Jet fragmentation study with particle correlations from the ALICE experiment at the LHC

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1 Jet fragmentation study with particle correlations from the ALICE experiment at the LHC Dong Jo,Kim University of Jyväskylä & Helsinki Institute of Physics for the ALICE Collaboration NN5, Catania, Italy June -6

2 Motivations Introduction Particle correlation measurements are good tools to Study the jet properties in pp Probe jet medium interactions in Heavy Ion collisions(di-hadron Tomography) dn h dξ Ξ,Τ OPAL, s 9 9 GeV in vacuum, Ejet GeV in medium, Ejet GeV TASSO, s 4 GeV in vacuum, Ejet 7 GeV in medium, Ejet 7 GeV Ξ ln x R AA - ALICE, Pb-Pb, ALICE (-5%) CMS (-5%) s NN =.76 TeV charged particles, η <.8 HT (Chen et al.) lower density HT (Chen et al.) higher density HT (A.M.) ASW (T.R.) YaJEM-D (T.R.) elastic (T.R.) large P esc elastic (T.R.) small P esc WHDG (W.H.) π lower limit WHDG (W.H.) π upper limit 4 5 p (GeV/c) T Figure : ξ = ln [/z], N. Borghini, U.A Wiedemann arxiv:hep-ph/568. Modification of the Fragmentation Function in Heavy Ion collisions Figure : Strong single particle suppression R AA (p T ) = (/Nevt AA ) d N ch AA /dηdp T N coll (/N evt pp ) d N pp ch /dηdp T Dong Jo,Kim (JYFL/HIP) Jet fragmentation study from ALICE at LHC /

Motivations Introduction Particle correlation measurements are good tools to Study the jet properties in pp Probe jet medium interactions in Heavy Ion collisions(di-hadron Tomography) dn h dξ Ξ,Τ

3 Motivations Introduction Particle correlation measurements are good tools to Study the jet properties in pp Probe jet medium interactions in Heavy Ion collisions(di-hadron Tomography) dn h dξ Ξ,Τ OPAL, s 9 9 GeV in vacuum, Ejet GeV in medium, Ejet GeV TASSO, s 4 GeV in vacuum, Ejet 7 GeV in medium, Ejet 7 GeV Ξ ln x Figure : ξ = ln [/z], N. Borghini, U.A Wiedemann arxiv:hep-ph/568. Modification of the Fragmentation Function in Heavy Ion collisions Figure : CMS, Phys. Rev. C 84, 496 () Strong Dijet Energy Asymmetry A J = p T, p T, p T, + p T, Dong Jo,Kim (JYFL/HIP) Jet fragmentation study from ALICE at LHC /

4 Motivations Introduction Particle correlation measurements are good tools to Study the jet properties in pp Probe jet medium interactions in Heavy Ion collisions(di-hadron Tomography) dn h dξ Ξ,Τ OPAL, s 9 9 GeV in vacuum, Ejet GeV in medium, Ejet GeV TASSO, s 4 GeV in vacuum, Ejet 7 GeV in medium, Ejet 7 GeV Ξ ln x Analysis of high-e T jets (ATLAS, CMS) /N jet dn track / dξ PbPb / pp CMS, PbPb, s NN =.76 TeV, L int anti-k T (R =.) PF Jets p > GeV/c, p > 4 GeV/c T, T, φ > π, Tracks in cone ( R <.) p track >4 GeV/c T Centrality -% Centrality -% ξ = ln(/z) - = 6.8 µb /N jet dn track / dξ PbPb / pp (a) Leading Jet pp reference Subleading Jet pp reference (c).5.5 Centrality -% Leading Jet Subleading Jet Centrality -% (b) (d) ξ = ln(/z) Figure : ξ = ln [/z], N. Borghini, U.A Wiedemann arxiv:hep-ph/568. Modification of the Fragmentation Function in Heavy Ion collisions Figure : CMS(JHEP () 87) No indication of modification of the fragmentation function, pt track > 4 GeV/c track cut. Dong Jo,Kim (JYFL/HIP) Jet fragmentation study from ALICE at LHC /

5 Motivations Introduction Particle correlation measurements are good tools to Study the jet properties in pp Probe jet medium interactions in Heavy Ion collisions(di-hadron Tomography) dn h dξ Ξ,Τ OPAL, s 9 9 GeV in vacuum, Ejet GeV in medium, Ejet GeV TASSO, s 4 GeV in vacuum, Ejet 7 GeV in medium, Ejet 7 GeV Ξ ln x Analysis of high-e T jets (ATLAS, CMS) /N jet dn track / dξ PbPb / pp CMS, PbPb, s NN =.76 TeV, L int anti-k T (R =.) PF Jets p > GeV/c, p > 4 GeV/c T, T, φ > π, Tracks in cone ( R <.) p track >4 GeV/c T Centrality -% Centrality -% ξ = ln(/z) - = 6.8 µb /N jet dn track / dξ PbPb / pp (a) Leading Jet pp reference Subleading Jet pp reference (c).5.5 Centrality -% Leading Jet Subleading Jet Centrality -% (b) (d) ξ = ln(/z) Figure : ξ = ln [/z], N. Borghini, U.A Wiedemann arxiv:hep-ph/568. Modification of the Fragmentation Function in Heavy Ion collisions Figure : CMS(JHEP () 87) No indication of modification of the fragmentation function, p track T = 4 GeV/c ξ Dong Jo,Kim (JYFL/HIP) Jet fragmentation study from ALICE at LHC /

6 Motivations Introduction Particle correlation measurements are good tools to Study the jet properties in pp Probe jet medium interactions in Heavy Ion collisions(di-hadron Tomography) Analysis of high-e T jets (ATLAS, CMS) dn h dξ Ξ,Τ OPAL, s 9 9 GeV 4 in vacuum, Ejet GeV in medium, Ejet GeV TASSO, s 4 GeV in vacuum, Ejet 7 GeV in medium, Ejet 7 GeV Ξ ln x Figure : ξ = ln [/z], N. Borghini, U.A Wiedemann arxiv:hep-ph/568. Modification of the Fragmentation Function in Heavy Ion collisions /N jet dn track /dξ PbPb/pp CMS PbPb s NN =.76 TeV 5 μb 7 % 5 7% PbPb pp reference data 5% <p jet < GeV/c T. < η jet < % p track T > GeV/c,R <. % ξ = ln(/z) ξ = ln(/z) ξ = ln(/z) ξ = ln(/z) ξ = ln(/z) Figure : CMS(PRC 9 (4) 498) Indication of modification of the fragmentation function, p T,h > GeV/c, p T,h = GeV/c ξ 4.5 for GeV jet Dong Jo,Kim (JYFL/HIP) Jet fragmentation study from ALICE at LHC /

7 Motivations Introduction Particle correlation measurements are good tools to Study the jet properties in pp Probe jet medium interactions in Heavy Ion collisions(di-hadron Tomography) Figure : Broadening in a static medium.longitudinal flow results in deformation of the conical jet shape Figure : Néstor Armesto, Carlos A. Salgado and Urs Achim Wiedemann, PhysRevLett.9.4 (4 < p T,trigg < 6 < p T,assoc < 4 GeV/c) Dong Jo,Kim (JYFL/HIP) Jet fragmentation study from ALICE at LHC /

8 Motivations Introduction Particle correlation measurements are good tools to Study the jet properties in pp Probe jet medium interactions in Heavy Ion collisions(di-hadron Tomography) Objectives Study modification of the jet shape and associated yields Increase of width (radiation) Increase of eccentricity (longitudinal flow) Study dependence on p T jet quenching effects expected to be strongest a low p T need to measure down to lowest possible p T ALICE is capable of measuring low p T particles and their PID Figure : Néstor Armesto, Carlos A. Salgado and Urs Achim Wiedemann, PhysRevLett.9.4 (4 < p T,trigg < 6 < p T,assoc < 4 GeV/c) Dong Jo,Kim (JYFL/HIP) Jet fragmentation study from ALICE at LHC /

9 Analysis ALICE Detectors Centrality determination by V( N ch with scintillators in.8 < η < 5. and.7 < η <.7) Tracking - TPC tracks constrained to the primary vertex and full azimuthal acceptance ( η <.9) Dong Jo,Kim (JYFL/HIP) Jet fragmentation study from ALICE at LHC /

Analysis Jet Properties from two particle correlation function N trigg d N assoc d φd η () φ = φ trigg φ assoc ( η = η trigg η assoc ) in a given p T,trigg and p T,assoc bins Normalized by the number

10 Analysis Jet Properties from two particle correlation function N trigg d N assoc d φd η () φ = φ trigg φ assoc ( η = η trigg η assoc ) in a given p T,trigg and p T,assoc bins Normalized by the number of trigger particles in a given p T,trigg bin Near-side( φ, η = ) and Away side( φ = π) peaks are reminiscent of back-to-back parton production (Jets) Dong Jo,Kim (JYFL/HIP) Jet fragmentation study from ALICE at LHC 4 /

11 Analysis Analysis Details Event sample 5M Pb-Pb events at s=.76 TeV in LHC run 55M pp events at s=.76 TeV in LHC run Track selection benefits from uniform φ acceptance of TPC η <.9 Event mixing corrects for two-track acceptance in bins of centrality and vertex position Per-trigger yields corrected for tracking efficiency and contamination same event pairs (a.u.) η ALI PERF ϕ (rad.) mixed event pairs (a.u.) η ϕ (rad.) Figure : Left: Same Events, Right: Mixed Events Dong Jo,Kim (JYFL/HIP) Jet fragmentation study from ALICE at LHC 4 /

12 Analysis Backgrounds in Correlation function in Heavy Ion collisions At low p T, correlations are dominated by collective effects (v, v,...) This background at low p T is well constrained by large η gap correlation method (Phys.Lett. B78 () 49-64) dn d φ dn + Σvncos n(φ ψn), single () dφ trig + Σvn vn assoc cos(n φ), pairs () Consistent results with event plane method(alice,arxiv:5.576) (a) Correlation function η >.8 Dong Jo,Kim (JYFL/HIP) Jet fragmentation study from ALICE at LHC 5 /

13 Results Jet Shapes in low p T, Broadening Near-Side Peak Shapes Can we see modification of the near-side peak? Dong Jo,Kim (JYFL/HIP) Jet fragmentation study from ALICE at LHC 6 /

14 Results Jet Shapes in low p T, Broadening Near-Side Peak Shapes Can we see modification of the near-side peak? Estimate η-independent effects (e.g. flow) by studying the long-range correlation region ( η > ) 4 GeV/c < p < 8 GeV/c GeV/c < p < GeV/c % dn assoc /d ϕ (/rad.) η <.. < η <.6 (scaled) Pb Pb.76 TeV Stat. unc. only /N trig ALI PREL ϕ (rad.) Dong Jo,Kim (JYFL/HIP) Jet fragmentation study from ALICE at LHC 6 /

15 Results Jet Shapes in low p T, Broadening Near-Side Peak Shapes Can we see modification of the near-side peak? Estimate η-independent effects (e.g. flow) by studying the long-range correlation region ( η > ) Remove from short-range region ( η < ) 4 GeV/c < p < 8 GeV/c GeV/c < p < GeV/c % dn assoc/d ϕ (/rad.) /N trig η <.. < η <.6 (scaled) Pb Pb.76 TeV Stat. unc. only ϕ (rad.) ALI PREL 4947 Dong Jo,Kim (JYFL/HIP) Jet fragmentation study from ALICE at LHC 6 /

16 Results Jet Shapes in low p T, Broadening Shape Evolution Dong Jo,Kim (JYFL/HIP) Jet fragmentation study from ALICE at LHC 7 /

17 Results Jet Shapes in low p T, Broadening Shape Evolution Dong Jo,Kim (JYFL/HIP) Jet fragmentation study from ALICE at LHC 7 /

18 Results Jet Shapes in low p T, Broadening Jet Shape Characterization Near-side peak fitted with D Gaussians shape parameters: σ η, σ φ Figure : Left:Data Middle:Fit Right:Residual Dong Jo,Kim (JYFL/HIP) Jet fragmentation study from ALICE at LHC 8 /

19 Results Jet Shapes in low p T, Broadening Near Side Peak, σ(fit) (fit) (rad.).8.7 Pb Pb s NN =.76 TeV pp s =.76 TeV η <.9 < p T,t < p T,t < < p T,a < 4 < p T,a < GeV/c < GeV/c σ η (fit).8.7 Pb Pb s NN =.76 TeV pp s =.76 TeV η <.9 < p T,t < p T,t < < p T,a < 4 < p T,a < GeV/c < GeV/c σ ϕ 4 < p T,t < 8 < p T,a < GeV/c 4 < p T,t < 8 < p T,a < GeV/c pp Centrality pp Centrality (a) σ φ (b) σ η Figure : Near side peak width No significant centrality dependence of σ φ Dependence on p T,assoc governed by j T p T,assoc σ φ Significant increase of σ η towards central events For the lowest p T bin, eccentricity ( (σ η σ φ )/ (σ η + σ φ )) increases from to. Smooth continuation from peripheral to pp Dong Jo,Kim (JYFL/HIP) Jet fragmentation study from ALICE at LHC 9 /

20 Results Jet Shapes in intermidiate p T, Narrowing I AA ( η ) and jet shape modification Analyze dn/d η (positive and corresp. negative bins are combined) Background estimated by a fit (Kaplan plus constant( parameters A,b,n,k) f ( η) = A( + b η ) n + k /N Pb Pb trig dn Pb Pb /d η p ; p I AA ( η ) = /N pp trig dnpp /d η dn/d η /N trig Pb Pb events at 8<p <5 GeV/c 4<p <6 GeV/c Centrality % s NN =.76 TeV 6/8/ η ALI PERF 776 p ; p Dong Jo,Kim (JYFL/HIP) Jet fragmentation study from ALICE at LHC /

21 Results Jet Shapes in intermidiate p T, Narrowing I AA ( η ) at high p T (8 < p < 5 GeV/c) Pb Pb events at s NN =.76 TeV I ( η ) AA I AA ( η ) 8<p <5 GeV/c 4<p <6 GeV/c Centr. % / pp 8<p <5 GeV/c 6<p <8 GeV/c Centr. % / pp 8<p <5 GeV/c 4<p <6 GeV/c Centr. 4% / pp 8<p <5 GeV/c 6<p <8 GeV/c Centr. 4% / pp 8<p <5 GeV/c 4<p <6 GeV/c Centr. 6 9% / pp 8<p <5 GeV/c 6<p <8 GeV/c Centr. 6 9% / pp ALI PREL 7759 η η η I AA shows a possible onset of jet shape modification in η (Narrowing). Dong Jo,Kim (JYFL/HIP) Jet fragmentation study from ALICE at LHC /

22 Summary Summary. Low momentum regions, the centrality and p T evolution of near-side peak shapes fitted with D Gaussians No significant centrality dependence of σ φ Significant increase of σ η towards central events. (Broadening). I AA ( η ) at high p T (8 < p < 5 GeV/c) a possible onset of jet shape modification in η (Narrowing). Perspectives These observations are intriguing and a combination of these studies seems promising PID-dependent shape, going down to lower p Ta with higher momentum trigger particles Away side correlation is under construction. Comparisons with various quenching models Dong Jo,Kim (JYFL/HIP) Jet fragmentation study from ALICE at LHC /

23 Backup Slides Dong Jo,Kim (JYFL/HIP) Jet fragmentation study from ALICE at LHC /

24 Model comparisons,near Side Peak, σ(fit) (fit) (rad.).8.7 Pb Pb s NN =.76 TeV pp s =.76 TeV η <.9 Data AMPT.5 / Pythia 6 P < p T,t < p T,t < < p T,a < 4 < p T,a < GeV/c < GeV/c σ η (fit).8.7 Pb Pb s NN =.76 TeV pp s =.76 TeV η <.9 Data AMPT.5 / Pythia 6 P < p T,t < p T,t < < p T,a < 4 < p T,a < GeV/c < GeV/c σ ϕ.6 4 < p T,t < 8 < p T,a < GeV/c.6 4 < p T,t < 8 < p T,a < GeV/c pp Centrality pp Centrality (a) σ φ (b) σ η Figure : Comparison to AMPT model AMPT (A MultiPhase Transport Code, Jun Xu, Che Ming Ko,PhysRevC.8.494) Initial conditions simulated using HIJING Parton scattering, Hadronization : String melting + Coalescence and Hadron scattering Lines are from AMPT.5 (Pb-Pb) and Pythia6 (Perugia) (pp) AMPT describes the main features of the near-side shape evolution observed in data Dong Jo,Kim (JYFL/HIP) Jet fragmentation study from ALICE at LHC /

25 I AA ( η ) at intermediate p T (6 < p Tg < 8 GeV/c).5 Pb Pb events at.5 s NN =.76 TeV.5 I ( η ) AA I AA ( η ).5 6<p <8 GeV/c <p <4 GeV/c Centr. % / pp 6<p <8 GeV/c 4<p <6 GeV/c Centr. % / pp.5 6<p <8 GeV/c <p <4 GeV/c Centr. 4% / pp 6<p <8 GeV/c 4<p <6 GeV/c Centr. 4% / pp.5 6<p <8 GeV/c <p <4 GeV/c Centr. 6 9% / pp 6<p <8 GeV/c 4<p <6 GeV/c Centr. 6 9% / pp η η η ALI PREL 478 (a) Dong Jo,Kim (JYFL/HIP) Jet fragmentation study from ALICE at LHC /

In-Medium Energy Loss and Correlations in Pb-Pb Collisions at 2.76 TeV with ALICE

In-Medium Energy Loss and Correlations in Pb-Pb Collisions at 2.76 TeV with ALICE Jan Fiete Grosse-Oetringhaus CERN/PH for the ALICE Collaboration Heavy Ions: Experiments Confront Theory Copenhagen, 8th