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

A spin analysis of the 4 pi 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 pi(0)pi(0)pi(0)pi(0), pi(+)pi(-)pi(+)pi(-) and pi(+)pi(-)pi(0)pi(0), have been studied at 450 GeV/c. There is evidence for an a(2)(1320)pi decay mode of the eta(2)(1645) and eta(2)(1870) in the pi(+)pi(-)pi(0)pi(0) and pi(+)pi(-)pi(+)pi(-) find states. The f(2)(1950) is consistent with being a single resonance with a dominant f(2)(1270)pi pi decay mode. The f(0)(1370) is found to decay dominantly to rho rho while the f(0)(1500) is found to decay to rho rho and sigma sigma. (C) 2000 Published by Elsevier Science B.V. All rights reserved

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

A study of the centrally produced eta pi(0) and eta pi(-) systems in pp interactions at 450 GeV/c

{A partial wave analysis of the centrally produced eta pi(0) and eta pi(-) channels has been performed in pp collisions using an incident beam momentum of 450 GeV/c. Clear a(0)(980) and a(2)(1320) signals have been observed in S and D+ waves respectively. The dP(T), phi and \textbackslash{}t\textbackslash{} distributions of these resonances are presented. (C) 2000 Elsevier Science B.V. All rights reserved.

A study of the eta eta channel produced in central pp interactions at 450 GeV/c

The reaction pp –> Pf(eta eta)p(s) has been studied at 450 GeV/c. For the first time a partial wave analysis of the centrally produced eta eta system has been performed. Signals for the f(0)(1500), f(0)(1710) and f(2)(2150) are observed and the decay branching fractions of these states are determined. (C) 2000 Elsevier Science B.V. All rights reserved

A study of the omega omega channel produced in central pp interactions at 450 GeV/c

The reaction pp –> p(f)(omega omega)p(s) has been studied at 450 CeV/e and a spin analysis of the omega omega channel has been performed for the first time in central production. Evidence is found for the f(2)(1910) in the f(2)(1910) in the J(PC) =2(++) wave with spin projection J(Z)= 2. This is the only state observed in central production with spin projection J(Z)= 2. Its dP(T) and phi dependencies are similar to those observed for other glueball candidates. In addition, evidence is found for a state with J(PC) = 4(++) consistent with the f(2)(2300). The f(0)(2000), previously observed in the rho rho final state, is confirmed. (C) 2000 Elsevier Science B.V. All rights reserved