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Medium Formation in Small Systems? Experimental Results from RHIC

This article discusses the experimental results on medium formation in small systems, specifically focusing on the effects of initial state and final state in d+Au collisions. It also explores flow-like correlations, heavy flavor production, and high-pT hadrons in these collisions.

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Medium Formation in Small Systems? Experimental Results from RHIC

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  1. Medium formation in small systems? Experimental results from RHIC Paul Stankus Oak Ridge National Lab Quark Matter 2015, Kobe, Japan

  2. Au d

  3. Old Idea d+Au reveals “initial-state” CNM effects

  4. New Idea Significant “final state effects”, medium creation in small system

  5. Broad checklist • Flow-like correlations • Heavy flavor production • High-pT hadrons (jet quenching) p, d,3He Au, Al p p

  6. Flow-like correlations Long Range CMS p+p, JHEP 09 (2010) 091 Near Side Flow checklist: Factorization Geometry influence pT dependence

  7. Long-range correlations in d+Au STAR, PLB 747, (2015) 265-271 d+Au 0-5% p+p min-bias PHENIX, PRL 114, 192301 (2015)

  8. Shape: -c2/c1 ~ Near/Away Near-side peak visible

  9. Geometry control at RHIC p+Au (2015) d+Au (2008) 3He+Au (2014) Initial State Final State Phys. Rev. Lett. 113, 112301 (2014), figure courtesy of B. Schenke

  10. Full palette of v2, v3 3He+Au d+Au p+Au Clear influence of initial geometries Fit by both hydro and parton cascade PHENIX, PRL 114, 192301 (2015) PHENIX, PRL 115, 142301 (2015) AMPT: arXiv:1501.06880 SONIC: arXiv:1502.04745 IP+Hydro:arXiv:1407:7557

  11. Ψ(2s) relative suppression More “stuff” J/Ψ Ψ’ PHENIX, PRL 111, 202301 (2013)

  12. Ψ(2s) relative suppression Ψ’ Ψ’ Less “stuff” More “stuff”

  13. Open charm de-correlation What is the site of any re-scattering? p+p μ- D- D+ e+ d+Au PHENIX, PRC 89, 034915 (2014)

  14. J/Ψ vs p+p multiplicity J/Ψ STAR, arXiv 1509.0644 (2015)

  15. Hadron RdAu Cronin; Radial flow? π0 Hint of jet quenching? STAR, PLB 637 (2006) 161 PHENIX, PRL 98, 172302 (2007)

  16. Jets in d+Au PHENIX, arXiv:1509.14657 Difficult to understand as a CNM effect! Strong hard/soft correlation – proton configurations?

  17. Checklist/Summary • Flow-like, long-range correlations in p,d,3He+Au follow hydro-like patterns, clearly reflect initial geometries • Evidence for in-medium re-scattering of heavy flavor from Ψ(2s)/Ψ(1s) relative suppression and open charm de-correlation • Traditional jet/high-pTquenching not in evidence; un-intuitive RdAu indicates important soft/hard process relationships • Recommendation: Important for theory calculations to reflect exact experimental event class definitions

  18. Extra material

  19. HBT in small systems Perfectly smooth continuum between d+Au, Au+Au systems; also p+Pb and Pb+Pb arXiv:1404.5291  Initial state size parameter

  20. Ψ(2s) relative suppression Ψ’ Ψ’ PHOBOS PRC72, 031901

  21. Charm boost follows NPart Heavy-flavor electrons in three systems d+Au meets Cu+Cu Single charm is pushed but never destroyed; is trend with NPart indicative of medium effect? arXiv:1310.8286

  22. Radial flow in d+Au? Was it the source of the Cronin effect? Blast-wave fits to identified light hadron spectra Heavy-flavor (charm) electron RdAu • Sickles, Phys. Lett. B731 51-56 (2014), • “Possible Evidence for Radial Flow of • Heavy Mesons in d+Au Collisions”

  23. Central d+Au vs Periph Au+Au d+Au Au+Au Phys. Rev. C 88, 024906 (2013)

  24. Caution: Cronin rides in e+A ReA Enhancement of (+) hadron yields at pT ~ 1-1.5 GeV/c is seen with increasing A in e+A. Pattern is sort of like radial flow? Moral: Need to look at small systems with full, proper models HERMES Nucl.Phys.B780:1-27,2007

  25. Mass splitting of v2(EP) RHIC LHC arXiv:1404.7461

  26. d+Au to forward/backward J/Psi RdAu for J/Psi in min-bias d+Au For inclusive d+Au, CNM modifications capture forward/backward difference (but geometry dependence is harder). PRL 107, 142301 (2011) xd<<xAu xd>>xAu xd~xAu South “Backward” North “Forward”

  27. Sort-of-heavy flavor in d+Au d+Au Φ d+Au J/Ψ PRL 107, 142301 (2011)

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