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Analysis of < p T > - N ch Correlations in pp and pp Collisions

Analysis of < p T > - N ch Correlations in pp and pp Collisions. Denis Derkach Saint-Petersburg State University, Russia. Erice, Italy, 05.09.2006 International Subnuclear Physics School. Outline. motivation; effective pomeron exchange model; <p t >-N ch correlation description;

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Analysis of < p T > - N ch Correlations in pp and pp Collisions

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  1. Analysis of <pT>-Nch Correlations in pp and pp Collisions Denis Derkach Saint-Petersburg State University, Russia Erice, Italy, 05.09.2006 International Subnuclear Physics School

  2. Outline • motivation; • effective pomeron exchange model; • <pt>-Nchcorrelation description; • experimental data description; • prospects for ALICE/CERN. D. Derkach, ISSP'06, Erice

  3. pp Collisions D. Derkach, ISSP'06, Erice

  4. Experimentally Observed pt-NchCorrelations D. Derkach, ISSP'06, Erice

  5. Experimentally Observed pt-NchCorrelations. Features • <pt>Nchdoes not grow with energy at low Nch. • <pt>Nchflattens at high Nch. • Experiments can be divided into two groups depending on the value of <pt> at Nch close to 0. D. Derkach, ISSP'06, Erice

  6. Experimentally Observed pt-NchCorrelations. Literature • NA49 collab. arXiv:hep-ex/0311009. • A.Breakstone et al. (ABCDHW Collaboration), Phys. Lett.132B (1983) 463. • UA1 collab., Nucl Phys 335B (1990) 261. • F.Abe et.al, Phys.Rev.Lett. 61 (1988) 1819. • C.De Marzo et al. Phys. Rev. 29D (1984) 363. • V.V. Aivazyan et al., Phys.Lett. 209B(1988)103. • T. Alexopoulos et al., Phys. Lett. 336B(1994)599. D. Derkach, ISSP'06, Erice

  7. Classical Multi-Pomeron Exchange Model Pomeron is a virtual particle that is exchanged during the inelastic scatering process with vacuum quantum numbers flow. It can be considered as a pair of strings. The number of pomerons exchanged rises with energy. Collective effects are not included in the model. A.B.Kaidalov and K.A.Ter-Martirosyan, Phys. Lett. B 117 (1982) 247 D. Derkach, ISSP'06, Erice

  8. String Formation A.Capella, U.P.Sukhatme, C.-I.Tan and J.Tran Thanh Van, Phys. Rep.236(1994)225 D. Derkach, ISSP'06, Erice

  9. Dual Parton Model calculations In this model an additional assumption was made: a transverse momentum of sea quarks was introduced as a parameter. This parameter was fitted to be 1.1 GeV. P. Aurenche, F. W. Bopp and J. Ranft, Phys. Lett. 147B, (1984) 212 D. Derkach, ISSP'06, Erice

  10. String Formation • Collective effects are observed. • Possible solution – string interactions. M.A.Braun and C.Pajares, Phys. Lett. B 287 (1992) 154; Nucl. Phys. B 390 (1993) 542,549 D. Derkach, ISSP'06, Erice

  11. Classical Multi-Pomeron Exchange Model normalized crosssectionof simultaneous production of n-pomeron showers probability for strings to give particles after hadronization transverse momentum distribution for particles coming from a single string • B. Kaidalov, K. A. Ter-Martirosyan Phys. Lett. 11B (1982) 247 D. Derkach, ISSP'06, Erice

  12. Classical Multi-Pomeron Exchange Model No correlations can be obtained from this distribution! D. Derkach, ISSP'06, Erice

  13. = = - parameter that accounts effectively collectivity Modifications. Basic formula D. Derkach, ISSP'06, Erice

  14. Parameters Classical model parameters: t – average string tension k – mean number of particles produced per unit rapidity by one string Modificated model parameter: - efficient string collective coefficient D. Derkach, ISSP'06, Erice

  15. Fitting Fitting was done for 11 different datasets. Energy range covered is 17-1800 GeV. The parameter values were extracted. D. Derkach, ISSP'06, Erice

  16. Fitting Fitting was done for 11 different datasets. Energy range covered is 17-1800 GeV. The parameter values were extracted. D. Derkach, ISSP'06, Erice

  17. Fit results D. Derkach, ISSP'06, Erice

  18. Fit results D. Derkach, ISSP'06, Erice

  19. <pt> vs. CM Energy D. Derkach, ISSP'06, Erice

  20. Mean number of pomerons D. Derkach, ISSP'06, Erice

  21. Dispersion in number of pomerons D. Derkach, ISSP'06, Erice

  22. LHC predictions from EPEM The predictions are made for both parameter t values. The plot should be chosen after specification of experimental data. D. Derkach, ISSP'06, Erice

  23. Conclusions • Experirmental results on mean pt and on pt-n correlation are summarized in a wide energy range. • Negative and positive correlations are reproduced in one approach of modified multi-Pomeron exchange model. • Smooth behavior of parameter “ ” with energy is observed. • Logarithmic growth of number of Pomerons and their dispersions with energy in the region 17 GeV – 1.8 TeV are related to observed experimental correlations. • First results on pp collisions in ALICE at the LHC at 5.5 TeV on the pt-Nch corelation at midrapidity should clarify the functional dependence of “ ”. D. Derkach, ISSP'06, Erice

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