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Forward-Backward Correlations in Heavy Ion Collisions Aaron Swindell, Morehouse College REU Cyclotron 2006, Texas A&M University Advisor: Dr. Che-Ming Ko
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Quantum Chromodynamics (QCD) Utilized to strong interactions Standard model: Quarks and Gluons Color charge (Red, Blue, and Green) Six flavors (up, down, charm, strange, top, bottom) SU(3) gauge group has 8 gauge bosons (gluon) QCD Lagrangian F=gluon field tensor Ψ=Quark field D=covariant derivative Pertubative QCD Running coupling: Q=momentum transfer asymptotic freedom Length scale converges Quark-Gluon Plasma
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QCD Matter (Quark Matter) Phase Diagram http://www.pparc.ac.uk/frontiers/current/feature4.asp
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QCD Matter (cont.) Experimental Heavy-Ion Collisions (CERN, BNL, etc.) Lorentz-contracted Nuclei Hard Parton collisions/Jet Interactions Parton Cascade/QGP Hadron Phase
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Quark-Gluon Plasma (QGP) Cosmic “soup” of almost-free quarks and gluons Lattice-Gauge Theory Used at low baryon densities & high temperatures Predicts QGP transition at
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QGP (Experimental) Collisions of large nuclei Au+Au, Pb+Pb @ BNL & CERN =200 GeV, 5.5 TeV respectively “Fireball” Main Observations EM observables: photon(2-4 GeV) and dilepton enhancement Strangeness: strangeness enhancement Kinetic observable: elliptic flow Hard probes: jet quenching, J/ψ suppression Correlation: HBT Interferometry, fluctuations
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Theoretical Models Thermal Yield of various particles, ratios Hydrodynamic Behavior of low particles, elliptic flow Transport Treat chemical/thermal freeze-out dynamically HBT Interferometry of hadrons
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A Multiphase Transport model (AMPT) Describes collisions ranging from p+A to A+A systems RHIC =200 GeV LHC (future) =5.5 TeV HIJING (Heavy Ion Jet Interaction Generator) Initial conditions ZPC (Zhang’s Parton Cascade) Lund string fragmentation/Quark coalescence ART (A Relativistic Transport)
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AMPT (cont.) Default model (v1.11)String melting (v2.11)
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Forward-Backward Multiplicity Correlations using AMPT Experimental collisions produce clusters of correlating partons Au+Au collisions = 200 GeV 0-20% central Event-wise observable (comparison) Measure the variance
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Preliminary Data Nucl-ex/0603026
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Rapidity Distributions
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Variance
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Variance (cont.)
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Analysis Evolution of hadrons in collisions is of much importance for fluctuations (the results from HIJING are much higher than from the AMPT model) Partonic cascade and hadronic evolution have similar effects on fluctuations The difference in magnitude between AMPT calculations and experimental data indicates that there may exist clusters of correlated particles in heavy ion collisions (clusters aren’t made in AMPT) L. J. Shi and S. Jeon, Phys. C72, 034904 (2005)
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Acknowledgements Cyclotron Institute Dr. Ko, Dr. Liu, Dr. Zhang NSF DOE Fellow REU Participants
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