lisa - quark matter 991 beam energy evolution of hbt sytematics at the ags mike lisa, the ohio state...
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Lisa - Quark Matter 99
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Beam Energy Evolution of HBT Sytematics at the AGS
Mike Lisa, The Ohio State Universityfor the E895 Collaboration
N.N. Ajitanand, J. Alexander, D. Best, P. Brady, T. Case, B. Caskey, D. Cebra,J. Chance, I. Chemakin, P. Chung, V. Cianciolo, B. Cole, K. Crowe, A. Das,
J. Draper, S. Gushue, M. Gilkes, M. Heffner, H. Hiejima, A. Hirsch, E. Hjort,L. Huo, M. Justice, M. Kaplan, J. Klay, D. Keane, J. Kintner, D. Krofcheck,
R. Lacey, J. Lauret, E. LeBras, M. Lisa, H. Liu, Y. Liu, B. McGrath, Z. Milosevich,D. Olson, S. Panitkin, C. Pinkenburg N. Porile, G. Rai, H.-G. Ritter, J. Romero,
R. Scharenberg, L. Schroeder, R. Sotlz, B. Srivastava, N. Stone, J. Symons, S. Wang,R. Wells, J. Whitfield,T. Wienold, R. Witt, L. Wood, X. Yang, Y. Zhang, W. Zhang
Auckland - BNL - CMU - Columbia - UC Davis - Harbin - KSU - LBL - LLNL - St. Mary’s College - OSU - Purdue - Stony Brook
• Motivation and Measurement
• Correlation Systematics at Intermediate AGS energy
• Ebeam Centrality y mT rp
• Summary
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HBT Excitation Function at AGS - Motivation
Characterize source geometry and dynamics as function ofEbeam, mT, y, rp
Watch for “anomalous” lifetimes/sizes (QGP@AGS?)
Test dynamical models that provide “hadronic baseline” - can they extrapolate to RHIC?
“”
withtransition
c
3D hydro modelRischke & GyulassyNPA 608, 479 (1996)
Eob
serv
able AGS SPS RHIC
Signatures of new physics may be subtle
E
obse
rvab
le AGS SPS RHIC
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Measurement with the EOS TPC
Up to ~350 particles/event (60 -) measured over large phase space
Good reaction plane resolution
p/p 3% (dominated by MCS)
5% e- contamination in -
Posters by D. Cebra & C. Pinkenburg Talk by G. Rai in Thurs. plenary session
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The E895 - HBT Analysis
Iterative correction for p (typical increase in fit parameters by ~ 8%)
2-track cut eliminates track merging limits analysis to low pT (< 0.4 GeV/c)
Full Coulomb-wave (= 5 fm) Coulomb correction employed
Analyze in frame fixed at ycm
Event-mixing with rp selection:
mix only events with “same” rp
Statistical uncertainties shown. Systematic errors of same order.
Passage of a track “kills” an area ~ (1 cm)2
on padrow merging
128 padrows
beam
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1-D Correlation Function Excitation Function at ycm
Smooth evolution of 1-D fit parameters with E
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Bertsch-Pratt projections(11% T ycm0.35 pT = 0.1-0.3 MeV/c)
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Evolution of the BP and YKP fit parameters
Increased production of long-lived --emitters fall in
Strong evolution of Rs (R) with beam energy
Hadronic model with or without meanfield underpredicts (apparent) geometric size at low beam energy
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Evolution of (apparent) Shape: Oblate to Prolate
Transition from oblate to prolate shape at AGS connects Bevalac observations to SPS
Transition in character of flow/expansion: transverse longitudinal?
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mT dependence at ycm for 2 AGeV central collisions
Dynamics (timescale/flow) radii drop with mT
- from decays at low mT increases with mT
x (fm)
y (f
m)
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mT dependence at ycm for 6 AGeV central collisions
At higher beam energy, RS falls more steeply
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Evolution of mT dependence (y=ycm0.5)
magnitude of RO(mT) falls with Ebeam.
Decline of RS with Ebeam driven primarily by increased falloff with mT at high energy.
RL(mT) roughly constant as function of Ebeam
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Evolution of systematics - data and model
Observed evolution of systematics not reproduced by model
Dynamics driving RS(mT) may not depend on collision energy within RQMD
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Testing the model at the SPS
For -...
Model underpredicts apparent size below 10 AGeV...
overpredicts size at 158 AGeV
Extrapolation to RHIC???
NA44 RQMD
Rout 4.88 0.21 6.96 0.14
Rside 4.45 0.32 6.23 0.20
Rlong 6.03 0.35 7.94 0.21
I.G. Bearden et al (NA44)PRC58, 1656 (1998)D. Hardtke, Ph.D. thesis (1997)
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Rapidity dependence
Rather flat dependence of fit parameters near ycm
Near beam rapidity (0.9, 1.4), radii begin to fall off when analyzed in Au+Au c.m. frame
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Longitudinal flow from cross-term and yso:
Rapidity dependence of Bertsch-Pratt Rol
2 and Yano-Koonin yso sensitive to longitudinal flow
2 AGeV: little longitudinal flow
8 AGeV: non-boost-invariant flow
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Centrality Dependence of the Correlations
suppressed for central collisions due to increased production of ,
Gentle fall of sideward radii as size of overlap region falls
b=27 fm: ~ 35% reduction in RMS
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Viewing the pion source in its natural frame
b0 collisions anisotropy in momentum space (elliptic flow)
Also visible in coordinate space?
P. Danielewicz et al,PRL 81, 2438 (1998)Also see E895 ellipticflow poster
toy example
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HBT with respect to the Reaction Plane - data
b 4 - 9 fm
Small but significant oscillation observed in sideward radius
Consistent with naïve geometrical view, and RQMD
Reduced strength of oscillation in Rout may give information on lifetime or effective opaqueness
Uncorrected for r.p. resolution
cuts not identical
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Evolution of HBT @ AGS - Summary
E895 has measured systematics of - interferometry at 2-8 AGeV no anomalous behaviour suggestive of QGP formation apparent sideward radius (and ) fall with E
mT-dependence of RS weak at low Ebeam: less flow? evolution from oblate (Bevalac-like) toward prolate (SPS-like) source y-dependence of Rol
2, ysoYKP little longitudinal flow at 2 AGeV
gentle centrality dependence - no surprises
The Next Frontier - Imaging the source in its natural frame ~0.5 fm oscillation of RS observed at low Ebeam - less at higher energy detailed study of source in natural frame may give info on opacity/lifetime
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Evolution of HBT @ AGS - Summary II
Excitation Function - powerful tool to test/tune understanding of “normal” physics in R.H.I.C.
RQMD does not reproduce evolution in detail underpredicts transverse size below ~10 AGeV - overpredicts size above
incorrect evolution of x-p correlation? correct outward radius an artifact of effective emission timescale? little (relevant) evolution of dynamics in AGS range
Plans detailed analysis of HBT(rp) (including dispersion corrections) - phasespace density as a function of p
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HBT with respect to the Reaction Plane - RQMD
(perfect r.p. resolution)
oscillation - elliptical flow?
Rout oscillates against Rside, with similar magnitude
Oscillation strength roughly constant with Ebeam
Rlong: ?
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Bertsch-Pratt projections - data and RQMD(11% T ycm0.35 pT = 0.1-0.3 MeV/c)
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Typical 1- Error contours for BP fits
Primary correlation is the familiar correlation between and radii
Large acceptance no strong correlations between radii
Cross-term uncorrelated with any other parameter
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- Acceptance