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 f(0)(1370), f(0)(1500), f(0)(2000) and f(2)(1950) observed in the centrally produced 4 pi final states

{The production and decay properties of the f(0)(1370), f(0)(1500), f(0)(2000) and f(2)(1950) have been studied in central pp interactions at 450 GeV/c. The dP(T), phi and \textbackslash{}t\textbackslash{} distributions of these resonances are presented. For the J= 0 states, the f(0)(1370) and f(0)(2000) have similar dP(T) and phi dependences. These are different to the dP(T) and phi dependences of the f(0)(980), f(0)(1500) and f(0)(1710). For the J = 2 states the f(2)(1950) has different dependences to the f(2)(1270) and f(2)(1520). This shows that the dP(T) and phi dependences are not just J phenomena. (C) 2000 Published by Elsevier Science B,V. All rights reserved.