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

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

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

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 Can we see the initial state effects?

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.

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] [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 , CERN, Geneva, 2001, 13p [2] Abramovskii V.A., Kancheli O.V. “On the multiplicity distribution of secondary hadrons” Letters to JETP 31 (1980) 532 Fig.1. Quark-gluon strings and schematics for studies of Long-Range Correlations[1]

Similar picture: formation of colour flux tubes

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

“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 different type sources !. [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 (2004) [4] N.Armesto, C.Saldago, U.Wiedemann, PRL94 (2005) [5] C. Pajares, arXiv:hep-ph/ v1 14 Jan 2005 Fluctuations !

Long-Range Correlations (LRC) CORRELATIONS BETWEEN OBSERVABLES MEASURED IN TWO RAPIDITY INTERVALS “BACWARD” (B) “FORWARD” (F) Y *THEORY: A.Capella,A.Krzywicki, Phys.Rev. D18, no11,(1978), A.Capella and J.tran Thanh Van, Z.Phys, C18(1983).85: A.Krzywicki, Phys.Rev. D29,No.5,(1984) N.S.Amelin, N.Armesto, M.A.Braun, E.G.Ferreiro and C.Pajares, Phys. Rev. Lett. {\bf 73} (1994) 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 (2004)

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):

Usually: Correlation coefficients are defined – in the region where some linearity exists-- for the absolute values of observables as: Correlation coefficients (for the normalized observables): Here the strength of the multiplicity correlation is measured by the coefficient

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, Min.bias data, 2 rapidity intervals: {-0.3,0.3} and {0.9,2.0} 05 октября NNPtNPtPt

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

Motivation: collectivity effects in pp experiment, charged particle multiplicity correlation (ppbar collisions TeV”, [2]) [2] E735 Collaboration, “ Charged particle multiplicity correlations in ppbar collisions at TeV”, Physics Letters B 353 (1995)

ParametersDescription MSUB(91)Elastic Scattering MSUB(92)Single Diffraction AB -> XB MSUB(93)Single Diffraction AB -> AX MSUB(94)Double Diffraction MSUB(95)Low Pt Production MSUB(96)Semihard QCD PARP(85) D=33% in v6.325 “Colour correlations” - probability that an additional interaction in the multiple interaction formalism gives two gluons, with colour connections to ‘nearest neighbours’ in momentum space PARP(86) D=66% in v6.325 “Gluon-gluon string formation” - probability that an additional interaction in the multiple interaction formalism gives two gluons, either as described in PARP(85) or as a closed gluon loop. Remaining fraction is supposed to consist of quark–antiquark pairs Torbjörn Sjöstrand, Leif Lönnblad, Stephen Mrenna, Peter Skands, “PYTHIA 6.3 Physics and Manual”, hep-ph/ , LU TP 03–38, August 2003 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

Final PYTHIA parameters were tuned using Nch -N ch correlation data: (report by A.Asryan at CERN, PWG ) Energy, GeV PYTHIA Parameters MSUB(91) MSUB(92) MSUB(93) MSUB(94) MSUB(95) MSUB(96) PARP(85) 90% PARP(86) 95% Values of parameters Low p t production Elastic scattering Single diffraction Double diffraction Semihard QCD Gluon string fusion Gluon string formation 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 2008 Mar 31 Page 17

pp столкновения 900 ГэВ 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 Colour correlations and Gluon-gluon string formation in PYTHIA : influence on Nch, p+pbar collisions, 900 GeV Distribution of # of particle emitting sources (strings) and “collectivity” 18 “Collectivity” in PYTHIA

Nch -N ch correlation and collectivity effects in pp and ppbar collisions at 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, (2008).

Long-range multiplicity correlation in ppbar collisions from TeV: experiment E735 ( Physics Letters B 353 (1995) ) 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 ).

Long-range multiplicity correlation in ppbar collisions from TeV: experiment (E735 Physics Letters B 353 (1995) , 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.

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)

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

Selection of “the very central events” using LRC data PYTHIA-simulations: “high collectivity - left and “ low collectivity” - rigth

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. 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 ~120 in vs. ~170 (see left column for 0 gap). Similar is the result for the gap=3.4 units(right column)

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

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

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

Features of “the plateau” (PYTHIA) events: increase of 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 values for “plateau” events 3) 1.5 increase of yields Λ/ for “plateau” events  The very central рр-collisions ! 29

The 1 st measurements of n, n and p_t correlations in рр collisions in ALICE at the LHC: 1) to start with SCAN IN 1) to start with SCAN IN η ∈ [-1.0, +1.0], δ = ) TO SCAN IN 2) TO SCAN IN [0, 2π], 3) TO SCAN INp_t, 2 GeV/c 3) TO SCAN IN p_t, 2 GeV/c Future : “net-charge” LRC Future : LRC for Strange and multistrange hyperons Future : TO SCAN IN Future : TO SCAN IN: η ∈ [-2.0, +2.0] ƞ Detectors: ITS, TPC, FMD Future : TO SCAN IN Future : TO SCAN IN: η ∈ [-3.7,+4.7]

The following set of pseudoarpidity intervals (“windows”) were selected within the TPC/ALICE domain (see Fig.1): 1. Correlation in full rapidity interval [ ] 2. Backward-forward correlation using data from symmetrical –variable width- windows of 0.2,0.4,0.6,0.8 pseudorapidity units 3. 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 Pseudorapidity intervals for the 1 st pp-collisions study (in the TPC domain)

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-N and Pt-Pt correlation coefficients.

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..0.8] rapidity windows (September 2009) b ~ GeV/c (PRELIMINARY)

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

Summary )It is proposed to start study of the n, n and p_t Long-Range Correlations (LRC) in рр collisions in ALICE at the LHC. 2)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 3)“Saturation effects” in n or 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.

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

BACK-UP SLIDES

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)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 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 ALICE collaboration “ALICE: Physics Performance Report, Volume II”, J. Phys. G: Nucl. Part. Phys. 32 (2006) (Section: Long- range correlations, p.1749)

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 10/16/ ). 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 x 10^5 events should be sufficient for the comparison to the existing data at 900 GeV ( E735 Collaboration, “ Charged particle multiplicity correlations in ppbar collisions at TeV”, Physics Letters B 353 (1995) ),where about 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 x 10^6. N-N long-range correlation saturation: study will require statistics of about 10^7 events.

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

Selection of “the very central events” using LRC data PYTHIA- simulations