Tsukuba Global Science Week 2016 Session 6 Universe

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

Jeju 2016 QM’ 97 QM’ 15 Kobe QM’ 97 Fuqiang Wang Tsukuba Global Science Week 2016 2 / 26

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

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

Why relativistic heavy ion collision? Phase diagram: how matter organizes itself at given degrees of freedom, e. g. water. QCD under extreme condition Quark-Gluon Plasma (QGP) The QCD phase diagram: structure of matter with quark and gluon (color) degrees of freedom. Fuqiang Wang Tsukuba Global Science Week 2016 5 / 26

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

Why relativistic heavy ion collision? Phase diagram: how matter organizes itself at given degrees of freedom, e. g. water. QCD under extreme condition Quark-Gluon Plasma (QGP) 1012 K x 5 The QCD phase diagram: structure of matter with quark and gluon (color) degrees of freedom. Fuqiang Wang Tsukuba Global Science Week 2016 7 / 26

Relativistic Heavy Ion Collider Brookhaven National Laboratory (BNL), Upton, NY PHOBOS BRAHMS RHIC PHENIX STAR - RHIC: high-energy heavy-ion collider AGS (i) Dedicated QCD collider (ii) √s. NN = 5 - 200 Ge. V (iii) p, d, Cu, Au, U TANDEMS Fuqiang Wang v = 0. 99995 c = 186, 000 miles/sec Au + Au at 200 Ge. V Tsukuba Global Science Week 2016 8 / 26

Large Hadron Collider - LHC: high-energy particle/heavy-ion collider (i) √s. NN 5000 Ge. V ~25 x of RHIC (ii) p, Pb CMS Fuqiang Wang LHCb ATLAS ALICE LHC Tsukuba Global Science Week 2016 9 / 26

Quantum Chromo. Dynamics Q • Complex to calculate: Lattice QCD • QCD-guided, driven by experiment • p. QCD Long distance Short distance nt Strong coupling QCD Matter Fuqiang Wang e m e n fi con Asymptotic freedom DOF well defined Tsukuba Global Science Week 2016 10 / 26

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

Nuclear modification factor small • • Interact with QGP, and changed by QGP Compare to pp/p. QCD leading to knowledge about QGP Nuclear modification factor: large Fuqiang Wang Tsukuba Global Science Week 2016 12 / 26

Hadron and (b)jet RAA Charged Particles Anti-k. T R=0. 3 Jets No flavor/mass dependence at high p. T Ncoll scaling works x 2 suppression Flavor/mass dependence seen at low p. T Fuqiang Wang CMS: EPJC 72 (2012) 1945 , HIN-12 -004, PRL 113 (2014) 132301, PLB 715 (2012) 66, JHEP 03 (2015) 022, PLB 710 (2012) 256 Tsukuba Global Science Week 2016 13 / 26

Dijet imbalance AA pp Constituent p. TCut = 2 Ge. V/c Reduce BG Reduce combinatorial jets Constituent p. TCut = 2 Ge. V/c = 0. 2 Ge. V/c Di-jet Selection: Jet p. TLead>20 Ge. V/c Jet p. TSub. Lead>10 Ge. V/c |Df-p|<0. 4 ATLAS, PRL 105, 252303 CMS, PRC 84, 024906 (2011) Fuqiang Wang Tsukuba Global Science Week 2016 14 / 26

Event Fraction Dijet imbalance @RHIC Anti-k. T R=0. 4, p. TLead>20 Ge. V & p. TSub. Lead>10 Ge. V with p. Tcut>2 Ge. V/c Sys. Uncertainties: - tracking eff. 6% - tower energy scale 2% p-value < 10 -4 (stat. error only) Central Au+Au anti-k. T, R=0. 4 p-value = 0. 8 (stat. error only) Preliminary Au+Au di-jets more imbalanced than p+p for p. Tcut>2 Ge. V/c Au+Au AJ ~ p+p AJ for matched di-jets (R=0. 4) |AJ| “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 Fuqiang Wang Tsukuba Global Science Week 2016 15 / 26

pp Dijet imbalance @LHC In-cone Out-ofcone PRC 84, 024906 (2011) Larger fraction of asymmetric PLB 712, 176 (2012) dijet events in central Pb. Pb RPC 84, 024906 (2011) § 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 Wang Tsukuba Global Science Week 2016 16 / 26

Quarkonia melting Fuqiang Wang Tsukuba Global Science Week 2016 17 / 26

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

Elliptic flow measurements RHIC 4 v 2 1+2 v 2 cos 2 f Hydro Small value of specific viscosity over entropy η/s Fuqiang Wang Model: Song et al. ar. Xiv: 1011. 2783 Tsukuba Global Science Week 2016 19 / 26

BNL press release 2005 RHIC Scientists Serve Up "Perfect" Liquid New state of matter more remarkable than predicted -- raising many new questions http: //www. bnl. gov/newsroom/news. php? a=1303 Infinite viscosity Very low viscosity η/s ≈ (1 -2)/4π Viscosity quantum limit: RHIC results Fuqiang Wang Tsukuba Global Science Week 2016 20 / 26

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

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

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

A bit of history… Fuqiang Wang Tsukuba Global Science Week 2016 24 / 26

Is there longitudinal flow effect? flow Tsukuba Global Science Week 2016 flow Fuqiang Wang 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 Wang Tsukuba Global Science Week 2016 26 / 26