DESY Results from DORIS

Drawing of an electron-muon event as seen in the PLUTO detector on the DORIS storage rings at DESY. They have added important evidence for the existence of heavy leptons. decided within GESSS (Group for European Superconducting Systems Study) that Karlsruhe would construct and install two quadrupole magnets for the SPS experiment WA2 which looks at the leptonic decays of hyperons. Two quadrupoles are required in the beam line to match the characteristics of the hyperon beam emerging from a target bombarded by the primary proton beam to the acceptance of the experiment's spectrometer. Due to the short lifetimes of the hyperons, their Compact design of magnets and (less than 3 %) for hadron misiden- path lengths need to be kept short and cryostats has kept the outer (warm) tification. It seems that the only way to this calls for the use of high field super diameter to 24cm in the end parts, explain this class of events by the reac conducting magnets wherever possi which can thus slip between the coils tion is in terms of an interaction in ble. By avoiding iron pole tips, the of neighbouring normal dipole which the electron and positron give a quadrupoles provide focusing for magnets. In this way, the effective pair of heavy leptons which then decay hyperons up to 1 50GeV/c with a peak length required for focusing in the to the known leptons. The production field gradient of 1 60T/m in magnets of beam is below 2 m. cross section has a threshold around 4 overall length 1.4m and 1.1m. The Coolants come from 5001 vessels of GeV indicating a lepton mass of about useful aperture is 3 cm diameter with liquid helium and nitrogen and their 2 GeV. If the interpretation is right, the bore at liquid helium temperature. regular refurbishing is the only task some of the two-prong events should Each magnet hasfour coils with 288 necessary during operation of the contain an electron rather than a muon superconducting turns. The cross sec magnets. Following commissioning in and indeed about 24 clean muon- tion of each coil is a rectangular block November 1976, the quadrupoles electron events were found. The whose position is chosen to minimize have worked continuously. 5001 of li electron spectrum agrees (within the field distortions in the useful aperture. quid helium, supplied via about 1 4m of still meager statistics) with the expec The coils are mounted on a central transfer lines, are sufficient for 60 tation for a heavy lepton with a support tube which serves as a hours of operation. branching ratio of about 20 % for each mechanical reference. Radial forces leptonic decay. are taken up by aluminium rings that The electron spectrum differs con are shrunk onto the coil assembly and siderably from the much softer elec the magnets are shrink-fitted into DESY tron spectrum which was observed cylindrical iron yokes to contain the Results from DORIS last year for the decays of charmed magnetic field. mesons. Additional evidence against Considerable training was observed Results from the two spectrometers an explanation in terms of charm during the test period and about 200 PLUTO and DASP at the DORIS decays is obtained from muon- quenches were required to achieve the electron-positron storage rings were electron events with multiprongs. For short-sample critical current. The reported at the Coral Gable Conference charm decays a relatively large number number of quenches was proportional in January and at the Chicago APS of such events is expected from kaon to the length of the magnets and meeting in February. decays which should accompany the further studies are being pursued to The most exciting result, obtained lepton emission but the observed check the conjecture that the training using PLUTO, is strong evidence for number is much too small. may be primarily due to the metal the existence of heavy leptons (see New facets can be added to the lurgical properties of the conductor also page 68). PLUTO studied two- charm picture by results from both itself rather than to its thermal or prong events with no other observed PLUTO and DASP. The theory predicts mechanical surroundings. Both particle at energies between 4 and 5 that the charm quark decays preferen magnets were trained to their short- GeV. One particle is identified over a tially to a strange quark and kaons sample limit and are operated at 90% large solid angle (43 % of 4 n) as a should therefore be produced abun of critical current. muon with only a small probability dantly in decays of charmed mesons. A 67 threshold in kaon production has now been detected, simultaneously, by People and things PLUTO (for neutral kaons) and by DASP (for charged kaons). Also, a remarkable anomaly was found — at the 4.4 GeV peak, the production rate is comparatively low which seems dif ficult to understand in terms of present theories. Recent theoretical papers have speculated about the existence of charmonium molecules made up of two pairs each consisting of a charmed Bits and Pieces U becomes less unknown quark-antiquark. If this were true, a particular decay mode involving a rear The book of the film 'The Key to the Further data from the electron- rangement of the four quarks ('charm Universe' — the television programme positron storage ring, SPEAR, at burning') would yield about 10 % of by Nigel Calder and Alec Nisbett on the Stanford supports the contention from J/psi particles. PLUTO measured the new physics — has been issued by earlier experiments that a heavy lepton inclusive J/psi production at 4.4 GeV BBC Publications at a price of £ 5.95. exists, with a mass around 1.9GeV. 3 and saw a yield of less than 4 x 10" Two blocks of concrete absorber which speaks strongly against the idea The cold box and engines of the interspersed with muon detectors of charmonium molecules. prototype satellite refrigerator for the were added on top of the famous Further interesting results were ob Energy Doubter/'Saver at Fermilab magnetic detector that saw the first tained for charmonium states by were successfully tested at the end of sign of heavy leptons. This has PLUTO. An analysis of events giving January. Twenty-four of these units improved the muon signals, and more two gammas and a J/psi taken at 3.7 will be distributed around the data has been collected in three energy GeV produced further confirmation for accelerator ring to cool the ranges. Each time anomalous muon the 3.454 GeV intermediate state superconducting magnets receiving signals with no conventional which has not been seen in hadronic liquid helium from a central plant. explanation were seen. decays. A few more decays into J/psi The earlier data was of electron and and a gamma have now been An 'Informal Report' has been issued at muon events which could result from observed. More statistics from DASP + Brookhaven (BNL 22160) entitled the decay of leptons named U , U~ on the J/psi decay into three gammas 'Beams at US High Energy Physics (U for unknown). The latest data adds gives three kinds of information. The Laboratories'. It gives the parameters more weight to this interpretation. existence of the X(2.8 GeV) state was of the beam lines in operation, or Information from the DORIS storage corroborated; the total width of the planned for the near future, at rings at DESY on the same topic is three photon decay is compatible with Argonne, Brookhaven, Cornell, presented on page 67. At a time when 2/3 charge of the quarks (but not with Fermilab and SLAC. a lot of particle physics seems to be integer charge); the branching ratios coming together, with the 'scent of a forJAi* x y, ii y, VY were found to be The Cancer Therapy Facility at new grand synthesis in the air' (Gell- in the ratio 1 : 1 1 : 30. Inclusive Fermilab now has 45 patients on its Mann's words), the U particle has the spectra for separated pions, kaons and books and 38 of them have already niggling quality of the pea (or should anti-protons between 3.5 and 5 GeV received neutron irradiations. The we say the Perl) under the mattress. It show scaling with energy at large Facility draws beam from the linac for could be a clue to lepton spectroscopy momenta whereas at low momenta about 60 hours per week and a third of and lepton structure which has not the cross section increases with this time is used for patient treatment. been foreseen as part of the grand energy. This implies that the rise in synthesis. Martin Perl prompted the total cross section at higher energies is Herman Winick has written a first heavy lepton analysis and G.J. associated with high multiplicity comprehensive, readable account of Feldman led the team from SLAC and events. synchrotron radiation research in the Berkeley which has provided this It becomes more and more obvious February issue of the 'SLAC Beam additional data. that the energy range between 4 and 9 Line'. GeV is an extremely rich field for further investigations and the Scien The Proceedings of the 1976 Future of the ZGS tific Council of DESY recommended DUMAND Summer Workshop held in on 1 March that DORIS should be Honolulu in September of last year are Present indications are that the Zero operated for particle physics for many available from the Physics Department Gradient Synchrotron at Argonne will years to come avoiding if possible a at Fermilab (P.O. Box 500, Batavia, continue operation until the end of reduction of utilization after PETRA Illinois 60510) price $15.50 surface 1979, as recommended by the 1976 comes into operation.

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