PLUTO was a detector for experimental high-energy

particle physics Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) and ...

at the German national laboratory

DESY The Deutsches Elektronen-Synchrotron (English ''German Electron Synchrotron''), commonly referred to by the abbreviation DESY, is a national research center in Germany. It operates particle accelerators used to investigate the structure of matt ...

Hamburg Hamburg (, ; nds, label=Hamburg German, Low Saxon, Hamborg ), officially the Free and Hanseatic City of Hamburg (german: Freie und Hansestadt Hamburg; nds, label=Low Saxon, Friee un Hansestadt Hamborg),. is the List of cities in Germany by popul ...

. It was operated from 1974 to 1978 at the DORIS synchrotron and was substantially upgraded between 1977 and 1978 for operation at the

PETRA Petra ( ar, ٱلْبَتْرَاء, Al-Batrāʾ; grc, Πέτρα, "Rock", Nabataean: ), originally known to its inhabitants as Raqmu or Raqēmō, is an historic and archaeological city in southern Jordan. It is adjacent to the mountain of Ja ...

accelerator, where it took data until 1979. The name is not an acronym, unlike the other detectors at DORIS.

Detector

PLUTO used the first electromagnetic superconductive

solenoid upright=1.20, An illustration of a solenoid upright=1.20, Magnetic field created by a seven-loop solenoid (cross-sectional view) described using field lines A solenoid () is a type of electromagnet formed by a helix, helical coil of wire whose ...

in the world, with a very uniform axial

magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and t ...

of 1.2 Tesla, to operate in a straight section of

electron The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary partic ...

–

positron The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. It has an electric charge of +1 '' e'', a spin of 1/2 (the same as the electron), and the same mass as an electron. When a positron collide ...

accelerators at

, first with DORIS I (a storage ring with center-of-mass energies of ~3–5 GeV) in 1974–1976, then with DORIS II (the upgraded DORIS storage ring at center-of-mass energies of ~7–10 Gev) in 1978 and later with PETRA (also a storage ring, at larger center-of-mass energies of ~10–45 GeV) in 1978–1982.

Experimental results

The PLUTO collaboration started with about 35 physicists from institutes of Aachen, DESY, Hamburg, Wuppertal and Siegen in Germany and subsequently gained new members from universities in the US, UK, Italy and Israel. The collaboration investigated electron–positron physics in a wide range of partly unexplored energies, contributed to new physics by exploring the just discovered

charm quark The charm quark, charmed quark or c quark (from its symbol, c) is the third-most massive of all quarks, a type of elementary particle. Charm quarks are found in hadrons, which are subatomic particles made of quarks. Examples of hadrons containi ...

and tau lepton, added important knowledge to

electroweak In particle physics, the electroweak interaction or electroweak force is the unified description of two of the four known fundamental interactions of nature: electromagnetism and the weak interaction. Although these two forces appear very differe ...

and

strong interaction The strong interaction or strong force is a fundamental interaction that confines quarks into proton, neutron, and other hadron particles. The strong interaction also binds neutrons and protons to create atomic nuclei, where it is called th ...

s (see review) and discovered new phenomena, by demonstrating that: * the Y(9.46 GeV) is a very narrow bottom–antibottom new

quark A quark () is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. All common ...

resonance (observed together with another experiment at DORIS), * the Y decays hadronically mostly (approx. 97%) into three

gluon A gluon ( ) is an elementary particle that acts as the exchange particle (or gauge boson) for the strong force between quarks. It is analogous to the exchange of photons in the electromagnetic force between two charged particles. Gluons bi ...

s, * gluons are fragmenting and hadronizing into jets (almost like quarks), seen as the three jets in the Y hadronic decays, * gluons have spin 1, * gluon

bremsstrahlung ''Bremsstrahlung'' (), from "to brake" and "radiation"; i.e., "braking radiation" or "deceleration radiation", is electromagnetic radiation produced by the deceleration of a charged particle when deflected by another charged particle, typicall ...

exists (found together with three more experiments at PETRA). All of these led to the discovery of the gluon and of gluon jets and to the confirmation of the

quantum chromodynamics In theoretical physics, quantum chromodynamics (QCD) is the theory of the strong interaction between quarks mediated by gluons. Quarks are fundamental particles that make up composite hadrons such as the proton, neutron and pion. QCD is a ty ...

(QCD) theory of strong interactions. A "Special High Energy and Particle Physics Prize" of the

European Physical Society The European Physical Society (EPS) is a non-profit organisation whose purpose is to promote physics and physicists in Europe through methods such as physics outreach. Formally established in 1968, its membership includes the national physical so ...

(EPS) was awarded in 1995 to the PLUTO, TASSO, MARK-J and

JADE Jade is a mineral used as jewellery or for ornaments. It is typically green, although may be yellow or white. Jade can refer to either of two different silicate minerals: nephrite (a silicate of calcium and magnesium in the amphibole gro ...

collaborations for ''"establishing the existence of the gluon in independent and simultaneous ways"'' (meant for the discovery of the gluon bremsstrahlung process at PETRA in 1979 by the four mentioned collaborations, and not for the discovery of the Y -> 3 gluons -> 3 jets decay by PLUTO at DORIS in 1978.)

Notes

References

{{Reflist Physics experiments Particle physics facilities Gluons