multiparticle correlations and charged jet studies in p+p, d+au, and au+au collisions at s nn =200...
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Multiparticle Correlations and Charged Jet Studies in p+p, d+Au, and Au+Au
Collisions at sNN=200 GeV.
Michael L. MillerMichael L. Miller
Yale UniversityYale University
For the STAR CollaborationFor the STAR Collaboration
May 2003 Mike Miller
Au Au jets
Jet Properties at RHIC
p p jets
Measure jets in “simple” system (p+p).
Use this information to measure jets in complex system (Au+Au).
May 2003 Mike Miller
1) Approximate jet axis by
leading particle ( )trigger
2) Study of
particles w.r.t.
associ
tri
ated
gger
Jets in Au+Au: Angular Correlations
Px (GeV/c)
Py
(GeV
/c)
-4 -3 -2 -1 0 1 2 3 4
-4
-3
-2 -
1
0 1
2
3
4
Particles from same jet are close in angle
Particles from di-jets are ~180 deg. apart
Select high-pT portion of event (pT>2 GeV)
May 2003 Mike Miller
Jets in p+p: Direct Identification
Cluster final state (charged!) hadrons from a common “parent” quark/gluon.
Reconstruct momentum of quark/gluon
2 2
distance measure:
R
Implemented, tested, using 4 jet-finding algorithms
Remember: only charged particles!
May 2003 Mike Miller
Di-jet Angular Distributions
Increase jet pT, tighten di-jet peakMeasure Nuclear kT in d+Au
di-jet from s=200 GeV p+p (Run II)
Raw STAR Preliminary
jet1 jet1
sin(2
t tt
p pk
6jettp GeV
May 2003 Mike Miller
chargeMeasure , , in jet and w.r.t. thrust axis
Measure underlying event dAu jet energy correction!
t tp N p
vs. all tracks
t leading jetp Jet-Event Shape and Size
Raw STAR Preliminary
<T
otal
pT>
(A
rbit
rary
Un
its)
Within away side jetWithin lead jet Transverse region
Raw STAR Preliminarys=200 GeV p+p (Run II)
May 2003 Mike Miller
Raw STAR Preliminarys=200 GeV p+p (Run II)
“Fragmentation” of Charged Jetstrackt
jett
pz
p
Selecting Jets with large Fragmentation Bias!
Events with pT>4 GeV track
All jets with at least one 2<pT<6 GeV track
What about “Correlation” jets?
Slope depends on jet-algorithm
May 2003 Mike Miller
What Does this Mean?1. At high jet-pT, leading particle
collinear with jet axis
2. Correlation jets: leading particle carries ~80% of reconstructed charged particle jet pT.
Leading particle is a good approximation of jet direction
Leading particle is easily related to jet pT
triggerjet t
Tc
pp
z
Mean trigger fragmentation
Defines the pQCD scale Defines jet Defines jet ppTT of away-side partner! of away-side partner!
May 2003 Mike Miller
Jets In d+Au CollisionsNo background subtraction
Central: top 20% of -3.8<η<-2.8 uncorrected multiplicity
Back-to-back jets are Back-to-back jets are notnot suppressed in central suppressed in central d+Aud+Au
underlying event: p+p d+Au minbias d+Au central
near-side: correlation strength and width similar
away-side: d+Au peak broader but with little centrality dependence
p+p: Adler et al., PRL90:082302 (2003), STAR
May 2003 Mike Miller
Au+Au, p+p: Adler et al., PRL90:082302 (2003), STAR
Jets In Least Violent Au+Au Collisions
“Near side” jet: consistent in all 3 systems
“away side” jet: consistent in all 3
systems
Au+Au: Subtract background from combinatorics, flow
d+Au: no suppression in central
collisions use min. bias.
d+Au: subtract underlying event.
May 2003 Mike Miller
Au+Au, p+p: Adler et al., PRL90:082302 (2003), STAR
Jets In Most Violent Au+Au Collisions
“Near side” jet: consistent in all 3 systems
“away side” jet: p+p
d+AuAu+Au
Au+Au: Subtract background from combinatorics, flow
d+Au: no suppression in central
collisions use min. bias.
d+Au: subtract underlying event.
May 2003 Mike Miller
Conclusions
1. p+p: pT>4 GeV particles are good approximation of jet direction, momentum
2. d+Au: no suppression of away-side jet in central collisions
3. Au+Au: strong suppression of away-side jet in central collisions.
CombinedCombined: Strong back-to-back suppression in : Strong back-to-back suppression in central central Au+AuAu+Au cannot be fully explained by cannot be fully explained by
initial state physicsinitial state physics
May 2003 Mike Miller
What’s Coming from STAR?
1. p+p: Run III data with E.M. Calorimeter 0<<1. Identified jets including 0.
2. d+Au: Same!
3. Au+Au: Run IV with expanded calorimeter and extensive high-pT triggered data.
Measure vacuum, in-medium Measure vacuum, in-medium “fragmentation” functions!“fragmentation” functions!
May 2003 Mike Miller
Backup slides
May 2003 Mike Miller
The STAR Detector
May 2003 Mike Miller
ZDCW
FTPCE
Au d
d+Au “Centrality” Tagging FTPCE multiplicity: -3.8<<-2.8 (Au fragmentation direction) ZDCW: single deuteron spectator
Uncorrected FTPCE multiplicity
minbias
single deuteron spectator
FTPCE multiplicity: defines “centrality” in d+Au events
May 2003 Mike Miller
chargeMeasure , , in jet and w.r.t. thrust axis
Measure underlying event dAu jet energy correction!
t tp N p
Raw STAR Preliminary
vs. from s=200 GeV p+pall tracks
t leading jetp Jet-Event Shape and Size
<T
otal
pT>
(A
rbit
rary
Un
its)
Within away side jetWithin lead jet Transverse region
May 2003 Mike Miller
Why Jets? Energy Loss in Dense Matter
Strong dependence of energy loss on gluon density glue• measure measure gluon density at early hot, dense phase
Thick plasma (Baier et al.):
glueSglue
Debye
sRBDMS
q
vLqC
E
2
2
ˆ
~ˆ4
L
ELogrdCE jet
glueSRGLV 23 2
,
Thin plasma (Gyulassy et al.):
Gluon Bremsstrahlung
May 2003 Mike Miller
“Fragmentation” of Charged Jetstrackt
jett
pz
p
Raw STAR Preliminary
Fragmentation slope scales with jet pT
beyond 6 GeV
How does the slope change as a function of jet pT?
May 2003 Mike Miller
“Fragmentation” of Charged Jetstrackt
jett
pz
p
Raw STAR Preliminary
Slope depends on jet-algorithm
What fraction of (reconstructed) jet pT does each particle carry?
May 2003 Mike Miller
Di-jet Angular Distributions
Increase jet pT, tighten di-jet peakMeasure Nuclear kT in d+Au
di-jet from s=200 GeV p+p
Raw STAR Preliminary
jet1 jet1
sin(2
t tt
p pk
6jettp GeV