roy a. lacey (suny stony brook ) c ompressed b aryonic at the ags: a review !! c ompressed b aryonic...
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Roy A. LaceyRoy A. Lacey(SUNY Stony Brook(SUNY Stony Brook))
CCompressed ompressed BBaryonic aryonic Matter at the at the AGS: AGS:
A Review !! A Review !!
CCompressed ompressed BBaryonic aryonic Matter at the at the AGS: AGS:
A Review !! A Review !!
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The AGSThe AGS
The Alternating Gradient Synchrotron (AGS) has been The Alternating Gradient Synchrotron (AGS) has been one of the world's premiere accelerators since 1960.one of the world's premiere accelerators since 1960.
The GSI Accelerator The GSI Accelerator facility has been one facility has been one
of the world'sof the world'spremier facilities for premier facilities for more than 25 years.more than 25 years.
Proposed
ExistingExisting
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A Diverse Range of Experimental Programs have been Carried out at the AGS
AGS Expts.AGS Expts.
E802/866E802/866
E810/891E810/891
E814/877E814/877
E864E864
E895E895
E917E917
DisclaimerDisclaimer
p+A, Si+A, Au+A 2 – 18 AGeV1986 - 14.6 AGeV/c Si1992 – 11.0 AGeV/c Au More thanMore than
200 pubs200 pubs
Only a Selection of the full range of Experimental Only a Selection of the full range of Experimental Results will be covered. Results will be covered.
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MotivationMotivation
Results & ImplicationsResults & Implications– Global ObservablesGlobal Observables
– Rapidity Distributions & StoppingRapidity Distributions & Stopping
– HBTHBT
– FlowFlow
– Particle ProductionParticle Production
Summary
OutlineOutline
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MotivationMotivation
Particular Particular FocusFocus
IdentificatioIdentification and Study n and Study of the of the LGPLGP and and QGPQGP
The Notion of a Phase Diagram for Nuclear Matter is PervasiveThe Notion of a Phase Diagram for Nuclear Matter is Pervasive
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F. WeberF. Weber s/
P ²e
Motivation – High Density Motivation – High Density Nuclear MatterNuclear Matter
Various competing forms of
matter are predicted at high
Baryon density
!! Crucial Information !!!! Crucial Information !!
•Property of Hadrons in Property of Hadrons in Dense nuclear MediumDense nuclear Medium
•Phase transition to Quark Phase transition to Quark Gluon Matter at high baryon Gluon Matter at high baryon densitydensity
•Nuclear Equation of State at Nuclear Equation of State at high baryon Densitieshigh baryon Densities
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Bao-an Li
Why Study Heavy Ion Reactions at the AGS ?Why Study Heavy Ion Reactions at the AGS ?Why Study Heavy Ion Reactions at the AGS ?Why Study Heavy Ion Reactions at the AGS ?
MotivationMotivation
Compressed Baryonic Matter is Produced at the AGS Compressed Baryonic Matter is Produced at the AGS
In an Interesting Region of the Phase Diagram ?In an Interesting Region of the Phase Diagram ?
Compressed Baryonic Matter is Produced at the AGS Compressed Baryonic Matter is Produced at the AGS
In an Interesting Region of the Phase Diagram ?In an Interesting Region of the Phase Diagram ?
Energy Density ~ 1 – 2 Gev/fmEnergy Density ~ 1 – 2 Gev/fm33
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Global Observables Barette et al., E877
Substantial Pseudorapidity Densities are achieved
Nc ~ 450 for central collisions
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time to thermalize the system (0 ~ 1 fm/c)~6.5 fm
dy
dE
RT
Bj0
2
11
Barette et al., E877
Bjorken~ 1.3 GeV/fm3
Critical Energy Density ~ 1-1.5 GeV/fm3
Energy Density
Large Energy Density pressure gradients & ExpansionLarge Energy Density pressure gradients & Expansion
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Significant Stopping is achieved in central collisions at the AGS
Rapidity Distributions and Baryon StoppingRapidity Distributions and Baryon Stopping
Holzmanet. alE917
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J. Klay et al. E895
Rapidity Distributions and Baryon StoppingRapidity Distributions and Baryon StoppingSi + Al Au + AuBraun-Munzinger et al.
2 cosh3
2 2
2 2
cosh cosh
my
TdN m mT e
dy T T y y
(T obtained from particle Spectra)
Maxwell-Boltzmann Distribution
Distributions are consistent with significant longitudinal Flow.
Longitudinal Flow Systematics
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Particle Spectra are compatible with
significant radial Flow.
Radial FlowRadial FlowAu + Au (-0.05 < y < 0.05
/2
1/ 22
1 sinhcosh
/ 1
tm T
t t t t
dN T Te
m dm m m
p T
and T
Sign
ifica
nt T
rans
vers
e
Sign
ifica
nt T
rans
vers
e
Expan
sion
Expan
sion
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HBTHBT
21
2
1224
14
2 xxxdxdC
In the Longitudinal CMS, where (p1+p2)beam = 0,
222TO
2TO
2TS
2TS
2L
2L2
2
2
2TO
2TO
2TS
2TS
2L
2L
ERqRqRqexp1C
2
t
R2
r
R2
r
R2
rexp,tr
21
21
2
exp2
dpd
dpd
dpdpd
C
expTOR
2
2expTS
2expTO2
222TO
2TO
2TS
2TS
2L
2L2
RR
RqRqRqexp1C
C2 is measured as,
Observables3 radii: duration time:
chaoticity:
222TO
expTOTSL RR,R,R
QTS QTO QL
Probability to detect 2 particles at p1 and p2,
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HBTHBT
expTOR
2
2expTS
2expTO2
222TO
2TO
2TS
2TS
2L
2L2
RR
RqRqRqexp1C
3
3
V ~ 2600 fm (2X Au)
~ 0.12/fm
Stachel et al.
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HBT – Reaction plane HBT – Reaction plane DependenceDependence
Rout < RsideInitial Overlap => Shape at freeze-out
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Flow
pass0 0
expant
2t
~
~
S
R
R
c
Low Energy:Low Energy:Squeeze-out
Pressure Gradients Drive Pressure Gradients Drive Transverse and Elliptic flowTransverse and Elliptic flow
High EnergyHigh Energy In-plane
1 2~ 1 2 cos( ) 2 cos(2 )dN
v vd
1 2~ 1 2 cos( ) 2 cos(2 )dN
v vd
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1 2
2
~ 1 2 cos( ) 2 cos(2 )
cos(2 )
dNv v
d
v
1 2
2
~ 1 2 cos( ) 2 cos(2 )
cos(2 )
dNv v
d
v
/
9s
dpK
d
VV22 is sensitive to the EOS is sensitive to the EOS
Danielewicz et al.
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VV22 is sensitive to the Phase Transition is sensitive to the Phase Transition
Danielewicz et al.
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FlowFlow
(E895)(E895)E877
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Good Agreement with theory, Softening of EOSGood Agreement with theory, Softening of EOS
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Differential Flow
Differential Differential MeasurementsMeasurements
(E895)(E895)
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•Differential Elliptic Flow Studies Provide Differential Elliptic Flow Studies Provide Important Additional Insights on the EOSImportant Additional Insights on the EOS•Differential Elliptic Flow Studies Provide Differential Elliptic Flow Studies Provide Important Additional Insights on the EOSImportant Additional Insights on the EOS
pass0 0
2t ~
R
pass
0 0
2t ~
R
1expant ~
S
d
c
1expant ~
S
d
c
2expant ~
S
d
c
2expant ~
S
d
c
d1
d2
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Good Agreement with Good Agreement with calculation which assumes calculation which assumes
p dependent meanfield p dependent meanfield
H. Liu E895 Sahu et al.
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New constraints for the EOS achievedNew constraints for the EOS achieved
Danielewicz et al.
FlowFlow
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Flow of Produced ParticlesFlow of Produced Particles
Clear Evidence for in-medium potentialClear Evidence for in-medium potential
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Particle ProductionParticle Production
OF Particular InterestOF Particular Interest• Enhancement in Strangeness Production
• Enhancement in the ratio Antihyperon/Antibaryon
Probes for the QGP
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Particle ProductionParticle Production
Yields Increase from Peripheral to Central CollisionsYields Increase from Peripheral to Central Collisions-- Consistent With Multiple Collisions per participant -- Consistent With Multiple Collisions per participant
F. Wang
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Particle ProductionParticle Production
Ratio increases with beam Ratio increases with beam energy… possible maximumenergy… possible maximum
p+p
Smooth Decrease in enhancementSmooth Decrease in enhancement
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Particle ProductionParticle Production
Ratio Increase from Peripheral to Central CollisionsRatio Increase from Peripheral to Central Collisions-- Reasonable agreement with model calculations-- Reasonable agreement with model calculations
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Particle ProductionParticle Production
Remarkable Agreement with Predictions of Thermal modelRemarkable Agreement with Predictions of Thermal model
& TB
Braun-Munzinger et al.
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Stachel et al.
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Compressed Baryonic Matter is Produced With Compressed Baryonic Matter is Produced With Significant Energy Density at the AGS.Significant Energy Density at the AGS.
The study of this matter has provided a wealth of insightsThe study of this matter has provided a wealth of insights Further Studies are Required for a more complete Further Studies are Required for a more complete
understanding as well as further mapping of the phase understanding as well as further mapping of the phase diagramdiagram
..
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New constraints for the EOS achievedNew constraints for the EOS achieved
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Motivation – Strange ParticlesMotivation – Strange Particles
K- & K0 attractive Interaction
K+ & K0 Repulsive Interaction
- Consequences for Flow
In QGP
Production in hadronic gas pairs of strange hadrons with
increased threshold
Strangeness Enhancement
The Production and Propagation of Strange Hadrons The Production and Propagation of Strange Hadrons
constitutes an Important Probeconstitutes an Important Probe
gg ss