The reaction pp -> pf (eta pi pi) ps has been studied at 450 GeV/c. There is
clear evidence for an a2(1320)pi decay mode of the eta2(1645) and eta2(1870).
In addition, there is evidence for an a0(980)pi$ decay mode of both resonances
and an f2(1270)eta decay mode of the eta2(1870). No evidence is found for a JPC
= 2++ a2(1320)pi wave.Comment: 15 pages, Latex, 4 Figures Branching ratio a2pi /f2 eta correcte

Barberis, D

Binon, F.G

Close, F.E

Danielsen, K.M

Donskov, S.V

Earl, B.C

Evans, D

French, B.R

Hino, T

Inaba, S

Jacholkowski, A

Jacobsen, T

Khaustov, G.V

Kinson, J.B

Kirk, A

Kondashov, A.A

Lednev, A.A

Lenti, V

Minashvili, I

Peigneux, J.P

Romanovsky, V

Russakovich, N

Semenov, A

Shagin, P.M

Shimizu, H

Singovsky, A.V

Sobol, A

Stassinaki, M

Stroot, J.P

Takamatsu, K

Tsuru, T

Villalobos Baillie, O

Votruba, M.F

Yasu, Y

Physics Letters B

English

arXiv

Barberis, Dario

Binon, Freddy

Close, F.E.

Danielsen, K.M.

Donskov, Sergey

Earl, B.C.

French, B.R.

Hino, T.

Inaba, Susumu

Jacholkowska, Agnieszka

Jacobsen, Torben

Khaustov, Guennady V.

Kinson, J.B.

Kirk, Andrew

Kondashov, Andrei A.A.

Lednev, Andrey

Lenti, V.

Minashvili, I.

Peigneux, Jean Pierre

Romanovsky, V.

DI-fusion

A study of the ηπ+π-channel produced in central pp interactions at 450 GeV/c

The reaction pp -> pf (eta pi pi) ps has been studied at 450 GeV/c. There is clear evidence for an a2(1320)pi decay mode of the eta2(1645) and eta2(1870). In addition, there is evidence for an a0(980)pi$ decay mode of both resonances and an f2(1270)eta decay mode of the eta2(1870). No evidence is found for a JPC = 2++ a2(1320)pi wave

Barberis, D.

Binon, F G.

Close, F E.

Danielsen, K M.

Donskov, S V.

Earl, B C.

Evans, D.

French, B R.

Inaba, S.

Jacholkowski, A.

Jacobsen, T.

Khaustov, G V.

Kinson, J B.

Kirk, A.

Kondashov, a A.

Lednev, a A.

Peigneux, J P.

Russakovich, N.

Semenov, A.

Shagin, P M.

Shimizu, H.

Singovsky, a V.

Sobol, A.

Stassinaki, M.

Stroot, J P.

Takamatsu, K..

Tsuru, T.

Villalobos Baillie, O.

Votruba, M F.

Yasu, Y.

Hal - Université Grenoble Alpes

A study of the $\eta\pi^{+}\pi^{-}$ channel produced in central pp interactions at 450 GeV/c

D Barberis

F.G Binon

F.E Close

K.M Danielsen

S.V Donskov

B.C Earl

D Evans

B.R French

T Hino

S Inaba

A Jacholkowski

T Jacobsen

G.V Khaustov

J.B Kinson

A Kirk

A.A Kondashov

A.A Lednev

V Lenti

I Minashvili

J.P Peigneux

V Romanovsky

N Russakovich

A Semenov

P.M Shagin

H Shimizu

A.V Singovsky

A Sobol

M Stassinaki

J.P Stroot

K Takamatsu

T Tsuru

O Villalobos Baillie

M.F Votruba

Y Yasu

Crossref

A study of the ηπ+π− channel produced in central pp interactions at 450 GeV/c

HAL Université de Savoie

A study of the ηpi+pi− channel produced in central ppinteractions at 450 GeV/cD. Barberis, F G. Binon, F E. Close, K M. Danielsen, S V. Donskov, B C.Earl, D. Evans, B R. French, T. Hino, S. Inaba, et al.To cite this version:D. Barberis, F G. Binon, F E. Close, K M. Danielsen, S V. Donskov, et al.. A study of theηpi+pi− channel produced in central pp interactions at 450 GeV/c. Physics Letters B, Elsevier,2000, 471, pp.435-439. <in2p3-00005399>HAL Id: in2p3-00005399http://hal.in2p3.fr/in2p3-00005399Submitted on 26 May 2000HAL is a multi-disciplinary open accessarchive for the deposit and dissemination of sci-entific research documents, whether they are pub-lished or not. The documents may come fromteaching and research institutions in France orabroad, or from public or private research centers.L’archive ouverte pluridisciplinaire HAL, estdestine´e au de´poˆt et a` la diffusion de documentsscientifiques de niveau recherche, publie´s ou non,e´manant des e´tablissements d’enseignement et derecherche franc¸ais ou e´trangers, des laboratoirespublics ou prive´s.25 November 1999A study of the +− channel produced in central ppinteractions at 450 GeV/cThe WA102 CollaborationD.Barberis4, F.G.Binon6, F.E.Close3,4, K.M.Danielsen11, S.V.Donskov5, B.C. Earl3,D. Evans3, B.R. French4, T.Hino12, S. Inaba8, A. Jacholkowski4, T. Jacobsen11,G.V.Khaustov5, J.B.Kinson3, A.Kirk3, A.A.Kondashov5, A.A. Lednev5, V. Lenti4,I.Minashvili7, J.P. Peigneux1, V.Romanovsky7, N.Russakovich7, A. Semenov7, P.M. Shagin5,H. Shimizu10, A.V. Singovsky1,5, A. Sobol5, M. Stassinaki2, J.P. Stroot6, K.Takamatsu9,T.Tsuru8, O.Villalobos Baillie3, M.F.Votruba3, Y.Yasu8.AbstractThe reaction pp ! pf(+−)ps has been studied at 450 GeV/c. There is clear evidencefor an a2(1320) decay mode of the 2(1645) and 2(1870). In addition, there is evidence foran a0(980) decay mode of both resonances and an f2(1270) decay mode of the 2(1870). Noevidence is found for a JPC = 2++ a2(1320) wave.Submitted to Physics Letters1 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.In an analysis of the +−+− final state the WA102 collaboration observed three peaksin the mass spectrum [1]. A spin analysis showed that the peak at 1.28 GeV was due tothe f1(1285), the peak at 1.45 GeV could be interpreted as being due to interference betweenthe f0(1370) and f0(1500) and the peak at 1.9 GeV, called the f2(1950), was found to haveIGJPC = 0+2++ and decay to f2(1270) and a2(1320) [1]. However, it was not possible todetermine whether the f2(1950) was one resonance with two decay modes, or two resonances,or if one of the decay modes was spurious.One of the major problems of studying the +−+− final state is the number of possibleisobar decay modes that are present. Therefore in this paper, in order to study the a2(1320)final state, an analysis is presented of the +− channel. In addition, the spin analysis of the+−+− channel showed evidence in the JPC = 2−+ a2(1320) wave for the 2(1645) and2(1870). There has been previous evidence [2] that the 2(1645) and 2(1870) may decay toa0(980) and f2(1270). These two decay modes will be searched for in the present analysis.The data come from the WA102 experiment which has been performed using the CERNOmega Spectrometer, the layout of which is described in ref. [3]. The selection of the reactionpp ! pf(+−)ps (1)where the subscripts f and s indicate the fastest and slowest particles in the laboratory respec-tively, has been described in ref. [4]. The  has been observed decaying to γγ and +−0.Fig. 1a) and 1b) show the +− mass spectra for the decays  ! γγ and  ! +−0respectively. The mass spectra are dominated by the 0 and f1(1285).In this current paper a spin-parity analysis of the +− channel is presented for the massinterval 1.0 to 2.0 GeV using an isobar model [5]. Assuming that only angular momenta upto 2 contribute, the intermediate states considered are a0(980), , f0(980), a2(1320), andf2(1270).  stands for the low mass  S-wave amplitude squared [6]. The amplitudes havebeen calculated in the spin-orbit (LS) scheme using spherical harmonics. In order to performa spin parity analysis the Log Likelihood function, Lj = ∑i log Pj(i), is defined by combiningthe probabilities of all events in 40 MeV +− mass bins from 1.0 to 2.0 GeV. The incoherentsum of various event fractions aj is calculated so as to include more than one wave in the fit,using the form:L = ∑ilog∑jajPj(i) + (1−∑jaj) (2)where the term (1 −∑j aj) represents the phase space background. This background term isused to account for the background below the  (which is 10 % for the γγ decay mode and 15 %for the +−0 decay mode), +− three body decays and decay modes not parameterisedin the fit. The negative Log Likelihood function (−L) is then minimised using MINUIT [7].Different combinations of waves and isobars have been tried and insignificant contributionshave been removed from the final fit.The spin analysis has been performed independently for the two  decay modes. As wasshown in the previous analysis [4], for both decay modes and for M(+− )  1.5 GeV theonly wave required in the fit is the JPC = 1++ a0(980) wave with spin projection jJZj = 1.No JPC = 0−+ a0(980) or any  waves are required in the fit. Fig. 2a) and 3a) showthe JPC = 1++ a0(980) wave where the f1(1285) and a shoulder at 1.4 GeV can be seen.2Superimposed on the waves is the result of the fit used in ref. [4] which uses a K matrixformalism including poles to describe the interference between the f1(1285) and the f1(1420).As can be seen from fig. 2a) and 3a) the parameterisation describes well the JPC = 1++ a0(980)wave.For M(+− )  1.5 GeV only waves with JPC = 2−+ and jJZ j = 1 are required in thefit. In contrast to what was found in the analysis of the +−+− final state [1] there isno evidence for any JPC = 2++ a2(1320) wave. The largest change in Log Likelihood comesfrom the addition of the JPC = 2−+ a2(1320) wave with jJZj = 1 which yields a Likelihooddifference ∆L = 562 and 203 for the  ! γγ and  ! +−0 decays respectively and areshown in fig. 2b) and 3b).As was observed in the case of the +−+− channel [1], the JPC = 2−+ a2(1320) waveis consistent with being due to two resonances, the 2(1645) and the 2(1870). Superimposedon figs. 2b) and 3b) is the result of a fit using a single channel K matrix formalism [9] with tworesonances to describe the 2(1645) and 2(1870). The masses and widths determined for eachresonance and each  decay mode are given in table 1. The parameters found are consistentfor the two decay modes and with the PDG [8] values for these resonances. An alternative fithas been performed using two interfering Breit-Wigners. The parameters presented include notonly the statistical error but also the systematic error, added in quadrature, representing thedifference in the two fits.The addition of the JPC = 2−+ a0(980) wave with jJZj = 1 yields a Likelihood difference∆L = 66 and 23 for the two  decay modes respectively and the waves are shown in figs. 2c)and 3c). Superimposed is the result of a fit using the parameters for the 2(1645) and the2(1870) determined from the fit to the a2(1320) final state. A good description of the datais found. The branching ratio of the 2(1645) and 2(1870) to a2(1320)=a0(980) in the final state can be determined. Neglecting unseen decay modes the branching ratio of 2(1645)to a2(1320)/a0(980) = 2.3  0.4 and 2.1  0.5 for the decays  ! γγ and  ! +−0respectively. The branching ratio of 2(1870) to a2(1320)/a0(980) = 5.0  1.6 and 6.0  1.9respectively.Correcting for the unseen a2(1320) decay modes using the PDG [8] branching ratio and usingthe branching ratio for the a0(980) to  determined by this experiment [4] of 0.86  0.10 andtaking the average of the two  decay modes the branching ratio to a2(1320)/a0(980) for the2(1645) is 13.0  2.7 and for the 2(1870) is 32.6  12.6.The addition of the JPC = 2−+ f2(1270) wave with jJZ j = 1 yields a Likelihood difference∆L = 42 and 12 and the waves are shown in figs. 2d) and 3d). The f2(1270) wave showslittle evidence for the 2(1645). Superimposed is the result of a fit using the parameters for the2(1870) determined from the fit to the a2(1320) final state. A satisfactory description of thedata is found. Correcting for the unseen a2(1320) and f2(1270) decay modes the branching ratioof the 2(1870) to a2(1320)=f2(1270) has been determined to be 38.5  14.4 and 56.0  33.4for the two  decay modes. The addition of the JPC = 2−+ f0(980) or JPC = 2−+  wavesproduces no significant change in the Likelihood and hence they have been excluded from thefit. The resulting background term is found to be smooth and structureless and corresponds to 40 % of the channel.In previous analyses it has been observed that when the centrally produced system has been3analysed as a function of the parameter dPT , which is the difference in the transverse momentumvectors of the two exchange particles [3, 10], all the undisputed qq states (i.e. , 0, f1(1285)etc.) are suppressed as dPT goes to zero, whereas the glueball candidates f0(1500), f0(1710)and f2(1950) are prominent [11]. In order to calculate the contribution of each resonance as afunction of dPT , the waves have been fitted in three dPT intervals with the parameters of theresonances fixed to those obtained from the fits to the total data. Table 2 gives the percentageof each resonance in three dPT intervals together with the ratio of the number of events for dPT< 0.2 GeV to the number of events for dPT > 0.5 GeV for each resonance considered. Thesedistributions are similar to what have been observed for other qq states [11].In addition, an interesting effect has been observed in the azimuthal angle  which is definedas the angle between the pT vectors of the two outgoing protons. For the resonances studiedto date which are compatible with being produced by DPE, the data [12]. are consistent withthe Pomeron transforming like a non-conserved vector current [13]. In order to determinethe  dependence for the resonances observed, a spin analysis has been performed in the+− channel in four different  intervals each of 45 degrees. The results are shown in fig. 4a)and b) for the 2(1645) and 2(1870) respectively.In order to determine the four momentum transfer dependence (jtj) of the resonances ob-served in the +− channel the waves have been fitted in 0.1 GeV2 bins of jtj with the param-eters of the resonances fixed to those obtained from the fits to the total data. Fig. 4c) and d)show the four momentum transfer from one of the proton vertices for the 2(1645) and 2(1870)respectively. The distributions cannot be fitted with a single exponential. Instead they havebeen fitted to the formddt= e−b1t + te−b2tThe parameters resulting from the fit are given in table 3.After correcting for geometrical acceptances, detector efficiencies, losses due to cuts, andunseen decay modes of the a2(1320), the cross-section for the 2(1645) and 2(1870) decayingto a2(1320) atps = 29.1 GeV in the xF interval jxF j  0:2 has been determined to be(2(1645)) = 1664  149 nb, and (2(1870)) = 1845  183 nb.A Monte Carlo simulation has been performed for the production of a JPC = 2−+ statewith spin projection jJZ j =1 via the exchange of two non-conserved vector currents using themodel of Close and Schuler [13] discussed in ref. [12]. The prediction of this model is found tobe in qualitative agreement with the observed , dPT and t distributions of the 2(1645) and2(1870). This will be presented in a later publication.In summary, there is evidence for an a2(1320) decay mode of the 2(1645) and 2(1870)in the +− final state. In addition, there is evidence for an a0(980) decay mode of bothresonances and possibly a f2(1270) decay mode of the 2(1870). There is no evidence for anyJPC = 2++ a2(1320) wave, in particular no evidence for the decay f2(1950) ! a2(1320).AcknowledgementsThis work is supported, in part, by grants from the British Particle Physics and AstronomyResearch Council, the British Royal Society, the Ministry of Education, Science, Sports andCulture of Japan (grants no. 07044098 and 1004100), the French Programme International4de Cooperation Scientifique (grant no. 576) and the Russian Foundation for Basic Research(grants 96-15-96633 and 98-02-22032).5References[1] D. Barberis et al., Phys. Lett. B413 (1997) 217.[2] K. Karch et al., Zeit. Phys C54 (1992) 33;B. Adomeit et al., Zeit. Phys C71 (1996) 227.[3] D. Barberis et al., Phys. Lett. B397 (1997) 339.[4] D. Barberis et al., Phys. Lett. B440 (1998) 225.[5] S. Abatzis et al., Phys. Lett. B324 (1994) 509.[6] B. S. Zou and D. V. Bugg, Phys. Rev. D48 (1993) R3948;K. L. Au, D. Morgan and M. R. Pennington, Phys. Rev. D35 (1987) 1633;D. Barberis et al., In preparation.[7] F. James and M. Roos, MINUIT Computer Physics Communications 10 (1975) 343;CERN-D506 (1989).[8] Particle Data Group, European Physical Journal C3 (1998) 1.[9] S.U. Chung et al., Ann. d. Physik. 4 (1995) 404.[10] F.E. Close and A. Kirk, Phys. Lett. B397 (1997) 333.[11] A. Kirk, Yad. Fiz. 62 (1999) 439.[12] D. Barberis et al., hep-ex/9909013 To be published in Phys. Lett.[13] F.E. Close and G. Schuler, Phys. Lett. B464 (1999) 279.6TablesTable 1: Parameters of the 2(1645) and 2(1870)Resonance Final state Mass (MeV) Width (MeV)2(1645)  1605  12 188  22 ! γγ2(1645)  1619  11 179  28 ! +−02(1870)  1841  18 249  30 ! γγ2(1870)  1831  16 219  33 ! +−07Table 2: Production of the resonances as a function of dPT expressed as a percentage of theirtotal contribution and the ratio (R) of events produced at dPT  0.2 GeV to the events producedat dPT  0.5 GeV.dPT0.2 GeV 0.2dPT0.5 GeV dPT0.5 GeV R = dPT0.2GeVdPT0.5GeV2(1645) 8.9  1.1 32.2  3.0 58.9  5.2 0.15  0.022(1870) 8.2  1.0 28.6  2.8 63.2  5.6 0.13  0.028Table 3: The slope parameters from a fit to the jtj distributions of the form dσdt= e−b1t+te−b2t. b1  b2GeV−2 GeV−22(1645) 0:4 0:1 6:4 2:0 2:6 0:9 7:3 1:32(1870) 0:3 0:1 5:9 3:5 4:3 1:5 8:3 2:09FiguresFigure 1: The +− mass spectrum for a)  ! γγ and b)  ! +−0.Figure 2: The +− mass spectrum for the decay  ! γγ. a) The JPC = 1++ a0(980)wave, b) the JPC = 2−+ a2(1320) wave, c) the JPC = 2−+ a0(980) wave and d) theJPC = 2−+ f2(1270) wave.Figure 3: The +− mass spectrum for the decay  ! +−0. a) The JPC = 1++ a0(980)wave, b) the JPC = 2−+ a2(1320) wave, c) the JPC = 2−+ a0(980) wave and d) theJPC = 2−+ f2(1270) wave.Figure 4: The azimuthal angle () between the two outgoing protons for a) the 2(1645) andd) the 2(1870). The four momentum transfer squared (jtj) from one of the proton vertices forc) the 2(1645) and d) the 2(1870) with fits described in the text.10Figure 111Figure 212Figure 313Figure 414

The reaction pp to p/sub f/( eta pi /sup +/ pi /sup -/)p/sub s/ has been studied at 450 GeV/c. There is clear evidence for an a/sub 2 /(1320) pi decay mode of the eta /sub 2/(1645) and eta /sub 2/(1870). In addition, there is evidence for an a/sub 0/(980) pi decay mode of both resonances and an f/sub 2/(1270) eta decay mode of the eta /sub 2/(1870). No evidence is found for a J/sup PC/=2/sup ++/a/sub 2 /(1320) pi wave. (8 refs).The reaction pp → p f ( ηπ + π − ) p s has been studied at 450 GeV/c. There is clear evidence for an a 2 (1320) π decay mode of the η 2 (1645) and η 2 (1870). In addition, there is evidence for an a 0 (980) π decay mode of both resonances and an f 2 (1270) η decay mode of the η 2 (1870). No evidence is found for a J PC =2 ++ a 2 (1320) π wave.The reaction pp -> pf (eta pi pi) ps has been studied at 450 GeV/c. There is clear evidence for an a2(1320)pi decay mode of the eta2(1645) and eta2(1870). In addition, there is evidence for an a0(980)pi$ decay mode of both resonances and an f2(1270)eta decay mode of the eta2(1870). No evidence is found for a JPC = 2++ a2(1320)pi wave

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A study of the $\eta \pi^{+} \pi^{-}$ channel produced in central pp interactions at 450 GeV/c

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

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

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