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Na Li Huazhong University of Science and Technology 7th International Workshop on CPOD ,

Considerations for Distinguishing Between Soft- and Hard-Component by Multiplicity Correlation. Na Li Huazhong University of Science and Technology 7th International Workshop on CPOD , 7 - 11 November 2011. Motivation. soft particles: from hot dense medium.

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Na Li Huazhong University of Science and Technology 7th International Workshop on CPOD ,

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  1. Considerations for Distinguishing Between Soft- and Hard-Component by Multiplicity Correlation Na Li Huazhong University of Science and Technology 7th International Workshop on CPOD, 7 - 11 November 2011

  2. Motivation • soft particles: • from hot dense medium Mixed when measured in experiment Particle production • jets: • beginning of the collision • hard process • Particles produced in different processes carry different information of the collisions. • It is important to distinguish the contribution of hydro part and non-hydro part, especially in the intermediate pT region. Na Li, CPOD, 2011. 11. 7-11

  3. F-B Elliptic Correlation Function Requirement: ●Jet randomly falls into one region in a single event. J. Liao and V. Koch, Phys. Rev. Lett. 103, 042302 (2009) … backward forward η • Assumption: • the multiplicity of flow particle in each side fluctuate independently -> <ηFηB>=0 g->0, (hydro dominance) CFB->1 g->1, (jet dominance) CFB->0 Na Li, CPOD, 2011. 11. 7-11

  4. Unsolved Problem 2 equations with 3 unknown variables! More measurement needed! Na Li, CPOD, 2011. 11. 7-11

  5. Multiplicity Correlation Function Definition: η … backward forward • The effect of <ηFηB> is small when g is relative large. jet contribution FB correlation of flow multiplicity Na Li, CPOD, 2011. 11. 7-11

  6. In A Multi-phase Transport Model (I) AMPT string melting model At low pT : • With the assumption of no jet contribution at low pT, we may obtain • Although the flow multiplicity exponentially decreases with pT , little pTdependence has been observed for <ηFηB>. Na Li, CPOD, 2011. 11. 7-11 6 Na Li, Hangzhou, 2011. 7. 18-21

  7. In A Multi-phase Transport Model (II) At intermediate pT : • The tail of hydro particle distribution may also caused the decreasing of FB multiplicity correlation function. • The data points from AMPT are lower than the hydro-only simulation. • The jet contribution can not be neglect in intermediate pT range. Na Li, CPOD, 2011. 11. 7-11 7 Na Li, Hangzhou, 2011. 7. 18-21

  8. Non-hydro Contribution in v2 If: the multiplicity of flow particle in each side fluctuate correlated L. X. Han, Phys.Rev.C 83, 047901 (2011) jet contribution correlation of flow multiplicity fluctuation Na Li, CPOD, 2011. 11. 7-11

  9. Elliptic Correlation in AMPT Results of AMPT model L. X. Han, Phys.Rev.C 83, 047901 (2011) • CFB is about 2 in central collisions. • <ηFη B> is close to 0.25 at low pT. • Inconsistent with the result from multiplicity correlation ? Na Li, CPOD, 2011. 11. 7-11

  10. v2 fluctuation Particles produced in in-plane and out-of-plane may fluctuate, thus ηF andηB are the functions of φ, which may cause the fluctuation of v2! For the flow dominate case: • Larger v2 fluctuation in central collision causes the larger CFB at low pT. 10

  11. Observables • Constant at low pT • Neglectable at large g Pure flow and jet v2 are expected to be extracted! Na Li, CPOD, 2011. 11. 7-11

  12. Summary • A multiplicity correlation is proposed to measure non-hydro contribution. • The forward-backward multiplicity correlation <ηFηB> is small in the transport model. • The jet contribution is significant in intermediate pT. • The elliptic anisotropy correlation is proposed to measure the non-collective contribution from elliptic flow. Thank You! Na Li, CPOD, 2011. 11. 7-11 12 Na Li, CPOD, 2011. 11. 7-11

  13. Multiplicity Correlation Simulation • Inputs: • Mflow and Mjet are constrained by g • (Mflow +Mjet ) fluctuates ±20% • φflow randomly generated between [0, 2π] • φjet randomly generated between [0, 2π] , and associated particles are generated within ±π/16 according to jet direction • The effect of <ηFηB> is small when g is relative large. • CFB is consistent with the theoretical value. • The method is not very sensitive with the pure multiplicity fluctuation. No correlation in the simulation Real case? Na Li, CPOD, 2011. 11. 7-11 13

  14. Non-hydro Contribution in v2 If: the multiplicity of flow particle in each side fluctuate correlated L. X. Han, Phys.Rev.C 83, 047901 (2011) jet contribution correlation of flow multiplicity fluctuation Na Li, CPOD, 2011. 11. 7-11

  15. Elliptic Correlation Simulation • Inputs: • Nflow and Njet are constrained by g • (Nflow +Njet ) fluctuates ±20% • Add in v2 signal • Associated particles are • generated within ±π/8 • according to jet direction grey markers: jet corn = π/4 A. M. Poskanzer, Phys.Rev.C 58, 1671(1998) • The pure jet elliptic anisotropy v2 could be extracted from when g≥0.3 Na Li, CPOD, 2011. 11. 7-11

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