Beam Energy Evolution of HBT Sytematics at the AGS

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16 Νοε 2013 (πριν από 3 χρόνια και 6 μήνες)

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Lisa
-

Quark Matter 99

1

Beam Energy Evolution of HBT Sytematics at the AGS

Mike Lisa, The Ohio State University

for 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



E
beam

Centrality y m
T

f
rp


Summary

2

Lisa
-

Quark Matter 99

HBT Excitation Function at AGS
-

Motivation

Characterize
p

source
geometry and dynamics
as function of

E
beam
, m
T
, y,
f
rp

Watch for “anomalous”
lifetimes/sizes
(QGP@AGS?)

Test dynamical models
that provide “hadronic
baseline”
-

can they
extrapolate to RHIC?


e


with

transition

e
c

3D hydro model

Rischke & Gyulassy

NPA
608
, 479 (1996)

E

observable

AGS

SPS

RHIC

Signatures of new physics may be subtle

E

observable

AGS

SPS

RHIC

3

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-

Quark Matter 99

Measurement with the EOS TPC

Up to ~350 particles/event (60
p
-
)
measured over large phase space

Good reaction plane resolution

d
p/p


3% (dominated by MCS)



5% e
-

contamination in
p
-

Posters by D. Cebra & C. Pinkenburg

Talk by G. Rai in Thurs. plenary session

4

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-

Quark Matter 99

The E895
p
-

HBT Analysis

Iterative correction for
d
p (typical
increase in fit parameters by ~ 8%)

2
-
track cut eliminates track merging
limits analysis to low p
T

(< 0.4 GeV/c)

Full Coulomb
-
wave (
s
= 5 fm)
Coulomb correction employed

Analyze in frame fixed at y
cm

Event
-
mixing with
f
rp
p

selection
:
mix only events with “same”
f
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

5

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-

Quark Matter 99

1
-
D Correlation Function Excitation Function at y
cm

Smooth evolution of 1
-
D fit parameters with E

6

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-

Quark Matter 99

Bertsch
-
Pratt projections

(11%
s
T

y
cm

0.35

p
T

= 0.1
-
0.3 MeV/c)

7

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-

Quark Matter 99

Evolution of the BP and YKP fit parameters

Increased production of long
-
lived
p
-
-
emitters


fall in
l

Strong evolution of R
s

(R

)
with beam energy

Hadronic model
with

or
without

meanfield underpredicts
(apparent) geometric size at
low beam energy


8

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-

Quark Matter 99

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?

9

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-

Quark Matter 99

m
T

dependence at y
cm

for 2 AGeV central collisions

Dynamics (timescale/flow)


radii drop with m
T


p
-

from decays at low m
T





l

increases with m
T

x (fm)

y (fm)

10

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-

Quark Matter 99

m
T

dependence at y
cm

for 6 AGeV central collisions

At higher beam energy,
R
S

falls more steeply

11

Lisa
-

Quark Matter 99

Evolution of m
T

dependence (y=y
cm

0.5)

magnitude of R
O
(m
T
) falls
with E
beam
.



Decline of R
S

with E
beam

driven primarily by increased
falloff with m
T

at high energy.


R
L
(m
T
) roughly constant as
function of E
beam

12

Lisa
-

Quark Matter 99

Evolution of systematics
-

data and model


Observed evolution of
systematics not reproduced
by model


Dynamics driving R
S
(m
T
)
may not depend on collision
energy within RQMD

13

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-

Quark Matter 99

Testing the model at the SPS

For
p
-
...

Model
under
predicts apparent
size below 10 AGeV...

over
predicts size at 158 AGeV

Extrapolation to RHIC???



NA44



RQMD

R
out

4.88


0.21

6.96


0.14

R
side

4.45


0.32

6.23


0.20

R
long

6.03


0.35

7.94


0.21

I.G. Bearden et al (NA44)

PRC
58
, 1656 (1998)

D. Hardtke, Ph.D. thesis (1997)

14

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-

Quark Matter 99

Rapidity dependence

Rather flat dependence of fit
parameters near y
cm

Near beam rapidity (0.9, 1.4),
radii begin to fall off when
analyzed in Au+Au c.m. frame

15

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-

Quark Matter 99

Longitudinal flow from cross
-
term and y
so
:

Rapidity dependence of
Bertsch
-
Pratt R
ol
2

and
Yano
-
Koonin y
so

sensitive to
longitudinal flow

2 AGeV: little longitudinal flow

8 AGeV: non
-
boost
-
invariant
flow

16

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-

Quark Matter 99

Centrality Dependence of the Correlations

l

suppressed for central
collisions due to increased
production of
L
,
h...

Gentle fall of sideward radii as
size of overlap region falls

b=2

7 fm:
~ 35% reduction in RMS

17

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-

Quark Matter 99

Viewing the pion source in its natural frame

b

0 collisions


anisotropy in
momentum space (elliptic flow)

Also visible in coordinate space?

P. Danielewicz et al,

PRL
81
, 2438 (1998)

Also see E895 elliptic

flow poster

toy example

18

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-

Quark Matter 99

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 R
out

may give information on
lifetime or effective opaqueness

Uncorrected for r.p. resolution

cuts not identical

19

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-

Quark Matter 99

Evolution of HBT @ AGS
-

Summary

E895 has measured systematics of
p
-

interferometry at 2
-
8 AGeV


no anomalous behaviour suggestive of QGP formation


apparent sideward radius (and
l
) fall with E


m
T
-
dependence of R
S

weak at low E
beam
: less flow?


evolution from oblate (Bevalac
-
like) toward prolate (SPS
-
like) source


y
-
dependence of R
ol
2
, y
so
YKP



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 R
S

observed at low E
beam

-

less at higher energy


detailed study of source in natural frame may give info on opacity/lifetime

20

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-

Quark Matter 99

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(
f
rp
) (including dispersion corrections)


p
-

phasespace density as a function of
p

21

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-

Quark Matter 99

HBT with respect to the Reaction Plane
-

RQMD

(perfect r.p. resolution)

l

oscillation
-

L

elliptical flow?


R
out

oscillates against R
side
,
with similar magnitude

Oscillation strength roughly
constant with E
beam


R
long
: ?

22

Lisa
-

Quark Matter 99

Bertsch
-
Pratt projections
-

data and RQMD

(11%
s
T

y
cm

0.35

p
T

= 0.1
-
0.3 MeV/c)

23

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-

Quark Matter 99

Typical 1
-
s

䕲牯爠捯湴潵牳E景爠䉐⁦楴B

Primary correlation is the
familiar correlation between
l

and radii

Large acceptance


no
strong correlations between
radii

Cross
-
term uncorrelated with
any other parameter

24

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-

Quark Matter 99

p
-

Acceptance