PHENIX Measurements of Azimuthal Anisotropy at RHIC Arkadiy Taranenko National Research Nuclear University MEPhI (Moscow Engineering Physics Institute) for the PHENIX Collaboration The XXIII International Workshop  High Energy Physics and Quantum Field Theory June 26– July 3,  2017 Yaroslavl, Russia

Azimuthal Anisotropy Measurements at PHENIX Motivation Methods : Vn measurements in PHENIX System size dependence of anisotropy in small systems PID Vn results in small systems at RHIC Beam energy scan for d+Au collisions at RHIC Summary ε2 ε3 ε4

The QGP Discovered at RHIC: 2005-2006 M. Roirdan and W. Zajc, Scientific American, May 2006

Anisotropic Flow in Heavy-Ion Collisions - methods CMS 1201.3158 Different methods, non-flow, fluctuations

Anisotropic Flow in HIC at RHIC: results n=2 for mesons and n=3 for baryons PoS 2006 (2006) 021 Gale, Jeon, et al., Phys. Rev. Lett. 110, 012302 Phys. Rev.C.93.051902(R) 5

Collectivity in Small Colliding Systems? Initial state Pre-equillibrium Quark Gluon Plasma? Hadronization Hadronic phase and freezeout QGP? Final state interactions: Hydrodynamic Flow? Initial momentum correlations: CGC? How to distinguish initial vs final state effects ? PLB 718 (2013) 795 PRL 115 (2015) 012301 PLB 726 (2013) 164

PHENIX Experiment at RHIC ZDC |η|>5.9 MPC/MPC-EX/ 7

PHENIX Flow Measurements : Methods Central Arms (CA) |η’| < 0.35 (particle detection) ψn RXN (|h|=1.0~2.8) MPC (|h|=3.1~3.7) BBC (|h|=3.1~3.9) From 2012: - FVTX (1.0<|h|<3) Correlate hadrons in central Arms with event plane (RXN, etc) ∆φ correlation function for EPN - EPS (II) (I) ∆φ correlation function for EP - CA

PHENIX Flow Measurements : Methods Vn (EP): Phys.Rev.Lett. 107 (2011) 252301   Phys. Rev. Lett. 105, 062301 (2010) Good agreement between Vn results obtained by event plane (EP) and two-particle correlation method (2PC) No evidence for significant η-dependent non-flow contributions from di-jets for pT=0.3-3.5 GeV/c. Systematic uncertainty : event plane: 2-5% for v2 and 5-12% for v3. ψn RXN (|h|=1.0~2.8) MPC (|h|=3.1~3.7) BBC (|h|=3.1~3.9)

Small system program at RHIC HeAu pAl pAu dAu Geometry Scan Different initial geometry  different final state particle emission for p+Au, d+Au and 3He+Au collisions 0-5% p+Au 0-5% d+Au 0-5% He+Au 2 0.23 0.54 0.50 3 0.16 0.19 0.28

Small system program at RHIC HeAu pAl pAu dAu Geometry Scan dAu 200GeV Beam Energy Scan (BES) will help us to search for the turning off the QGP signatures dAu 39GeV dAu 62.4GeV 0-5% p+Au 0-5% d+Au 0-5% He+Au 2 0.23 0.54 0.50 3 0.16 0.19 0.28 dAu 19.6GeV Energy Scan 11

Ridge in small systems ( 200 GeV) 12 The near side long-range angular correlation (“ridge”) is observed in small systems for high multiplicity d+Au and 3He+Au events

Estimation of Non-Flow Estimating Non-Flow Estimation of Non-Flow c2 (pT) = c2Non-Elementary + c2Elementary c2 (pT) = c2Non-Elementary + c2p+p x Charge at Forward h in p+p Charge at Forward h in p+Au v2: 7% in 3He+Au,10% in d+Au; 25% in p+Au  increases in smaller systems v3 : 15% in 3He+Au cited as a systematic uncertainty 13

Vn in small systems ( 200 GeV) v2(3HeAu) ~ v2(dAu) > v2(pAu) ~ v2(pAl) v3(3HeAu) > v3(dAu) Hierarchy compatible with initial geometry + final state effects

Comparison with viscous hydro calculations Hydro without preflow (SONIC) Better describes the data Hydro with preflow (super SONIC) over estimates v3 and v2 15

Identified particles v2 A clear mass ordering is seen in d/3He+Au collision while not in p+Au A stronger radial flow in d/3He+Au?

Identified particle v2 comparison with hydro p+Au d+Au 3He+Au Well described p/d/3He+Au results at low pT Smaller mass split for v2 in p+Au is predicted High pT data are not reproduced - recombination not included

Number of Quark Scaling in central 3He+Au The familiar behavior of number of quark scaling observed in Au+Au collisions is also seen in the small 3He+Au system

V2 vs collision energy in d+Au The v2 in 62.4 and 200 GeV dAu collisions are very similar At lower collision energy, the v2 increase at high pT which may due to large non-flow

V2 vs collision energy in Au+Au 10-20 % 20-30 % 30-40 % 40-50 %

Comparison with viscous Hydro. Both SONIC and super SONIC calculations are lower than measurements at lower collision energies. It further indicates the large non-flow

√s dependence of c2{4} at RHIC Surprising features: v2{4} larger at lower √s, reaching v2{2}. Difficult to describe in both CGC and hydro Important to understand non-flow in standard cumulant method

Summary By scanning different colliding systems PHENIX found that the initial geometry play an important roles for the ridge and vn in small systems. And these results can be well described by the viscous hydro calculations. RHIC geometry scan suggest ordering of vn follows that of εn. The mass ordering, NCQ scaling and four particles cumulant results indicate a collective behavior in small systems The v2 has been measure in small system from 200 GeV to 19.6 GeV by event plane method, but nonflow effect need to be further studied v2{4} larger at lower √s, reaching v2{2}.

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