PLUTO was a detector for experimental high-energy

particle physics Particle physics or high-energy physics is the study of Elementary particle, fundamental particles and fundamental interaction, forces that constitute matter and radiation. The field also studies combinations of elementary particles up to the s ...

at the German national laboratory

DESY DESY, short for Deutsches Elektronen-Synchrotron (English: ''German Electron Synchrotron''), is a national research centre for fundamental science located in Hamburg and Zeuthen near Berlin in Germany. It operates particle accelerators used to ...

Hamburg Hamburg (, ; ), officially the Free and Hanseatic City of Hamburg,. is the List of cities in Germany by population, second-largest city in Germany after Berlin and List of cities in the European Union by population within city limits, 7th-lar ...

. It was operated from 1974 to 1978 at the DORIS

synchrotron A synchrotron is a particular type of cyclic particle accelerator, descended from the cyclotron, in which the accelerating particle beam travels around a fixed closed-loop path. The strength of the magnetic field which bends the particle beam i ...

and was substantially upgraded between 1977 and 1978 for operation at the

PETRA Petra (; "Rock"), originally known to its inhabitants as Raqmu (Nabataean Aramaic, Nabataean: or , *''Raqēmō''), is an ancient city and archaeological site in southern Jordan. Famous for its rock-cut architecture and water conduit systems, P ...

accelerator, where it took data until 1979.PLUTO experiment
record on

INSPIRE-HEP INSPIRE-HEP is an open access digital library for the field of high energy physics (HEP). It is the successor of the Stanford Physics Information Retrieval System (SPIRES) database, the main literature database for high energy physics since the 1 ...

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 whos ...

in the world, with a very uniform axial

magnetic field A magnetic field (sometimes called B-field) is a physical 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 ...

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 charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...

–

positron The positron or antielectron is the particle with an electric charge of +1''elementary charge, e'', a Spin (physics), spin of 1/2 (the same as the electron), and the same Electron rest mass, mass as an electron. It is the antiparticle (antimatt ...

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

(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 is an elementary particle found in composite subatomic particles called hadrons such as the J/psi meson and the charmed baryons created in particle accelerator collisions. Several bosons, including th ...

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 fundamental interactions of nature: electromagnetism (electromagnetic interaction) and the weak interaction. Although these two forc ...

and

strong interaction In nuclear physics and particle physics, the strong interaction, also called the strong force or strong nuclear force, is one of the four known fundamental interaction, fundamental interactions. It confines Quark, quarks into proton, protons, n ...

s 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 nucleus, atomic nuclei ...

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

gluon A gluon ( ) is a type of Massless particle, massless elementary particle that mediates the strong interaction between quarks, acting as the exchange particle for the interaction. Gluons are massless vector bosons, thereby having a Spin (physi ...

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 In particle physics, bremsstrahlung (; ; ) is electromagnetic radiation produced by the deceleration of a charged particle when deflected by another charged particle, typically an electron by an atomic nucleus. The moving particle loses kinetic ...

exists (found together with three more experiments at

). 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 study 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 type of ...

(QCD) theory of strong interactions. A "Special High Energy and Particle Physics Prize" of the European Physical Society (EPS) was awarded in 1995 to the PLUTO,

TASSO TASSO (Two Arm Spectrometer SOlenoid) was a particle detector at the PETRA particle accelerator at the German national laboratory DESY. The TASSO collaboration is best known for having discovered the gluon, the mediator of the strong interaction an ...

, MARK-J and

JADE Jade is an umbrella term for two different types of decorative rocks used for jewelry or Ornament (art), ornaments. Jade is often referred to by either of two different silicate mineral names: nephrite (a silicate of calcium and magnesium in t ...

collaborations for ''"establishing the existence of the gluon in independent and simultaneous ways"'' (meant for the discovery of the gluon bremsstrahlung process at

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