G.Feofilov, A.Ivanov, V.Vechernin (for the ALICE Collaboration) V. Fock Institute for Physics

1. First analysis of Long-Range (Forward-Backward) pt and multiplicity correlations in ALICE in pp collisions at 900 GeV G.Feofilov, A.Ivanov, V.Vechernin(for the ALICE Collaboration) V. Fock Institute for Physics Saint-Petersburg State University The 5th International Nordic "LHC and Beyond" Workshop "The First LHC Physics and Major Spin-Offs",8-11 June 2010

2. Goal: We continue studies of Long-range correlations proposed for ALICE[1] “Forward-Backward” correlations (“FB”) here refer to the limited rapidity coverage of the ALICE central barrel Measurement of the correlation coefficients by scanning in separated pseudorapidity intervals is a model independent method to reveal the presence of the collective effects, relevant to the early stages of hadronic matter formation both in pp and AA collisions [1] 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) 2

3. Outline • “Forward-Backward” correlations (FB) • Comparison of simulated and reconstructed PYTHIA data in the framework of ALICE experimental setup in terms of FB correlations • pp@900GeV FB correlations analysis • Conclusions and outlook

4. Forward-Backward/Long-RangeCORRELATIONS: 2 rapidity intervals separated by gap “BACWARD”“FORWARD” • For each event: • 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 mean value • of the observable in one rapidity window • at the given value of another observable in the second window(regression), for example:

5. Forward-Backward/Long-RangeCORRELATIONS: 2 rapidity intervals separated by gap “BACWARD”“FORWARD” • Types of correlations: • <n>-n - the correlation between the event mean charged particle multiplicity in one rapidity interval and the charged particle multiplicity in another interval • <pt>-n - the correlation between the event mean transverse momentum in one rapidity interval and the charged particle multiplicity in another interval. • <pt>-pt - the correlation between the event mean transverse momentum obtained in the backward (B) rapidity window • and the event mean transverse momentum in the forward (F) rapidity window 5

6. 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

7. Long-Range correlations dependence on η gap and on η window size Ƞ windows Analysis General: study of <n>-n ,<pt>-n and <pt>-pt correlation coefficient dependences on η windows size and positions. Now: only ITS+TPC data Plans: to include FMD as multiplicity detector for <n>-n and <pt>-n correlations. 0 -0.8 -0.4 0.4 0.8

8. Comparison of simulated and reconstructed PYTHIA data in the framework of ALICE experimental setup in terms of FB correlations Comparison of Kinematics and ESD in Pythia LHC10a8 production in terms of FB correlations:<n>-n and <pt>-n correlation functions in relative observables. Forward η window (-0.8 – 0.0) Backward η window (0.0 – 0.8) Pt cut (0.3 < Pt < 1.5 ), Kinematics events are triggered together with ESDs. N-N correlation Pt-N correlation 8

9. ALICE performance ALICE performance The 1st analysis of BF <n>-n and <p_t>-n correlations in pp@900GeV:“B”{-0.8, 0.0}, “F”{0.0, 0.8}. pp 900GeV run 104892 pass 5 ESDs :Global tracking, TPC clusters > 80 , Sigma < 3.5. No kink daughters. normalized values of observablesp_t cut: (0.3 < P_t < 1.5 ) A.U. A.U.

10. ALICE performance ALICE performance ALICE performance ALICE performance <n>-n “FB” correlation in pp@900GeV: narrow (0.2) windows, ƞ gap dependence A.U. A.U. A.U. A.U.

11. ALICE performance ALICE performance ALICE performance ALICE performance <pt>-nFB correlation in pp@900GeV: narrow (0.2) windows, ƞ gap dependence A.U. A.U. A.U. A.U.

12. <n>-n and <pt>-n FB correlations in pp@900GeV: ƞ gap dependence ALICE performance ALICE performance ALICE performance Correlation coefficient dependence on ƞ gap between window centers and windows size (δƞ). 0 1 2 A.U. 0 1 2 A.U. 0 1 2 A.U. 12

13. ALICE performance ALICE performance <n>-n and <pt>-n FB correlations in pp@900GeV: ƞ gap dependence Correlation coefficient dependence on ƞ gap between window centers. Windows in ƞ: of 0.2 units. Data in comparison with results of Pythia D6T LHC10a8 Pt-N correlations N-N correlations 0 1 2 A.U. 0 1 2 A.U.

14. Conclusions • First LRC analysis is completed on pp 900GeV ALICE ITS+TPC data • The good agreement of simulated and reconstructed PYTHIA data in the framework of ALICE experimental setup shows that the use of the relative observables for selected pt region (0.3 GeV/c < pt < 1.5 GeV/c) allows one to obtain the unbiased correlation functions without the additional systematic corrections. • Noticeable FB/Long-Range <n>-n ,<pt>-n and <pt>-pt correlations are observed in pp collisions at 900 GeV with the rapidity gap extented up to 1.4 units of pseudorapidity • We see also a difference between Pythia D6T and the data

15. Thanks for attention

16. Backup

17. Long-Range correlations dependence on ETA gap and window size ETA windows Azimuthal windows Jet dependence analysis Event asymmetry study May be sensible to flow Main analysis: Study of <n>-n and <n>-n and <p_t>-p_t correlation coefficient dependences on windows size and positions. Now only in TPC acceptance, plans for FMD as multiplicity detector for <n>-n and <p_t>-n . 0 -0.8 -0.4 0.4 0.8

18. LONG RANGE CORRELATIONS:Absolute and relative observables “BACWARD”“FORWARD” Everything is Uncorrected Absolute observables Relative observables