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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)
Norbert Novitzky for PHENIX 5
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
Norbert Novitzky for PHENIX 6
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
Norbert Novitzky for PHENIX 8
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
Norbert Novitzky for PHENIX 15
• 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
Norbert Novitzky for PHENIX 16
RAA towards more peripheral region shows less suppression.
62.4 and 200 GeV are similar for pT > 6 GeV
arXiv:1204.1526v1
pT averaged
Norbert Novitzky for PHENIX 17
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
Norbert Novitzky for PHENIX 22
Theory vs Data
Norbert Novitzky for PHENIX 23
RAA in Bjorken energy density
Norbert Novitzky for PHENIX 24
+ ALICE data?
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