1 Unveiling Jet Topology via Multi- Particle Correlations Unveiling Jet Topology via Multi- Particle Correlations N. N. Ajitanand Nuclear Chemistry, SUNY, Stony Brook

2 A Cue from Lattice QCD: Phase Transition Brief historical perspective : For phase transition to occur necessary to create energy density > 0.6 – 1.0 GeV/fm 3 For phase transition to occur necessary to create energy density > 0.6 – 1.0 GeV/fm 3

N. N. Ajitanand Jyvaskyla PRL87, (2001) Central collisions peripheral collisions time to thermalize the system (  0 ~ fm/c)  Bjorken  ~ GeV/fm 3 ~ 35 – 100 ε 0 Extrapolation From E T Distributions Achieved Energy Density is Well Above the Predicted Value for the Phase Transition Predicted Value for the Phase Transition Achieved Energy Density is Well Above the Predicted Value for the Phase Transition Predicted Value for the Phase Transition 200 GeV Au+Au Collisions studies at RHIC!

N. N. Ajitanand Jyvaskyla Quark scaling of v2 indicates flow sets in at the partonic stage Strong quenching observed for high pt hadrons hydro-like flow observed High Energy Density matter produced in 200 GeV Au + Au Initial anisotropy gives large pressure gradients

N. N. Ajitanand Jyvaskyla Even the phi which has a very low hadronic scattering cross-section develops a v2 which scales with the mesons. Strong indication of flow developing at the partonic stage Phi meson Flow

N. N. Ajitanand Jyvaskyla lambdas and cascades also show strong v2 according to the expected scaling pattern further supporting the view that flow sets in at the partonic stage Lambda & Cascade Flow

N. N. Ajitanand Jyvaskyla Observation of significant flow for the D meson which implies charm flow D Meson Flow

N. N. Ajitanand Jyvaskyla G. D. Moore, D. Teaney hep-ph/ Calculation of the charm spectrum and the elliptic flow as a function of the diffusion coefficient implies surprisingly strong rescattering behaviour for the heavy quark. An indication of the rather special attributes of the matter formed. Strongly coupled liquid ? Charm Diffusion

N. N. Ajitanand Jyvaskyla Although a part of this effect may be trivially related to the contribution of resonances, the possibility of medium modification contributions is an interesting area of investigation. PHENIX Data to be published in PRL One way to do this would be to look at the source function at different orientations with respect to a high pt particle Imaging Studies Source functions extracted for charged pions produced in Au+Au collisions show non-Gaussian tails.

N. N. Ajitanand Jyvaskyla Such a low value is consistent with the observation of substantial elliptic flow and may provide the conditions for a special medium response to hard probes such as Mach flow R. Lacey et al. Phys. Rev. Lett. 98, (2007) The shear viscosity to entropy ratio (eta /s) is estimated for the hot and dense QCD matter created in 200 GeV Au+Au collisions at RHIC. A very low value ~0.1 is found which is close to the conjectured lower bound (1/4 pi ) Shear viscosity to Entropy ratio

N. N. Ajitanand Jyvaskyla There is strong evidence to support the view that the medium thermalizes rapidly during the partonic stage and exhibits a high degree of collectivity. Study of the medium response to high pT probes is a natural next step

12 Jets are a natural probe of the Medium In relatvistic heavy ion collisions hard parton- parton processes occur early Following hard collisions, scattered partons propagate through the medium radiating gluons and interacting with partons of the medium Finally partons fragment, (possibly) outside the medium

13 Jet Study via Assorted Correlations Associated low pT particle pT High pT Hadron Correlation Function N(pT)

N. N. Ajitanand Jyvaskyla It is necessary to decompose the correlation function to obtain the Jet Function! H(v2)Obtain using BBC Reaction Plane Large η gap Two source model gives : Correlation Flow Jet Correlation Jet Sets a0 Condition Zero Yield At Minimum Evaluate a0 nucl-ex/ Ajitanand et. al.

N. N. Ajitanand Jyvaskyla Simulation Test of Jet Recovery Di-jet faithfully recovered Normal Jet Shape abnormal Jet Shape Line : Input Jet Correlation Squares : Extracted Jet Correlation

GeV Au+Au : Hadron Jet Shapes Jet-pair distributions resulting from decomposition show significant modification Jet-pair distributions resulting from decomposition show significant modification PRL 97, (2006) 200 GeV Au+Au 1<pT<2.5 vs 2.5<pT<4.0

17 Meson vs. Baryon associated partner (for fixed Hadron trigger) Associated mesons and baryons are similarly modified as would be expected If in-medium modification is the cause of the away side bending PHENIX Preliminary

18 Armesto,Salgado,Wiedemann hep-ph/ Possible Modifications of Jet Topology Mach Cone,Wake Effect or “sonic boom” Stoecker nucl-th/ Muller,Ruppert Hep-ph/ Casalderrey-Solana, Shuryak, Teaney, arXiv hep ph/ (2004) Flow induced Deflection Cherenkov Cone A. Majumdar Hard Probes 2006

19 J. Friess, S. Gubser, G. Michalogiorgakis, S. Pufu hep-th/ Graviton perturbations of AdS_5- Schwarzschild generated by a string trailing behind an external quark moving with constant velocity are studied. Mach cone signals are generated in the medium Components of the stress tensor exhibit directional structures in Fourier space at both large and small momentum. The Mach cone angle seen is similar to that in the experiment ADS-CFT duality

N. N. Ajitanand Jyvaskyla Dip Shoulder Identify “Mach Cone ” region with shoulder and normal jet region with dip Analysing two-particle Jet correlations from Mach cone perspective

N. N. Ajitanand Jyvaskyla Dip to Shoulder ratio vs pT for different trigger pT ranges Behaviour for Au+Au is quite different from p+p indicating medium modification

N. N. Ajitanand Jyvaskyla Shoulder does not quench rapidly medium dominance Dip quenches rapidly jet dominance The away side Icp Ratio of per-trigger yield: I cp

23 along azimuth Polar plot 3 Particle Correlations in High pT Framework (*) Normal Jet Same Side Away Side Assoc. pTs (2,3) *  12 *  = along radius *  12 *  13 *  _ = Hi pT(1)

24 Deflected jet sim 3-Particle di-jet correlations allow a distinction between different mechanistic scenarios ! Mach Cone sim Deflected and Cone Jet Sims 2-particle Correlations matched High pT(1)

25 PHENIX SIM Test of Harmonic removal Jet+Harmonic ZYAM gives good Jet Recovery Input Jet Harmonic removed Jet Correlation = Total Correlation – a0*(Harmonic Correlation) “ao” is adjusted till Jet Correlation surface goes to zero at its minimum (ZYAM ) Phys. Rev. C 72, (2005) Ajitanand et.al. Phys. Rev. C 72, (2005)

26 Blue : Input Red : Recovered True 3P correlations successfully recovered (2+1) correlations obtained taking 2P in event 1 and 1P from event 2 For data relative amounts of soft-soft and hard-soft correlations set by relative strengths of observed 2P correlations True 3P Correlations absent True 3P Correlations present Test of (2+1) removal (2+1) processes successfully removed Flat Correlation Surface (offset added)

N. N. Ajitanand Jyvaskyla Pairs per trigger from Correlation Pairs per trigger Input Pairs/trigger can be calculated from correlation function knowing detected singles and detected triplets

28 3-particle Correlations without harmonic removal PHENIX Preliminary Data Most central shows jet dominated landscape with strong away side modification % 0-5 %5-10 % %40-60 %60-90 %

N. N. Ajitanand Jyvaskyla Total 3-particle Jet Correlation Strong away side modification in both total and true 3P Jet Correlations Radial section True 3-particle Jet Correlation Jet Correlations

30 Data Simulated Deflected jet Simulated Mach Cone The data validates the presence of a Mach Cone away-side jet but does not rule out contributions from other topologies. Total 3P jet correlations True 3P jet correlations Azimuthal Sections

N. N. Ajitanand Jyvaskyla Simulated LHC Event Phi Eta Et Phi Et Eta (PYTHIA + HIJING) PYTHIA Jets Jetfinder algorithms

32 Start Step 1 Step 8Step 20 PYTHIA Jet A novel method of jet location in an event has been developed which utilizes successive filtering of soft background using other events Soft background

N. N. Ajitanand Jyvaskyla Expected triplet jet correlation function for Mach flow signal in LHC events Once hard jet candidates have been identified in a large number of events, the three-particle correlation method can be applied to look for medium modification

N. N. Ajitanand Jyvaskyla Conclusions The high pt frame is a suitable choice for the study of jet topology via 3- particle correlations 3- particle jet correlations obtained for 200 GeV Au+Au 3-particle c orrelation without harmonic removal for most central case shows abnormal jet topology 3- particle Jet correlation s show strong away side modification True 3-particle jet correlations validate presence of Mach Cone jets but do not rule out contributions from other topologies. Method a potential tool for jet study at the LHC

N. N. Ajitanand Jyvaskyla Tsunami : Nature’s awesome medium response to a hard event !!