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APS President Barry Barish (right) presents the plaque to Brookhaven Laboratory Director Samuel Aronson.
Plaques Recognize Physics Milestones
In 1947, a consortium of nine northeastern universities established a nuclear science research center on a slip of land on Long Island, New York. Brookhaven National Laboratory (BNL) was built on the site of a former military camp and became one of the world's foremost research institutions. Its many contributions to myriad branches of physics, chemistry, materials science, biology, and environmental science are renowned, and have resulted in seven Nobel Prizes (so far).
As part of the APS Historic Sites Initiative, on September 23, 2011, APS President Barry Barish presented a plaque to Brookhaven Laboratory Director Samuel Aronson in recognition of BNL's far-reaching influence and the strategic role it has played in the advancement of critical scientific knowledge for the last 65 years. The presentation took place during a special symposium at Brookhaven to mark the historic-site designation. As written in the citation: "At this laboratory, over many years, scientists and engineers have made numerous fundamental discoveries in the fields of nuclear and high energy physics, the physics and chemistry of materials, energy and environment, biology and medicine. Among many landmark experiments are establishing the spin direction (helicity) of the electron neutrino, first observation of solar neutrinos, proof of more than one species of neutrinos, first observation of a lack of symmetry between matter and antimatter, and the principle of strong focusing that led to more compact and powerful accelerators."
BNL is home to some of the world's most powerful accelerators, including a 3 GeV proton synchrotron (Cosmotron)(1952), a 33 GeV alternating gradient proton synchrotron (AGS) (1960), and a 100 GeV/nucleon superconducting relativistic heavy-ion storage ring-collider (RHIC) (2000). It also has the National Synchrotron Light Source (NSLS), 800 MeV and 2.5 GeV electron synchrotrons (1982-84) that generate uv and x-ray beams for condensed matter and biological research. Research conducting using the AGS alone resulted in three Nobel Prizes.
An ingenious experiment in 1958 by M. Goldhaber, L. Grodzins, and A. W. Sunyar of the BNL staff established that the helicity of the neutrino emitted in electron capture is negative (that is, the neutrino is "left-handed"). BNL researchers also discovered more than one species of neutrino. In 1962, L. M. Lederman, M. Schwartz and J. Steinberger of Columbia, and other colleagues, brought a 15 GeV proton beam from the AGS onto a beryllium target, followed by a 3-meter pion decay region. Careful analysis of the neutrino flux so created showed that there were two species of neutrinos, one associated with electrons and the other associated with muons.
The discovery of violation of CP symmetry was another historic achievement. In the 1950s, after the discovery of nonconservation of space inversion symmetry (P, or parity), the current theoretical belief was that charge conjugation symmetry (C, really particle-antiparticle symmetry) was also violated, but the product of the two symmetry operations (CP) was conserved.
In 1964, working at the AGS, V. L. Fitch and J. W. Cronin of Princeton and colleagues unequivocally established a small violation of CP invariance in decays of the neutral K meson.
In another set of ground-breaking experiments, performed in deep mines, Raymond A. Davis, Jr., a Brookhaven chemist was the first to actually observe neutrinos from the sun. However, there was a surprise—the observed flux of neutrinos was a third of what was expected. This mystery was eventually resolved by the fact that neutrinos exist in three varieties, corresponding to the electron, muon, and tau particles, only the first of which was observable in Davis's detector.
Among other significant achievements by BNL scientists are: