 |
| Spectrometer
used to discover upsilon particle,
composed of b quarks |
In "one of the most expected surprises
in particle physics," physicists led
by Leon Lederman at Fermi National
Accelerator Laboratory established
the third family of quarks in 1977
when they discovered the upsilon particle—a
"bottom" (or b) quark bound with its
anti-quark. Quarks are believed to
be the smallest particles of matter;
at the time of this discovery, the
b quark was the heaviest particle
ever found. This work satisfied predictions
for three families of matter set forth
in the Standard Model, physicists'
theory of matter and fundamental forces
of nature. Each family consists of
quarks and other particles called
leptons, as well as their anti-particles.
The tau lepton, the first evidence
of the third family, had just been
discovered in other research funded
by the Office of Science. Although
the discovery of the b quark was of
little surprise, the experiment provided
much excitement, including a false
positive result (a fluctuation thought
to be a particle, dubbed the "oopsLeon")
and a fire in the particle detector
that required a salvage expert from
Europe to treat some 900 electronic
circuit boards. The study of quarks,
first predicted and observed in the
1960s, has led to a number of Nobel
prizes.
Scientific Impact:
This was the first major discovery
for Fermilab and, by indicating a
third generation of quarks to go along
with the newly discovered lepton,
helped to restore symmetry to the
Standard Model. B physics (focusing
on b quarks and particles containing
them) was described by Lederman as
a "bonanza of new physics," opening
the door to many discoveries.
Social Impact: These
studies answer questions about the
constituents and history of the universe,
extending human understanding of nature
and contributing to improvements in
science education. In addition, although
basic research is by definition a
search for new knowledge without regard
to its practical implications, such
work often contributes to technologies
with commercial value; examples include
computers, lasers, and cancer treatments.
Reference: "Observation
of a Dimuon Resonance at 9.5 GeV in
400-GeV Proton-Nucleus Collisions,"
S. W. Herb et al., Phys. Rev.
Lett. 39: 252-255 (1977).
URL:
http://www.fnal.gov/pub/inquiring/physics/discoveries/bottom_quark.html
Technical Contact:
Dr. Leon Lederman, lederman@fnal.gov
Press Contact: Jeff
Sherwood, DOE Office of Public Affairs,
202-586-5806
SC-Funding Office:
Office of High Energy and Nuclear
Physics |
