E895 Excitation Functions at the AGS Mike Lisa, The Ohio State University E895 Motivation and Measurement Excitation functions sidewards flow elliptic flow strangeness HBT Summary

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 UniversityM. 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. Mary’s CollegeJ. Kintner Harbin Institute (China)L. Huo, Y. Liu, W. Zhang Kent State UniveristyM. Justice, D. Keane, H. Liu, S. Panitkin, S. Wang, R. Witt Lawrence Livermore LabV. Cianciolo, R. Sotlz Ohio State UniversityA. 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

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 E beam varied (or is systematics smooth)? Hydro suggests a “condensed matter” type of QGP search Do medium effects AGS? Bevalac experience -- one point is not enough to tell Can we constrain parametrization of medium effects in models?

~ 500k - 1M Au+Au collisions measured at 2, 4, 6, 8 AGeV with full coverage

Good PID by ionization in gas Momentum resolution ~ 1%

Systematics/meta-analysis suggest approach to maximum AGS energy interesting... P. Braun-Munzinger and J. Stachel, NPA606, 320 (1996) B. Hong et al. (FOPI) Proceedings of International Workshop, Poiana Brasov, Romania (1996)

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

Reconstructed reaction plane flat in lab  Dispersions (and corrections) get large for 8 AGeV, where flow is small Plots by C. Pinkenburg Reaction plane reconstructed by method of Danielewicz/Odyniec

Flow correction 1) grows 2) depends on algorithm when flow gets small Analysis by C. Pinkenburg, N.N. Ajitanand

Proton sidewards flow excitation function Analysis by H. Liu no sharp behavior in sidewards flow E beam systematics powerful test of dynamical models some medium effects needed in addition to hadronic scattering

Elliptic flow - measure of in/out of plane emission P. Danielewicz et al., nucl-th/ 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

Elliptic flow below (and above?) 10 AGeV sensitive to medium effects RQMD v2.3 BUU P. Danielewicz et al., nucl-th/

Elliptic flow below (and above?) 10 AGeV sensitive to medium effects RQMD v2.3 BUU P. Danielewicz et al., nucl-th/

Excitation function of elliptic flow Sideflow- peaking at 0  (180  ) at y>y cm (y<y cm ) Elliptic flow - second order moment clearest at y cm vanishes near 4 AGeV

Analysis by C. Pinkenburg no obvious sharp behavior in data maybe something more subtle… softening of EoS around 4 AGeV???

Neutral strange mesons and baryons *** put mass peaks here *** 3-5% reconstruction efficiency Analyses by P. Chung and D. Best. Plots by P. Chung

Strangeness excitation functions - no sharp structure Analysis by P. Chung TAPS e Nag K + KAOS K + FOPI K + KAOS K - FOPI K - E895 K 0

K 0 flow (medium bias events) May provide sensitivity to strange scalar and vector potentials

 - HBT - a proposed QGP threshold signature “”“” “c”“c” Rischke & Gyulassy NPA 608, 479 (1996) At energies much above theshold, increased timescale signal vanishes as the plasma explodes and cools quickly

Singles coverage for pions p T cut at 100 MeV/c helps remove e - contamination

Track merging/splitting effects removed by requiring >15 well- separated padrow crossings Q resolution ~ 10 MeV/c (better when refitting track with primary vertex) NOTE: finite Q resolution not corrected for in present results

All processed events (~8% data taken, 50% for 4 GeV) - no cuts

Only  - used in HBT analysis Restrictive cuts  actual  - multiplicity higher

“top 10%  T ” y = y cm  0.25

1D HBT excitation function - Central Au+Au, midrapidity 1D HBT parameters show no sharp anomoly

3D HBT - 4 AGeV central collisions midrapidity Performed in y cm frame R out  R side R ol  0 Some systematics to come...  2 / = 5797/6694 = 0.57  0.04 R ol = 0.5  2 R out = 5.23  0.31 R side = 5.31  0.27 R long = 4.41  0.27

3D HBT - 4 AGeV central collisions forward rapidity Performed in y cm frame R out  R side R ol  0 R ol = 3.4  1.3 R out = 5.45  0.21  2 / = 5337 / 6694 = 0.59  0.03 R side = 4.47  0.14 R long = 4.73  0.18

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