Later in his career, he worked in experimental cosmology, measuring polarization in the microwave background radiation whose properties date back to the early universe.
[1] After a distinguished early career in experimental elementary particle physics, Winstein spent a year in Princeton as a Guggenheim Fellow, studying astrophysics in general and the microwave background radiation in particular.
[3] In 1999, he was leader of Fermilab's KTeV experiment, which produced the first definitive evidence for direct CP violation, an important proof that matter and anti-matter are not perfect twins.
[2][4] He was also leader of the QUIET experiment, a multi-year international collaboration that sought to detect gravity waves in the early universe by measuring polarization in the microwave background radiation.
Panofsky Prize in Experimental Particle Physics, with the following citation: "For leadership in the series of experiments that resulted in a multitude of precision measurements of properties of neutral K mesons, most notably the discovery of direct CP violation.