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Long Range Correlations in String Fusion Model

Long Range Correlations in String Fusion Model. V.V.Vechernin, R.S. Kolevatov V.A. Fock Institute of Physics, St.-Petersburg State University. Introduction. Two stage scenario

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Long Range Correlations in String Fusion Model

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  1. Long Range Correlations in String Fusion Model V.V.Vechernin, R.S. Kolevatov V.A. Fock Institute of Physics, St.-Petersburg State University

  2. Introduction Two stage scenario A.Capella, U.P.Sukhatme, C.--I.Tan and J.Tran Thanh Van, Phys. Lett. B81 (1979) 68; Phys. Rep. 236 (1994) 225.A.B.Kaidalov, Phys. Lett., 116B (1982) 459; A.B.Kaidalov K.A.Ter-Martirosyan, Phys. Lett., 117B (1982) 247. • At the first stage a certain number of colour strings are formed stretched in rapidity space between the incoming partons • At the second stage these strings decay into the observed secondary hadrons.

  3. String fusion • M.A.Braun and C.Pajares, Phys.Lett.B287 (1992)154; Nucl. Phys.B390(1993) 542, 549 String Fusion as a source of Long Range correlations • N.S.Amelin, N.Armesto, M.A.Braun, E.G.Ferreiro and C.Pajares,Phys. Rev. Lett.73(1994) 2813.

  4. Fusion Scenarios • The rapidity intervals must exclude fragmentation regions to exclude the influence of pt of the parent partons • Fusion affects particle production in both rapidity windows

  5. Correlations

  6. Sources of correlations in the model • Fluctuations in the number of strings • Fluctuations of strings positions in the transverse plane • As a consequence – fluctuations of string density per unit area.

  7. Positive pt-nand pt-pt correlations, transition from positive to negative forpt-n

  8. Calculations • Input parameters xandrstrmay be fixed by comparing <p_t> and dN/dyfor AA and pp collisions • Possible ways of fixing centrality in correlation study Restriction on the impact parameter Restriction on Npart

  9. Energy and impact parameter fluctuations dependence of the correlations

  10. PbPb 5500 GeV

  11. AuAu 130 GeV

  12. pt−n, n−n correlations study in PbPb at 17.3 GeV (NA49 Collaboration at CERN) and G.Feofilov, R.Kolevatov, V.Kondratiev, P.Naumenko, V.Vechernin; reported by G. Feofilov at ISHEPP-XVII, JINR,Dubna (to be published)

  13. Correlations in the central class (reproduced from G. Feofilov report) • Correlation coefficients not normalized • Black squares – experiment (Ev window is 4625±dEveto); open circles – SFM with number of strings fixed in terms of participants (simulations of Ev)

  14. When centrality is fixed in terms of impact parameter pt-n correlations stay positive even for fixed b

  15. Conclusions • SFM predicts significant long-range correlations of the types n-n, pt-n, pt-pt. • These types of correlation involving mean transverse momentum do not vanish with energy. • SFM gives a qualitative description of the correlations at the NA 49 experiment • Centrality should be treated in a proper way in the calculations

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