PLUTO detector

PLUTO, constructed at DESY laboratories in Hamburg in 1973-1974 and substantially upgraded in 1977-1978, was an experimental detector for high energy particle physics.

Experimental detector

PLUTO was the first electromagnetic superconductive solenoid in the world, with a very uniform axial magnetic field of 12000 Gauss,^[1] to operate in a straight section of e⁺e⁻ accelerators at DESY, first with DORIS I (a storage ring at center of mass energies of ~3-5 GeV) in 1974-1976, then with DORIS II (the upgraded storage ring of DORIS I 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 (see review^[2]).

Experimental results

The experimental collaboration PLUTO, first with about 35 German physicists from Institutes of Aachen, DESY, Hamburg, Wuppertal and Siegen, enlarged subsequently by international colleagues from Universities in USA, Great Britain, Italy and Israel, investigated the e⁺e⁻ physics in a wide range of partly unexplored energies, contributed effectively to new physics by the exploration of the just discovered charm quark and tau lepton, added important knowledge to electroweak and strong interactions (see review^[2]) and discovered new phenomena (see recollection^[3]), by demonstrating that:

• the Y(9.46 GeV) is a very narrow bottom-antibottom new quark resonance (observed together with an other experiment at DORIS),
• the Y decays hadronically mostly (approx. 97%) into 3 gluons,
• the gluons are fragmenting and hadronizing into jets (almost like quarks), seen as the three jets in the Y hadronic decays,
• the gluons have the spin 1,
• the gluon bremsstrahlung exists (found together with three more experiments at PETRA),

all of these leading to the discovery of the gluon and of the gluon jets and the confirmation of the Quantum Chromodynamics (QCD) theory of strong interactions (see also review,^[4] concerning the first gluon evidence by PLUTO at DORIS, see page 247 and pages 264-268 (ch. 4: "Gluon Jets in Y decays")).

A "Special High Energy and Particle Physics Prize" of the European Physical Society (EPS) was awarded in 1995 to the PLUTO collaboration (together with the TASSO, MARK-J and JADE collaborations) for "establishing the existence of the gluon in independent and simultaneous ways" was implicitly meant for the discovery of the gluon bremsstrahlung process at PETRA in 1979 done by the four mentioned collaborations and not for the discovery of the Y -> 3 gluons -> 3 jets decay done by PLUTO at DORIS in 1978.

References

1. Such magnets were later used for Nucelar Magnetic Resonance (NMR) spectroscopy for medical analysis
2. L. Criegee and G. Knies (1982). "e⁺e⁻ physics with the PLUTO detector". Physics Reports. 83: 151–280. Bibcode:1982PhR....83..151C. doi:10.1016/0370-1573(82)90012-6.
3. B.R. Stella and H.-J. Meyer (2011–2012). "Y(9.46 GeV) and the gluon discovery (a critical recollection of PLUTO results)". European Physical Journal H. 36: 203–243. arXiv:1008.1869v3. Bibcode:2011EPJH...36..203S. doi:10.1140/epjh/e2011-10029-3.
4. A. Ali and G. Kramer (2011). "JETS and QCD: A historical review of the discovery of the quark and gluon jets and its impact on QCD". European Physical Journal H. 36: 245–326. arXiv:1012.2288. Bibcode:2011EPJH...36..245A. doi:10.1140/epjh/e2011-10047-1.