Recent highlights of PHENIX at RHICNorbert Novitzky for PHENIX collaborationStony Brook University

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4th International Conference on New Frontiers in Physics, ICNFP 2015

PHENIX detector

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Central Arm, |h| < 0.35:• Tracking:

• Drift Chambers (DC) dp/p = 0.7 % + 1.1%p

• Pad Chambers (PC)s = ±1.7 mm

• Electromagnetic Calorimeter:• 2 PbGl: 0.8 % + 5.9 %/√E• 6 PbSc: 2.1 % + 8.1 %/√E

• Particle Identification:• RICH – e±

• TOF East and TOF West:• sT ≅ 100ps• p/K pT < 2.5 GeV/c• K/p pT < 4.0 GeV/c

• EMCal timing:• sT ≅ 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 Geometryand Hydrodynamic flow

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RP

multiple scattering

larger pressure gradient in plane

less yield out-/more in-plane

xy z

Reaction Plane

Spatial asymmetry eccentricity

Mom. Asymmetry elliptic flow

• From pion-interferometry we extract the HBT radii as a function of the reaction plane (Df (f-Yn))

• PHENIX and STAR observed 2nd 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

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PHENIX, PRL 112, 222301 (2014)

detector

detector

1p

2p

R long

Rside

Rout

Sliced view

Beam

Rside Rout Rlong

Measuring of the size of the system

n =

2n

= 3

Ros - asymmetries in the emission region

HBT vs energy

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PHENIX, STAR and ALICE results combined

• Non-monotonic behavior of Rout2 – Rside

2 (proportional to emission duration) and (Rside -√2R)/ Rlong (related to medium expansion velocity).

• softening of equation of state near the Critical End Point?

Measuring the dynamics of the system with v2

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arXiv:1412.1043

inclusive charged hadrons

inclusive charged hadrons

Systematic study of the v2 in heavy ion collisions:• Variation of collision energy: 200 and 62.4 GeV• Variation of system size: Au+Au, Cu+Cu

Except the v2 in CuCu @ 62.4 GeV, all the v2 results are very similar.

Scaling properties

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Phys. Rev. Lett. 103, 142301 • N1/3part is proportional to the length scale of the

system

• e2 is corresponding to initial geometrical anisotropy

• HBT radii scale with the N1/3part

• v2 scales with e2*N1/3part (except CuCu @62.4GeV)

arXiv:1412.1043

Gla

uber

Mod

el

Small system collisions

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Schenke & Venugopalan arXiv:1407.7557

• 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”.

2015 2003 and 2008 2014

Correlation functions in d+Au

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Central-Forward correlation function:The correlation function is fitted to extract the first and second order Fourier components

Correlation coefficients

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Fourier decomposition:

• requiring d2N/dDf2 = 0 at Df = 0 leads to -c2/c1 = 0.25

• -c2/c1 ratio shows relative increase of flow-like component, assuming that c1 is dominated by jet contributions

• The flow-like behavior decrease at higher pT’s

• pT ~ 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

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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:1507.06273

Extracting the v2 of small systems

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arXiv:1507.06273

Extracting the v2:• The d+Au and He3+Au results

are comparable within uncertainties

• v3 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?

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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 pT 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:1405.3940, PRC91, 064904 (2015)

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Integrated thermal photon yield• Npart dependence of integrated yield has same slope even as the integration range is varied

• dN/dy ~Nparta: a= 1.48+/- 0.08 (stat) +/- 0.04 (syst)

• dN/dy ~Nqpa: a= 1.31+/- 0.07 (stat) +/- 0.03 (syst)

• Possible difference between data and model may be from more HG contribution in data?

PRC 89 044910 (Shen, Heinz)arXiv:1405.3940, PRC91, 064904 (2015)

Recent result on photon v2 and v3

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• Some centrality dependence in v2, weak dependence in v3

• Similar trend and amplitude as for charged hadrons (PRL 107, 252301 (2011)) and p0.

• General trend to note: v3 ~ v2/2

The high thermal photon yield and large photon flow is currently not fully understood by theoretical models

Recent Upgrades of PHENIX

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VTX+FVTX detector 2011-2015

MPC-EX detector 2015

HBD detector 2007, 2009-10

Hadron Blind Detector (HBD):• Electrons, CentralVertex detector (VTX):• Heavy flavor tagging, c and b, CentralForward Vertex FVTX:• Muons in Forward, heavy flavor taggingMPC-EX:• p0 and direct gamma in Forward

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A New Detector at RHIC

High data acquisition rate capability, 15 kHz

Sampling 0.6 trillion Au+Au interactions in one-yearMaximizing efficiency of RHIC running

BaBar Magnet 1.5 T

Coverage |h| < 1.1

All silicon trackingHeavy flavor tagging

ElectromagneticCalorimeter

Hadronic Calorimeter

Future of PHENIX -> sPHENIXdetails in Mike McCumber’s talk

Starts in 2020

Summary• HBT radii were measured in various heavy ion collision systems

• Systematic study of v2 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-pT 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

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BACKUPS 20

• Charged pion HBT results favor flow anisotropy dominant scenario

21PRC88, 044914 (2013)

Flow anisotropy dominant

Dotted- Geometry dominantSolid- Flow dominant

3rd o

rder

/ave

rage

radi

i rati

o

PRL 112, 222301 (2014)

Geometry or flow dominant?

Measurement of ratio of v2 to v3

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• Overall trends both for p+/- and direct photons are well described by the calculation• Based on arXiv:1403.7558, private communication for RHIC energy

• Systematic error estimate is currently very conservative• Working on better understanding of systematic errors

sPHENIX performance

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The direct photon yield from PHENIX

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PHENIX Phys.Rev.C87 (2013) 054907

PHENIX Phys.Rev.Lett 104 (2010) 132301

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

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