Observation of a J^PC = 1-+ exotic resonance in diffractive dissociation of 190 GeV/c pi- into pi- pi- pi+

The COMPASS experiment at the CERN SPS has studied the diffractive dissociation of negative pions into the pi- pi- pi+ final state using a 190 GeV/c pion beam hitting a lead target. A partial wave analysis has been performed on a sample of 420000 events taken at values of the squared 4-momentum transfer t' between 0.1 and 1 GeV^2/c^2. The well-known resonances a1(1260), a2(1320), and pi2(1670) are clearly observed. In addition, the data show a significant natural parity exchange production of a resonance with spin-exotic quantum numbers J^PC = 1-+ at 1.66 GeV/c^2 decaying to rho pi. The resonant nature of this wave is evident from the mass-dependent phase differences to the J^PC = 2-+ and 1++ waves. From a mass-dependent fit a resonance mass of 1660 +- 10+0-64 MeV/c^2 and a width of 269+-21+42-64 MeV/c^2 is deduced.Comment: 7 page, 3 figures; version 2 gives some more details, data unchanged; version 3 updated authors, text shortened, data unchange

THE SLOW POSITION-SENSITIVE TIME-OF-FLIGHT DETECTOR OF THE GAMS NA 12/2 EXPERIMENT OF CERN

A large time-of-flight detector has been built by the GAMS NA12/2 experiment at CERN. It surrounds a 60 cm long liquid hydrogen target. With a time resolution better than sigma = 350 ps, pion/proton separation is achieved up to a 800 MeV/c momentum

Experimental evidence for a vector-like behaviour of Pomeron exchange

Evidence is presented that the Pomeron acts as a non-conserved vector current. A study has been made of the azimuthal angle phi, which is defined as the angle between the p(T) vectors of the two outgoing protons, in the reaction pp–>pp(X-0) for those resonances (X-0) which are compatible with being produced by double Pomeron exchange. These distributions have been compared with a moder which describes the Pomeron as a non-conserved vector current and a qualitative agreement is found. In addition, when one of the particles exchanged is known to have spin 0, namely pi-Pomeron exchange, the phi distribution is flat. (C) 1999 Elsevier Science B.V. All rights reserved

A coupled channel analysis of the centrally produced K+K- and pi(+)pi(-) final states in pp interactions at 450 GeV/c

A coupled channel analysis of the centrally produced K+K- and pi(+)pi(-) final states has been performed in pp collisions at an incident beam momentum of 450 GeV/c. The pole positions and branching ratios to pi pi and K (K) over bar of the f(0)(980), f(0)(1370), f(0)(1500) and f(0)(1710) have been determined. A systematic study of the production properties of all the resonances observed in the pi(+)pi(-) and K+K- channels has been performed. (C) 1999 Elsevier Science B.V. All rights reserved

A study of the eta eta ` and eta `eta ` channels produced in central pp interactions at 450 GeV/c

The reactions pp –> p(f)(X-0)p(s), where X-0 is observed decaying to eta eta’ and eta’eta’, have been studied at 450 GeV/c. This is the first time that these channels have been observed in central production and only the second time that the eta’eta’ channel has been observed in any production mechanism. In the eta eta’ channel there is evidence for the f(0)(1500) and a peak at 1.95 GeV. The eta’eta’ channel shows a peak at threshold which is compatible with having J(PC) = 2(++) and spin projection J(Z) = 0. (C) 2000 Published by Elsevier Science B.V. All rights reserved