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The story of v 3. John Chin-Hao Chen ( 陳勁豪 ) for PHENIX Collaboration Stony Brook University Moriond QCD 2011/03/23. outline. What is v 3 ? How to measure v 3 ? How do theorist think of v 3 ? Does v 3 explains the jet shape modification (ridge and shoulder)?. v n : particle anisotropy. - PowerPoint PPT Presentation
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2011/03/23 Moriond QCD 2011 John Chin-Hao Chen 1
The story of v3
John Chin-Hao Chen (陳勁豪 )for PHENIX Collaboration
Stony Brook UniversityMoriond QCD2011/03/23
2011/03/23 Moriond QCD 2011 John Chin-Hao Chen 2
outline
• What is v3?
• How to measure v3?
• How do theorist think of v3?
• Does v3 explains the jet shape modification (ridge and shoulder)?
2011/03/23 Moriond QCD 2011 John Chin-Hao Chen 3
vn: particle anisotropy
• Spatial distribution of colliding area is “almond” like due to overlap of two colliding nuclei.
• dN/d(-) =N0((1+2vncosn(-)))
• v2 = elliptic flow• If nuclei is perfect
spherical-> no vodd
• With some initial state fluctuation -> finite vodd?
2011/03/23 Moriond QCD 2011 John Chin-Hao Chen 4
Glauber initial state
• The nuclear is not perfect in shape
• Nucleon distribution is not smooth
• Azimuthal symmetry no longer holds
• vodd is possible
2011/03/23 Moriond QCD 2011 John Chin-Hao Chen 5
2-D correlations
shoulder ridge
rad
Peripheral Au+Au/pp Central Au+Au
Both near and away sideare modified!
2011/03/23 Moriond QCD 2011 John Chin-Hao Chen 6
v3, reason for ridge and shoulder?
• Ridge sits at ~ 0, shoulder sits at ~2/3, 4/3– A 3-peak structure!
• v3 (Fourier Coefficient of the cos3term) gives a natural 3-peak structure
• Is v3 the explanation?
• Need to measure v3 to answer this question!
2011/03/23 Moriond QCD 2011 John Chin-Hao Chen 7
How do we measure v3?
• Reaction plane method– Use forward detector to determine the n-th
reaction plane• Two particle correlation method
– No need to determine the reaction plane– central-central two particle correlations
2011/03/23 Moriond QCD 2011 John Chin-Hao Chen 8
S. Esumi, WWND2011
2011/03/23 Moriond QCD 2011 John Chin-Hao Chen 9
Measuring vn with n
• Use the forward detector to determine the nth event plane, n
• Measure vn respect to n and correct with reaction plane resolution n
2011/03/23 Moriond QCD 2011 John Chin-Hao Chen 10
S. Esumi, WWND2011
2011/03/23 Moriond QCD 2011 John Chin-Hao Chen 11
vn from two particle correlations
• Standard v2(v4): single particle vs. reaction plane dN/d(
• Can also measure vn via two particle correlation– Central-central correlation (0.3<||<0.7)– PHENIX: Phys. Rev. Lett. 89, 212301 (2002)– dNAB/d= N(1+ (2Cncos(n))), Cn = vn
AvnB
• the two particles are in the same event, therefore share the same reaction plane
• When pTA = pT
B, vn = sqrt(Cn)
• With low partner pT (below 1 GeV), the jet contribution can be ignored, but not at high pT
2011/03/23 Moriond QCD 2011 John Chin-Hao Chen 12
v2{2p}, v3{2p} from two particle correlations
• v2{2p} agrees with previous PHENIX measurements at low pT
• v3{2p}– Nonzero– Increases with pT (NB: may have non-flow effects in this method)– Increases with centrality
v 2{2
p},
v 3{2
p},
Dash line is PHENIX v2 measured by event planePhys. Rev. Lett. 105, 062301 (2010)
2011/03/23 Moriond QCD 2011 John Chin-Hao Chen 13
• 2-particle (small ) v3 higher than reaction plane (large v3
• should expect non-flow contribution i.e. jets
Compare with v3 measured by 3
RP2P
v3
2011/03/23 Moriond QCD 2011 John Chin-Hao Chen 14
Compare with Hydro calculation
• Large gap measurement (bulk only) agrees well with hydro prediction!
2011/03/23 Moriond QCD 2011 John Chin-Hao Chen 15
What about non-flow in v3?
• Use jets in p+p to calibrate!• Do a Fourier analysis of the per trigger yield jet
function – JF = Cn cos(n) – For Au+Au: combinatorial background
“b0(1+2v2trigv2
partcos2)” removed via ZYAM– ZYAM will not change any Fourier coefficients, except
C0 and C2
• Various centrality and partner pT bins for initial insights into bulk vs. jet contributions
2011/03/23 Moriond QCD 2011 John Chin-Hao Chen 16
Baseline comparison
• Dijet (pp) and away-side suppressed dijet– pp tells us the pure jet contribution– pp nearside only: the awayside jet is fully suppressed
• The jets in AuAu (nearside jet + “head”) should fall in between.
• Fourier strength beyond this is not from the jets.– Jet-bulk contribution!
• v2 of bulk (background) flow subtracted when making the jet function
2011/03/23 Moriond QCD 2011 John Chin-Hao Chen 17
Fourier Spectra of Jet Function
v3 from jet
v3 from jet+bulk+jet-medium int.?
•No significant contribution above c4
•Removing the awayside pp enhances the codd terms
•The c3 in AuAu has contributions from both jet and bulk!
2011/03/23 Moriond QCD 2011 John Chin-Hao Chen 18
summary• v2, v3 and v4 are measured with n and two
particle correlations. • v3 measured by two particle correlations (small
gap) are consistent with but larger than reaction plane method (large gap)
• v3 from reaction plane method agrees with hydro prediction
• The third Fourier coefficient in jet function is significantly enhanced in central AuAu collisions due to the v3 from bulk, but also have some contributions from the jet