Recent highlights of PHENIX at RHIC Norbert Novitzky for PHENIX collaboration Stony Brook University 1 4 th International Conference on New Frontiers in Physics, ICNFP 2015

PHENIX detector 2 Central Arm, |  | < 0.35: Tracking: Drift Chambers (DC)  p/p = 0.7 % + 1.1%p Pad Chambers (PC)  = ±1.7 mm Electromagnetic Calorimeter: 2 PbGl: 0.8 % %/√E 6 PbSc: 2.1 % %/√E Particle Identification: RICH – e ± TOF East and TOF West:  T ≅ 100ps  /K p T < 2.5 GeV/c K/p p T < 4.0 GeV/c EMCal timing:  T ≅ 600ps Forward detectors: Muon Tracking, Muon ID Forward Electromagnetic Calorimeter (MPC)

Outline – selected highlights System size measurements Hanbury Brown and Twiss (HBT) interferometry Collectivity in terms of energy and system size Collectivity in small systems Thermal radiation of the medium Upgrades/Future of PHENIX Summary 3

Nuclear Geometry and Hydrodynamic flow 4  RP multiple scattering larger pressure gradient in plane less yield out-/ more in-plane less yield out-/ more in-plane x y z Reactio n Plane Spatial asymmetry eccentricity Mom. Asymmetry elliptic flow

From pion-interferometry we extract the HBT radii as a function of the reaction plane (  (  -  n )) PHENIX and STAR observed 2 nd order modulation of HBT radii in 200GeV Au+Au collisions Both the source shape at freeze-out and the emission duration of particles have elliptic pattern PHENIX observed the triangular pattern, too 5 PHENIX, PRL 112, (2014) detector R long R side R out Sliced view Beam R side R out R long Measuring of the size of the system n = 2 n = 3 R os - asymmetries in the emission region

HBT vs energy 6 PHENIX, STAR and ALICE results combined Non-monotonic behavior of R out 2 – R side 2 (proportional to emission duration  and (R side -√2R)/ R long (related to medium expansion velocity).  softening of equation of state near the Critical End Point?

Measuring the dynamics of the system with v 2 7 arXiv: inclusive charged hadrons Systematic study of the v 2 in heavy ion collisions: Variation of collision energy: 200 and 62.4 GeV Variation of system size: Au+Au, Cu+Cu Except the v 2 in 62.4 GeV, all the v 2 results are very similar.

Scaling properties 8 Phys. Rev. Lett. 103, N 1/3 part is proportional to the length scale of the system  2 is corresponding to initial geometrical anisotropy HBT radii scale with the N 1/3 part v 2 scales with  2 *N 1/3 part (except arXiv: Glauber Model

Small system collisions 9 Schenke & Venugopalan arXiv: At first the small system collisions were considered as control measurement for “cold” nuclear matter effect – no QGP is created Recently, the high multiplicity collisions with small systems gained interest. It may not be as “cold” and

Correlation functions in d+Au 10 Central-Forward correlation function: The correlation function is fitted to extract the first and second order Fourier components

Correlation coefficients 11 Fourier decomposition: requiring d 2 N/d  2 = 0 at  = 0 leads to -c 2 /c 1 = c 2 /c 1 ratio shows relative increase of flow-like component, assuming that c 1 is dominated by jet contributions The flow-like behavior decrease at higher p T ’s p T ~ 5-6 GeV the difference between central d+Au and p+p ratio is a possible hint for energy loss (?)

Changing the initial geometry of the collisions: He3 + Au 12 Using the Glauber MC, one can study the change of the geometry from d+Au to He3+Au collision Correlation functions in He3+Au were extracted using inclusive charge tracks. arXiv:

Extracting the v 2 of small systems 13 arXiv: Extracting the v 2 : The d+Au and He3+Au results are comparable within uncertainties v 3 was extracted only from He3+Au. Comparison with theoretical models: Different models show good agreement with the data within the uncertainties The hydro-dynamical evolution seems to agree with the data – possible QGP droplets?

14 Thermal photon spectra Thermal photon spectra are obtained by subtracting hard photons from all direct photon spectra Hard photon contribution is estimated from p+p times Ncoll Fitting to low p T region gives T~240MeV/c, almost independent of centrality The Slope parameter reflects the convolution of the instantaneous rates with the time-dependent temperature. One has to assume time profile to obtain the temperature at given time. arXiv: , PRC91, (2015)

15 Integrated thermal photon yield N part dependence of integrated yield has same slope even as the integration range is varied dN/dy ~N part  :  = 1.48+/ (stat) +/ (syst) dN/dy ~N qp  :  = 1.31+/ (stat) +/ (syst) Possible difference between data and model may be from more HG contribution in data? PRC (Shen, Heinz) arXiv: , PRC91, (2015)

Recent result on photon v 2 and v 3 16 Some centrality dependence in v 2, weak dependence in v 3 Similar trend and amplitude as for charged hadrons (PRL 107, (2011)) and  0. General trend to note: v 3 ~ v 2 /2 The high thermal photon yield and large photon flow is currently not fully understood by theoretical models

Recent Upgrades of PHENIX 17 VTX+FVTX detector MPC-EX detector 2015 HBD detector 2007, Hadron Blind Detector (HBD): Electrons, Central Vertex detector (VTX): Heavy flavor tagging, c and b, Central Forward Vertex FVTX: Muons in Forward, heavy flavor tagging MPC-EX:  0 and direct gamma in Forward

18 A New Detector at RHIC High data acquisition rate capability, 15 kHz Sampling 0.6 trillion Au+Au interactions in one-year Maximizing efficiency of RHIC running BaBar Magnet 1.5 T Coverage |  | < 1.1 All silicon tracking Heavy flavor tagging Electromagnetic Calorimeter Hadronic Calorimeter Future of PHENIX -> sPHENIX details in Mike McCumber’s talk Starts in 2020

Summary HBT radii were measured in various heavy ion collision systems Systematic study of v 2 in collision energy and system size Small system collisions are showing very similar results as A+A collisions Is there a QGP droplet formed? Direct photon results show large excess at low-p T and large flow. This is currently not explained by theoretical models Recent and future upgrades at PHENIX will help us for more precise measurements of QGP properties 19

BACKUPS 20

Charged pion HBT results favor flow anisotropy dominant scenario 21 PRC88, (2013) Flow anisotropy dominant Dotted- Geometry dominant Solid- Flow dominant 3 rd order /average radii ratio PRL 112, (2014) Geometry or flow dominant?

Measurement of ratio of v 2 to v 3 22 Overall trends both for  +/- and direct photons are well described by the calculation Based on arXiv: , private communication for RHIC energy Systematic error estimate is currently very conservative Working on better understanding of systematic errors

sPHENIX performance 23

The direct photon yield from PHENIX 24 PHENIX Phys.Rev.C87 (2013) PHENIX Phys.Rev.Lett 104 (2010) Direct photon production is consistent with the pQCD calculation in p-p collisions, the direct photon yield exceeds the calculation in heavy ion collisions. Virtual photon measurement

System size scaling 25