1. Review of Nuclear Reactions @ AGS
Craig Ogilvie, Jan 2001
Properties of dense hadronic matter
review of pA and AA experimental results
Link to SPS 40, 160 AGeV
Future Opportunities
GSI, JHF upgrades, AGS in RHIC era

2. Mean-Free Path of Hadrons at High Density
Mean free-path very short, possibility of multi-body collisions
Working ansatz
instead of explicitly calculating n-body collisions
calculate collisions between pairs of hadrons
resonances, formation and decay of strings
effects of dense medium incorporated in a mean field U(r,p)
1/15/2001
Craig Ogilvie, Iowa State University

3. Possible Change of Hadron Properties
changes as function of T, m
(hep-ph/ Halasz et al)
This is an average over full system
both “inside” and “outside” hadrons
does any one hadron experience this reduced condensate
hence change its mass T m
1/15/2001
Craig Ogilvie, Iowa State University

4. High-Density QGP: Color Superconducting Phase?
1/15/2001
Craig Ogilvie, Iowa State University

5. Sideways Flow: Probe of Pressure Gradients in Collision Zone
<px> y
<px> mean transverse momentum
in reaction plane
pressure gradients within reaction zone can cause deflection of baryons x z
1/15/2001
Craig Ogilvie, Iowa State University

6. Repulsion Driven by Gradients in Mean-Field
Flow decreases smoothly function of Ebeam
Measured sideways flow cannot be reproduced by cascade calculations (RQMD 2.3)
Gradient of “thermal” pressure insufficient to deflect protons
Requires additional repulsion caused by gradients in mean-field
<px> (pt) suggests need for momentum-dependent mean-field
Mike Lisa E895 Talk
E895, Phys. Rev. Lett 84, 5488 (2000)
1/15/2001
Craig Ogilvie, Iowa State University

7. Mean-Field Has Complicated r, p Dependence
E866 Phys. Rev C
57,R466 (98)
P.K. Sahi et al.,
Nucl. Phys.A
672, 276 (2000)
W. Cassing et al,
Nucl. Phys. A 674, 249 (2000)
Momentum dependence of
mean-field required to reproduce
proton pt distribution
1/15/2001
Craig Ogilvie, Iowa State University

8. Critical Check I : pA Proton Distributions
p + Be 12 GeV/c E910 preliminary
x = p/pz beam
protons shift sharply backwards as number of collisions increase
use to confront microscopic dynamical models
basic rescattering process within cascade
see Brian Cole pA Talk
1/15/2001
Craig Ogilvie, Iowa State University

9. Critical Check II: Au+Au 6, 8, 10 AGeV
Centrality dependence of proton distributions
Could test momentum, density dependence of the mean-field
1/15/2001
Craig Ogilvie, Iowa State University
Burt Holzman E917 Talk

10. Critical Check III: Dynamics via Azimuthal HBT
Extracted HBT parameters vs reaction plane
e.g when f = 0, Rout < Rside
In-plane components (x, z)
source is tilted, same direction as proton flow x y
Rout
Rside
1/15/2001
Craig Ogilvie, Iowa State University
Mike Lisa E895 Talk

11. Do Produced Particles Experience a Mean-Field?
K- and K0 have attractive resonant interactions with baryons,
For K+ and K0 the interaction is repulsive
Model as either mean-field or effective mass
Signatures
increased NN=>K-K+ phase space, increased K- yield
directed flow of K+, K0 , repulsed from baryon flow K+ K-
W. Weise
NPA610 35c, 96
Plotted at momentum = 0
1/15/2001
Craig Ogilvie, Iowa State University

12. K0short Anti-Flow Au+Au 6 AGeV
proton
K0short
Chung et al.,
Phys. Rev Lett
85, 940 (2000)
Pal et al.,
Phys. Rev. C
62,
(2000)
Striking opposite flow for K0short
Reproduced using repulsive mean-field for kaons
1/15/2001
Craig Ogilvie, Iowa State University
Chris Pinkenberg E895 Talk

13. Hadron Properties In Medium
No e+e- at AGS
KEK result
More statistics, HADES
1/15/2001
Craig Ogilvie, Iowa State University
Ozawa Talk

14. Craig Ogilvie, Iowa State University
Particle Production
pi production in pA
1/15/2001
Craig Ogilvie, Iowa State University
Brian Cole E910 Talk

15. K pi Production vs Centrality
1/15/2001
Craig Ogilvie, Iowa State University

16. Ebeam Dependence of Kaon Enhancement
KaoS, E866
WA87 (L)
CERN-EP/98-64
Exponent, a, lower Ebeam
secondary collisions more important at lower Ebeam
closer to K+ threshold
longer time during reaction for rescattering ?
1/15/2001
Craig Ogilvie, Iowa State University

17. K+/p+ at Mid-Rapidity in Central Au+Au
(replace with up to date figures
prelim
prelim 2 2
K+/p+ in A+A increases with Ebeam, SPS similar to AGS
Divide by K+/p+ (p+p) : enhancement largest at lower Ebeam
interpolate enhancement => maximum in A+A K/pi
1/15/2001
Craig Ogilvie, Iowa State University

18. Craig Ogilvie, Iowa State University
K- Ebeam
1/15/2001
Craig Ogilvie, Iowa State University

19. Craig Ogilvie, Iowa State University
Strange Anti-baryons
Si+Au 14.6AGeV/c (E859)
Au+Au 10.7AGeV (E917) direct L
Indirect measurement derived from E864 vs E878 anti-protons
1/15/2001
Craig Ogilvie, Iowa State University
Burt Holzman E917 Talk

20. Craig Ogilvie, Iowa State University
Strangelet Limits
1/15/2001
Craig Ogilvie, Iowa State University
E864 Talk

21. Thermal Model Does Well
Plots from Cleymans
1/15/2001
Craig Ogilvie, Iowa State University

22. Strangeness Saturation
gamma_s vs Ebeam
1/15/2001
Craig Ogilvie, Iowa State University

23. Can Microscopic Dynamic Models Produce Enough Strangeness
HSD failure
RQMD failure
RQMD 2.3
1/15/2001
Craig Ogilvie, Iowa State University

24. Craig Ogilvie, Iowa State University
K- Difficulty
1/15/2001
Craig Ogilvie, Iowa State University

25. Craig Ogilvie, Iowa State University
p+A, E910
measure p + A -> L + X
correlated with # of collisions L D p
Multiple collisions rapidly increase strangeness
Use as a benchmark for microscopic dynamic models
1/15/2001
Craig Ogilvie, Iowa State University

26. Lambda-bar May Be Outside All Models
Thermal underpredict
Hadronic dynamic
1/15/2001
Craig Ogilvie, Iowa State University

27. How Significant Are These Discrepancies ?
Study the evolution of the data as a function of Ebeam
SPS 40 A GeV
K/pi maximum ?
within range expected by decreasing enhancement ?
gamma_s vs. Ebeam
lambda-bar/pbar
GSI upgrade 1 – 25 AGeV
JHF funded for proton beams
1/15/2001
Craig Ogilvie, Iowa State University