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UA1

UA1, short for Underground Area 1, was a general‑purpose particle physics detector at CERN’s Super Proton–Antiproton Synchrotron (SppS) collider. Commissioned in the early 1980s, it was built to study proton–antiproton collisions and to search for the weak vector bosons predicted by the electroweak sector of the Standard Model. The experiment featured a layered, hermetic detector system comprising a central tracking chamber within a magnetic field, electromagnetic and hadronic calorimeters, and an outer muon detection system, enabling measurements of charged particle trajectories as well as energy and momentum of leptons and jets. The collider operated at center-of-mass energies around 540 GeV, suitable for W and Z production.

UA1 competed with the UA2 detector to explore high-energy collisions. In 1983, both UA1 and UA2 reported

The UA1 detector’s legacy lies in its general‑purpose approach and its successful demonstration of detecting leptons

observations
consistent
with
the
production
and
decay
of
W
and
Z
bosons,
providing
the
first
clear
experimental
evidence
for
these
gauge
bosons
and
a
crucial
test
of
the
Standard
Model.
The
W
and
Z
discoveries,
led
by
CERN
physicists
and
international
collaborators,
earned
the
1984
Nobel
Prize
in
Physics
for
Carlo
Rubbia
and
Simon
van
der
Meer,
in
recognition
of
the
broader
SppS
program.
and
jets
in
high-energy
proton–antiproton
collisions.
Its
design
influenced
later
detectors
at
CERN
and
other
facilities,
contributing
to
precision
tests
of
electroweak
theory
and
to
the
overall
advancement
of
collider
physics.