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Near-side correlations of high-p t hadrons from STAR Jörn Putschke for the STAR collaboration Lawrence Berkeley National Laboratory. “Ridge” observation. d+Au, 40-100%. - PowerPoint PPT Presentation
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Near-side
correlations of high-pt
hadrons from STAR
Jörn Putschke for the STAR collaboration
Lawrence Berkeley National Laboratory
2Jörn Putschke, Hard Probes 2006, Monterey
“Ridge” observation
Additional near-side long range corrl. in (“ridge
like” corrl.) observed.
Dan Magestro, Hard Probes 2004, STAR, nucl-ex/0509030 and P. Jacobs,
nucl-ex/0503022
d+Au, 40-100% Au+Au, 0-5%
3 < pT(trig) < 6 GeV2 < pT(assoc) < pT(trig)
3Jörn Putschke, Hard Probes 2006, Monterey
Outline
2-particle correlations:
How to extract the “ridge” yield ? (additional near-side long range corrl. in )
Quantify ridge properties in Au+Au (Cu+Cu)200 GeV collisions
Summary & discussion
Au+Au 0-10%preliminary
3<pt,trigger<4 GeV
pt,assoc.>2 GeV
4Jörn Putschke, Hard Probes 2006, Monterey
Components of correlations
Au+Au 20-30%
a
b
c c
b
a) Near-side jet-like corrl.+ ridge-like corrl. + v2 modulated bkg.
b) Ridge-like corrl. + v2 modulated bkg.
c) Away-side corrl.+ v2 modulated bkg.
Au+Au 0-10%preliminary
Strategy: Subtract from projection to isolate the ridge-like correlation
5Jörn Putschke, Hard Probes 2006, Monterey
(J+R)
||<1.7
J = near-side jet-like corrl.
R = “ridge”-like corrl.
v2 modulated bkg. subtracted
(J+R)
||<1.7
flow (v2)corrected
Extracting near-side “jet-like” yields
1
Au+Au 20-30%
2
2
(J+R)- (R)
con
st b
kg.
sub
tra
cte
d
(J
)
||
<0.
7
(J)
no bkg. subtraction
const bkg. subtracted
(J)
||<0.7
6Jörn Putschke, Hard Probes 2006, Monterey
pt,assoc. > 2 GeV
preliminary
Jet+
Rid
ge y
ield
(
)
Jet yield ()
Jet and Jet+Ridge yields & widths
• Jet+Ridge yield increasing with centrality
•Jet+Ridge shape asymmetric in and
preliminary
pt,assoc. > 2 GeV
Jet+
Rid
ge w
idth
(
)
central
Correlate Jet ((J)) and Jet+Ridge ((J+R)) widths & yields via centrality
Jet width ()
preliminarycentral
periph.
periph.Yield Width
7Jörn Putschke, Hard Probes 2006, Monterey
Jet yields & widths: vs.
Correlate Jet ((J)) and Jet ((J)) widths and yields via centrality
pt,assoc. > 2 GeV pt,assoc. > 2 GeV
•Jet yield ~ symmetric in • Jet shape ~ symmetric in for pt,trig > 4 GeV
(asymmetric in for pt,trig < 4 GeV)
preliminary preliminary
centralperiph.
Jet yield ()
Jet y
ield
(
)
Jet width ()Je
t wid
th (
)
Yield
Width
8Jörn Putschke, Hard Probes 2006, Monterey
Extracting the ridge yield
Definition of “ridge yield”:
i) ridge yield := Jet+Ridge( Jet()
ii) relative ridge yield := ridge yield / Jet()
preliminaryJet+Ridge ()
Jet ()
Jet)
yiel
d
,)
Npart
3 < pt,trigger < 4 GeV and pt,assoc. > 2 GeV
9Jörn Putschke, Hard Probes 2006, Monterey
Ridge shape measurement in central Au+Au
• ridge yield as function of saturates at high non-uniform ridge shape in • ridge more collimated in for higher trigger pt
Au+Au 0-10%
preliminary
pt,assoc. > 2 GeV r
idge
yie
ld
10Jörn Putschke, Hard Probes 2006, Monterey
Ridge yield in Au+Au
pt,assoc. > 2 GeV
preliminary
Ridge yield slightly decreasing (~ constant) as function of trigger pt
11Jörn Putschke, Hard Probes 2006, Monterey
“Jet yield” vs. pt,assoc. in central Au+Au
“Jet spectrum” much harder than inclusive h and increasing with pt,trigger
preliminaryJe
t yi
eld
inclusive
12Jörn Putschke, Hard Probes 2006, Monterey
Ridge yield vs. pt,assoc. in central Au+Au
preliminary
“Ridge spectrum” slightly harder than inclusive h and ~ independent of pt,trigger
inclusive
13Jörn Putschke, Hard Probes 2006, Monterey
“Jet”/ridge yield vs. pt,assoc. in central Au+Au
preliminaryAu+Au 0-10%preliminary
Rid
ge
/ Jet
yie
ld
preliminary
RidgeJet
preliminary“jet” sloperidge slopeinclusive slope€
dN /dpt ∝ pte−p t /T
14Jörn Putschke, Hard Probes 2006, Monterey
Pion vs. Proton ridge yield
preliminary
pt,assoc. > 2 GeV
Au+Au 0-10%
Proton content of ridge larger than of jet part(more from strange assoc. particles in Janas talk)
Assoc. ProtonsAssoc. PionsAssoc. h
15Jörn Putschke, Hard Probes 2006, Monterey
Ridge yield in Au+Au and Cu+Cu
Relative ridge yield comparable at same Npart in Au+Au and Cu+Cu
pt,assoc. > 2 GeV
preliminary
preliminary
relative ridge yield relative ridge yield
rela
tive
ridge
yie
ld
rela
tive
ridge
yie
ld
16Jörn Putschke, Hard Probes 2006, Monterey
Scenarios
i) Parton radiates energy before fragmenting
and couples to the longitidunal flow— Gluon bremmstrahlung of hard-scattered parton
— Parton shifted to lower pt
— Radiated gluon contributes to broadening
contradicts surface bias emission picture !
ii) Parton recombination (Chiu & Hwa Phys. Rev. C72:034903,2005)
— Recombination of thermal partons only indirectly affected
by hard scattering not part of the jet
iii) Radial flow + jet-queching (Voloshin nucl-th/0312065)
Armesto et al, nucl-ex/0405301
17Jörn Putschke, Hard Probes 2006, Monterey
Discussion
pt,assoc.
ridge
/jet y
ield
h+,-
ridgejet
increasing
pt,trig
• ridge spectrum harder than inclusive h+,-
(~ 40-50 MeV in slope parameter)
consistent with parton recombination
(T~15 MeV) ?
• agreement with radial flow + jet quenching ?
• ridge spectrum qualitatively in agreement with
parton energy loss and coupling to longitudinal flow
• quantitative calculation for comparison needed
18Jörn Putschke, Hard Probes 2006, Monterey
Outlook
• Study geometry effects in more detail:
Look at near-side modifications in Au+Au with respect to the reaction plane
• PID ridge yield study with pions, protons and strange particles (see Janas talk)
• 3-particle near-side correlations
Part/Col Au+Au 30-40% Part/Col Cu+Cu 0-10%
Part ~ energy density
Coll ~ parton origin
x [fm] x [fm]
y [f
m]
y [f
m]
very preliminary !
12
1
3
19Jörn Putschke, Hard Probes 2006, Monterey
Backup slides
20Jörn Putschke, Hard Probes 2006, Monterey
Analysis methods cont.
preliminary
v2 subtraction and systematic error estimation Au+Au:
• Used v2 values = mean between v2 RP and v2{4} measurements
• Systematic errors mainly due to uncertainties in v2;
use v2 RP and v2{4} as upper and lower limit
v2 subtraction and systematic error estimation Cu+Cu:
a) Used v2 values = v2{CuCu-pp}
b) Systematic errors mainly due to uncertainties in v2;
use v2 RP and no flow as upper and lower limit
QM051. Use event-mixing to account for pair
acceptance & use eff. correction for ass. particles
2. Background:
a) Subtract constant backgroundfor (J) method
b) Subtract v2 modulated background for (J+R) method
3. Assume Gaussian correlation shape:yield() = gaus integral / bin counting () = gaus width
21Jörn Putschke, Hard Probes 2006, Monterey
Au+Au near-side (J)(J+R) yields & widths II
pt,assoc. > 3 GeV
yiel
d
(J+
R))
yield(J))
preliminary
Correlate (J) and (J+R) widths & yields via centrality
•(J) yield ~ J+R)yield
• J) and J+R)widths ~ constant
pt,assoc. > 3 GeV
preliminary
(J)
(J+
R)
22Jörn Putschke, Hard Probes 2006, Monterey
Relative ridge yield in Au+Au
pt,assoc. > 2 GeV
preliminary
Relative ridge yield strong increasing with centrality for lower trigger pt
rela
tive
ridge
yie
ld
23Jörn Putschke, Hard Probes 2006, Monterey
Summary
• Ridge shape non-uniform in in central Au+Au collisions
• Ridge yield slightly decreasing (~ constant) as function of pt,trigger
• Ridge spectrum independent of pt,trigger and slightly harder than
inclusive charged hadron spectrum (~40-50 MeV in slope parameter)
• Relative ridge yield for identified assoc. pions suppressed with respectto charged hadrons (identified assoc. protons enhanced)
• At the same Npart the relative ridge yield seems to be comparable in
periph. Au+Au (30-40%) and in central Cu+Cu (0-10%) collisions