Near-side correlations of high-p t hadrons from STAR Jörn Putschke for the STAR collaboration
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Transcript of Near-side correlations of high-p t hadrons from STAR Jörn Putschke for the STAR collaboration
![Page 1: Near-side correlations of high-p t hadrons from STAR Jörn Putschke for the STAR collaboration](https://reader030.fdocuments.in/reader030/viewer/2022032313/56812be6550346895d90633c/html5/thumbnails/1.jpg)
Near-side
correlations of high-pt
hadrons from STAR
Jörn Putschke for the STAR collaboration
Lawrence Berkeley National Laboratory
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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)
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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19Jörn Putschke, Hard Probes 2006, Monterey
Backup slides
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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
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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)
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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
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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