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E.G.Boos, N.S.Pokrovsky, V.V.Samoilov, T.Temiraliev, R.A.Tursunov, B.O.Zhautykov

INVESTIGATION OF MULTIPLE PRODUCTION OF HADRONS IN ANTIPROTON-PROTON AND PROTON-PROTON INTERACTIONS AT 22.4, 32 AND 69 GeV/c. E.G.Boos, N.S.Pokrovsky, V.V.Samoilov, T.Temiraliev, R.A.Tursunov, B.O.Zhautykov Institute of Physics and Technology Ministry of Education and Science

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E.G.Boos, N.S.Pokrovsky, V.V.Samoilov, T.Temiraliev, R.A.Tursunov, B.O.Zhautykov

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  1. INVESTIGATION OF MULTIPLE PRODUCTION OF HADRONS IN ANTIPROTON-PROTON AND PROTON-PROTON INTERACTIONS AT 22.4, 32 AND 69 GeV/c. E.G.Boos, N.S.Pokrovsky, V.V.Samoilov, T.Temiraliev, R.A.Tursunov, B.O.Zhautykov Institute of Physics and Technology Ministry of Education and Science Republic of Kazakhstan Almaty The correlations of secondary pions in annihilation and non-annihilation channels are investigated.

  2. Experimental material on - interactions has been obtained using hydrogen bubble chamber (HBC) «Ludmila» [6] (22.4 GeV/c) and HBC «Mirabelle» [7] ( 32 GeV/c), and on - inelastic events - HBC «Mirabelle» [8] (69 GeV/c). The bubble chambers were exposed at Serpukhov accelerator. The separation of antiproton-proton annihilation events from the total statistics of -interactions was performed in two stages: first of all – by using the results of identification non-annihilation events were excluded; secondly – separation of non-annihilation events by using additional information on missing mass.

  3. The interactions, remained after procedure of exclusion of events with protons and antiprotons, can be divided into three groups: ( I ) - the group of annihilation reactions, in which neutrons (antineutrons) are absent in the final state , where k is the integer; x0 - neutral system; (II) - the group of non-annihilation reactions, containing neutrons and antineutrons in the final state ; (III) - the group with non-identified protons and antiprotons among charged particles. At the second stage in mentioned three groups the values of missing masses were calculated on the basis of charged particles (1). Corresponding distributions are shown in Fig. 1.

  4. N M,GeV/c2 M- distributions. Unshaded parts – distributions on . Shaded parts – distributions on effective mass . a) – 2-prongs; b) – 4-prongs; c) – 6-prongs; d) – 8-prongs; e) – 10-prongs; f) – summary distribution. Fig.1

  5. It can be seen from Fig. 1 that in six-, eight-, and ten-prong events the admixture of non-annihilation processes into reactions corresponding to annihilation, is practically absent. This admixture equals to about 40% for 2-prong events, < 3% for 4 -and more prong events and  12% for the total distribution. Separation of annihilation events begins from those ones, which have the smallest missing masses; the numbers of selected events (arrows in the Fig.1) corresponds to cross-sections, evaluated for semi - inclusive antiproton-proton reactions.

  6. Comparison of quasirapidity correlations in antiproton-proton annihilation events with corresponding data for inelastic - and non-annihilation - interactions. Separation of the individual events corresponding to antiproton-proton annihilation gives the possibility to carry out the analysis of multiparticle correlations for generated particles and to compare them with corresponding data for inelastic and non-annihilation interactions. Let us consider the correlation function [10,11] , (2) where - the difference of quasirapidities; and - quasirapidities of boundary particles of the interval with (k - 1) charged particles inside it; - measured differential distribution; - expected differential distribution in the absence of correlations (background distribution).

  7. Figure 2.RK dependence on G in non-annihilation channels{ at 22.4 GeV/c – a); at 32 GeV/c – b)} and in at 69 GeV/c – c).

  8. It is visible, that in the region of small rapidity intervals (0G1) and in the region of large rapidity intervals (G> G2) positive correlation RK (G)> 0 is observed, and in the region of (G1 <G <G2) the value of RK (G) becomes negative for all considered values к=(25). Here G1 - the left point of crossing of function RK (G) with axis G; G2 – the-right point of crossing of function RK (G) with axis G. In Fig.3 the results obtained for dependence RK on G at the analysis of inclusive reactions of antiproton-proton annihilation for k=(25) at momenta 22.4 GeV/c (Fig 3a) and 32 GeV/c (Fig.3b) are presented.

  9. Figure 3. RK dependence on G:a) -annihilation at 22.4 GeV/c; b) - annihilation at 32 GeV/c.

  10. From comparison of Figures 2 and 3 it can be seen that in non-annihilation - interactions the noticeable, in comparison with annihilation events, correlation of particles is observed, qualitatively coinciding with correlation of particles in inelastic - interactions at 69 GeV/c. This effect could be connected with nucleon isobar production. In antiproton-proton annihilation events at 32 GeV/c the positive values of RK(G) in the region of small G at k=(3÷5) are observed (Fig.3b), whereas at antiproton momentum 22.4 GeV/c (Fig.3a) such correlation is absent. In Fig.4 the dependences of RK on G are presented at each multiplicity for antiproton-proton annihilation at momentum 32 GeV/c with the purpose to find out the connection of correlations observed with multiplicity.

  11. Figure 4. RK dependence on G for -annihilation at 32 GeV/c:a)       8-prongs; b) 10-prongs; c) 12-prongs.

  12. Thus, observed correlations of particles in inclusive channel of antiproton-proton annihilation are caused by interactions with multiplicities 8 and more. From here it is possible to make the conclusion that at momentum 32 GeV/c there is a new reaction channel with creation of meson resonances decaying into 4 and more charged particles. The authors are sincerely grateful to participants of international collaborations «Ludmila» and «Mirabelle» for fruitful joint work in obtaining primary experimental data. References  1.   Raja R. // Phys. Rev.1977, v.D16, p.142. 2.   Boos E.G., Ermilova D.I. et al. // Nucl. Phys.1977, v. B121, p.381. 3.   Smirnova L.N. // Sov. J. Nucl. Phys. 1988, v.47, p. 419. 4.   Ward C.P., Ward D.R. et al. // Nucl. Phys. 1979, v. B153, p.299. 5.   Boos E.G., Temiraliev T., Pokrovsky N.S., Samoilov V.V., Lonskaya G.E. // Izv. MON RK-NAN RK, ser. fiz.- mat., 2000,№2,p.35. 6.   Batyunya B.V. et al. // Preprint JINR E1-81-739, Dubna, 1981. 7.   Hanumaiah B., Sarycheva L.I. et al. // Il Nuovo Cimento 1982, v.68A, p.161. 8.   Bumazhnov V.A., Ermolov P.F., Fenyuk A.S. et al. // Phys. Lett. 1974, B50, p.283. 9. Boos E.G., Ermilova D.I. et al. // Sov. J. Nucl. Phys.1986, v.43, p.105. 10. Boos E.G., Vinitsky A.A., Ermilova D.I. et al. //Preprint HEPI AN KazSSR 90-03, Alma-Ata, 1990. 11. Boos E.G., Temiraliev T. et al. //Izv.MON RK-NAN RK, ser.fiz.-mat., 2002, №2, p.59.

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