P P article article correlations correlations at STAR at STAR Jan Pluta Heavy Ion Reactions Group (HIRG), Faculty of Physics, Warsaw University of Technology Some results from the STAR HBT group, presented recently by: Z.Chajecki, A.Kisiel, M.Lisa, M.Lopez-Noriega, S.Panitkin, F.Retiere, P.Szarwas. 3-rd Budapest Winter School on Heavy Ion Physics, 10 XII 2003
P article correlations at STAR. Jan Pluta Heavy Ion Reactions Group (HIRG), Faculty of Physics, Warsaw University of Technology. Some results from the STAR HBT group, presented recently by: Z.Chajecki, A.Kisiel, M.Lisa, M.Lopez-Noriega, S.Panitkin, F.Retiere, P.Szarwas. - PowerPoint PPT Presentation
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
PParticle correlationsarticle correlations at STARat STAR
Jan Pluta
Heavy Ion Reactions Group (HIRG),
Faculty of Physics,
Warsaw University of Technology
Some results from the STAR HBT
group, presented recently by:
Z.Chajecki, A.Kisiel, M.Lisa,
M.Lopez-Noriega, S.Panitkin,
F.Retiere, P.Szarwas.
3-rd Budapest Winter School on Heavy Ion Physics, 10 XII 2003
Outline:
•The STAR experiment
•RHIC HBT Puzzle
•General analysis
•asHBT
•Two K0-short correlations
•p-Au, d-Au data
•Nonidentical particles - emission asymmetry
•Plans for future
Relativistic Heavy Ion Collider (RHIC)
2:00 o’clock
4:00 o’clock6:00 o’clock
8:00 o’clock
10:00 o’clock
STARPHENIX RHIC
AGS
LINACBOOSTER
TANDEMS
9 GeV/uQ = +79
1 MeV/uQ = +32
HEP/NP
g-2U-line
BAF (NASA)
PHOBOS12:00 o’clock BRAHM
S
Beam energy up to 100 GeV/A (250 GeV for p) Two independent rings (asymmetric beam collisions are
possible) Beam species: from p to Au Six interaction points Four experiments: STAR, PHENIX, PHOBOS and BRAHMS
=3.8 km1740 superconducting magnets
Solenoidal Tracker At RHIC
STAR Detector – side viewSTAR Detector – side view
and STAR Collaboration – face view
STAR Collaboration• 500 Collaborators
including– ~65 graduate students– ~60 postdocs
• 12 countries• 49 institutions• Spokesperson:
John Harris 1991 - 2002
Tim Hallman 2002 - now
USA, Brazil, China, Croatia Czech Republich, England, France, Germany, India, Netherlands, Poland, Rusia
HBT+FSI
Space-time
sizes anddynamics
Correlation function
Momenta andmomentum difference
The idea:
Quantum statistics and Final-State Interaction
Particle correlations
STAR Event 2
Central Event: AuAu 200GeV/A
Real-time track reconstruction Pictures from Level 3 Trigger, online display.
Typically 1000 to 2000 tracks per event into the
TPC
4m
Event and Particle SelectionAu+Au Collisions at Sqrt(SNN)=200GeV
• Particle identification via specific ionization (dE/dx)electron band removed by cuts
Pion Correlations d-Au and p-AuPion Correlations d-Au and p-Au
p-Au selection:p-Au selection:
Using information from ZDC-d STAR can separate events with neutron spectator from deuteron
ZDC-dAu d
ZDC-Au
FTPC E -Au
All trigger events
1D Correlation Function:1D Correlation Function:
Gaussian fit:
➢ CF is very wide (rel Au-Au)➢ Coulomb/merging less important➢ CF looks reasonable➢ 1D Gaussian fit is not good➢
needed more deeply study of fit
method
STAR preliminarytheoretical CF: R
inv=6 fm, = 0.5
d*-Au : d-Au without p-Au
collision 1.89 +- 0.01 0.364 +- 0.003 4672 / 33
d – Au 1.85 +- 0.01 0.362 +- 0.003 5359 / 33
Rinv [fm] NDF
d* – Au
only statistical error included !
3D Correlation Function:3D Correlation Function:
Gaussian parametrization is not perfect but HBT radii characterize the width of CF
cut on the others Q's
components < 30 MeV/c
3D Gaussian fit:
STAR preliminary
d – Au p – Au
1.58 +- 0.02 1.21 +- 0.03
1.51 +- 0.01 1.21 +- 0.02
1.71 +- 0.02 1.67 +- 0.05
0.354 +- 0.003 0.372 +- 0.008
Rout
Rside
Rlong
Fit results:
Rout
, Rside
sensitive to the number of participants
[GeV/c]
KKTT dependence: dependence:
p – Au d – Au
● clear KT dependence
●Rout
and Rside
- sensitive to the number of participants●R
long – the same K
T
dependence for dAu and pAu
STAR preliminary
KKTT dependence: d-Au & Au-Au divided by p-p dependence: d-Au & Au-Au divided by p-p
● the same trend of KT
dependence for d-Au
and Au-Au as for p-p ● HBT radii are scaled by constant factors
STAR preliminary
for different collisions
MMTT dependence of R dependence of Rlonglong: :
STAR preliminary
Rlong
= const (mT)-
p-p d-Au Au-Au Au-Au peripheral midcentral
STAR preliminary
mTk
T2 + mass
Sinyukov fit:
Centrality definition in d-Au:Centrality definition in d-Au:
centrality bin FTPC multiplicity percent of events
1 [0 , 9] 100 – 40
2 [10 , 16] 40 – 20
3 [17 , 99] 20 – 0
FTPC-Au: charged primary particle multiplicity in -3.8<<-2.8
ZDC-dAu d
ZDC-Au
FTPC E -Au
321
most peripheral
most central
Centrality dependence:Centrality dependence:
● clear centrality dependence
● similar to AuAu
● connection to geometry
p – Au d – Au
centrality
minbias
STAR preliminary
1 2 3
4.3 +- 0.1 10.4 +- 0.4 16.3 +- 0.7<Npart> [*]
<Nch
> TPC . 7.9 . . 12.1 . . 17.1 .
<Nch
> FTPC E . 5.2 . . 12.8 . . 24.3 .
[*] - Glauber calculations (Mike Miller)
K0sK0
s Correlations
mt scaling violation?
Next RHIC HBT puzzle ?
inv
The asymmetry analysis
Catching up•Interaction time larger•Stronger correlation
Moving away•Interaction time smaller•Weaker correlation
“Double” ratio•Sensitive to the space-time asymmetry in the emission Kinematics selection
on any variablee.g. kOut, kSide, cos(v,k) R.Lednicky, V. L.Lyuboshitz,
B.Erazmus, D.Nouais,Phys.Lett. B373 (1996) 30.
Non-identical particle correlations:
Double ratio definitions
p1
p1
p2
p2
2k* = p1 – p
2 P = p1 + p
2
kside
< 0
kside
> 0
kout
> 0
kout
> 0
kksideside signselectionarbitrary
kkoutout signselection determined by the directionof the pair momentum P
Correlationfunctions
Double ratios
kklong long is the z componentof the momentumof first particle in LCMS
2k* [GeV/c]
simulation
What to expect from double ratios
• Initial separation in Pair Rest Frame (measured) can come from time shift and/or space shift in Source Frame (what we want to obtain)
• We are directly sensitive to time shift, the space shift arises from radial flow – possibility of a new radial flow measurement
r
T
F
x
yobservedtransversevelocity
thermal velocity
Flow velocity Out direction
Side direction
What do we probe?
Source ofparticle 1
Source ofparticle 2
Boost to pair rest frame
• Mean shift (<r*>) seen in double ratio
• Sigma (r*) seen in height of CF
r* =pairr–pairt
Separation between source 1 and 2 in pair rest frame
r
r (fm) r* (fm)
<r*>
r*
Separation due to space and/or time
shift
t
Correlation functions and ratios
Good agreement for like-sign and unlike-sign pairs points to similar emission process for K+ and K- Out
Side
Long
CF
Clear sign of emission asymmetry
Two other ratios done as a double check – expectedto be flat
Preliminary
STARpreliminary
Results for Pion-Proton 130 AGeV
• Similar preliminary analysis done for pion-proton
• We observe Lambda peaks at k*~m
inv of Λ
• Good agreement for identical and non-identical charge combinations
Λ peaks
Preliminary results for Kaon-Proton
• Using data from Year2 (200 AGeV) – sufficient statistics
• No corrections for momentum resolution done
• No error estimation yet – fit indicates theoretical expectations
K+ pK- anti-pBest Fit
STARpreliminary
Modeling the emission asymmetry
• Need models producing strong transverse radial flow:– Blast-wave as a
baseline– RQMD– UrQMD– T. Humanic's
rescattering model
• What do we measure and how to compare it to the models?
• Is our fitting method working? And if yes, what does it tell us?
• Need to disentangle flow and time shift
Understanding modelsBlast wave = Flow baseline
• Blast wave– Parameterizes source size
(source radius) radial flow (average flow rapidity) and momentum distribution (temperature):
– No time shift– Only spatial shift due to flow
– Infinitely long cyllinder (neglects long contribution)
R
t
RsideRout
Kt = pair Pt
Parameterizationof the final state
Blast wave: how does the flow workBlast wave: how does the flow work
Pionp
t = 0.15 GeV/c
t = 0.73
Kaonp
t = 0.5 GeV/c
t = 0.71
Protonp
t = 1. GeV/c
t = 0.73
Average emission points
Spatial shifts (r) Particle momentum
Fitting and quantitative comparisons
• Fits assume gaussian source in PRF
• r*out
distributions have non-
gaussian tails• Use the same fitting
procedure for models and data - correlation functions constructed with “Lednicky's weights”
Example of r*out
distribution from RQMD
Comparing models to data
• Rescattering models and blast-wave are consistent with data
• Blast wave parameters constrained by STAR measurements
• In models flow is required to reproduce the data
• More points in βt needed to map and discriminate the flow profile – needs
STAR upgrades in PID capability (TOF barrel)
STAR HBT Matrix (circa 2003)
+ - + - 0 p p ++ +
0 -
+
-
Sergei's HBT matrix 0
Y1 p
Y1 ? p
Y2
“traditional”HBT axis
Analysisin progress
published
3 Correlations (accepted PRL)asHBTPhase space densityCorrelations with CascadesdAu, ppCascades
submittedNot shown:
What have we learned so far?
• RHIC HBT puzzle– Break down of theoretical description of correlations at RHIC– Indication of short source lifetime and freeze-out duration at RHIC– Short lived hadronic phase?
• Out of plane extended pion source in non-central collisions– Also points to short emission times
• Weak energy dependence of the HBT radii– Where is the phase transition?
• Large pion phase space densities (non-universal)– Small entropy per pion?
• Chaotic pion source from 3p correlations– No multiparticle effects above Pt~200 MeV/c
• Source asymmetries from non-identical correlations– Consistent with collective flow and short time scales
• Only systematics measurements may provide answers!
What will affect STAR HBT analysis?
• RHIC upgrades progress• STAR upgrades• Various other measurements (e.g. spectra,
high Pt,
strangeness, flow, etc)• New theoretical ideas
Consequences for STAR HBT• Large statistics AuAu datasets • Plans for 2004: 14 weeks of AuAu “physics” running:
– ~30M central, ~50M peripheral events• What can be done? Many analysis which were statistics limited!
– Rare particle correlations W, X,L, etc (identical, non-identical)• Early freeze-out, sequence of emission, flow, FSI, etc
– Correlations relative to reaction plane• Kaons• Non-identical