Louisiana. These interferometers are designed to measure displacement changes between mirrors to a relative precision of about 10^-22 at frequencies of about 100 Hz, allowing detection of minute ripples in space-time caused by the passage of gravitational waves. Riles leads the LSC Detector Characterization group and collaborates with University of Michigan Research Scientist Richard Gustafson who works in residence at the LIGO Hanford Observatory. The U-M group focuses its analysis work on the search for periodic sources of gravitational waves, in particular, radiation from rotating neutron stars. Data taking has begun, and searches are now underway.

Professor Riles is also a member of the L3 Collaboration at CERN's LEP Collider, together with U-M Professors Byron Roe and Lawrence Jones. In collaboration with University of Michigan postdoctoral fellows and graduate students, he has carried out a variety of measurements and searches for new particles using the interactions of electrons and positrons colliding at center of mass energies ranging from 91 to 209 GeV. Measured quantities have included production of events with two leptons and two energetic photons; chirality of the tau neutrino; the fraction of hadronic Z bosons decaying into bottom quark-antiquark pairs; the time dependence of neutral B meson mixing; and the W boson mass and width. New particles that have been searched for include the Standard Model Higgs boson and Supersymmetic Higgs bosons. Riles has advised six Ph.D. recipients in these measurements and searches.

Professor Riles also spends part of his research time studying the physics potential and the detector requirements of a future linear electron positron collider with a center of mass energy of 350 GeV and higher. His main focus in this work is contributing to the design and the R&D for a large charged-particle tracker with state-of-the art momentum and position precision.

First Upper Limits from LIGO on Gravitational Wave Bursts (B. Abbott et al.), to appear in Phys. Rev. D (December, 2003).

Setting Upper Limits on the Strength of Periodic Gravitational Waves Using the First Science Data from the GEO600 and LIGO Detectors (B. Abbott et al.), Phys. Rev. D (August, 2003).

Standard Model Higgs Boson with the L3 Experiment at LEP, (M. Acciarri et al.), Phys. Lett. B 517, 317 (2001).

Measurement of Mass and Width of the W Boson at LEP, (M. Acciarri et al.), Phys. Lett. B 454, 386 (1999).

Measurement of the Michel Parameters and the Average Tau-Neutrino Helicity from Tau Decays at LEP, (M. Acciarri et al.), Phys. Lett. B 438, 405 (1998).

Measurement of Tau Polarization at LEP, (M. Acciarri et al.), Phys. Lett. B 429, 387 (1998).