Energy Scan of Hadron (p0) Suppression and

Flow in Au+Au Collisions at

PHENIXNorbert Novitzky for PHENIX collaboration

University of Jyväskylä, FinlandHelsinki Institute of Physics, Finland

Norbert Novitzky for PHENIX 1

Outlook Introduction

Nuclear Modification Factor (RAA)

Flow measurement (v2)

Low-energy scan: Motivation Global observables in energy scan v2 results of p0

Low-energy p+p and Au+Au spectra, xT scaling

RAA results of p0

Fractional energy loss studies in low-energy scan

Summary

Norbert Novitzky for PHENIX 2

Nuclear modification factor

Norbert Novitzky for PHENIX 3

A+A

varies with impact parameter b

p+p

Nuclear Geometryand Hydrodynamic flow

Norbert Novitzky for PHENIX 4

RP

thermalization

larger pressure gradient in plane

less yield out more in plane x

y z

Reaction Plane

Spatial asymmetry eccentricityMom. Asymmetry

elliptic flow

High pT

v2 versus RAA(Df,pT)

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The connection between RAA and v2 :

where

The RAA with respect to reaction plane:

approximation

What is the connection of measure v2 and RAA(Df,pT) at high pT?

Motivation – Suppression in low energy

scan

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Phys. Rev. Lett.101, 162301 (2008)

Cu+Cu energy scan:• Centrality dependence of RAA at √sNN = 200 and 62.4

GeV• NO centrality dependence of RAA at √sNN = 22.4 GeV

dN/dh and dET/dhenergy scan

Norbert Novitzky for PHENIX 7

There is no significant change in the centrality dependence of dN/dh and dET/dh distributions in energy range of 7.7 GeV Au+Au – 2.76 TeV Pb+Pb.

= transverse overlap area of the nuclei. Determined from the Glauber model.t = formation timedET/dh is multiplied by 1.25 to obtain dET/dy at SPS energies.

Bjorken energy density

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v2 in energy scan

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Phys. Rev. Lett. 105, 142301 (2010)

Is v2 saturated in √sNN=39-200GeV?

arXiv:1011.3914

From RHIC to LHC the increase is due to the increase of mean-pT

p0 invariant yields of the Au+Au at 62.4 and 39

GeV

Norbert Novitzky for PHENIX

n200GeV = 8.06 ± 0.03 n62GeV = 10.60 ± 0.03 n39GeV = 13.1 ± 0.1

The minimum bias spectra are fitted with a power-law shape function for pT > 4 GeV/c :

10

In LO of the QCD:

To lower √s the contribution from other processes are larger:• Running a(Q2) • PDF evolution• kT smearing• Higher-twist

phenomena

62.4 GeV

39 GeV

arXiv:1204.1526v1

xT scaling – I.

Norbert Novitzky for PHENIX 11

The xT scaling law for the hard scattering region:

ArXiv:1202.1762

The n(xT) should equal to 4 in LO QCD.

The isolated photons show the xT scaling with the n(xT)=4.5

The LO QCD is dominant process for the isolated photons

xT scaling – II.

Norbert Novitzky for PHENIX 12

Extracting the power with the linear variation of the logarithm of the ratio of the yields at different √sNN:

• All p+p data shows similar scaling behavior and the neff(xT) are comparable

• The 62.4 and 200 GeV Au+Au data agrees with the p+p data• The neff(xT) of the 39 and 200 GeV Au+Au show the xT scaling is

not working below xT < 0.2 (the end of overlapping region)

arXiv:1204.1526v1

62.4 GeV p+p reference extrapolation

Norbert Novitzky for PHENIX 13

• Data from PHENIX are available up to

pT < 7 GeV/c

• To extrapolate to higher pT points power-law function was used:

The limit of the fits is vital ––> systematic errors.

• The systematic uncertainty is calculated from the errors of the power-law fit

• It agrees well with the CCOR data (ISR) in pT 7-10 GeV/c region

• For extrapolation the fit above pT>3.5 GeV is used

39 GeV p+p reference

Norbert Novitzky for PHENIX 14

• Acceptance correction based on PYTHIA8 simulation.

• The systematic uncertainty of the correction function is calculated based on data to PYTHIA8 comparison.

• p+p data measured only in fix-target experiment by E0706 at Tevatron with 800 GeV beam energy. (Phys.Rev.D68:052001,2003)

• The E0706 has different rapidity acceptance

-1.0 < y < 0.5 (PHENIX |y|<0.35).Acceptance correction function

E0706 PHENIX

RAA in energy scan

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• RAA at 39 GeV shows strong suppression in the most central collision.

• The 62.4 and 200 GeV RAA data points are comparable for pT > 6 GeV/c.

• In mid-peripheral collision, 39 GeV data shows so suppression while in higher √sNN the suppression is still significant.

• The data in most central collision are compared with two calculation of the GLV model, where the difference is the magnitude of the Cronin effect.

arXiv:1204.1526v1

RAA vs pT in all centralities

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RAA towards more peripheral region shows less suppression.

62.4 and 200 GeV are similar for pT > 6 GeV

arXiv:1204.1526v1

pT averaged

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RAA in different sNN:

• 62.4-200 GeV are strongly suppressed

• 39.0 GeV data shows suppression for higher centrality only (Npart>100)

• For pT > 6 GeV/c the 62.4 and 200 GeV data points are comparable

arXiv:1204.1526v1

Fractional Energy-Loss

Norbert Novitzky for PHENIX 18

The definition of the energy loss is the “horizontal” shift of the p+p spectrum towards the TAA scaled Au+Au spectra:

= 0

TAA*(p+p)

Au+Au (0-10%)

dpT/pT

Fractional energy loss:

Sloss

Norbert Novitzky for PHENIX 19

The fractional energy loss study:

• 200 GeV exhibits the largest energy loss

• 62 GeV and 39 GeV data points are in agreement for pT<5 GeV/c

arXiv:1204.1526v1

Sloss in all centralities

Norbert Novitzky for PHENIX

Same results as the RAA:

Towards more peripheral collisions the energy loss is decreasing.

In mid-peripheral collision the 39 GeV data have “negative” energy loss. Consistent with RAA>1.

arXiv:1204.1526v1

SummaryPHENIX after 10 years of data taking in the inclusive sector:

Centrality dependence of global observables do not change from 7.7 GeV to 2.76 TeV.

xT scaling: neff(xT) for 39 and 200 GeV is very different in p+p and Au+Au

p0 v2 seems to saturate already at 39 GeV - 200 GeV

p0 RAA was measured in lower energies:The 39 GeV most central is still suppressed62.4 and 200 GeV are comparable for pT>6

GeV/c39 GeV shows suppression for Npart>100

Norbert Novitzky for PHENIX 21

Backup

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Theory vs Data

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RAA in Bjorken energy density

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+ ALICE data?