The STAR Experiment at RHIC - First Collisions
M.A. Lisa, for the STAR Collaboration
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Overview
Y1 configuration
Performance
First collisions!
Early Physics
 elliptic flow
 Summary
M.A. Lisa
RHIC/AGS User's Meeting - 7 Aug 2000
1
STAR
STAR Institutions
England:
U.S. Labs:
Argonne, Berkeley, and Brookhaven
National Labs
U.S. Universities:
Arkansas, UC Berkeley, UC Davis,
UCLA, Carnegie Mellon, Creighton,
Indiana, Kent State, MSU, CCNY,
Ohio State, Penn State, Purdue,
Rice, Texas A&M, UT Austin,
Washington, Wayne State, Yale
Brazil:
Universidade de Sao Paolo
China:
IHEP - Beijing, IPP - Wuhan
University of Birmingham
France:
Institut de Recherches Subatomiques
Strasbourg, SUBATECH - Nantes
Germany:
Max Planck Institute – Munich
University of Frankfurt
Poland:
Warsaw University
Warsaw University of Technology
Russia:
MEPHI – Moscow, LPP/LHE JINR –
Dubna, IHEP - Protvino
M.A. Lisa
RHIC/AGS User's Meeting - 7 Aug 2000
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STAR
Geometry of STAR
Year 1: Magnet, TPC, CTB, ZDC, RICH
Magnet
Coils
TPC Endcap
& MWPC
Time
Projection
Chamber
Silicon
Vertex
Tracker
FTPCs
ZDC
Endcap
Calorimeter
Barrel EM
Calorimeter
ZDC
Vertex
Position
Detectors
Central Trigger
Barrel or TOF
RICH
M.A. Lisa
RHIC/AGS User's Meeting - 7 Aug 2000
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STAR
STAR Detector Acceptances
(1st Year)
MWC
CTB Trigger
MWC
EMC
ZDC
TPC
ZDC
RICH
M.A. Lisa
RHIC/AGS User's Meeting - 7 Aug 2000
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STAR
STAR Detector Acceptances
(2nd Year)
EMC
FTPC
TPC
FTPC
SVT
RICH
TOF
M.A. Lisa
RHIC/AGS User's Meeting - 7 Aug 2000
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STAR
Silicon Vertex Tracker
•
•
•
•
•
•
SVT IS A 3 LAYER VERTEX
DETECTOR WITH 216 ELEMENTS
“Solid state TPC “
~20 micron position resolution
Dec. 99--Single ladder with 7 elements
installed in STAR
Matching achieved in cosmic ray tests
Y1 collision data show expected response
# TPC tracks
–
–
M.A. Lisa
0<vz<30 cm
S:N = 25
cluster shape and integrated charge
•
FULL SVT INSTALLATION DURING
SHUTDOWN
•
Silicon Strip Detector (SSD) gives 4th layer
between SVT and TPC
# SVT clusters
RHIC/AGS User's Meeting - 7 Aug 2000
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STAR
Ring Imaging Cerenkov Counter
 PID for Kaon/Pion/Proton
1-3 GeV/c for K/p
1.5-5 GeV/c for p/anti-p
 Located at y=0 in STAR
 C6F14 Liquid Radiator
 CsI Photo Cathode
 MWPC with 16,000 Pads
M.A. Lisa
RHIC/AGS User's Meeting - 7 Aug 2000
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STAR
• Active volume: Cylinder r=2 m, l=4 m
– 139,000 electronics channels
sampling drift in 512 time buckets
STAR TPC
On-board FEE Card:
Amplifies, samples,
digitizes 32 channels
• cosmic ray event in the TPC 
M.A. Lisa
RHIC/AGS User's Meeting - 7 Aug 2000
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STAR
Position resolution
(cosmic rays)
Track Reconstruction
Reconstructed Laser Event
~ 500 mm
Momentum resolution (cosmics)
M.A. Lisa
RHIC/AGS User's Meeting - 7 Aug 2000
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STAR
Summed CTB
First Trigger - Zero Degree Calorimeter
“single n”
Summed CTB
Summed ZDC
West ZDC Sum
•
•
•
•
common to all RHIC experiments
luminosity measure
centrality measure
low-level trigger
M.A. Lisa
RHIC/AGS User's Meeting - 7 Aug 2000 10
STAR
Au on Au Event at CM Energy ~ 130 AGeV
Data Taken June 25, 2000.
Pictures from Level 3 online display.
M.A. Lisa
RHIC/AGS User's Meeting - 7 Aug 2000 11
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Offline Reconstruction (Au+Au at 130 GeV)
(modest multiplicity shown so details are visible)
All hits and tracks:
- red = low pT
- violet = high pT
Hits not assigned to tracks:
mostly noise and low
momentum spirals
M.A. Lisa
RHIC/AGS User's Meeting - 7 Aug 2000 12
STAR
Particle Identification via dE/dx in TPC - June 2000
Excellent dE/dx resolution
approaching expected 8%
Preliminary
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RHIC/AGS User's Meeting - 7 Aug 2000 13
STAR
pTArm
Topological Strangeness Measurements
K s0

p p
  p  p

a

 p

 p  p
_
(and +)
Km+
M.A. Lisa
RHIC/AGS User's Meeting - 7 Aug 2000 14
STAR
Expected Physics Measurements this year
Some physics measurements we expect to accomplish with this year’s data,
given a good month of RHIC running
• dN/d for charged particles (||  ~1.5)
particle density, entropy
• dN/dy for p, K, p
chemistry, stopping
(-1  y  1)
• Particle Spectra for identified particles
(-1  y  1)
• K/p
temperature, radial flow
strangeness production
• Neutral particle decays ’s, K0’s, 
-
- / p,  / 
•p
(-1  y  1)
stopping
• Particle correlations (HBT)
geometry, collective flow
• Correlated observables for event classes
non-statistical fluctuations
• Anisotropic Flow
early dynamics, pressure
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RHIC/AGS User's Meeting - 7 Aug 2000 15
STAR
Elliptic Flow - A Sensitive Probe of Early Dynamics
• Spatial anisotropy in non-central collisions & response
of the system to early pressure  emission anisotropy
• Elliptic flow predictions from hydro/transport models
sensitive to underlying dynamics of initial system
P.F. Kolb, et al, (QM99)
• A natural measurement for STAR
M.A. Lisa
RHIC/AGS User's Meeting - 7 Aug 2000 16
STAR
Azimuthal correlations - Event plane resolution
A
B
2nd order event plane of
independent sub-events A&B
  w i  sin 2i  


1
2A , B  Tan 1 i



2
w

cos
2


i
i 

 i

A
-1<<-0.05
B
0.05<<1
PRELIMINARY
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RHIC/AGS User's Meeting - 7 Aug 2000 17
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Quality Check: Some Details
PRELIMINARY
Particle  distribution in the lab
(used as weights)
Flat event plane distribution
TPC sector boundaries
Note: Highly suppressed zero
(fluctuations ~3%)
Particle Correlation with
respect to event plane
M.A. Lisa
RHIC/AGS User's Meeting - 7 Aug 2000 18
STAR
Inclusive elliptic flow systematics
PRELIMINARY
• roughly linear growth with pT
• flat in  at midrapidity
• v2 signal increased from SPS energy
NA49 Collab, Nucl. Phys. A661, 341 (1999)
Pb+Pb s=17.3 GeV
note: expect small v1 in TPC
M.A. Lisa
RHIC/AGS User's Meeting - 7 Aug 2000 19
STAR
Current Status and Summary
• STAR detector is performing extremely well
• Event reconstruction producing high quality data
•
•
•
•
dE/dx
V0 reconstruction
primary vertex reconstruction
…
• Currently intense effort to fully understand details of performance
• detailed checking of calibration effects
• embedding simulated particles into real events
• Even with only few 104 events, STAR begins to harvest a rich crop of physics
• Preliminary observation of pronounced elliptic flow
• increasing signal with pT
• stronger flow signal than at SPS
• A good month’s running before shutdown will allow full promise of STAR Y1
M.A. Lisa
RHIC/AGS User's Meeting - 7 Aug 2000 20
STAR
Centrality Dependence of Elliptic Flow
Differential measure of response to intial geometry
PRELIMINARY
(scaled) spatial asymmetry
centrality
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RHIC/AGS User's Meeting - 7 Aug 2000 21
STAR
Centrality Dependence of Elliptic Flow
Differential measure of response to intial geometry
PRELIMINARY
Hydro prediction
centrality
J.-Y. Ollitrault, PRD46, 229 (1992)
M.A. Lisa
RHIC/AGS User's Meeting - 7 Aug 2000 22
STAR
Summed CTB
(vertex in TPC)
First Trigger - Zero Degree Calorimeter
“single n”
Summed CTB
Summed ZDC
West ZDC Sum
•
•
•
•
common to all RHIC experiments
luminosity measure
centrality measure
low-level trigger
M.A. Lisa
RHIC/AGS User's Meeting - 7 Aug 2000 23
STAR
Peripheral Au+Au Collision at 130 AGeV
Data Taken June 25, 2000.
Pictures from Level 3 online display.
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RHIC/AGS User's Meeting - 7 Aug 2000 24
STAR
STAR Physics Program
Relativistic Heavy Ion Physics
• High Density QCD Matter
• QCD Deconfinement Phase Transition
• Chiral Phase Transition
Polarized Proton-Proton Interactions
• Spin Structure of the Nucleon
2-Photon Physics
• Intense EM Fields of Passing Nuclei
 Coherent Source of g’s
• Investigate the Plethora of Particles in 1 - 2 GeV Mass Range
(cannot be fit by QCD)
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RHIC/AGS User's Meeting - 7 Aug 2000 25
STAR
STAR RHI Physics Program
Initial Conditions
•
Nuclear (q and g) structure functions, nuclear shadowing
PQCD Probes
•
Parton (jet, mini-jet, high Pt particle) propagation/attenuation in matter
•
High Pt spectra (gluon versus quark jet production)
EM Probes
•
Virtual photons (e+e-)
Probes of Deconfinement
•
J/P suppression (e+e-)
•
Flavor equilibrium (strangeness saturation, multiply-strange baryons)
•
Critical (non-statistical, dynamical) fluctuations
Probes of Chiral Restoration
•
Resonance widths, masses, and branching ratios
•
Isospin fluctuations, disoriented chiral condensates (charge to neutral ratios)
Kinematic Probes
•
Hadronic p.I.d. spectra (y, Pt) - thermalization (T, mB, s, ms, …) and freeze-out
•
HBT - space-time evolution (possible phase change)
•
E-by-E (Pt, HBT, collective flow, strangeness content - i.e. T, mB, s, ms, …)
M.A. Lisa •
Anti-baryons, anti-nuclei
RHIC/AGS User's Meeting - 7 Aug 2000 26
STAR
Overview of STAR Physics in the 2nd Year
•
Additional physics beyond Year 1
– charged hadrons at low Pt (with SVT)
– multiply-strange baryon (, W yields & slopes (with SVT)
– increased statistics for strange particles (with increase in efficiency of SVT)
– po identification, yields, slopes(with EMC)
– high Pt triggering (with EMC)
– transverse energy measurements (with EMC)
– measurements of charged hadrons and strange particles at forward rapidities
(with FTPCs)
– increased coverage for event-by-event physics
(flow, correlations, fluctuations, dimensional analysis)
•
Start modest polarized proton program
– transverse analyzing power (AT)
requires ~ pb-1 transversely polarized protons
polarimetry at RHIC (possibly STAR)
– inclusive jets  ALL which is sensitive to DG(x)
requires spin rotators at STAR & jet triggering
M.A. Lisa
RHIC/AGS User's Meeting - 7 Aug 2000 27
STAR
STAR is On-line!
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RHIC/AGS User's Meeting - 7 Aug 2000 28
STAR
Rough STAR Data Acquisition Rates
Trigger
Event Size
rate (~1%Lo)
~ Bandwidth
events in 4 wks
(e = 25%)
Central
(5% s geo)
20 MS
~1/s
90%  18 MB/s
0.5 M
Min. Bias
(95% s geo)
1 MB
~ 20 / s
10%  2 MB/s
1.0 M
gg (gP,PP)
0.2 MB
~2/s
5%  1 MB/s
1.0 M
Design luminosity: 0.2 mb-1 sec-1
sT ~ 6 b --> 1200 collisions/sec --> 60 central (5% sT) collisions/sec
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RHIC/AGS User's Meeting - 7 Aug 2000 29
STAR
STAR Detector (year-by-year)
Magnet
1st year detectors (now)
implementation until 2003
2nd year detectors
year-by-year
installation in
2003
Time
Projection
Chamber
Coils
Silicon
Vertex
Tracker *
TPC Endcap &
MWPC
FTPCs (1 + 1)
ZCal
ZCal
Endcap
Calorimeter
Vertex
Position
Detectors
Barrel EM
Calorimeter
Central
Trigger Barrel
+ TOF patch
M.A.RICH
Lisa
* yr.1 SVT ladder
RHIC/AGS User's Meeting - 7 Aug 2000 30
STAR
STAR Year 1 Detector Configuration
•
Baseline Detector
–
Solenoid Magnet
–
TPC and Electronics
–
DAQ and Online
–
Trigger Detectors
• Central Trigger Barrel
• Multi-wire Chamber Readout
•
•
•
•
• Zero Degree Calorimeter
RICH ~10 msr at yc.m.
– - 0.3 <  < 0.3, D = 20º
EMC ~ 4 % of eventual (D = 2, D = 2p) coverage
– 0 <  < 1, D = 24º
FTPC - 1 of 2 to be installed in Spring 2000
– 2.5 <  < 4.0, D = 2p
Level 3 Trigger
– presently 1 a processor per two TPC sectors (x 2 by Summer)
M.A. Lisa
RHIC/AGS User's Meeting - 7 Aug 2000 31
STAR
STAR Year 2 Detector Configuration
(additions)
•
Baseline Detector (Magnet, TPC, Trigger detectors, DAQ, Online)
•
RICH ~ 10 msr at yc.m.
•
EMC increase to ~ 30 % of eventual (-1 < | | < 1, D = 2p) coverage
•
SVT - -1 < | | < 1, D = 2p
•
FTPC #2 - 2.5 < | | < 4.0, D = 2p
•
TOF Patch - 0 <  < 1, D = 6º
•
Level 3 Trigger
– 2 a processors per TPC sector
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RHIC/AGS User's Meeting - 7 Aug 2000 32
STAR
Magnet - Status
BR Measurements
• The Magnet has achieved full field
operation
M.A. Lisa
User'shalf-field
Meeting - 7 Aug 2000 mapping
33
• Full field (0.5RHIC/AGS
T) and
K. Foley
S. Trentalange
STAR
The Forward TPCs
•
•
•
•
•
•
2 chambers; 1 for each end;
Radial drift TPC
First chamber assembly almost complete
with 30 readout chambers installed
HV testing in progress
FEE Board design complete
– 64 channels per board
– Smaller package for SAS & SCA chips
• Installation in fall 2000
M.A. Lisa
RHIC/AGS User's Meeting - 7 Aug 2000 34
STAR
Barrel EMC - an AEE project
• Full Size prototype module and Shower Max
detector (SMD) successfully tested in AGS Test
Beam
• Module and SMD production ongoing; 14
modules and 24 SMD complete
• 4 modules with SMD installed in STAR; will
have prototype electronics for upcoming RHIC
run
• Production and Installation of EMC modules
will be phased over the next three years.
M.A. Lisa
RHIC/AGS User's Meeting - 7 Aug 2000 35
STAR
End Cap EM Calorimeter
• Lead/scintillator
projective towers; with
shower max
• Funded by NSF,
Indiana Univ.; IUCL;
DOE
• Design almost
complete
M.A. Lisa
• Successful test of
prototype
in SLAC
RHIC/AGS User's Meeting - 7 Aug 2000
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STAR
Projection for Next Year's Running
• Au + Au beam at top energy
(possibly at lower energy)
• Si + Si and p + p at top energy
(possibly at lower energy)
• Polarized p + p
• Possible other beam/energy changes,
depending upon what we see in this year’s data
M.A. Lisa
RHIC/AGS User's Meeting - 7 Aug 2000 37
STAR
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RHIC/AGS User's Meeting - 7 Aug 2000 38
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RHIC/AGS User's Meeting - 7 Aug 2000 39
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M.A. Lisa
RHIC/AGS User's Meeting - 7 Aug 2000 40
STAR
Au on Au Event at CM Energy ~ 130 AGeV
Data Taken June 25, 2000.
Pictures from Level 3 online display.
M.A. Lisa
RHIC/AGS User's Meeting - 7 Aug 2000 41
STAR
Au on Au Event at CM Energy ~ 130 AGeV
Data Taken June 25, 2000.
M.A. Lisa
RHIC/AGS User's Meeting - 7 Aug 2000 42
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STAR
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RHIC/AGS User's Meeting - 7 Aug 2000 43
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More sophisticated triggers
Level 3 Online Diagnostic Display
This analysis is produced and
displayed in Real time (~1 sec.) as
events are taken. Additional L3 online
plots show:
• PT distribution for tracks
• Number of reconstructed hits on tracks
• Number of hits on primary tracks
• Number of reconstructed hits vs
potential number of hits
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RHIC/AGS User's Meeting - 7 Aug 2000 44
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