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Long-Range Multiplicity and Transverse Momentum Correlations in pp Collisions in ALICE at the LHC

Long-Range Multiplicity and Transverse Momentum Correlations in pp Collisions in ALICE at the LHC. (for ALICE Collaboration) A.ASRYAN, G.FEOFILOV, A.IVANOV, A.GREBENYUK, P.NAUMENKO, V.VECHERNIN V. Fock Institute for Physics of Saint-Petersburg State University

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Long-Range Multiplicity and Transverse Momentum Correlations in pp Collisions in ALICE at the LHC

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  1. Long-Range Multiplicity and Transverse Momentum Correlations in pp Collisions in ALICE at the LHC (for ALICE Collaboration) A.ASRYAN, G.FEOFILOV, A.IVANOV, A.GREBENYUK, P.NAUMENKO, V.VECHERNIN V. Fock Institute for Physics of Saint-Petersburg State University Reported by G.Feofilov , at the “V Workshop on Particle Correlations and Femtoscopy” , 15 October 2009

  2. Outline • Motivation • Long-range correlations and collectivity effects in pp and ppbar collisions (experiment and PYTHIA) • ALICE • Conclusions

  3. Space-time evolution of relativistic nuclei collisions. I — initial state, II — QGP, III —mixed phase, IV — hadron gas, V — free particles I.L.Rosental, Yu.A.Tarasov, UFN,v 163, № 7б 1993

  4. Space-time evolution of relativistic nuclei collisions. I — initial state, II — QGP, III —mixed phase, IV — hadron gas, V — free particles I.L.Rosental, Yu.A.Tarasov, UFN,v 163, № 7б 1993 Can we see the initial state effects?

  5. Motivation: 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.

  6. Motivation for studies of Long-Range Correlations:“STRING FUSION”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[1]. Fig.1. Quark-gluon strings and schematics for studies of Long-Range Correlations[1] [1] M.A.Braun, C.Pajares and V.V.Vechernin "Forward-backward multiplicity correlations, low p_t distributions in the central region and the fusion of colour strings", Internal Note/FMD, ALICE-INT-2001-16, CERN, Geneva, 2001, 13p [2] Abramovskii V.A., Kancheli O.V. “On the multiplicity distribution of secondary hadrons” Letters to JETP 31 (1980) 532

  7. Similar picture: formation of colour flux tubes

  8. Similar picture:L.Mc Lerran et al.: Color Glass Condensate and Glasma (see the report at the present Workshop)

  9. “Percolating color strings approach''. With growing energy and/or atomic number of colliding particles, the number of strings grows and they start to overlap, forming clusters [3-5]. E-by-E Fluctuations are due to the mixture of differenttype sources ! . Fluctuations ! [3] M.A.Braun and C.Pajares, Eur. Phys. J. C16 (2000) 349.M.A.Braun,R.S.Kolevatov,C.Pajares.V.V.Vechernin, ''Correlations between multiplicities and everage transverse momentum in the percolating color strings approach'', Eur.Phys.J.C.32.535-546(2004)[4] N.Armesto, C.Saldago, U.Wiedemann, PRL94 (2005) 022002. [5] C. Pajares , arXiv:hep-ph/0501125v1 14 Jan 2005

  10. Long-Range Correlations (LRC)CORRELATIONSBETWEEN OBSERVABLES MEASURED IN TWO RAPIDITY INTERVALS “BACWARD” (B) “FORWARD”(F) Y *THEORY: • A.Capella,A.Krzywicki, Phys.Rev. D18, no11,(1978),4120-4133 • A.Capella and J.tran Thanh Van, Z.Phys, C18(1983).85: • A.Krzywicki, Phys.Rev. D29,No.5,(1984)1007-1009. • N.S.Amelin, N.Armesto, M.A.Braun, E.G.Ferreiro and C.Pajares,Phys. Rev. Lett. {\bf 73} (1994) 2813. • M.A.Braun and C.Pajares, Eur. Phys. J. {\bf C16} (2000) 349.M.A.Braun,R.S.Kolevatov,C.Pajares.V.V.Vechernin, ''Correlations between multiplicities and everage transverse momentum in the percolatin color strings approach'', Eur.Phys.J.C.32.535-546(2004)

  11. HOW TO MEASURE THE LONG RANGE CORRELATIONS: Observables For each event: 1) the event mean multiplicity in BACKWARD or FORWARD rapidity windows: 2) the event mean transverse momentum for BACKWARD and FORWARD rapidity windows: Event-by-event: We define the average value of the observable in one rapidity window at the given value of another observable in the second window(regression):

  12. Correlation coefficients (forthe normalizedobservables): Usually: Correlation coefficients are defined – in the region where some linearity exists-- for the absolutevalues of observables as: Here the strength of the multiplicity correlation is measured by the coefficient

  13. NA49 Collaboration and Feofilov G.A., Kolevatov R.S., Kondratiev V.P., Naumenko P.A. , Vechernin V.V., “Long-Range Correlations in PbPb Collisions at 158 AGeV”. Reported in 2004 at XVII ISHEPP. In: Relativistic Nuclear Physics and Quantum Chromodynamics, Proc. XVII Internat.Baldin Seminar on High Energy Physics Problems, vol.1, JINR, Dubna, 2005, 222-231 Min.bias data, 2 rapidity intervals: {-0.3,0.3} and {0.9,2.0} NN PtN PtPt 05 октября 200913

  14. Long-range correlations and collectivity effects in pp and ppbar collisions: experiment and PYTHIA 14

  15. Motivation: collectivity effects in pp experiment, charged particle multiplicity correlation (ppbar collisions0.3-1.8 TeV”, [2]) [2] E735 Collaboration, “Charged particle multiplicity correlations in ppbar collisions at 0.3-1.8 TeV”, Physics Letters B 353 (1995) 155-160

  16. Collectivity Effects in PYTHIA v6.3 PYTHIA Model of multiple interactions T. Sjöstrand, “Monte Carlo Generators”, European School of High-Energy Physics 2006, Aronsborg, Sweden, 27 June 2006 Torbjörn Sjöstrand, Leif Lönnblad, Stephen Mrenna, Peter Skands, “PYTHIA 6.3 Physics and Manual”, hep-ph/0308153, LU TP 03–38, August 2003

  17. Elastic scattering Single diffraction Single diffraction Double diffraction Low pt production Semihard QCD Gluon string fusion Gluon string formation Final PYTHIA parameters were tuned using<pt>Nch-Nchcorrelation data: (report by A.Asryan at CERN, PWG2 31.03.08) Values of parameters Results are based on fitting of experimental data on Pt-N correlations in p-p and p-pbar collisions from 17 to 1800 GeV. In PYTHIA version 6.4 and higher these values of parameters are set as default. See also R. Fields’ studies in http://www.phys.ufl.edu/~rfield/cdf/ 2008 Mar 31 Page 17

  18. “Collectivity” in PYTHIA Colour correlations and Gluon-gluon string formation in PYTHIA : influence on <p_t>Nch, p+pbar collisions, 900 GeV Distribution of # of particle emitting sources (strings) and “collectivity” ppстолкновения 900ГэВ Effective Multi Pomeron Exchange Model (EPEM): N. Armesto, A. Asryan, D. Derkach, G. Feofilov, “Analysis of pt-Nch Correlations in pp and ppbar Collisions”, ALICE physics week, Erice, Italy, 09 December 2005 18

  19. <pt>Nch-Nchcorrelation and collectivity effects in pp and ppbar collisions at 17-1800 GeV [5] Fig.4. Experimental data and model [5] [5] N. Armesto, D. Derkach, G. A. Feofilov, “pt–Multiplicity Correlations in a Multi-pomeron Exchange Model With String Collectivity Effects”; Physics of Atomic Nuclei, 71,No.12, 2087-2095(2008).

  20. Long-rangemultiplicity correlation in ppbar collisions from 0.3-1.8 TeV: experiment E735 ( Physics Letters B 353 (1995) 155-160) and our PYTHIA 6.4 results (no fits!) Fig.8. Correlation coefficient as a function of the rapidity gap between two rapidity intervals (“backward” and “forward” intervals of 0.2 units ).

  21. Long-range multiplicity correlation in ppbar collisions from 0.3-1.8 TeV: experiment (E735 Physics Letters B 353 (1995) 155-160, LEFT FIGURE) and our PYTHIA 6.4 results(RIGHT) Fig. 9. Correlation coefficient as a function of the 2 rapidity interval width. There is no gap between the “forward” and “backward” regions.

  22. Predictions for ALICE: pp-collisions at 10 TeV Fig.10. The n-n correlation strength for pp data, as a function of rapidity gap for pp collisions at √sNN = 10 TeV at ALICE for 2 sets of collectivity parameters : 0.33,0.63} (pink circles), 0.9, 0.95(black circles)

  23. “Saturation” effect in long-range multiplicity correlation and selection of “the very central” events in pp-collisions at the LHC

  24. Selection of “the very central events” using LRC dataPYTHIA-simulations: “high collectivity - left and “ low collectivity”- rigth

  25. Some predictions for ALICE: Collectivity and “Saturation” effects in long-range multiplicity correlation Collectivity effects in PYTHIA In case of large collectivity parameter set, the “plateau” observed in multiplicity correlation is expected to start earlier and to have lower value: at the level of <nB>~120 in vs. <nB>~170 (see left column for 0 gap). Similar is the result for the gap=3.4 units(right column) Fig.11. Collectivity and “Saturation” effect in long-range multiplicity correlation: PYTHIA predictions for ALICE, pp collisions at √sNN = 10 TeV for 2 sets of collectivity parameters : 0.33,0.63} (lower raw), 0.9, 0.95(upper raw) . Figures are for 2 values of rapidity gap: 0 (left column) and 3.34 (right column). Backward and forward rapidity intervals are of 0.2 units of rapidity.

  26. “Saturation” effects in long-range multiplicity correlation vs. “collectivity in PYTHIA” (PARP(85) and PARP(86)): Multiplicity “plateau”

  27. “Saturation” effects in long-range <p_t>-multiplicity correlation vs. “collectivity in PYTHIA” (PARP(85) and PARP(86): : <p_t>-”plateau”

  28. “Saturation” effects in long-range <p_t>-multiplicity correlation for strange particles Λ, <multipllclty> -“plateau”vs. “collectivity in PYTHIA” (PARP(85) and PARP(86)): For “plateau” events: “High” collectivity: <nB_lamdas>/<Nch_plateau>= 1.8/60.3=0.03 (!) “Low” collectivity: <nB_lambdas>/<Nch_plateau>= 2.3/98=0,023

  29. Features of “the plateau”(PYTHIA) events: increaseof collectivity effects in PYTHIA (of Colour correlations and Gluon-gluon string formation) leads to: 1) Increased formation of the number of paticle emitting sources 2) Damping of the mean multipliicty of “plateau” events 3) Increased <p_t> values for “plateau” events 3) 1.5 increase of yields Λ/<Nch> for “plateau” events  The very centralрр-collisions!

  30. -1.0 0 ƞ The 1st measurements of <n>n, <p_t>n and <p_t>p_tcorrelations in рр collisions in ALICE at theLHC: 1.0 1) to start with SCAN IN η∈ [-1.0, +1.0], δ = 0. 2 2) TO SCAN IN [0, 2π], 3) TO SCAN INp_t, <1 Gev/c, 1-2GeV/c, и >2 GeV/c Future : “net-charge” LRC Future : LRC for Strange and multistrangehyperons Future : TO SCAN IN: η∈ [-2.0, +2.0] Detectors: ITS, TPC, FMD Future : TO SCAN IN: η∈ [-3.7,+4.7]

  31. Pseudorapidity intervals for the 1st pp-collisions study (in the TPC domain) -0.8 -0.4 0 0.4 0.8 • The following set of pseudoarpidity intervals (“windows”) were selected within the TPC/ALICE domain (see Fig.1): • Correlation in full rapidity interval [-0.8 .. 0.8] • Backward-forward correlation using data from symmetrical –variable width- windows of 0.2,0.4,0.6,0.8 pseudorapidity units • Correlation for symmetrical windows of 0.2,0.4,0.6, units, - scanning of the gap width Fig/1. The complete set of 11 pseudoarpidity intervals proposed f or LRC study within the TPC/ALICE domain

  32. LRC Library • LRC Library includes 5 classes:TFit, TLRC, TNN, TPtN, TPtPt, • Long Range Correlation library algorythms provide: • Vizualization of regression curves, calculation of correlation coffecients, statistical errors estimates of N-N, Pt-NandPt-Pt correlation coefficients.

  33. Examples of the Long-Range correlations analysis AliROOT for ALICE at the LHC 10TeV PDC’09 P-P data (run LHC9a4) Pythia Pt -Nch correlation for [-0.8..0],[0..0.8] rapidity windows (September 2009) b ~ 0.009 GeV/c (PRELIMINARY)

  34. PDC’09 P-P data (run LHC9a4) Pythia Pt -Nch correlation for [-0.2..0],[0..0.2] rapidity windows (September 2009) b ~ 0.016 GeV/c (PRELIMINARY)

  35. Summary • It is proposed to start study of the <n>n, <p_t>nand <p_t> p_t Long-Range Correlations (LRC) in рр collisions in ALICE at the LHC. • This will provide a new information on the number of particle emitting sources, formed in the collisions and to select a class of unique events that might be characterized as “the very central collisions” , possessing the maximal energy density • “Saturation effects” in <n>n or <p_t>n correlations in pp collisions, - in case if they are confirmed experimentally, - are important for the future analysis of possible formation and hadronisation processes of the QGP.

  36. Acknowledgemnts Authors are grateful to T. Sjöstrand for permanent interest to these studies and fruitful discussions. THANK YOU FOR YOUR ATTENTION!

  37. BACK-UP SLIDES

  38. Since 2002: Long-Range Correlations as a method to study string fusion pheneomenon in ALICE • P.A.Bolokhov, M.A.Braun, G.A.Feofilov, V.P.Kondratiev, V.V.Vechernin, Internal Note/PHY.ALICE-INT-2002-20(2002)16p; • P.A.Bolokhov, M.A.Braun, G.A.Feofilov,V.P.Kondratiev and V.V.Vechernin,\\``Forward-Backward Correlations in Relativistic Heavy Ion Collisions''.In: Relativistic Nuclear Physics and Quantum Chromodynamics.\\Proceedings of the XVI International Baldin Seminar on High Energy PhysicsProblems (2002),vol.1, JINR, Dubna, 2004, pp. 263-271 • P.A.Bolokhov, M.A.Braun, G.A.Feofilov,V.P.Kondratiev and V.V.Vechernin,\\ ``Experimental Studies of Colour String Fusion at ALICE'‘ , In: Relativistic Nuclear Physics and Quantum Chromodynamics.\\ Proceedings of the XVI International Baldin Seminar on High Energy Physics Problems (2002), vol.1.,JINR, Dubna, 2004, pp. 272-278 • ALICE collaboration “ALICE: Physics Performance Report, Volume II”, J. Phys. G: Nucl. Part. Phys. 32 (2006) 1295-2040 (Section: 6.5.15 - Long-range correlations, p.1749)

  39. Feasibility of the measurement of the long-range correlations in terms of statistics and systematic errors during the first pp run at 0.9/10 TeV in 2008 in ALICE • 1). Short 900 GeV min bias pp run is interesting for this analysis to start and to compare to the existing data on multiplicity correlation • N-N long-range correlation : Statistics about 1 - 2 x 10^5 eventsshould be sufficient for the comparison to the existing data at 900 GeV( E735 Collaboration, “Charged particle multiplicity correlations in ppbar collisions at 0.3-1.8 TeV”, Physics Letters B 353 (1995) 155-160 ),where about 150000 events data were accumulated • 2). 10 TeV min bias run has to provide 2-3 x 10^5 of events • for p_t-n correlation coefficient determination (This corresponds to [-1..0], [0..1] rapidity windows). • In a case of smaller windows of 0.2 units of rapidity the minimal required statistics will be 1 - 2 x 10^6 . • N-N long-range correlation saturation: study will require statistics of about 10^7 events.

  40. Результаты PYTHIA v6.325 p-pbar при 200 ГэВp-pbar при540ГэВ p-antip столкновения 200ГэВ |η| ≤ 2.5 SppS (UA1) p-antip столкновения 540ГэВ |η| ≤ 2.5 ISR (ABCCDHW) 05 октября 200942

  41. Selection of “the very central events” using LRC dataPYTHIA-simulations

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