Quark Gluon Plasma Researches at RHIC/LHC Fuqiang Wang Purdue University Tsukuba Global Science Week 2016 Session #6 "Universe Evolution and Matter Origin"

Fuqiang WangTsukuba Global Science Week 2016 QM’97 QM’15 Kobe Jeju / 26

Quark Gluon Plasma Researches at RHIC/LHC Fuqiang Wang Purdue University Tsukuba Global Science Week 2016 Session #6 "Universe Evolution and Matter Origin"

What is relativistic heavy ion collision? High energy physics Proton-proton collisions Exclusive physics processes High energy nuclear physics nucleus-nucleus collision Many body physics Nuclear Matter Condensed matter physics ∞ body physics Physics is known Artist’s view of heavy ion collision Fuqiang WangTsukuba Global Science Week 2016 Gold High energy condensed matter physics More is different! 4 / 26

Why relativistic heavy ion collision? Quark-Gluon Plasma (QGP) The QCD phase diagram: structure of matter with quark and gluon (color) degrees of freedom. Phase diagram: how matter organizes itself at given degrees of freedom, e.g. water. QCD under extreme condition Fuqiang WangTsukuba Global Science Week / 26

The early universe was a QGP Fuqiang WangTsukuba Global Science Week 2016 Anisotropic expansion Expansion 6 / 26

Why relativistic heavy ion collision? Quark-Gluon Plasma (QGP) x K The QCD phase diagram: structure of matter with quark and gluon (color) degrees of freedom. Phase diagram: how matter organizes itself at given degrees of freedom, e.g. water. QCD under extreme condition Fuqiang WangTsukuba Global Science Week / 26

Relativistic Heavy Ion Collider Brookhaven National Laboratory (BNL), Upton, NY Fuqiang WangTsukuba Global Science Week 2016 AGS TANDEMS PHOBOS STAR BRAHMS PHENIX v =  c = 186,000 miles/sec Au + Au at 200 GeV - RHIC: high-energy heavy-ion collider (i) Dedicated QCD collider (ii) √s NN = GeV (iii) p, d, Cu, Au, U - RHIC: high-energy heavy-ion collider (i) Dedicated QCD collider (ii) √s NN = GeV (iii) p, d, Cu, Au, U 8 / 26

Fuqiang WangTsukuba Global Science Week LHC: high-energy particle/heavy-ion collider (i)√s NN  5000 GeV ~25x of RHIC (ii) p, Pb - LHC: high-energy particle/heavy-ion collider (i)√s NN  5000 GeV ~25x of RHIC (ii) p, Pb CMS LHCb ATLAS ALICE Large Hadron Collider 9 / 26

Quantum ChromoDynamics Fuqiang WangTsukuba Global Science Week 2016 Short distance Long distance Asymptotic freedom confinement Q Complex to calculate: Lattice QCD QCD-guided, driven by experiment pQCD DOF well defined Strong coupling QCD Matter 10 / 26

Study QCD by heavy-ion collisions Fuqiang WangTsukuba Global Science Week 2016 One of the challenges is to infer the earlier state QGP through final state hadrons Outline for the rest of the talk 1.Hard processes, short distance, rare probes 2.Soft processes, long distance, bulk particles 11 / 26

Nuclear modification factor Interact with QGP, and changed by QGP Compare to pp/pQCD leading to knowledge about QGP Nuclear modification factor: Fuqiang WangTsukuba Global Science Week 2016 small large 12 / 26

Hadron and (b)jet R AA Anti-k T R=0.3 JetsCharged Particles N coll scaling works No flavor/mass dependence at high p T x2 suppression Flavor/mass dependence seen at low p T CMS: EPJC 72 (2012) 1945, HIN , PRL 113 (2014) , PLB 715 (2012) 66, JHEP 03 (2015) 022, PLB 710 (2012) 256EPJC 72 (2012) 1945 Fuqiang WangTsukuba Global Science Week / 26

Dijet imbalance Fuqiang WangTsukuba Global Science Week 2016 Constituent p T Cut = 2 GeV/c  Reduce BG  Reduce combinatorial jets Di-jet Selection: Jet p T Lead >20 GeV/c Jet p T SubLead >10 GeV/c |  -  |<0.4 Constituent p T Cut = 0.2 GeV/c ATLAS, PRL 105, CMS, PRC 84, (2011) pp AA Constituent p T Cut = 2 GeV/c 14 / 26

Dijet Fuqiang WangTsukuba Global Science Week 2016 Anti-k T R=0.4, p T Lead >20 GeV & p T SubLead >10 GeV with p T cut >2 GeV/c |A J | Preliminary Sys. Uncertainties: - tracking eff. 6% - tower energy scale 2% Au+Au di-jets more imbalanced than p+p for p T cut >2 GeV/c Au+Au A J ~ p+p A J for matched di-jets (R=0.4) Event Fraction p-value < (stat. error only) p-value = 0.8 (stat. error only) Central Au+Au anti-k T, R=0.4 “Lost” energy seems contained within R=0.4 and low p T Imbalance remains for smaller cone or higher constituent cutoff  Observed Broadening and Softening jet-by-jet 15 / 26

Dijet pp PRC 84, (2011) PLB 712, 176 (2012) RPC 84, (2011) Larger fraction of asymmetric dijet events in central PbPb In-cone Out-of- cone  Many theoretical ideas such as –Jet collimation, decoherence, hydro, turbulence cascade, third jet, etc.  Further development of jet analysis –Detailed angular distribution of the quenched energy flow and jet shape Fuqiang WangTsukuba Global Science Week / 26

Quarkonia melting Fuqiang WangTsukuba Global Science Week / 26

Fuqiang WangTsukuba Global Science Week 2016 Soft probes: collective phenomena 4v 2 coordinate-space-anisotropy  momentum-space-anisotropy Pressure gradient 18 / 26

Elliptic flow measurements  Small value of specific viscosity over entropy η/s Model: Song et al. arXiv: v 2 Fuqiang WangTsukuba Global Science Week 2016 RHIC Hydro 1+2v 2 cos2  19 / 26

BNL press release 2005 RHIC Scientists Serve Up "Perfect" Liquid New state of matter more remarkable than predicted -- raising many new questions Very low viscosityInfinite viscosity η/s ≈ (1-2)/4π Viscosity quantum limit: RHIC results Fuqiang WangTsukuba Global Science Week / 26

Number of Constituent Quark Scaling Fuqiang WangTsukuba Global Science Week 2016 It is the constituent quarks that are flowing 21 / 26

Heavy quarks flow! Heavy quarks produced early by hard scattering Heavy, does not easily flow, not easily thermalized Fuqiang WangTsukuba Global Science Week 2016 Even heavy quarks flow and nearly thermalized; light quarks must have been thermalized. not fully thermalized? 22 / 26

But there may be problems… proton LEAD Fuqiang WangTsukuba Global Science Week 2016 Yeah…pPb, even pp creates a QGP! Maybe we need to rethink about the whole paradigm… 23 / 26

A bit of history… Fuqiang WangTsukuba Global Science Week / 26

Is there longitudinal flow effect? Fuqiang WangTsukuba Global Science Week 2016 flow 江角晋一, 筑波大学 25 / 26

Summary Relativistic heavy ion physics is a rich and vibrant field. QCD in matter under extremis. The QCD matter is opaque to hard probes The QCD matter is fluid/perfect/explosive, but small systems pose challenges Fuqiang WangTsukuba Global Science Week / 26