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in this paper we present a partial wave analysis ( pwa ) of a high - statistics sample of events corresponding to the production of the @xmath13 system produced in @xmath14 collisions in two modes : @xmath15 and @xmath16 . this sample size exceeds , by at least an order of magnitude , the largest published sample size of @xmath17 events to date . previous @xmath17 analyses led to the discovery and/or determination of properties of the @xmath4 , @xmath5 , @xmath6 , @xmath18 and the @xmath7 resonances @xcite .    in 1998 , the e852 collaboration reported evidence for the @xmath19 , a @xmath8 exotic hybrid meson with a mass of 1.6  gev/@xmath10 decaying into @xmath11 @xcite . that analysis was based on 250,000 events of the reaction @xmath20 collected in 1994 . we report on the analysis of additional data collected in 1995 including 3.0 m events of the reaction @xmath21 and 2.6 m events of the reaction @xmath20 . the identification of exotic mesons requires a pwa to extract signals . the @xmath17 system provides a particularly attractive venue for such searches since earlier work suggests a rich spectrum of meson resonances . if an exotic meson is produced with relatively small amplitude , its interference with nearby well - established resonances is a sensitive search tool .    in almost all of the published amplitude analyses of the @xmath17 system , the _ isobar _ model was employed a @xmath17 system with a particular @xmath22 is produced and decays into a di - pion resonance with well - defined quantum numbers and a bachelor @xmath23 followed by the decay of the di - pion resonance . this assumption is successful in describing many features of the @xmath17 system and is motivated by the observation that the di - pion effective mass spectrum shows prominent resonance production , for example , the @xmath24 and the @xmath25 . the di - pion resonances considered in this analysis include the @xmath26 , @xmath24 , @xmath25 and the @xmath27 . we also include parametrizations of @xmath28-wave @xmath29 scattering .    in this analysis , we observe the @xmath4 , @xmath5 , @xmath6 and the @xmath7 in appropriate partial wave intensities and in their relative phase differences . we also searched for , but find no evidence for , the @xmath8 exotic @xmath19 in either the @xmath15 or @xmath16 mode . in order to extract reliable information from a partial wave analysis it is important to establish a procedure for determining a sufficient set of partial waves . failure to include important partial waves in the series expansion may lead to inconsistent results and erroneous conclusions . in this paper we describe our procedure for determining a sufficient wave set . that procedure includes a comparison of moments as calculated from pwa solutions with those computed directly from data . we emphasize that this analysis is similar to that of references   @xcite in that the same isobar model assumptions are made but the final set of partial waves used is different . both analyses make the same assumptions about coherence between different partial waves . it is possible that relaxing these coherence assumptions could lead to different results in both analyses . the @xmath17 system with non - zero charge has isospin @xmath31 , and , since no flavor exotic mesons have been found , we assume @xmath32 . since a state with an odd number of pions has negative @xmath33  parity , the relationship @xmath34 implies positive @xmath35  parity for the @xmath12 system . the simultaneous observation of the two @xmath12 modes , @xmath15 and @xmath16 , in the same experiment provides important cross checks . consider the production of resonance @xmath36 and its subsequent decay into @xmath12 via an intermediate di - pion resonance . if the intermediate di - pion resonance is an isoscalar , then the yield into @xmath16 should be twice that into @xmath15 . similarly , if the di - pion is an isovector , then there should be equal yields into @xmath16 and @xmath15 . since the @xmath0 and @xmath1 modes rely on different elements of the detector , any misunderstandings in the acceptance would affect the two modes differently and ultimately lead to inconsistent interpretations of the pwa results . this underscores the importance of having these two different modes to validate the analysis . quantum chromodynamics ( qcd ) predicts a spectrum of mesons beyond the @xmath37 bound states of the conventional quark model . the spin ( @xmath38 ) , parity ( @xmath39 ) and charge conjugation ( @xmath35 ) quantum numbers of a @xmath37 system are : @xmath40 where @xmath41 is the angular momentum between the quarks and @xmath42 is the total quark spin , @xmath43 and @xmath44 . the @xmath22 combinations : @xmath45 are not allowed and are called _ exotic _ . lattice qcd @xcite and qcd - inspired models predict that the excitation of the gluonic field within a meson leads to _ hybrid _ mesons , where the gluonic degrees of freedom allow hybrid mesons to have exotic quantum numbers . the observation of hybrid mesons and measurement of their properties provides experimental input necessary for an understanding of quark and gluon confinement in qcd . this paper is organized as follows . section  [ sec : experiment ] is a discussion of experimental details , including a description of the apparatus ( [ sec : apparatus ] ) , event reconstruction and selections ( [ sec : data ] ) and distributions in effective mass before and after acceptance corrections ( [ sec : masses ] ) . an overview of the pwa methodology , including selection of the wave set , is given in section  [ sec : pwamethod ] . section  [ sec : pwaresults ] is a presentation of the pwa results for individual partial waves using the wave set used in this analysis and the wave set used in the analysis of references @xcite for both the @xmath46 and @xmath47 modes . section  [ sec : exotica ] focuses on the exotic @xmath8 waves and how the failure to include important @xmath48 waves could lead to misleading conclusions regarding the existence of an exotic resonance . section  [ sec : systematics ] discusses studies of systematic uncertainties and the conclusions are presented in section  [ sec : conclude ] . the e852 experiment used the upgraded multiparticle spectrometer ( mps ) at the alternating gradient synchrotron ( ags ) at brookhaven national lab ( bnl ) . the apparatus is described in detail elsewhere @xcite and is shown schematically in figure  [ mps ] . the mps was upgraded for e852 with the inclusion of a cylindrical drift chamber ( tcyl ) @xcite and a cylindrical cesium iodide ( csi ) detector @xcite , both concentric with a lh@xmath49 target . downstream of the target were proportional wire chambers ( pwcs ) for triggering and tracking , a lead / scintillator array ( dea ) and a 3000-element lead glass electromagnetic calorimeter ( lgd ) . the csi calorimeter consisted of 180 segments  10 longitudinal segments and 18 azimuthal segments . the dea had the geometry of a picture frame with a rectangular central hole . a scintillation counter ( cpv ) was placed just upstream of and matched the geometry of the dea . the lead glass blocks of the lgd @xcite were each 45  cm long with a transverse area of @xmath50  @xmath51 and were arranged in a @xmath52  @xmath51 stack with a 2  block @xmath53 2  block beam hole to allow for passage of non - interacting beam particles . the dea and csi detected low - energy photons that miss the lgd . the lgd was used to measure energies and positions of photons from @xmath54 and @xmath55 mesons . the mps included an analyzing magnet with a 1  t field and drift chambers for tracking . the lh@xmath49 target was 30  cm long and 6  cm in diameter . the beam was an 18.3  gev/@xmath3 negatively charged beam consisting mainly ( 95% ) of @xmath56 and had a momentum bite @xmath57 of 3% and a momentum resolution @xmath58 of 1% . the target to lgd distance was approximately 5  m. the interacting beam trigger required no signal from a small scintillation counter placed in the path of the beam in coincidence with beam defining counters upstream of the mps . event triggers included all - neutral , all charged and a mix of neutral plus charged particle topologies . the neutral particle requirement depended on energy and/or multi - photon effective mass information from the lgd . we refer to the @xmath59 system as the _ neutral _ mode and the @xmath60 system as the _ charged _ mode . in tables [ cutsn ] and [ cutsc ] the selection requirements and resulting event sample sizes are summarized for the neutral and charged modes respectively . in what follows we discuss details of these requirements @xcite . .[cutsn]summary of requirements applied to the data set leading to @xmath61 . [ cols="<,>",options="header " , ]     another arbiter of wave set sufficiency is the comparison of moments , @xmath62 , of the @xmath63 functions as calculated directly from the data and as calculated using the results of pwa fits . a pwa using a sufficient set of partial waves will reproduce all angular distributions of the data as evidenced by the agreement of the observed and calculated moments . we define @xmath64 where @xmath65 represents the euler angles of the @xmath17 system and the intensity @xmath66 is determined directly from experiment or computed using the results of the pwa fits . both of these techniques were used in this analysis . the @xmath29 isobars included in this analysis are the @xmath67 , @xmath26 , @xmath24 , @xmath25 and @xmath27 where @xmath68 is meant to indicate a @xmath28-wave @xmath29 system as described in @xcite . in addition , a background wave is included . the background wave is characterized by a uniform distribution in the relevant decay angles and is added incoherently with the other waves . we restrict the parent wave set to those with @xmath69 , @xmath70 and @xmath71 . waves were sequentially removed from the parent set and the resulting change in likelihood ( @xmath72 ) examined @xcite . three passes were used . first , waves with an l=0 isobar ( @xmath73 @xmath28-wave and @xmath74 ) were examined . subsequent passes examined @xmath75 ( @xmath76 ) and @xmath77 ( @xmath78 ) isobar partial waves . a pwa with the wave in question removed was performed and the resulting likelihood compared to pwa including the wave . if the change in @xmath79 was less than 40 the wave was removed . figure  [ sig_nosig ] shows the change in @xmath79 when a significant , but not a dominant , wave ( @xmath80wave ) is removed compared to when an insignificant wave ( @xmath81wave ) is removed . certain partial waves that would have been removed by this selection criterion were kept because the existence of signals in these waves is under consideration . the negative reflectivity exotic @xmath82 partial waves were kept even though they would have been chosen for removal by the above criterion . the positive reflectivity exotic partial wave failed the selection criterion everywhere above 1.4 @xmath83 and exhibited large fluctuations in intensity below this mass . this partial wave was also kept and its contribution to the likelihood is further examined below using the final set of partial waves . finally , the @xmath84-wave ( which failed the selection test ) was kept to serve as a possible reference wave for evaluation of phase differences of negative reflectivity partial waves . based on these criteria the compiled set includes 35 waves and a background wave . we refer to this as the _ high - wave set_.    the analysis reported in reference  @xcite used a wave set consisting of 20 waves including the background wave  we refer to this as the _ low - wave set_. table  [ thewaves ] lists the waves used in low - wave and high - wave sets . the waves included only in the low - wave set are labeled with [ l ] in table  [ thewaves ] while the waves included only in the high - wave set are labeled with [ h ] and those included in both sets are labeled with [ b ] .      the pwa solutions obtained with the two wave sets were used to compute moments that were then compared directly with data . in figure  [ fig2 ] we show the @xmath85 and @xmath86 moment comparisons as a function of @xmath17 mass for the @xmath46 mode for low - wave and high - wave set pwa fits . we also show the difference between data and pwa calculations of the moments as @xmath87 ( summing differences squared divided by errors squared summed over all mass bins and divided by the number of mass bins ) for various moments . similar plots are shown in figure  [ fig3 ] for the @xmath88 mode . the moments calculated using the pwa results from the high wave set have better agreement with experimental moments , but there are moments ( such as @xmath85 - shown in part ( a ) of figure  [ fig3 ] ) for which agreement is not achieved . this may be due to the inherent inadequacy of the isobar model in describing the underlying production mechanism . an examination of figures  [ fig2](c ) and [ fig3](c ) show that for all the moments , the moments calculated using the high - wave set have better agreement with data than do moments calculated using the low - wave set . the pwa results presented in this section were for data with @xmath89  ( gev/@xmath3)@xmath90 referred to as @xmath91 in table  [ tbins ] . the analysis was also carried out in 11 other bins in @xmath92  some results of which will also be summarized below .    figure  [ nc_all_bkg ] shows the sum of all waves in the high - wave set along with the background wave for both the charged and neutral modes . the fitting procedure constrains the sum of all the waves to agree with the acceptance - corrected @xmath17 mass distribution . the background wave ( uniform in all angles ) is added incoherently with the other waves . as can be seen , the contribution from the background wave is small ( of order 1% ) . there is a systematic disagreement in the relative normalization between the two modes resulting from an overall per track inefficiency of 5% in the trigger pwc s . the overall inefficiency has no bearing on the features of the acceptances and was thus not incorporated into the monte carlo corrections , but results in the neutral mode having a yield consistently 25% higher than the charged mode . the neutral mode required only one forward - going charged particle in the trigger while the charged mode required three .    in the following we discuss intensities and phases of individual partial waves . a partial wave intensity corresponds to a single term of equation  ( [ int ] ) which is a product of the fitted partial wave amplitude , @xmath93 , and the isobar amplitude @xmath94 . similar to the procedure followed in references  @xcite , the intensities are integrated over acceptance corrected data , and are normalized to the total number of events . the coherent sum of the @xmath95 @xmath96-waves is shown in figure  [ coherent1pp ] for the @xmath47 and @xmath46 modes . for each the results from the high wave set and low wave set are shown . the @xmath95 wave is a dominant wave and the results of the pwa for the two wave sets ( high and low ) are in good agreement . the yield for the two charged modes is also consistent with expectations from isospin for the @xmath96 system .    the @xmath95 @xmath96 @xmath97-wave is not included in the high - wave set , since it did not meet criteria for inclusion , but it is included in the low - wave set . the observed ratio of @xmath95 @xmath96 @xmath28-wave to @xmath97-wave in the low - wave set is consistent with that of reference  @xcite . figure  [ 2pp ] shows the @xmath98-wave @xmath96 partial wave as a function of @xmath99 for both the neutral and charged modes . a clear @xmath5 signal is observed . for a pure @xmath96 isovector resonance , we expect an equal number of charged mode and neutral mode events . this wave is clean and robust and will be used for interferometry to study the phase motion of other waves relative to this wave . figures  [ 2mps ] and [ 2mpd ] show the intensities for the @xmath100-wave @xmath101 and @xmath102-wave @xmath101 waves respectively for both the charged and neutral modes . note that the relative yields between charged and neutral modes , for these @xmath101 decays are consistent with expectations from isospin , after taking into account the overall 25% reduction in yield for the charged mode . these intensities are also compared with those measured by daum  _ et . @xcite in a similar amplitude analysis of diffractive @xmath17 production in @xmath14 interactions at 63 and 94  gev/@xmath10 . the daum results have been arbitrarily scaled by a factor of 5 . the @xmath28 and @xmath97 @xmath101 modes both show a resonant - like structure but not at the same peak position . the @xmath28 wave peaks at approximately 1.6  gev/@xmath10 while the @xmath97 wave peaks at approximately 1.8  gev/@xmath10 . this shift in the peak position has been observed in other analyses  @xcite . this has been interpreted as the @xmath101 decay mode of two different resonances . the pdg places the @xmath6 @xmath103 resonance at a mass of 1.67  gev/@xmath10 based on fits to the @xmath28 wave mode alone . figure  [ a4 ] shows the @xmath104-wave @xmath96 intensity as a function of @xmath99 for both the neutral and charged modes . comparing figures [ a4 ] and [ 2pp ] the yield of @xmath7 is about 3% that of the @xmath5 indicating the sensitivity of the pwa within the isobar model for finding states with relatively low production cross - sections . the @xmath105-wave @xmath96 partial wave and its interference with the @xmath106 wave are shown in parts ( a ) and ( b ) of figures  [ exotic_n ] and [ exotic_c ] for the neutral mode ( @xmath46 ) and charged mode ( @xmath47 ) . when the low - wave set is used in the fit , an enhancement is observed for the exotic @xmath82 wave in the @xmath17 mass region around 1.6  gev/@xmath10 , consistent with the observation of @xcite . the enhancement disappears when the high wave set is used . this effect is observed for both @xmath17 channels . the phase of the exotic wave relative to the dominant @xmath106 wave ( see figures  [ exotic_n](b ) and [ exotic_c](b ) ) is similar for both wave sets and dominated by the phase of the @xmath5 . the apparent phase motion beginning around 1700  mev/@xmath10 is likely due to the @xmath107  @xcite , but the unreliability of the exotic intensity makes this an inappropriate place for its study . one source of leakage into the exotic wave for the pwa carried out with the low - wave set is the @xmath6 . in figure [ leaks ] the coherent sum of the intensities for the @xmath108-wave @xmath96 , @xmath109-wave @xmath96 and @xmath110-wave @xmath96 waves for the charged and neutral modes are shown . these waves are allowed decay modes of the @xmath6 . a clear peak is seen at the @xmath6 mass , the same mass region where the purported exotic meson was seen using the low - wave set . the three waves shown in figure  [ leaks ] were not included in the low - wave set . the pwa fit was repeated for the high wave set but with the @xmath108-wave @xmath96 , @xmath109-wave @xmath96 and @xmath110-wave @xmath96 waves removed . the resulting @xmath111-wave @xmath96 intensities for the neutral mode for this modified high wave set fit , along with the unmodified high wave set and low wave set , are shown in figures  [ neut_mod ] . the corresponding results for the charged mode are shown in figure  [ chrgd_mod ] . the agreement between the modified high wave set and the low wave set shows that the @xmath112-wave @xmath96 decays and the @xmath110-wave @xmath96 decay of the @xmath113 are the source of leakage leading to the observed exotic peak in the low wave set . a similar phenomenon is observed in the @xmath106 wave in the low wave set where the @xmath104-wave @xmath96 is not included . as discussed above , the @xmath104-wave @xmath96 in the high wave set clearly shows the @xmath7 . figure  [ leakage_2_4 ] shows a semi - log plot of the the @xmath106 intensity for charged @xmath17 mode for the high wave set ( filled circles ) and low wave set ( open circles ) . the @xmath114 intensity for the high wave set is also shown ( filled triangles ) . the @xmath5 is dominant in the @xmath106 intensity in both high and low wave sets . the @xmath106 intensity for the low wave set shows a resonance - like structure near 2  gev/@xmath10 in low wave set but not the high wave set . however the @xmath106 low wave set intensity agrees well with the @xmath114 high wave set intensity . in this case , leaving out the @xmath114 in the low wave set forces a enhancement at @xmath115  gev/@xmath10 in the @xmath106 wave . the contribution to the @xmath116 of the positive reflectivity exotic partial wave was examined by removing this wave from the high wave set and comparing the resulting likelihood with that of the original high wave pwa . figure [ exot_dlnl ] shows the resulting change in likelihood . the sign convention of this difference is such that positive ( negative ) values indicate inclusion of this partial wave improved ( degraded ) the fit quality . as can be seen from figure [ exot_dlnl ] there is no region of @xmath117 effective mass where this partial wave is consistently required by the fit . this behavior is seen in all t - bins presented here . we examined the stability of the exotic wave intensity and the intensity of other waves across the 12 @xmath118-bins shown in table  [ tbins ] for the high wave fit in the charged @xmath17 . as noted in table  [ tbins ] , the width of the @xmath92 bin for the first five bins is 0.02  ( gev/@xmath3)@xmath90 and 0.05  ( gev/@xmath3)@xmath90 for the other bins . figures  [ exoticw ] , [ pi2 t ] and [ phasex ] show the variation of the @xmath105-wave @xmath96 intensity , the @xmath100-wave @xmath101 intensity and the phase difference between the @xmath82 and @xmath103 amplitudes for the charged @xmath17 mode for the 12 @xmath118-bins . the @xmath100-wave @xmath101 intensity is stable across the 12 @xmath118 bins . we note that although the @xmath105-wave @xmath96 intensity may indicate an enhancement in the vicinity of @xmath119  gev/@xmath10 for some of the higher @xmath118 bins in figure  [ exoticw ] , the corresponding phase difference shown in figure  [ phasex ] is not consistent with resonant behavior . indeed the @xmath100-wave @xmath101 and @xmath105-wave @xmath96 are phase - locked in the 1.6  gev/@xmath10 region . one possible explanation is production of an exotic resonance with the same mass , width and phase motion as the @xmath6 . another is some residual leakage of the @xmath6 in the exotic wave in the high - wave set . the @xmath98-wave @xmath96 intensity ( shown in figure  [ plot_a2 ] ) and the @xmath104-wave @xmath96 intensity ( shown in figure  [ plot_a4 ] ) are shown for the 12 @xmath118 bins . for completeness , in figure  [ dsdt_a2 ] , we compare the @xmath118 dependence of the @xmath98-wave @xmath96 intensity , dominated by the @xmath5 , in both @xmath17 modes in this experiment , with other measurements of @xmath120 at 18.8  gev/@xmath3@xcite . studies were carried out to determine the effect on the pwa of varying the parameters that define the selection criteria as described in section  [ sec : data ] . different criteria were found to effect the results in different ways but no significant change in our conclusions was observed . the effects of these perturbations on the analysis are described individually below . the beam hole cut is nominally @xmath121 . values of @xmath122 and @xmath123 systematically increased and decreased the intensity of the @xmath124 @xmath28-wave below 1.2  gev/@xmath10 but left the mass region above 1.2  gev@xmath125 indistinguishable from the unperturbed analysis . the changes observed were approximately 5% of the intensity . conclusions regarding the low mass behavior of this partial wave should take into account this systematic effect . other partial waves were unaffected . the cut to remove the @xmath126 in the charged sample affected the data only above 2.0 gev/@xmath10 . removing this cut from the analysis increased the intensity of the @xmath127 @xmath28-wave by approximately twice its error between 2.0 and 2.4 gev/@xmath128 . the systematic effect on other partial waves is insignificant when compared with their statistical errors . the effect of removing the dea cut was similar to using a less restrictive value for the beam hole cut . small , but statistically significant , increases in the intensity of the @xmath127 @xmath28-wave were observed between 1.2 and 1.6 gev/@xmath128 . increasing ( decreasing ) the confidence level cut to 0.3 ( 0.1 ) changed the observed intensities everywhere by a mass independent scale factor . the same effect was observed for the csi cut . removing this cut increased all intensities by a factor of 1.66 but left their shapes unchanged .    in summary , we have investigated the effect of perturbing the selection criteria summarized in tables  [ cutsn ] and [ cutsc ] on the results of the partial wave fit and have shown that our results do not depend on the specific values used in the criteria . we used the isobar model , following the same methodology employed in references  @xcite . this model uses two - body amplitudes for the @xmath29 system . the @xmath129 isovector and @xmath130 isoscalar amplitudes were parametrized using breit - wigner amplitudes . there are various @xmath131 , isoscalar parametrizations available in the literature . in general the @xmath29 amplitude is dominated by a broad @xmath68 meson , the @xmath26 and several resonances above @xmath132 , depending on the specific parametrization . the results presented in this paper were all based on the parametrization used in references  @xcite . this is based on the model of  @xcite with the possibility of direct @xmath26 production ; the @xmath26 was subtracted from the elastic @xmath29 amplitude and added as a breit - wigner resonance . we have also studied other parametrizations , _ e.g. _ based on ( 1 )  @xmath133 dispersion relations , ( 2 )  explicit inclusions of the @xmath134 channel and/or ( 3 )  including direct production of scalar resonances above @xmath135  @xcite . all give qualitatively identical results . a partial wave analysis of the @xmath136 and @xmath137 systems has been presented using a data set whose statistics exceeds published analyses of the @xmath17 systems . the @xmath4 , @xmath5 , @xmath6 and @xmath7 mesons were observed . the data provide no evidence for an exotic @xmath8 meson as had been reported earlier using a smaller sample of the @xmath136 mode alone @xcite . this analysis included the study of criteria for defining a set of partial waves sufficient to describe the data including a study of the effect on the fit quality by removing individual waves and also a comparison of observed moments of the data with moments computed from pwa solutions . the wave set thus established contained more waves than were used in the analysis reporting evidence for the exotic meson . our studies indicate that leaving out partial waves corresponding to decay modes of the @xmath6 lead to a false enhancement in the exotic @xmath82 wave . this analysis and the analysis of references  @xcite were based on the isobar model . the isobar model is known to suffer some limitations , as has been pointed by others @xcite . the so - called _ deck mechanism _ @xcite is particularly relevant to the production of the @xmath17 system and is being applied to these data . results will be presented in a forthcoming paper . the authors thank jozef dudek , geoffrey fox and matt shepherd for enlightening discussions and for their careful read and critique of this paper . this work was supported by grants from the united states department of energy ( de - fg-91er40661/task  d and de - fg0287er40365 ) , the national science foundation ( eia-0116050 ) for avid , the russian ministry of science and technology and russian ministry of science and education . the authors of this paper have made available technical notes and pwa results online @xcite . the notes include ( 1 )  details of the data selection ; ( 2 )  a comparison of the software used in this analysis with that used in the analysis of reference  @xcite ; ( 3 )  the monte carlo details for this analysis ; ( 4 )  a full description of the pwa formalism ; ( 5 )  the moments method technique and definition of angles ; ( 6 )  a study of background contributions to partial wave intensities ; ( 7 )   stability of pwa results against variations in data selection criteria ; ( 8)   acceptance and resolution ; ( 9 )  the determination of the minimal partial wave set and ( 10 )  @xmath28-wave parametrization . in addition , pwa results ( amplitudes and phases ) are available for 12  bins in @xmath118 and for various wave sets . a. r. dzierba _ et . the authors of this paper have posted notes on the web regarding the 3@xmath23 data processing and selection , pwa formalism , software and other details . url : dustbunny.physics.indiana.edu/3pi_paper ( 2005 ) .
a partial wave analysis ( pwa ) of the @xmath0 and @xmath1 systems produced in the reaction @xmath2 at 18  gev/@xmath3 was carried out using an _ isobar _ model assumption . 
 this analysis is based on 3.0 m @xmath1 events and 2.6 m @xmath0 events and shows production of the @xmath4 , @xmath5 , @xmath6 and @xmath7 resonances . 
 results of detailed studies of the stability of partial wave fits are presented . 
 an earlier analysis of 250k @xmath0 events from the same experiment showed possible evidence for a @xmath8 exotic meson with a mass of @xmath91.6  gev/@xmath10 decaying into @xmath11 . in this analysis of a higher statistics sample of the @xmath12 system in two charged modes 
 we find no evidence of an exotic meson .