Collectivity in the Middle Years

Symposium on Collectivity, March 15, 2013 1

1992

What does “middle” refer to?

2

1978

2004

Art, Grazyna & Kai: Lots of territory ranging from Plastic Ball (Bevalac & CERN), STAR, many years as RNC Head….

This talk: Focus on 1990s – Bevalac Sci. Director; EOS at Bevalac & AGS; early planning for RHIC.

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1

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Phys. Lett. 110B, 185 (1982)

Phys. Lett. 129B, 283 (1983)

“It is important to emphasize that the only true signature of collective flow is a clear maximum of dN / d cos1 away from 1 = 0.”

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PRL 52, 1590 (1984)

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P. Danielewicz & G. Odyniec, PL 157B, 146 (1985)

Bevalac streamer chamber: 1.8 A GeV Ar + KCl

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Central collision: 1.8 A GeV Ar + Pb

Plastic Ball: Good statistics; Relatively quick analysis; Complex acceptance (theorists must filter via Art’s SIMDAT.FOR)

Streamer Chamber: Simple, uniform acceptance/efficiency Slow & laborious data analysis; Very small event samples; Poor PID.

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Original EOS proposal (1986)by Pugh, Odyniec, Rai, Seidl: Cylindrical TPC, solenoidal magnet (“mini-STAR”)

Less expensive EOS (1988) by Weiman, Rai et al.:Rectangular TPC designed to fit inside existing HISS dipole

EOS

1989-90: project funded. Hans Georg came back from CERN to lead the science.

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Stick 1

Stick 128

...“father” of NA49 TPCs and “grandfather” of STAR TPC

DSP code written by Hans Georg

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Water-cooled boards extensively use custom chips, & mate directly to pad plane

All time buckets from each of >15K pads read out via ~100 fibers

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HGR Symposium, March 15, 2013 16

Yiping Youn Brijesh Howard Penny HGR Doug Shao Choi Srivastava Wieman Warren Olson

Marvin Dean Daniel Chuck Walter Mark Jim Eric Justice Chacon Cebra McParland Mueller Tincknell Elliott Hjort

Gulshan Martin Howard Alan Rai Partlan Matis Scott

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~8 Million events 3.5 TB raw data

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…but definitely not a problem for flow measure- ment!

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M. D. Partlan et al., PRL 75, 2100 (1995).

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At these energies, there is an out-of-plane enhancement (negative v2).

Unlike at RHIC, the v2 here is stronger in rotated coords.

Elliptic flow can be described as a sinusoidal modulation of the radial velocity, . A single parameter can describe the full pT dependence of elliptic flow.

out-of-plane

in-plane

S. Wang et al., PRL 76, 3911 (1996).

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M. Justice, NIM A 400, 463 (1997).

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Published in 1997

1993-2000: lean time for US RHI physics;

Bevalac shut down,

RHIC not yet started,

AGS operated ~10 yrs at a single energy.

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Helmuth Von Moltke (1800 – 1891)Served in armies of Denmark & Prussia Prolific writer on many topics

Scientific Corollary:“No plan of experimental research survives contact with the data”

“No plan survives contact with the enemy”

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“When you talk with experimentalists, it is extremely important to understand exactly what they are doing…… in the case of theorists, it is not so important” – Sid Kahana, BNL theorist & AGS PAC member at time of E895 proposal

Up to 350 tracks

Founding Spokesperson:Gulshan Rai

E895 published 12 journals papers, including 9 in PRL.

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D. H. Rischke et al., Heavy Ion Phys. 1, 309 (1995). H. Stoecker,

Nucl. Phys. A 750, 121 (2005).

Before E895pp

Fy

v2

T

Ebeam

Region where inel takes off and rises steeply.

Baryon density (by certain measures) peaks near here.

Empirically, many ‘bulk’ observables show transitions in this region.

Some hydro models predict softening due to 1st order PT near here.

Importance of energy regionfrom 2 to ~10 A GeV (fixed target):

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QM ’01 slide by Mike Lisa

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Beam energy in A GeV

Elab (A GeV)

0.04

-0.08

-0.04

0

1 10

v 2

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Elab (A GeV)1 101 10

F (

GeV

/c)

0

0.1

0.2

0.3

dy'

pdF x

PRL 83, 1295 (1999)

PRL 84, 5488 (2000)

No trend resembling hydro with 1st-order phase transition

No single model parameterization reproduces flow details

Strong sensitivity to contributions to pressure from medium

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E895 directed flow: 6 A GeV Au+Au

yCM

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H. Stoecker, Nucl. Phys. A 750, 121 (2005).

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12 years on, the same message

holds for Hans Georg himself

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This talk was designed to “plug the gaps” in areas the other speakers this afternoon are not going to cover.

Art’s talk will include a wide-ranging list of Hans Georg’s major accomplishments.

This is a summary only – conclusions at this stage would be premature.

Stay tuned for update in 2025, when Hans Georg will reach Art’s age today.

In the meantime: many congratulations & happy (early) birthday, Hans Georg!!