Download - Experimental Overview
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based on input frommy heavy ion colleagues
at RHIC!
Experimental Overview M. Grosse Perdekamp UIUC and RBRC
RHIC Physics in the Context of the Standard Model
o Overview
o Heavy Ion Physics
Experimental challenges RBRC contributions
o Experimental Results
Initial state Elliptic Flow Hard Probes Heavy Flavor
STARSTAR
pp2pppp2pp
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Workshop on Heavy Ion Physics 2 June 19th
Overview: Strong Interaction Physics at RHIC
o Quark Matter at high Temperatures and Densities
ion-ion collisions (Cu-Cu, Au-Au: √sNN=22.5, 62, 130, 200 GeV)
o Proton Spin Structure
polarized proton-proton collisions (p-p: √s=200 to 500 GeV)
o Low-x and high Parton Densities
ion-deuteron collisions (d-Au: √sNN=200 GeV)
very active field: 74 PRL letters in the first 5 years
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Workshop on Heavy Ion Physics 3 June 19th
(I) RHIC 2001 – 2005 : Discovery
Key Observations
1. Jets are suppressed in central Au + Au collisions– Suppression is flat up to pt ~ 10 GeV/c– Absence of suppression in d+Au
2. Strong elliptic flow– Scaling of v2 with eccentricity shows that a high degree of collectivity
builds up at a very early stage of collision – evidence for early thermalization
– Data described by ideal hydrodynamic models fluid description of matter applies.
3. Energy density allows for a non-hadronic state of matter– Energy density estimates from measurements of dN/dy are well in
excess of the ~1 GeV/fm3 lattice QCD prediction for the energy density needed to form a deconfined phase.
Strongly interacting Quark Matter
RBRC workshop, May 2004 served as starting point for the white paper discussion: Nucl. Phys. A757, 2003
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Workshop on Heavy Ion Physics 4 June 19th
(II) Survey of sQGP Properties at RHIC
Formulate sQGP predictions and test withpresent and future precision data from RHIC,examples:
• RAA at very high pT
• Charm energy loss• Baryon multiplicities in hadronization• Chiral symmetry restoration• Thermal radiation • J/• Modification of jets
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Workshop on Heavy Ion Physics 5 June 19th
Structure of Neutron Stars
physics goal
to find quark matter and survey it’s properties
experimental method
heavy ion collisions at high energies
Brief History
A brief history of Heavy Ion Experiment Bevalac AGS GSI SPS RHIC LHC
Find quark matter andsurvey it’s properties
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Workshop on Heavy Ion Physics 6 June 19th
From Nuclear Physics and HEP to Heavy Ions The Experimental
ChallengeContact between final state and the physics of the fire ball ?
Variable collision systems and energy
Control measurements and their systematics
Event Characterization
Occupancy
Backgrounds
Data Volume
Central Au-Au at RHIC
√s = 38 TeV
~28 TeV released in the collisions
~ 7500 particles in the final state
Heavy ion physics has advanced the frontiers for accelerators, experiment and theory!
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Workshop on Heavy Ion Physics 7 June 19th
RHIC Four Complementary Experiments
Design, R&D, construction, operation and analysis
~ 6400 man-years
HBD (Hadron Blind Detector)
Silicon (VTX, FVTX)Muon TriggerForward Calorimeter
FMS (Forward Meson Spectrometer)
TOF HFT (Heavy Flavor Tracker)
Tracking UpgradeDAQ
RHIC Luminosity and Detector Upgrades
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Workshop on Heavy Ion Physics 8 June 19th
RBRC Contributions, Examples
(I) hard probes in pQCD Studying the
medium withhigh pT probes
q g
RBRC (Theory):
Werner Vogelsang
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Workshop on Heavy Ion Physics 9 June 19th
• NLO-pQCD calculation from W. Vogelsang
– CTEQ6M PDF– direct photon + fragmentation photon– Set Renormalization scale and factorization scale pT/2,pT,2pT
NLO pQCD shows good agreement with the experimentalcross section for p-p collisionsat √s=200 GeV.
Direct Photons: NLO pQCD vs RHIC Data
RBRC (analysis):
Kensuke Okada
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Workshop on Heavy Ion Physics 10
June 19th
Direct Photons in Au+Au
PRL 94, 232301
Expectation for Ncoll scaling of
direct photons
Resummed pQCD calculationspermit calibration of hard probesat RHIC in a model independentway.
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Workshop on Heavy Ion Physics 11
June 19th
RBRC Contributions, Examples
(II) Event Mixing for neutral pion recon- struction (Sasha Bazilevsky, Hisayuki Torii) reconstruction of π0 in central Au-Au collisions possible
invariant mass
N(2
γ)
N(2
γ)
N(2
γ)
Photon pairs from different events
Photon pairs from same events
RBRC (analysis):
Hisayuki Torii, Sasha Bazilevsky
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Workshop on Heavy Ion Physics 12
June 19th
pp
AuAubinaryAuAuAA Yield
NYieldR
/
Au-Au s = 130 GeV: High pT Suppression!
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Workshop on Heavy Ion Physics 13
June 19th
Examples
(III) Event selection (Yuji Goto, Kensuke Okada, Hisayuki Torii, MGP, Wei Xie)
selection of π0 in d-Au collisions at high rates makes control experiment possible. RBRC (hardware):
Yujie Goto, Kensuke Okada,Hisayuki Torii, MGP, Wei Xie
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Workshop on Heavy Ion Physics 14
June 19th
• Significantly different and opposite centrality evolution of Au+Au experiment from d+Au control.
Au + Au Experiment d + Au Control Experiment
Jet Suppression: A Final State Effect
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Workshop on Heavy Ion Physics 15
June 19th
RBRC Contributions, Examples
(IV) Transfer and analysis of large data samples.
Transfer of 270 TByte from BNL – Wako
rate : 60MB/s duration : April 16th – June 25th
first large scale application of grid technology
Cern Courier
Science Grid
RBRC (operation):
Hisayuki Torii, YasushiWatanabe, Satoshi Yokkaichi,Hiro Hiejima, MGP
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Workshop on Heavy Ion Physics 16
June 19th
Run5 0 Cross Section Analysis
• Consistent with previous PHENIX results from runs 3+4
• Extends previous results to pT of 20 GeV/c.
• Theory is consistent with data over nine orders of magnitude.
preliminary0 cross section vs perturbative QCD (W. Vogelsang)
Data – Theory)/Theory
RBRC (analysis): Sasha Bazilevsky
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Is the Initial State in Heavy IonCollisions Determined by Saturation
Effects in the Gluon Field ?
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Workshop on Heavy Ion Physics 18
June 19th
BRAHMS, PRL 93, 242303 and R. Debbe
RdAu= YdAu
NcollYpp
BRAHMS d+Au Fesults as Function of Rapidity and Centrality
Hadron production is suppressed at large rapidityconsistent with saturation effects at low x in the Au gluon densities CGC
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Workshop on Heavy Ion Physics 19
June 19th
PRL 94, 082302
PRC 70, 061901(R)
Suppression in the d direction and enhancement in the Au frag. region
Similar Effects Seen by PHENIX and PHOBOS
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Workshop on Heavy Ion Physics 20
June 19th
Theory vs DataA. Dumitriu et al. Nucl. Phys. A770 57-70,2006
Not bad! However, Large K factors, η-dependent. We hope for NLO calculations soon …
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Elliptic Flow Strong Evidence for sQGPPDFs (partonic degrees of freedom)?!
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Workshop on Heavy Ion Physics 22
June 19th
Flow: A Collective Effect
Elliptic flow = v2 = 2nd Fourier coefficient of momentum anisotropy
dn/d ~ 1 + 2 v2(pT) cos (2 ) + ...Initial spatial anisotropy is converted into momentum anisotropy. Efficiency of the conversion depends on the properties of the medium
x
yz
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Workshop on Heavy Ion Physics 23
June 19th
v2 Large for all Particles
Large v2 of heavier particles: d.
Even open charm flows (measured through single electrons)
Strong interactions at early stage early thermalization.
RBRC (analysis):
Etsuji Taniguchi
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Workshop on Heavy Ion Physics 24
June 19th
Flow Extends to Very High pT
charged hadrons
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Workshop on Heavy Ion Physics 25
June 19th
Comparison to Models
Hydro works at low pT
solid: STARopen: PHENIX PRL91(03)
Partonic scaling works
at intermediate pT
Also for heavier particles
Strong case for sQGP with early thermalization of partonic matter made of constituent quarks
RBRCTetsufumi Hirano next!
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High pT
Suppression
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Workshop on Heavy Ion Physics 27
June 19th
π0 pT spectra at √sNN = 200 GeV
AuAu Run4
High quality data:
9 centrality bins 36 pT bins high statistics!
RBRC (analysis):
Hisayuki Torii, Wei Xie, EtsujiTaniguchi
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Workshop on Heavy Ion Physics 28
June 19th
Suppression Extends to 20 GeV/c
• Suppression is strong (RAA =0.2) and flat up to 20 GeV/c
• Matter is extremely opaque• The data should provide a lower bound on the initial gluon density
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Workshop on Heavy Ion Physics 29
June 19th
Theory Reproduces RAA for RHIC and SPS
SPS data, dNg/dy~400-600 I.Vitev, nucl-th/0404052
Au+Au 200, dNg/dy~1200 I.Vitev, nucl-th/0404052
Cu+Cu 200 X-N Wang PL B595, 165 (2004)
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Workshop on Heavy Ion Physics 30
June 19th
RAA vs Reaction Plane
Energy lossdepends on the path-length
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Heavy FlavorPhysics
RBRC (theory):
Dima Kharzeev et al.,Peter Petreczky
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June 19th
Heavy Quark Suppression and Flow!
• Suppression is approximately the same as for hadrons.
• Challenge for energy loss models.
PHENIX RAA
Charm quark is suppressed and has large v2!!
• Strong coupling of charm quark to medium.
• Contribution from b quark at high pT.
0-10% 10-20%
20-40% 40-60%
60-92% min bias.
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Workshop on Heavy Ion Physics 33
June 19th
NA50 J/
Reanalysis of data:
Normal nuclear absorption derived
from pA data only = 4.18±0.35 mb
S-U consistent with normal nuclear
absorption
Only Pb-Pb shows additional
suppression
Systematic errors of ~8% not shown
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Workshop on Heavy Ion Physics 34
June 19th
NA50 - NA60 Comparison
NA50 and NA60 data
consistent with each other.
Npart seems to be a good scaling factor to take account of system size.
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Workshop on Heavy Ion Physics 35
June 19th
NA60 J/ Comparison to Models
Satz, Digal, Fortunato (percolation)Rapp, Grandchamp, Brown (diss. and recomb.)Capella, Ferreiro (comovers)
Models (tuned to reproduce the NA50 data and with specific predictions for In-In) faill to describe the observed suppression pattern for NA60
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Workshop on Heavy Ion Physics 36
June 19th
J/ at RHIC PHENIX : Muon Arms
CuCu
200 GeV/c
AuAu
200 GeV/c
dAu
200 GeV/c
J/ muon arm
1.2 < |y| < 2.2
RBRC (muon identifier):
Kazu Kurita, AtsuhiTaketani, Hiroki Sato,Nobu
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Workshop on Heavy Ion Physics 37
June 19th
CuCu
200 GeV/c
AuAu
200 GeV/c
dAu
200 GeV/c
AuAuee
200 GeV/c
CuCuee
200 GeV/c
J/ muon arm
1.2 < |y| < 2.2
J/ eeCentral arm
-0.35 < y < 0.35
J/ at RHIC PHENIX : Muon + Central Arms
RBRC (analysis):
Yasuyuki Akiba, Wei Xie
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Workshop on Heavy Ion Physics 38
June 19th
CuCu
200 GeV/c
AuAu
200 GeV/c
dAu
200 GeV/c
AuAuee
200 GeV/c
CuCu
62 GeV/c
J/ muon arm
1.2 < |y| < 2.2
J/ eeCentral arm
-0.35 < y < 0.35
Factor ~3suppression
in central events
CuCuee
200 GeV/c
Data show the same trend within errors for all species and even 62 GeV
J/ at RHIC PHENIX
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Workshop on Heavy Ion Physics 39
June 19th
RAA vs Npart: PHENIX and NA50
NA50 data normalized to NA50
p+p point.
Suppression level is similar in
the two experiments, although
the collision energy is 10 times
higher (200GeV in PHENIX wrt
17GeV in NA50)
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Workshop on Heavy Ion Physics 40
June 19th
Comparison to Theory (I): Nuclear Absorption
Central arm
Vogt (nucl-th/0507027) Cold nuclear matter absorption model in agreementwith dAu: Tendency to underpredict suppression in most central events
Muon arm
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Workshop on Heavy Ion Physics 41
June 19th
Comparison to theory (II)
Models that were successful in describing SPS data fail todescribe data at RHIC - too much suppression!
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Workshop on Heavy Ion Physics 42
June 19th
Comparison to theory (III)
Adding recombination Much better agreement With the data.
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Workshop on Heavy Ion Physics 43
June 19th
Summary
o Enormous effort and advances to build RHIC with it’s detectors as the first facility optimally adapted for Heavy Ion Physics.
o Discovery of the strongly interacting quark gluon plasma. Many independent channels. Among the most important:
strong elliptic flow large suppression large energy densities o Enter second phase of the experimental program at RHIC to survey the sQGP.
o Additional tools: detector upgrades in PHENIX and STAR; electron cooling in RHIC.