D.Barberis,W .Beusch,F.G.Binon,A.M .Blick,F.E.Close,K.M .Danielsen, A.V.Dolgopolov,S.V.Donskov,B.C.Earl,D.Evans,B.R.French,T.Hino,S.Inaba, A.V.Inyakin,T.Ishida,A.Jacholkowski,T.Jacobsen,G.T Jones,G.V.Khaustov, T.Kinashi,J.B.Kinson,A.Kirk,W .Klem pt,V.Kolosov,A.A.Kondashov, A.A.Lednev,V.Lenti,S.M aljukov,P.M artinengo,I.M inashvili,T.Nakagawa, K.L.Norm an,J.P.Peigneux,S.A.Polovnikov,V.A.Polyakov,V.Rom anovsky, H.Rotscheidt,V.Rum yantsev,N.Russakovich,V.D.Sam oylenko,A.Sem enov,M .Sen e, R.Sen e,P.M .Shagin,H.Shim izu,A.V.Singovsky,A.Sobol,A.Solovjev, M .Stassinaki,J.P.Stroot,V.P.Sugonyaev,K.Takam atsu,G.Tchlatchidze,T.Tsuru, M .Venables,O.VillalobosBaillie,M .F.Votruba,Y.Yasu.

The reaction pp --> p(f)(pi (0)pi (0)pi (0))p(s) has been studied at 450 GeVc. The pi (0)pi (0)pi (0) effective mass spectrum shows clear eta (547) and pi (2)(1670) signals. Branching ratios for the eta (547) and pi (2)( 1670) are given as well as upper limits for the decays of the omega (782), a(1)(1260) and a(2)(1320) into 3 pi (0). (C) 2001 Published by Elsevier Science B.V.

The reaction pp ! pf( 000 )ps has been studied at 450 GeV/c. The 000 eective mass spectrum shows clear (547) and 2(1670) signals. Branching ratios for the (547) and 2(1670) are given as well as upper limits for the decays of the !(782), a1(1260) and a2(1320) into 3 0 .

The reactions pp -> pf (X0) ps, where X0 is observed decaying to pi0pi0pi0pi0, pi+pi-pi0pi0 and pi+pi-pi+pi-, have been studied at 450 GeV/c. There is evidence for an a2(1320)pi decay mode of the eta2(1645) and eta2(1870) in the pi+pi-pi0pi0 and pi+pi-pi+pi- final states. The f2(1950) is consistent with being a single resonance with a dominant f2(1270)pipi decay mode. The f0(1370) is found to decay dominantly to rho-rho while the f0(1500) is found to decay to rho-rho and sigma-sigma.

A search for centrally produced charmonium states has been presented. There is no significant evidence for any charmonium production. An upper limit of 2 nb is found for the cross section of chi(c) production using the decay chi(c)(1P) --> J/psi gamma. (C) 2000 Elsevier Science B.V. All rights reserved.

Ž . The reaction ppTMp vv p has been studied at 450 GeVrc and a spin analysis of the vv channel has been performed f s Ž . PC qq for the first time in central production. Evidence is found for the f 1910 in the J s2 wave with spin projection 2 J s2. This is the only state observed in central production with spin projection J s2. Its dP and f dependencies are Z Z T similar to those observed for other glueball candidates. In addition, evidence is found for a state with J s4 consistent Ž . Ž . with the f 2300 . The f 2000 , previously observed in the rr final state, is confirmed. q 2000 Elsevier Science B.V. All 4 0 rights reserved. Ž . E-mail address: andrew.kirk@cern.ch A. Kirk . 0370-2693r00r$ see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž . PII: S0370-2693 00 00622-5 ( ) D. Barberis et al.rPhysics Letters B 484 2000 198–204 199 The vv channel has been studied in several different production mechanisms. In pp interactions the vv final state has been studied by the w x w x NA12 1 and VES 2 collaborations. In both experiments clear signals were observed at 1.6 and 1.9 GeV and were found to have J P C s2, called the Ž . Ž . w x f 1640 and X 1910 3 . In addition, the VES 2 collaboration reported evidence for an vv decay Ž . mode of the f 2050 and, more recently, for a 4 P C qq w x J s4 object in the 2.3 GeV region 4 . In pp annihilations C. Baker et al., using the data from the w x Crystal Barrel experiment 5 , have reported eviŽ . dence for a structure similar to the f 1640 in the 2 vv final state but have shown that this state can be Ž . interpreted as being due to the f 1565 previously 2 w x w x observed in the pp final state 3 . The PDG 3 lists Ž . the X 1910 observed in the vv final state with another J P C s2 resonance with similar mass and width observed in the hh final state. In central production the WA102 experiment did not observe Ž . w x the f 1565 in the pp final state 6 , therefore, the 2 centrally produced vv channel can give information Ž . Ž . on the validity of the f 1565 rf 1640 assignment. 2 2 In addition, in the hh final state of the WA102 w x experiment 7 a peak was observed at 1.9 GeV which was consistent in mass and width with the Ž . X 1910 . A spin analysis showed that this state was consistent with having J P C s1 with spin projection J s1 or J P C s2 with spin projection J s Z Z 2. If the latter hypothesis were true then this was the first time that a state had been observed in central production that was produced with spin projection J s2. Hence, if the states observed in vv and hh Z Ž . P C qq are the same and the X 1910 has J s2 , the Ž . X 1910 should be observed in the J s2 projection Z in the vv final state. In central production, the vv final state was previously observed by the WA76 w x experiment 8 but only 80 events were observed and hence no strong conclusions could be drawn. In this paper, a study is presented of the vv final state formed in the reaction ppTMp vv p 1 Ž . Ž . f s at 450 GeVrc. It represents more than a factor of 60 increase in statistics over previous data on the cenw x trally produced vv final state 8 and, moreover, will present a spin analysis of this channel in central production. The data come from the WA102 experiment which has been performed using the CERN Omega Spectrometer, the layout of which is dew x Ž . scribed in Ref. 9 . Reaction 1 has been isolated using the ppp 0 decay mode of both vs. The reaction ppTMp ppppp p 0 p Ž . f s has been isolated from the sample of events having six outgoing charged tracks and four g s reconstructed in the GAMS-4000 calorimeter, by first imposing the following cuts on the components of < < the missing momentum: missing P -17.0 GeVrc, x < < < < missing P -0.16 GeVrc and missing P -0.12 y z GeVrc, where the x axis is along the beam direction. The two photon mass spectrum, when the mass of the other 2g-pair lies within a band around the p 0 Ž . 0 mass 100–170 MeV , shows a clear p signal with small background. Events containing a fast qqŽ . Ž q. D 1232 were removed if M p p -1.3 GeV, f which left 294 463 centrally produced pp ppp p 0 events. Ž q y 0. Fig. 1a shows a lego plot of M p p p versus Ž q y 0. Ž . M p p p four combinations per event . A clear signal of the vv channel can be observed. Fig. 1b shows the ppp 0 mass spectrum if the other ppp 0 combination is compatible with being an Ž Ž q y 0. . v 0.76FM p p p F0.81 GeV where a clear v signal can be observed. A tight cut has been used around the v signal to increase the signal to background ratio in the selected sample. In order to decrease the background further the parameter l is introduced which describes the v decay on the Dalitz plot and is defined as: < < 2 p =p q y ls 2 3 1 2 2 m ymp ž / 4 9 < < where p =p is proportional to the decay matrix q y element for vTMppp , p is the three momen" tum of the p " in the v rest frame and m is the ppp 0 effective mass squared. Superimposed on Fig. 1b as a shaded histogram is the ppp 0 mass distribution for l)0.3. As can be seen the signal to background ratio in the v region has increased. The vv final state has been selected using the ppp 0 mass cuts described above and by requiring that the l)0.3 for each v candidate. The ( ) D. Barberis et al.rPhysics Letters B 484 2000 198–204 200 Ž . Ž q y 0 . Ž q y 0 . Ž . Ž q y 0 . q y 0 Fig. 1. Selection of the vv final state: a M p p p versus M p p p , b M p p p if the other p p p combination is in Ž Ž q y 0 . . Ž . the v band 0.76FM p p p F0.81 GeV . Superimposed as a shaded histogram is the case for l)0.3. c The vv mass spectrum. Superimposed as a shaded histogram is an estimation of the background contribution. resulting vv mass spectrum is shown in Fig. 1c and consists of 5067 events. As can be seen there is a peak in the 1.9 GeV region. The background below the v signal has several sources including combinatorics and other channels. The combinatorial background is removed, in part, in the selection procedure. The remaining background is approximately 27%. Four methods have been used to determine the effects of this background; studying the side bands around the v signal, studying events that do not balance momentum, studying events that do not pass the l selection cuts and studying events from the pppppp channel. Since the majority of the background is due to other physical Ž . Ž . Ž . channels for example a 1260 a 1260 or v a 1260 1 1 1 production, the two methods that best reproduce the background are the one using events that do not pass the l cut and the other uses events from the pppppp channel. These two methods give a very similar representation of the background. ( ) D. Barberis et al.rPhysics Letters B 484 2000 198–204 201 In the remainder of this paper the method used to determine the background will be the mean of these two methods. Superimposed on the vv mass spectrum in Fig. 1c as a shaded histogram is the estimate of the background. A spin analysis of the centrally produced vv system has been performed using the method dew x scribed in Ref. 10 for the rr final state modified for the vv channel. The z axis is defined by the momentum vector of the exchanged particle with the greatest four-momentum transferred in the vv centre of mass. Assuming that only angular momenta up to 4 contribute, the amplitudes have been calculated Ž . in the spin-orbit LS scheme using spherical harmonics. In order to perform a spin parity analysis the log Ž . likelihood function, L sÝ log P i , is defined by j i j combining the probabilities of all events in 50 MeV vv mass bins from 1.5 to 3.0 GeV. The incoherent sum of various event fractions a is calculated so as j to include more than one wave in the fit, Ls log a P i q 1y a 2 Ž . Ž . Ý Ý Ý j j j ž / ž / i j j Ž . where the term 1yÝ a represents the phase space j j background. The negative log likelihood function Ž . w x yL is then minimised using MINUIT 11 . Coherence between different J P states has been neglected in the fit. Different combinations of waves have been tried and insignificant contributions have been removed from the final fit. It is found necessary to introduce the J P C s2 wave with both J s0 and 2, the J P C s0 wave Z and the J P C s4 wave with J s1. The results of Z the best fit are shown in Fig. 2. The J P C s2 wave with J s2 shows a peak Z at 1.9 GeV. This wave has been fitted using a spin 2 relativistic Breit-Wigner and a linear background and is shown superimposed. The fit gives Ms1897"11 MeV, Gs202 " 32 MeV, parameters consistent Ž . X with those of the X 1910 found from a fit to the hh w x final state 7 . Hence this consistent with the fact that Ž . X the X 1910 has vv and hh decay modes, and we Ž . shall refer to it as the f 1910 hereafter. Correcting 2 for the unseen decay modes and the effects of the X Ž . detector, the branching ratio vvrhh of the f 1910 2 is 2.6 " 0.6. There was no evidence for any wave with J s2 in the hh final state of the WA102 Z w x experiment 12 and hence an upper limit for the X Ž . branching ratio hhrhh of the f 1910 has been 2 Ž . calculated to be 0.2 90% CL . The J P C s2 wave with J s0 shows a broad Z enhancement. Superimposed on the wave is a shaded Ž . histogram representing the f 1640 . As can be seen 2 the J P C s2 wave with J s0 is not compatible Z Ž . with the f 1640 observed by other experiments. 2 This non observation does not contradict the claim Ž . that the f 1640 is an vv decay mode of the 2 Ž . f 1565 since this state is also not observed in 2 central production. The J P C s0 wave shows some activity near threshold and a broad enhancement around 2 GeV. In a previous analysis of the 4p channel, the WA102 experiment observed a similar structure in the J P C s0 rr wave which was identified with the Ž . f 2000 . Superimposed on the wave is a shaded 0 Ž . histogram representing the f 2000 assuming that 0 the branching ratio rrrvv s 3 as expected for a isoscalar resonance. This well represents the wave in the 2 GeV region. The J P C s4 wave with

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 \t\ distributions of these resonances are presented. (C) 2000 Elsevier Science B.V. All rights reserved.

The reaction pp → pf(ηη)ps has been studied at 450 GeV/c. For the first time a partial wave analysis of the centrally produced ηη system has been performed. Signals for the f0(1500), f0(1710) and f2(2150) are observed and the decay branching fractions of these states are determined. Submitted to Physics Letters 1 LAPP-IN2P3, Annecy, France. 2 Athens University, Physics Department, Athens, Greece. 3 School of Physics and Astronomy, University of Birmingham, Birmingham, U.K. 4 CERN European Organization for Nuclear Research, Geneva, Switzerland. 5 IHEP, Protvino, Russia. 6 IISN, Belgium. 7 JINR, Dubna, Russia. 8 High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan. 9 Faculty of Engineering, Miyazaki University, Miyazaki 889-2192, Japan. 10 RCNP, Osaka University, Ibaraki, Osaka 567-0047, Japan. 11 Oslo University, Oslo, Norway. 12 Faculty of Science, Tohoku University, Aoba-ku, Sendai 980-8577, Japan. The ηη , ηη and ηη channels are important for the determination of the gluonic content of mesons, since it is thought likely that glueballs will decay with the emission of ηs and ηs [1, 2]. In addition, central production is proposed as a good place to produce glueballs via Double Pomeron Exchange (DPE) [2, 3]. Hence the interest of the present paper which studies the centrally produced ηη system. The ηη channel has been studied previously in radiative J/ψ decays by the Crystal Ball experiment [4], in πp interactions by the NA12 experiment [5, 6], in central production by NA12/2 [7] and in pp annihilations by the Crystal Barrel Collaboration [8] and E760 at Fermilab [9]. In all these reactions evidence for the f0(1500) has emerged. In addition, in pp annihilation evidence is claimed for a f0(2100) [9, 10] and an ηη decay mode of the f2(1950) [10]. In π p interactions the NA12 experiment claim a f0(2000) [6]. In radiative J/ψ decays evidence was reported for the fJ(1710) [4]. In central production the NA12/2 experiment claimed evidence for a f2(2175) [7]. In this paper a study is presented of the ηη final state formed in the reaction pp→ pf(ηη)ps (1) at 450 GeV/c. It represents more than a factor of 6 increase in statistics over the only other data on the centrally produced ηη final state [7] and moreover will present the first partial wave analysis of this channel in central production. The data come from the WA102 experiment which has been performed using the CERN Omega Spectrometer, the layout of which is described in ref. [11]. Reaction (1) has been isolated using the following decay modes: η → γγ η → γγ η → γγ η → πππ η → πππ η → πππ The above decay modes account for 38.8 % of the total. Fig. 1a) shows a scatter plot of M(γγ) versus M(γγ) which has been extracted from the sample of events having two outgoing charged tracks and four γs reconstructed in the GAMS4000 calorimeter using momentum and energy balance. A clear signal of the ηη channel can be observed. Fig. 1b) shows the γγ mass spectrum if the other γγ pair is compatible with being an η (0.48 ≤ M(γγ) ≤ 0.62 GeV) where a clear η signal can be observed. The ηη final state has been selected using the mass cuts described above. Fig. 1c) shows a scatter plot of M(γγ) versus M(πππ) for the sample of events having four outgoing charged tracks and four γs reconstructed in the GAMS-4000 calorimeter after imposing momentum and energy balance. A clear signal of the ηη channel can be observed. Fig. 1d) shows the πππ mass spectrum if the γγ mass is compatible with being an η (0.48 ≤ M(γγ) ≤ 0.62 GeV) and fig 1e) shows the γγ mass spectrum if the πππ mass is compatible with being an η (0.52 ≤ M(πππ) ≤ 0.58 GeV). The ηη final state has been selected by requiring that 0.48 ≤ M(γγ) ≤ 0.62 GeV and 0.52 ≤ M(πππ) ≤ 0.58 GeV. Fig. 1f) shows a scatter plot of M(πππ) versus M(πππ) for the the sample of events having six outgoing charged tracks and four γs reconstructed in the GAMS-4000 calorimeter after imposing momentum and energy balance. A signal of the ηη channel can be observed.

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 \t\ 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.

A search for centrally produced charmonium states has been presented. There is no significant evidence for any charmonium production. An upper limit of 2 nb is found for the cross section of x production using the decay c

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 KKand ppfinal states has been performed in pp collisions Ž . at an incident beam momentum of 450 GeVrc. The pole positions and branching ratios to pp and KK of the f 980 , 0 Ž . Ž . Ž . f 1370 , f 1500 and f 1710 have been determined. A systematic study of the production properties of all the resonances 0 0 0 observed in the ppand KKchannels has been performed. q 1999 Elsevier Science B.V. All rights reserved. 0370-2693r99r$ see front matter q 1999 Elsevier Science B.V. All rights reserved. Ž . PII: S0370-2693 99 00909-0 ( ) D. Barberis et al.rPhysics Letters B 462 1999 462–470 463 Recently the WA102 collaboration has published the results of partial wave analyses of the centrally q y 0 0 w x q y w x 0 0 produced K K , K K 1 , p p 2 and p p S S w x 3 channels. A striking feature of these analyses was Ž . Ž the result that the f 1710 has Js0 we shall refer J Ž . . to it as the f 1710 hereafter . In these papers the 0 S-wave from each channel was fitted independently using interfering Breit-Wigners and a background. In this present paper we will first show how the resulting parameters change if a different method of fitting is used, namely, a T-Matrix analysis and a K-Matrix w x analysis using the methods described in Ref. 4 . Next we will perform a coupled channel fit to the KKand ppfinal states in order to determine the pole positions and branching ratios of the observed mesons. Finally we will present information on the production kinematics of these resonances. In our previous publication a fit has been performed to the ppS-wave using a coherent sum of relativistic Breit-Wigner functions and a background

0 q y A study of the centrally produced pp, ppp , ppp p and LL channels has been performed in pp collisions using an incident beam momentum of 450 GeVrc. No significant new structures are observed in the mass spectra, however, 0370-2693r99r$ see front matter q 1999 Published by Elsevier Science B.V. All rights reserved. Ž . PII: S0370-2693 98 01565-2 ( ) D. Barberis et al.rPhysics Letters B 446 1999 342–348 343 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. q 1999 Published by Elsevier Science B.V. All rights reserved. Experiment WA102 is designed to study exclusive final states formed in the reaction ppTMp X 0 p 1 Ž . Ž . f s at 450 GeVrc. The subscripts f and s indicate the fastest and slowest particles in the laboratory respectively and X 0 represents the central system that is presumed to be produced by double exchange processes. The experiment has been performed using the CERN Omega Spectrometer, the layout of which is w x described in Ref. 1 . In previous analyses of other channels it has been observed that when the centrally produced system has been analysed as a function of the parameter dP , which is the difference in the T transverse momentum vectors of the two exchange w x particles 1,2 , all the undisputed qq states are suppressed at small dP , in contrast to glueball candiT dates. 0 This paper presents a study of the pp, ppp , q y ppp p and LL final states at a centre of mass q y ' energy of s s29.1 GeV. The pp, ppp p and ' LL channels have previously been studied at s s w x 12.7 GeV 3 . In recent years there have been claims of the observation of two different resonant signals in the pp channel. The first claim is for the observaŽ . tion of the j 2220 , with a width of 20 MeV, in radiative Jrc decays made by the BES collaboraw x Ž . tion 4 . The j 2220 is claimed to be a good candidate for the tensor glueball. To date, every established J P C s0 and 2 glueball candidate has been observed in central pp collisions. Therefore, it is important to look for these new states in central production in order to learn more about the Ž . nature andror existence of the j 2220 . The second claimed observation is for a state with a mass of 2.02 GeV and a width of less than 10 MeV observed in central baryon exchange by the WA56 w x experiment 5 . It is claimed that this state could be interpreted as a baryonium candidate. Although the current experiment does not study baryon exchange it does study central production and hence a search for this state may be of interest. In addition to these searches, an analysis of the production kinematics of baryon-antibaryon production is presented which can give information on the mechanism of the formation of these final states in central production. The reaction ppTMp pp p 2 Ž . Ž . f s has been isolated from the sample of events having four outgoing charged tracks, by first imposing the following cuts on the components of the missing < < < momentum: missing P -14.0 GeVrc, missing x < < < P -0.16 GeVrc and missing P -0.08 GeVrc, y z where the x axis is along the beam direction. A correlation between pulse-height and momentum obtained from a system of scintillation counters was used to ensure that the slow particle was a proton. In order to select the pp system, information from ˇ the Cerenkov counter was used. One centrally produced charged particle was required to be identified ˇ as a p or an ambiguous Krp by the Cerenkov counter and the other particle was required to be consistent with being a proton. The method of Ehrlich w x et al. 6 , has been used to compute the mass squared of the two centrally produced particles assuming them to have equal mass. The resulting distribution is shown in Fig. 1a where a clear peak can be seen at the proton mass squared. This distribution has been fitted with Gaussians to represent the contributions q y q y from the p p , K K and pp channels. From this fit the number of pp events is found to be 6256 " 220. A cut on the Ehrlich mass squared of 0.65FM 2 X 2 F1.15 GeV has been used to select a sample of pp events. The resulting pp effective mass distribution is shown in Fig. 1b. There are no significant structures in the mass spectrum, in particular there is no Ž . evidence for the j 2220 that has been claimed in w x the pp channel by the BES collaboration 4 nor is there evidence for the narrow structure at 2.02 GeV claimed to have been observed in central baryon w x exchange reactions 5 . The mass resolution of the WA102 experiment in each region is better than 10 ( ) D. Barberis et al.rPhysics Letters B 446 1999 342–348 344 Ž . Ž . Ž . Fig. 1. a The Ehrlich mass squared distribution and b the pp mass spectrum for the pp channel. c The Ehrlich mass squared 0 0 Ž . distribution and d the ppp mass spectrum for the ppp channel. MeV. We can calculate an upper limit for the crosssections for the production of these claimed resoŽ Ž .. nances in central pp interactions to be s j 2220 Ž . -1.6 nb and s 2.02 GeV -1.4 nb at 95 % confidence level. The reaction 0 ppTMp ppp p 3 Ž . Ž . f s where the p 0 has been observed decaying to gg , has been isolated from the sample of events having four outgoing charged tracks plus two g s each with energy greater than 0.5 GeV reconstructed in the electromagnetic calorimeter , by first imposing the 1 The showers associated with the impact of the charged tracks on the calorimeter have been removed from the event before the requirement of only two g s was made. following cuts on the components of the missing < < < momentum: missing P -17.0 GeVrc, missing x < < < P -0.16 GeVrc and missing P -0.12 GeVrc. y z One centrally produced charged particle was required to be identified as a p or an ambiguous Krp ˇ by the Cerenkov counter and the other particle was required to be consistent with being a proton. The Ehrlich mass distribution is shown in Fig. 1c where a clear peak can be seen at the proton mass squared. This distribution has been fitted with Gaussians to represent the contributions from the ppp , q y 0 0 K K p and ppp channels. From this fit the 0 number of ppp events is found to be 877 " 85. A cut on the Ehrlich mass squared of 0.65FM 2 F1.15 X 2 0 GeV has been used to select a sample of ppp 0 events. The resulting ppp effective mass distribution is shown in Fig. 1d where no significant struc( ) D. Barberis et al.rPhysics Letters B 446 1999 342–348 345 0 ture can be observed. Similarly, the pp, pp and 0 pp mass spectra do not show any significant strucŽ . tures not shown . The reaction q y ppTMp ppp p p 4 Ž . Ž . f s has been isolated from the sample of events having six outgoing charged tracks, by first imposing the following cuts on the components of the missing < < < momentum: missing P -14.0 GeVrc, missing x < < < P -0.12 GeVrc and missing P -0.08 GeVrc. y z q y In order to select the ppp p system an event was accepted if a positive or negative particle was ˇ identified as a p or a Krp by the Cerenkov system and the other particle with the same charge was consistent with being a p . A modified method of w x Ehrlich et al. 6 , has been used to compute the mass squared of the two highest momentum central particles assuming the other two particles to be pions. The resulting distribution is shown in Fig. 2a where a clear peak can be seen at the proton mass squared. This distribution has been fitted with Gaussians to represent the contributions from the pppp , q y q y q y K K p p and ppp p channels. From this fit q y the number of ppp p events is found to be 2076 " 160. A cut on the Ehrlich mass squared of 0.65FM 2 F1.15 GeV 2 has been used to select a X q y q y sample of ppp p events. The resulting ppp p effective mass spectrum is shown in Fig. 2b and shows a broad distribution with a maximum near threshold. A study has been performed of the various two and three body subsystems but no structure has been q y q y Ž . Ž . Ž . Fig. 2. For the ppp p channel a the Ehrlich mass squared distribution, b the ppp p mass spectrum and c the scatter plot of y q Ž . Ž . M pp versus M pp . ( ) D. Barberis et al.rPhysics Letters B 446 1999 342–348 346 q y Ž . Ž . Ž . Ž . Ž . Ž . Fig. 3. For the LL channel a the scatter plot of M p p versus M pp , b the M pp mass distribution and c the LL mass

A partial wave analysis of the centrally produced KK channel from the WA76 experiment has been performed and Ž . Ž . shows evidence for peaks in the S-wave due to the f 1500 and f 1710 with Js0. The D-wave shows no evidence for a 0 J statistically significant contribution in the 1.7 GeV mass region. q 1999 Elsevier Science B.V. All rights reserved. One of the fundamental predictions of QCD is the existence of glueballs. Current theoretical predictions based on lattice gauge calculations indicate that the lowest lying scalar glueball should be in the mass w x Ž . range 1500–1700 MeV 1 . The f 1500 and the 0 Ž . f 1710 display clear glueball characteristics in that J they are both produced in glue-rich production mechanisms and are either not seen, or are heavily suppressed in normal hadronic interactions. In addiŽ . tion, the f 1710 is observed to decay dominantly to J y KK and yet it is not produced in K p interactions w x Ž . 2 . However, the spin of the f 1710 is still uncerJ tain with Js0 or 2 being possible. w x Recently, the CERN WA102 experiment 3 has published the results of a partial wave analysis of the centrally produced KK system which shows that Ž . the f 1710 has Js0. In 1989 the WA76 collaboJ ration published results from the analysis of the w x centrally produced KK system 4 . In an attempt to Ž . assess the spin of the f 1710 the angular distribuJ tions in the 1.5 and 1.7 GeV mass intervals were studied. The two regions were found to be similar, and since it was assumed that the signal at 1.5 GeV X Ž . was due to the f 1525 , it was concluded that the 2 signal at 1.7 GeV was also spin two. From these two Ž . observations the f 1710 was allocated spin two. J w x However, the recent WA102 analysis 3 showed that the 1.5 GeV region had a large component due to the Ž . f 1500 . 0 This paper presents a reanalysis of the WA76 KK final state formed in the reaction ppTMp KK p 1 Ž . Ž . f s 0370-2693r99r$ see front matter q 1999 Elsevier Science B.V. All rights reserved. Ž . PII: S0370-2693 99 00747-9 ( ) B.R. French et al.rPhysics Letters B 46