# PowerPoint Presentation - Phenix by yurtgc548

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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. Miller
Yale University
For the STAR Collaboration
Jet Properties at RHIC

Au  Au  jets                      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
Jets in Au+Au: Angular Correlations
Select high-pT portion                  Particles from same
of event (pT>2 GeV)                    jet are close in angle
Py (GeV/c)

Particles from di-jets are
4

~180 deg. apart
3
2
0 1

1) Approximate jet axis by
-4 -3 -2 -1

2) Study  of associated
particles w.r.t. trigger
-4 -3 -2 -1   0 1   2    3   4   Px (GeV/c)
May 2003                                                                                    Mike Miller
Jets in p+p: Direct Identification
Cluster final state
a common “parent”              R   2   2
quark/gluon.

Reconstruct momentum
of quark/gluon
Implemented, tested,
using 4 jet-finding
algorithms

Remember: only charged particles!
May 2003                                             Mike Miller
Di-jet Angular Distributions
di-jet  from s =200 GeV p+p (Run II)

 ptjet1  ptjet1 
kt                     sin( 
        2        
Raw STAR Preliminary

pt  6GeV
jet

Increase jet pT, tighten di-jet peak
Measure Nuclear kT in d+Au
May 2003                                                    Mike Miller
Jet-Event Shape and Size
<Total pT> (Arbitrary Units)              ptall tracks vs. leading jet

s =200 GeV p+p (Run II)
RawRaw STAR Preliminary
STAR Preliminary

Within lead jet     Transverse region         Within away side jet

Measure pt ,                                 N charge ,    p    t     in jet and w.r.t. thrust axis
Measure underlying event  dAu jet energy correction!
May 2003                                                                                                           Mike Miller
“Fragmentation” of Charged Jets
p track
What about “Correlation” jets?        z  t jet
pt

Slope depends on jet-
algorithm

Events with pT>4 GeV
s =200 GeV p+p (Run II)              track
Raw STAR Preliminary                  All jets with at least
one 2<pT<6 GeV track

Selecting Jets with large Fragmentation Bias!
May 2003                                                         Mike Miller
What Does this Mean?
1.   At high jet-pT, leading particle
collinear with jet axis
carries ~80% of reconstructed
pttrigger
charged particle jet pT.                                   pTjet   
zc
Mean trigger
Leading particle is a good         fragmentation
approximation of jet direction

Leading particle is easily related to jet
pT

Defines the pQCD scale            Defines jet pT of away-side partner!
May 2003                                                                      Mike Miller
Jets In d+Au Collisions
No background subtraction          p+p: Adler et al., PRL90:082302 (2003), STAR

Central: top 20% of -3.8<η<-2.8
uncorrected multiplicity

underlying event: p+p < d+Au
minbias < d+Au central
 near-side: correlation strength
and width similar
but with little centrality
dependence

Back-to-back jets are not suppressed in central d+Au
May 2003                                                                     Mike Miller
Jets In Least Violent Au+Au Collisions
Au+Au, p+p: Adler et al., PRL90:082302 (2003), STAR

Au+Au: Subtract background
from combinatorics, flow
d+Au: no suppression in central
collisions  use min. bias.
d+Au: subtract underlying event.

“away side” jet:
consistent in all 3           “Near side” jet: consistent
systems                       in all 3 systems
May 2003                                                                        Mike Miller
Jets In Most Violent Au+Au Collisions
Au+Au, p+p: Adler et al., PRL90:082302 (2003), STAR

Au+Au: Subtract background
from combinatorics, flow
d+Au: no suppression in central
collisions  use min. bias.
d+Au: subtract underlying event.

“away side” jet:
p+p d+AuAu+Au                 “Near side” jet: consistent
in all 3 systems
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.
Combined: Strong back-to-back suppression in
central Au+Au cannot be fully explained by
initial 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
“fragmentation” functions!

May 2003                                           Mike Miller
Backup slides

May 2003                   Mike Miller
The STAR Detector

May 2003                       Mike Miller
d+Au “Centrality” Tagging
 FTPCE multiplicity: -3.8<<-2.8
(Au fragmentation direction)
 ZDCW: single deuteron spectator                              FTPCE
ZDCW
Au                         d
Uncorrected
FTPCE multiplicity
minbias

FTPCE multiplicity: defines
single deuteron                  “centrality” in d+Au events
spectator

May 2003                                                       Mike Miller
Jet-Event Shape and Size
 ptall tracks vs. leading jet from s=200 GeV p+p
<Total pT> (Arbitrary Units)

Raw STAR Preliminary

Within lead jet   Transverse region         Within away side jet

Measure pt ,                                 N charge ,   p   t     in jet and w.r.t. thrust axis
Measure underlying event  dAu jet energy correction!
May 2003                                                                                                          Mike Miller
Why Jets? Energy Loss in Dense Matter
Thick plasma (Baier et al.):
C R s 2 ~
EBDMS             ˆ
qL v
4
    2

q
ˆ          S  glue
Debye
Gluon Bremsstrahlung
glue
 2 E jet 
 CR  d glue  , r  Log 2 
Thin plasma
EGLV          3
S                          L
(Gyulassy et al.):                                                     
Strong dependence of energy loss on gluon density glue:
• measure E  measure gluon density at early hot, dense
phase
May 2003                                                                 Mike Miller
“Fragmentation” of Charged Jets
How does the slope change as a      p track
function of jet pT?         z  t jet
pt

Fragmentation slope
scales with jet pT
beyond 6 GeV
Raw STAR Preliminary

May 2003                                                  Mike Miller
“Fragmentation” of Charged Jets
What fraction of (reconstructed)      p track
jet pT does each particle carry?   z  t jet
pt

Slope depends on jet-
algorithm

Raw STAR Preliminary

May 2003                                                      Mike Miller
Di-jet Angular Distributions
di-jet  from s =200 GeV p+p

 ptjet1  ptjet1 
kt                     sin( 
        2        
Raw STAR Preliminary

pt  6GeV
jet

Increase jet pT, tighten di-jet peak
Measure Nuclear kT in d+Au
May 2003                                                   Mike Miller

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