NEW GAMS RESULTS ON MESON SPECTROSCOPY

Results on meson spectroscopy obtained in 1993 by the GAMS Collaboration are presented. Model-independent measurements of the omega --> etagamma decay branching ratio, as well as the observation of the X(1740) state in the K(s)0K(s)0 decay mode, are considered. The results on the partial-wave analysis of the omegapi0 and pi0pi0 systems produced at small momentum transfer in pi-p charge-exchange reactions are discussed. The experiments on resonant etaeta-system production on a central region of the pp interaction are also discussed

GAMS RESULTS ON THE OMEGA-PI(0) SYSTEM

The first results on the omega-pi-0 system produced in the charge-exchange reaction of pi--p scattering at 38 GeV/c and 100 GeV/c are presented. The omega-pi-0 mass spectrum shows, alongside with the well-known b1(0) (1235) and rho-3(0) (1690) mesons, a new neutral state with mass 2200 +/- 20 MeV and width 260 +/- 50 MeV. This meson, X(2200), is produced like rho-3 through one-pion exchange. X(2200) is a candidate for the 1-- multiplet, and its possible interpretation is a 2(3)D1 excitation of the rho-0. Its production cross section at 3 S GeV/c is equal to sigma(pi--p --> Xn) . BR (X --> omega-pi-0) = 120 +/- 25 nb. Cross sections for b1 and rho-3 have also been measured. The energy dependences have been determined

STUDY OF THE OMEGA-PI(0) SYSTEM AT HIGH MASSES

The first results are presented on the study of the omega-pi-0 system produced in the charge-exchange reaction of pi-p scattering at the momenta 38 and 100 GeV/c. Together with the well known b1(0) (1235) and rho-3 (1690) mesons, in the mass spectrum of the omega-pi-0 system one observes a new neutral state with mass 2200 +/- 20 MeV and width 260 +/- 50 MeV, produced, like the rho-3, via one-pion exchange. This meson, X(2200), is a candidate for the 1- -multiplet. A possible interpretation is that it is a 2(3)D1 radial excitation of the rho-0 meson. Its production cross section at 38 GeV/c is sigma[pi-p --> X(2200)n]BR[X(2200) --> omega-pi-0] = 120 +/- 25 nb, and it falls off quadratically with increasing energy, which is consistent with one-pion exchange

Study of the pi(0)pi(0) system in pp central collisions at 450 GeV/c

The effective mass spectrum of pi(0) pairs produced in pp central collisions (pp --> pf pi(0) pi(0)p(s)) at 450 GeV/c, root s = 29 GeV, below 1 GeV differs from that observed in peripheral charge exchange reactions, In particular, there is a large number of events between pi pi-threshold and 1 GeV, that interfere with f(0)(980) destructively. The possible existence of a broad S-wave state is suggested. (C) 1997 Published by Elsevier Science B.V

A kinematical selection of glueball candidates in central production

A study of central meson production as a function of the difference in transverse momentum (dP(T)) of the exchanged particles shows that undisputed <q(q)over bar> mesons are suppressed at small dP(T) whereas the glueball candidates are enhanced. (C)1997 Elsevier Science B.V

A study of the centrally produced baryon-antibaryon systems in pp interactions at 450 GeV/c

A study of the centrally produced p (p) over bar, p (p) over bar pi(0), p (p) over bar pi(+)pi(-) and Lambda Lambda channels has been performed in pp collisions using an incident beam momentum of 450 GeV/c. No significant new structures are observed in the mass spectra, however, important new information on the production dynamics is obtained. A systematic study of the production properties of these systems has been performed and it is found that these systems are not produced dominantly by double Pomeron exchange. (C) 1999 Published by Elsevier Science B.V. All rights reserved

Observation of vertex factorisation breaking in central pp Interactions

Central pi(+)pi(-) events produced in pp interactions are studied in terms of correlations between the outgoing protons. It is observed there is more rho(0)(770) and f(2)(1270) production in reactions where the outgoing protons are on opposite sides of the beam. This effect is not attributable to the trigger or the experimental acceptance, and suggests that the vertices do not factorise

A study of the centrally produced pi(+) pi(-) pi(+) pi(-) channel in pp interactions at 450 GeV/c

The reaction pp –> P-f(pi(+) pi(-)pi(+)pi(-))p(s) has been studied at 450 GeV/c in an experiment designed to search for gluonic states. A spin analysis has been performed and the dP(T) filter applied. In addition to the well known f(1)(1285) there is evidence for two J(PC) = 2(-+) states called the eta(2)(1620) and eta(2)(1875) and a broad scalar called the f(0)(2000). The production of these states as a function of the dP, kinematical filter shows the behaviour expected for q (q) over bar states. In contrast, there is evidence for two states at 1.45 GeV and at 1.9 GeV which do not show the behaviour observed for q (q) over bar states. (C) 1997 Elsevier Science B.V

A partial wave analysis of the centrally produced pi(+) pi(-) system in pp interactions at 450 GeV/c

A partial wave analysis of the centrally produced pi(+)pi(-) channel has been performed in pp collisions using an incident beam momentum of 450 GeV/c. An unambiguous physical solution has been found. Evidence is found for the f(0)(980), f(0)(1300), f(0)(1500) and f(J)(1710) with J = 0 in the S-wave. The rho(770) is observed dominantly in the P-0(-)-wave and the f(2)(1270) is observed dominantly in the D-0(-)-wave. In addition, there is evidence for a broad enhancement in the D-wave below 1 GeV. (C) 1999 Published by Elsevier Science B.V. All rights reserved

A study of the centrally produced pi(+)pi(-)pi(0)channel in pp interactions at 450 GeV/c

The reaction pp –> p(f)(pi(+)pi(-)pi(0))p(s) has been studied at 450 GeV/c in an experiment designed to search for gluonic status. A spin analysis has been performed and the dP(T) filter applied. The analysis confirms the previous observation that all undisputed (<q(q)over bar> states are suppressed at small dP(T). In addition, a clear difference is observed in the production mechanism for the eta and omega. (C) 1998 Elsevier Science B.V