E895 Excitation Functions at the AGS Mike Lisa, The Ohio State University

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E895 Excitation Functions at the AGSMike Lisa,
The Ohio State University

• E895 Motivation and Measurement
• Excitation functions
• sidewards flow
• elliptic flow
• strangeness
• HBT
• Summary

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Lawrence Berkeley Lab D. Best, T. Case, K.
Crowe, D. Olson, G. Rai, H.-G. Ritter,
L. Schroeder, J. Symons, T. Wienold Brookhaven
National Lab S. Gushue, N. Stone Carnegie Mellon
University M. Kaplan, Z. Milosevich, J.
Whitfield Columbia University I. Chemakin, B.
Cole, H. Hiejima, X. Yang, Y. Zhang U.C. Davis
P. Brady, B. Caskey, D. Cebra, J. Chance, J.
Draper, M. Heffner, J. Romero, L. Wood St.
Marys College J. Kintner Harbin Institute
(China) L. Huo, Y. Liu, W. Zhang Kent State
Univeristy M. Justice, D. Keane, H. Liu, S.
Panitkin, S. Wang, R. Witt Lawrence Livermore
Lab V. Cianciolo, R. Sotlz Ohio State
University A. Das, M. Lisa, R. Wells University
of Auckland (NZ) D. Krofcheck Purdue University
M. Gilkes, A. Hirsch, E. Hjort, N. Porile, R.
Scharenberg, B. Srivastava S.U.N.Y. Stony Brook
N.N. Ajitanand, J. Alexander, P. Chung, R.
Lacey, J. Lauret, E. LeBras, B. McGrath, C.
Pinkenburg
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E895 mission - continuation of EOS mission
map out energy dependence of all physics
variables as a function of energy
Large acceptance device with good PID to
characterize each event

• Hope to answer
• Is there a sign of anomolous behavior in data as
  Ebeam varied (or is systematics smooth)?
• Hydro suggests a condensed matter type of QGP
  search
• Do medium effects matter _at_ AGS?
• Bevalac experience -- one point is not enough to
  tell
• Can we constrain parametrization of medium
  effects in models?

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500k - 1M AuAu collisions measured at 2, 4, 6,
8 AGeV with full coverage
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Good PID by ionization in gas
Momentum resolution 1
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Systematics/meta-analysis suggest approach to
maximum AGS energy interesting...
B. Hong et al. (FOPI) Proceedings of
International Workshop, Poiana Brasov, Romania
(1996)
P. Braun-Munzinger and J. Stachel, NPA606, 320
(1996)
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Perhaps some signals only apparent near threshold
D. Rischke, NPA 610, c88 (1996)
Magnitude, position, (existence?) of deviations
due to phase transistion unclear
concentrate on data systematics
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Reaction plane reconstructed by method of
Danielewicz/Odyniec
Reconstructed reaction plane flat in lab
Ö
Dispersions (and corrections) get large for 8
AGeV, where flow is small
Plots by C. Pinkenburg
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Flow correction 1) grows 2) depends on
algorithm when flow gets small
Analysis by C. Pinkenburg, N.N. Ajitanand
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Proton sidewards flow excitation function
Analysis by H. Liu

• no sharp behavior in sidewards flow
• Ebeam systematics powerful test of dynamical
  models
• some medium effects needed in addition to
  hadronic scattering

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Elliptic flow - measure of in/out of plane
emission
Elliptic flow sensitive to competition
between timescales in collision
At Bevalac and MSU energies, elliptic flow
(squeeze-out) provided most sensitivity to EoS
Max AGS energy (E877) emission is in-plane
P. Danielewicz et al., nucl-th/9803047
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Elliptic flow below (and above?) 10 AGeV
sensitive to medium effects
BUU P. Danielewicz et al., nucl-th/9803047
RQMD v2.3
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Elliptic flow below (and above?) 10 AGeV
sensitive to medium effects
BUU P. Danielewicz et al., nucl-th/9803047
RQMD v2.3
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Excitation function of elliptic flow
Sideflow- peaking at 0 (180)
at ygtycm (yltycm)
Elliptic flow - second order moment
clearest at ycm vanishes near 4 AGeV
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• no obvious sharp behavior in data
• maybe something more subtle softening of EoS
  around 4 AGeV???

Analysis by C. Pinkenburg
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Neutral strange mesons and baryons
3-5 reconstruction efficiency
put mass peaks here
Analyses by P. Chung and D. Best. Plots by P.
Chung
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Strangeness excitation functions - no sharp
structure
TAPS e Nag K KAOS K FOPI K KAOS K- FOPI
K- E895 K0
Analysis by P. Chung
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K0 flow (medium bias events)
May provide sensitivity to strange scalar and
vector potentials
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p- HBT - a proposed QGP threshold signature
Rischke Gyulassy NPA 608, 479 (1996)
At energies much above theshold, increased
timescale signal vanishes as the plasma explodes
and cools quickly
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Singles coverage for pions
pT cut at 100 MeV/c helps remove e- contamination
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Q resolution 10 MeV/c (better when refitting
track with primary vertex)
Track merging/splitting effects removed by
requiring gt15 well-separated padrow crossings
NOTE finite Q resolution not corrected for in
present results
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All processed events (8 data taken, 50 for 4
GeV) - no cuts
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(No Transcript)
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Only p- used in HBT analysisRestrictive cuts
actual p- multiplicity higher
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top 10 sT
y ycm 0.25
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1D HBT excitation function - Central AuAu,
midrapidity
1D HBT parameters show no sharp anomoly
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3D HBT - 4 AGeVcentral collisionsmidrapidity
Some systematics to come...
c2/n 5797/6694 l 0.57 0.04
Rol 0.5 2 Rout 5.23 0.31
Rside 5.31 0.27

• Performed in ycm frame
• Rout Rside
• Rol 0

Rlong 4.41 0.27
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3D HBT - 4 AGeVcentral collisionsforward
rapidity
c2/n 5337 / 6694 l 0.59 0.03
Rol 3.4 1.3 Rout 5.45 0.21
Rside 4.47 0.14

• Performed in ycm frame
• Rout Rside
• Rol gt 0

Rlong 4.73 0.18
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Summary

• No drastic signatures of transition in AGS energy
  range
• sideflow, elliptic flow, strangeness, HBT
• Medium effects impt. at AGS
• collective motion excitation function provides
  true challenge to models parametrization of
  medium effects (or lack thereof)
• models tuned to reproduce data at one energy
  often fail elsewhere