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Some critical phenomena in AA and pp collisions and percolation string model

Some critical phenomena in AA and pp collisions and percolation string model. G.A. Feofilov, O.A. Kochebina Reporter O.A. Kochebina. St. Petersburg State University. The 5th International Nordic "LHC and Beyond" Workshop "The First LHC Physics and Major Spin-Offs", 9 June 2010. Outline.

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Some critical phenomena in AA and pp collisions and percolation string model

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  1. Some critical phenomena in AA and pp collisions and percolation string model G.A. Feofilov, O.A. Kochebina Reporter O.A. Kochebina St. Petersburg State University The 5th International Nordic "LHC and Beyond" Workshop "The First LHC Physics and Major Spin-Offs", 9 June 2010

  2. Outline 1. Introduction and motivation. 2. Onset of the ridge at 62 GeV and 200 GeV and percolation model 3. Discussion and conclusions

  3. Phase transitions See NA61. Physics goals. https://na61.web.cern.ch Phases of strongly interacting matter in AA collisions Phases of water but the properties of the transition between hadron gas and quark-gluon plasma still have to be uncovered The phase diagram of water is well established critical point 1st order phase transition

  4. Example New threshold (?) phenomena in AA collisions observed by STAR [1] Variation of low-pT “ridge” with centrality (Npart). (pt> 0.15 GeV/c ) 55-65% 83-94% 0-5% 46-55% STAR Preliminary STAR Preliminary STAR Preliminary STAR Preliminary ηΔ width Large change within ~10% centrality Smaller change from transition to most central Low-pTmanifestation of the “ridge” Shape changes little from peripheral to the transition The data showed a sharp transition at some definite energy-dependent centrality: growing of peak amplitude and pseudorapidity stretching of width. [1]Anomalous centrality variation of minijet angular correlations in Au-Au collisions at 62 and 200 GeV from STAR. M. Daugherity. QM2008.

  5. Variation of low-pT “ridge” with centrality (Npart). A sudden increase of the peak amplitude and η width of the near-side low p_t ridge were found at an energy-dependentcentrality point at definite number of participating nucleons Npart. Transverse Particle Density Peak Amplitude Peak η Width Npart Peak η Width STAR Preliminary STAR Preliminary 200 GeV 62 GeV STAR Preliminary STAR Preliminary 200 GeV 62 GeV Npart Npart Same-side gaussian peak amplitude, width. Points show eleven centrality bins for each energy (84-93%, 74-84%, 65-74%, 55-65%, 46-55%, 37-46%, 28-37%, 19-28%, 9-19%, 5-9%, and 0-5%) transformed to tranvserse density. 62 GeV “Critical value” Npart≈90 200 GeV “Critical value” Npart≈40 S Anomalous centrality variation of minijet angular correlations in Au-Au collisions at 62 and 200 GeV from STAR. M. Daugherity. QM2008.

  6. Motivation(theory) Application of string model. Investigations of the charged particles long-range multiplicity correlations, measured for well separated rapidity intervals, can give us information on the number of emitting centers and hence on the fusion of colour strings[2,3]. Fig.1. Quark-gluon strings and schematics for studies of Long-Range Correlations[2] [2] M.A.Braun, C.Pajares and V.V.Vechernin, Low pT Distributions in the Central Region and the Fusion of Colour Strings, Internal Note/FMD ALICE-INT-2001-16 [3] А. Абрамовский, О.В. Канчели// Письма в ЖЭТФ, т.31, 566, 1980

  7. String model. Estimate ofstring percolation parameter. With growing energy and/or atomic number of colliding particles, the number of strings grows and they start to overlap, forming clusters, new type of particle emitting source. At a critical density a macroscopic cluster appears that marks the percolation phase transition.[3] Percolation parameter: S ηс= 1,15([4]) NStr - number of strings, πr02string transverse area, Soverlap area of two nucleons. r0=0,2-0,3fm– change of string radius value results indifferent percolation parameter [4] J.Dias de Deus and A. Rodrigues// Phys. Rev. C 67, 064903 (2003) [3] C. Pajares // arXiv:hep-ph/0501125v1 14 Jan 2005

  8. Number of strings x – parameter Nstr(pp) - the number of strings in pp collision Ncoll – number of nucleon - nucleon collisions Npart – number of nucleon participants Npart, Ncoll - from MC calculation [9] Nstr(pp) – theoretical estimates [8] x - ? [8]V.V. Vechernin, R.S. Kolevatov, 2007, published in Yadernaya Fizika, 2007, Vol. 70, No. 10, pp. 1858–1867. [9]G.Feofilov,A.Ivanov //Journal of Physics: Conference Series 5 (2005) 230–237

  9. Percolation model parameters at the “critical“ point Our calculation New! Percolation parameter Transverse particle density S-?

  10. Example of calculation Percolation parameter η vs. number of participants: “Critical value” Npart ≈ 90 ηсrit = 1,15 ρсrit = 2,6 GeV/fm-2 r0=0,28 fm √s= 62 GeV, Au+Au GM Nstr ≈ 275 Ns ≈ 220 Ncoll ≈ 150 MGM (momentum loss) Nstr ≈275 Ns ≈ 216 Ncoll ≈ 168 x=0,39±0,07 x=0,34±0,06 ______ - GM - - - - - - - MGM[7] [7] G.Feofilov,A.Ivanov, “Number of nucleon‐nucleon collisions vs. energy in modified Glauber calculations”,Journal of Physics: Conference Series 5 (2005) 230–237]

  11. Extrapolation of percolation model parameters for energy 17,3 GeV and 3500 GeV GM √s= 17,3 GeV => x=0,18±0,02 √s= 3500 GeV => x=1,0±0,3 MGM 200 GeV 62 GeV √s= 17,3 GeV => x=0,19±0,02 √s= 3500 GeV => x=0,8±0,4

  12. Percolationparametervs. number of participants: It is possible to try to search for the onset of the near-side low p_t “ridge” in the very central Pb+Pb at 17,3 GeV(SPS) or AuAu collisions 19,6 GeV (RHIC) and in very peripheral collisions or maybe even in pp collisions at LHC energies.

  13. Transverse particle density vs. percolation parameter

  14. Transverse particle density vs. percolation parameter ρ = 0,60+ 1,75 η From experimental data [11] for dNch/dy Obtained Nstr was checked and has agreement at theoretical predictions for Nstr[12] (for energy 17,3 GeV, 200 GeV, 900GeV) [11] ALICE Collaboration: arXiv:1004.3034[hep-ex], arXiv: 1004.3514[hep-ex] [12]N. Armesto, D. Derkach and G. A. Feofilov, Phys. At. Nucl. 71 (2008) 2122–2131

  15. Conclusions • The hypothesis of percolation transition looks reasonable in the description of the onset of the near side low-pt ridge phenomenon at RHIC energies. • it is possible to try to search for the onset of the “near-side low p_t “ridge” phenomenon” in the very central Pb+Pb at 17,3 GeV(SPS) or in Au+Au at 19.6 GeV (RHIC). • At the LHC energy one may expect the observation of the low p_t ridge phenomenon in ALL centrality classes and the onset in peripheral PbPb or pp collisions. • The method for obtaining the number of sea strings following the concept of valent and sea strings is checked on the data of the ridge onset in Au+Au collisions at RHIC. • The method for finding the total number of strings for pp collisions at LHC energies is proposed.

  16. Thank you!

  17. Backup slides

  18. Ncolldepends on the model: • Classical Glauber model (GM) • Modified Glauber model (MGM) (takes into account moment losses)[7] Systematic uncertainties: 1. String radius (r0=0,2-0,25 fm) 2. Estimate of overlap area S 3. Estimate of Ncoll(Classical or Modified Glauber ) [7] G.Feofilov,A.Ivanov //Journal of Physics: Conference Series 5 (2005) 230–237

  19. New! Our calculation ∙- sphere nuclear shape ∙- WSnuclear shape Npart b, fm S(bcrit) ηсrit= 1,15 r0=0,2 fm ηсrit /πr0 = Nstr/S(bcrit) “Critical value” Nstr

  20. Percolation parameter vs. number of participants: √s= 200 GeV, Au+Au “Critical value” Npart ≈ 40 ηсrit= 1,15 r0=0,2 fm GM Nstr ≈ 300 Ns ≈ 460 Ncoll ≈ 50 MGM Nstr ≈ 360 Ns ≈ 260 Ncoll ≈ 40 a=5,0±2,2 a=6,7±2,9 ______ - r0=0,2 fm (GM) - - - - - - - r0=0,25 fm (GM) ..-..-..- - line r0=0,2 fm (MGM)[7] [7] G.Feofilov,A.Ivanov, “Number of nucleon‐nucleon collisions vs. energy in modified Glauber calculations”, Journal of Physics: Conference Series 5 (2005) 230–237]

  21. Extrapolation of percolation model parameters to lower energy. Classical Glauber model Modified Glauber model 17,3 17,3 Preliminary Preliminary 62 GeV a = 2,9±0,8 62 GeV a = 3,8±0,8 200 GeV a = 5,0±2,2 200 GeV a = 6,7±2,9 17,3 GeV a=1,2±0,1 17,3 GeV a=1,4±0,1

  22. Percolation parameter vs. number of participants: Theoretical estimates made by Tarnowsky (2007) Our estimates based on RHIC experimental data Au+Au, 200 GeV Au+Au, 62 GeV Au+Au 62 GeV Npart ≈ 75 200 GeV Npart ≈ 20 ηсrit= 1,175 Au+Au 62 GeV Npart ≈ 90 200 GeV Npart ≈ 40 ηсrit= 1,15 [8]Terence J. Tarnowsky*, Brijesh K. Srivastava, Rolf P. Scharenberg (for the STAR Collaboration)/ arXiv:nucl-ex/0606019v2 10 Apr 2007 ______ - r0=0,2 fm (GM) - - - - - - - r0=0,25 fm (GM) ..-..-..- - line r0=0,2 fm (MGM)[7] [7] G.Feofilov,A.Ivanov,”,Journal of Physics: Conference Series 5 (2005) 230–237

  23. New threshold (?) phenomena in AA collisions Onset of manifestation of the near-side low p_t “ridge” (pt> 0.15 GeV/c ) Ref.: [1]   M. Daugherity for the STAR Collaboration//arXiv:0806.2121v2 [nucl-ex] 13 Jun 2008; M. Daugherity// Report on QM2008. [2] J. Putschke et al. [STAR], J. Phys. G 34, S679 (2007). [3] Adams J et al (STAR Collaboration) 2006 Phys. Rev. C 73 064907 [4] Adams J et al (STAR Collaboration) 2007 J. Phys. G: Nucl. Part. Phys. 34 799 [5] Jana Bielcikova, Acta Physica Polonica B Vol. 1 Proceedings Supplement No 3, (2008) 611-614 Ridge: see J. Putschke et al. [STAR], J. Phys. G 34, S679 (2007). Low-p_t near side ridge: see Daugherity report at QM2008 Pair densities : Δρ ≡ ρsib−ρref, where ρsib is sibling pair densities, ρref - the uncorrelated reference from different events measures Near-side low p_t “ridge” in dihadron correlations that were studied recently in Au+Au collisions at the collision energies √s= 62 and 200 GeV, demonstrate a number of interesting features as a function of collision centrality, transverse momentum and particle composition

  24. Percolation parameter vs. Transverse Particle Density r0 =0.2 fm PHOBOS Collaboration, B. B. Back et al., Phys. Rev. C 65, 061901 (2002); 70, 021902 (2004). PRL 94(2005) 022002 Modified Glauber model Preliminary 17,3 GeV a= 1,4±0,1 62 GeV a= 3,8±0,8 200 GeV a= 6,7±2,9 obtained in our calculations

  25. Percolation parameter vs. number of participant (J/psi). “Critical value” Npart≈110[7] r0=0,2 fm We obtain a=3,0±0,5 G.Feofilov, O. Kochebina. J/psi suppression, percolation model and the critical energy density in AA collisions at SPS and RHIC energies with the account of centrality.//Baldin ISHEPP XIX. Dubna, Oct 2, 2008 [7] CERN–2005–005 arXiv:hep-ph/0412158v2 26 Jul 2005, p. 428

  26. Percolation parameter vs. number of participant: Systematicuncertainties Systematic uncertainties: 1. Nstr 2. String radius 3. S – overlap area All parameters is the same r0=0,2 fm a= 4,2±0,5 Upper estimate Uncertainties r0 (0.25 fm) Modified Glauber[11] estimate Uncertainties Nstr Experimental data for J/Psi suppression “Critical value” Npart ≈ 50 [11] G.Feofilov,A.Ivanov, “Number of nucleon‐nucleon collisions vs. energy in modified Glauber calculations”, Journal of Physics: Conference Series 5 (2005) 230–237]

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