UA1 experiment

Last updated
Super Proton–Antiproton Synchrotron
(SppS)
SppbarS schematics.png
Key SppS Experiments
UA1 Underground Area 1
UA2 Underground Area 2
UA4 Underground Area 4
UA5 Underground Area 5
SppS pre-accelerators
PS Proton Synchrotron
AA Antiproton Accumulator
The central section of the UA1 experiment on display at the Microcosm museum at CERN UA1.jpg
The central section of the UA1 experiment on display at the Microcosm museum at CERN
Interior of the central section of the UA1 experiment on display at the Microcosm museum at CERN UA1 detector chamber.jpg
Interior of the central section of the UA1 experiment on display at the Microcosm museum at CERN

The UA1 experiment (an abbreviation of Underground Area 1) was a high-energy physics experiment that ran at CERN's Proton-Antiproton Collider (SppS), a modification of the one-beam Super Proton Synchrotron (SPS). The data was recorded between 1981 and 1990. The joint discovery of the W and Z bosons by this experiment and the UA2 experiment in 1983 led to the Nobel Prize for physics being awarded to Carlo Rubbia and Simon van der Meer in 1984. Peter Kalmus and John Dowell, from the UK groups working on the project, were jointly awarded the 1988 Rutherford Medal and Prize from the Institute of Physics for their outstanding roles in the discovery of the W and Z particles.

Contents

It was named as the first experiment in a CERN "Underground Area" (UA), i.e. located underground, outside of the two main CERN sites, at an interaction point on the SPS accelerator, which had been modified to operate as a collider. The UA1 central detector was crucial to understanding the complex topology of proton-antiproton collisions. It played a most important role in identifying a handful of W and Z particles among billions of collisions. [1]

Section of the UA1 detector at Museo nazionale della scienza e della tecnologia Leonardo da Vinci of Milan Rivelatore UA1 Museo scienza e tecnologia Milano.jpg
Section of the UA1 detector at Museo nazionale della scienza e della tecnologia Leonardo da Vinci of Milan

After the discovery of the W and Z boson, the UA1 collaboration went on to search for the top quark. Physicists had anticipated its existence since 1977, when its partner — the bottom quark — was discovered. It was felt that the discovery of the top quark was imminent. In June 1984, Carlo Rubbia at the UA1 experiment expressed to the New York Times that evidence of the top quark "looks really good". [2] Over the next months it became clear that UA1 had overlooked a significant source of background. [3] The top quark was ultimately discovered in 1994–1995 by physicists at Fermilab with a mass near 175 GeV.

The UA1 was a huge and complex detector for its day. It was designed as a general-purpose detector. [4] The detector was a 6-chamber cylindrical assembly 5.8 m long and 2.3 m in diameter, the largest imaging drift chamber of its day. It recorded the tracks of charged particles curving in a 0.7 Tesla magnetic field, measuring their momentum, the sign of their electric charge and their rate of energy loss (dE/dx). Atoms in the argon-ethane gas mixture filling the chambers were ionised by the passage of charged particles. The electrons which were released drifted along an electric field shaped by field wires and were collected on sense wires. The geometrical arrangement of the 17000 field wires and 6125 sense wires allowed a spectacular 3-D interactive display of reconstructed physics events to be produced. [5]

The UA1 detector was conceived and designed in 1978/9, with the proposal submitted in mid-1978. [6]

Since the end of running, the magnet used in the UA1 experiment has been used for other high energy physics experiments, notably the NOMAD and T2K neutrino experiments.

See also

Related Research Articles

<span class="mw-page-title-main">CERN</span> Research centre in Switzerland

The European Organization for Nuclear Research, known as CERN, is an intergovernmental organization that operates the largest particle physics laboratory in the world. Established in 1954, it is based in a suburb of Geneva, on the France–Switzerland border. It comprises 23 member states. Israel, admitted in 2013, is the only non-European full member. CERN is an official United Nations General Assembly observer.

<span class="mw-page-title-main">Carlo Rubbia</span> Italian particle physicist and Nobel Prize winner (born 1934)

Carlo Rubbia is an Italian particle physicist and inventor who shared the Nobel Prize in Physics in 1984 with Simon van der Meer for work leading to the discovery of the W and Z particles at CERN.

<span class="mw-page-title-main">Tevatron</span> Defunct particle accelerator at Fermilab in Illinois, USA (1983–2011)

The Tevatron was a circular particle accelerator in the United States, at the Fermi National Accelerator Laboratory, east of Batavia, Illinois, and is the second highest energy particle collider ever built, after the Large Hadron Collider (LHC) of the European Organization for Nuclear Research (CERN) near Geneva, Switzerland. The Tevatron was a synchrotron that accelerated protons and antiprotons in a 6.28 km (3.90 mi) ring to energies of up to 1 TeV, hence its name. The Tevatron was completed in 1983 at a cost of $120 million and significant upgrade investments were made during its active years of 1983–2011.

In particle physics, the W and Z bosons are vector bosons that are together known as the weak bosons or more generally as the intermediate vector bosons. These elementary particles mediate the weak interaction; the respective symbols are
W+
,
W
, and
Z0
. The
W±
 bosons have either a positive or negative electric charge of 1 elementary charge and are each other's antiparticles. The
Z0
 boson is electrically neutral and is its own antiparticle. The three particles each have a spin of 1. The
W±
 bosons have a magnetic moment, but the
Z0
has none. All three of these particles are very short-lived, with a half-life of about 3×10−25 s. Their experimental discovery was pivotal in establishing what is now called the Standard Model of particle physics.

<span class="mw-page-title-main">Large Electron–Positron Collider</span> Particle accelerator at CERN, Switzerland

The Large Electron–Positron Collider (LEP) was one of the largest particle accelerators ever constructed. It was built at CERN, a multi-national centre for research in nuclear and particle physics near Geneva, Switzerland.

<span class="mw-page-title-main">Gargamelle</span> CERN Bubble chamber particle detector

Gargamelle was a heavy liquid bubble chamber detector in operation at CERN between 1970 and 1979. It was designed to detect neutrinos and antineutrinos, which were produced with a beam from the Proton Synchrotron (PS) between 1970 and 1976, before the detector was moved to the Super Proton Synchrotron (SPS). In 1979 an irreparable crack was discovered in the bubble chamber, and the detector was decommissioned. It is currently part of the "Microcosm" exhibition at CERN, open to the public.

<span class="mw-page-title-main">Simon van der Meer</span> Dutch physicist

Simon van der Meer was a Dutch particle accelerator physicist who shared the Nobel Prize in Physics in 1984 with Carlo Rubbia for contributions to the CERN project which led to the discovery of the W and Z particles, the two fundamental communicators of the weak interaction.

<span class="mw-page-title-main">UA2 experiment</span> Particle physics experiment at CERN

The Underground Area 2 (UA2) experiment was a high-energy physics experiment at the Proton-Antiproton Collider — a modification of the Super Proton Synchrotron (SPS) — at CERN. The experiment ran from 1981 until 1990, and its main objective was to discover the W and Z bosons. UA2, together with the UA1 experiment, succeeded in discovering these particles in 1983, leading to the 1984 Nobel Prize in Physics being awarded to Carlo Rubbia and Simon van der Meer. The UA2 experiment also observed the first evidence for jet production in hadron collisions in 1981, and was involved in the searches of the top quark and of supersymmetric particles. Pierre Darriulat was the spokesperson of UA2 from 1981 to 1986, followed by Luigi Di Lella from 1986 to 1990.

<span class="mw-page-title-main">Super Proton Synchrotron</span> Particle accelerator at CERN, Switzerland

The Super Proton Synchrotron (SPS) is a particle accelerator of the synchrotron type at CERN. It is housed in a circular tunnel, 6.9 kilometres (4.3 mi) in circumference, straddling the border of France and Switzerland near Geneva, Switzerland.

<span class="mw-page-title-main">Collider Detector at Fermilab</span>

The Collider Detector at Fermilab (CDF) experimental collaboration studies high energy particle collisions from the Tevatron, the world's former highest-energy particle accelerator. The goal is to discover the identity and properties of the particles that make up the universe and to understand the forces and interactions between those particles.

<span class="mw-page-title-main">Antiproton Accumulator</span> Part of the CERN proton-antiproton collider

The Antiproton Accumulator (AA) was an infrastructure connected to the Proton–Antiproton Collider – a modification of the Super Proton Synchrotron (SPS) – at CERN. The AA was built in 1979 and 1980, for the production and accumulation of antiprotons. In the SppS the antiprotons were made to collide with protons, achieving collisions at a center of mass energy of app. 540 GeV. Several experiments recorded data from the collisions, most notably the UA1 and UA2 experiment, where the W and Z bosons were discovered in 1983.

Peter Ignaz Paul Kalmus, is a British particle physicist, and emeritus professor of physics at Queen Mary, University of London.

<span class="mw-page-title-main">Vinod Chohan</span> Tanzanian-born engineer (1949–2017)

Vinod Chandrasinh Chohan was a Tanzanian-born accelerator specialist and engineer. He was a Senior Staff Member at CERN for nearly 40 years.

<span class="mw-page-title-main">Luigi Di Lella</span> Italian experimental particle physicist

Luigi Di Lella is an Italian experimental particle physicist. He has been a staff member at CERN for over 40 years, and has played an important role in major experiments at CERN such as CAST and UA2. From 1986 to 1990 he acted as spokesperson for the UA2 Collaboration, which, together with the UA1 Collaboration, discovered the W and Z bosons in 1983.

<span class="mw-page-title-main">Pierre Darriulat</span> French experimental particle physicist

Pierre Darriulat is a French experimental particle physicist. As staff member at CERN, he contributed in several prestigious experiments. He was the spokesperson of the UA2 collaboration from 1981 to 1986, during which time the UA2 collaboration, together with the UA1 collaboration, discovered the W and Z bosons in 1983.

<span class="mw-page-title-main">Super Proton–Antiproton Synchrotron</span> Particle accelerator at CERN

The Super Proton–Antiproton Synchrotron was a particle accelerator that operated at CERN from 1981 to 1991. To operate as a proton-antiproton collider the Super Proton Synchrotron (SPS) underwent substantial modifications, altering it from a one beam synchrotron to a two-beam collider. The main experiments at the accelerator were UA1 and UA2, where the W and Z bosons were discovered in 1983. Carlo Rubbia and Simon van der Meer received the 1984 Nobel Prize in Physics for their contributions to the SppS-project, which led to the discovery of the W and Z bosons. Other experiments conducted at the SppS were UA4, UA5 and UA8.

<span class="mw-page-title-main">UA8 experiment</span> High-energy physics experiment at CERN

UA8 experiment was a high-energy physics experiment at the Proton-Antiproton Collider at CERN. The proposal for the experiment was done by physicists at the University of California, and it was approved in April 1985. Its spokesperson was Peter Schlein.

<span class="mw-page-title-main">David B. Cline</span> American particle physicist

]

<span class="mw-page-title-main">UA6 experiment</span>

The Underground Area 6 (UA6), also referred to as PHOTONS, experiment was a high-energy physics experiment at the Proton-Antiproton Collider, a modification of the Super Proton Synchrotron (SPS), at CERN. The experiment ran from 1984 to 1990, with the purpose of studying inclusive electromagnetic final states and lambda production in proton-antiproton and proton-proton interactions. Towards the end of its run it focused more on direct-photon and J/ψ production. The experiment is complementary to the UA1, UA2 and CDF experiments.

References

  1. "ua1 central detector: Topics by WorldWideScience.org". Archived from the original on 2011-10-03.
  2. Sullivan, Walter. "Physicists May Have Tracked Last Quark to Lair". The New York Times. No. 25 June 1984. Retrieved 23 June 2017.
  3. Staley, Kent W. (2004). The Evidence for the Top Quark: Objectivity and Bias in Collaborative Experimentation. Cambridge University Press. p. 80.
  4. "The UA1 detector - CERN Courier". Archived from the original on 2012-03-19.
  5. "ua1 central detector: Topics by WorldWideScience.org". Archived from the original on 2011-10-03.
  6. "When CERN saw the end of the alphabet". CERN Courier . 1 May 2003.

Further reading

CERN-UA-01 experiment record on INSPIRE-HEP