Laying the groundwork at the AGS:
Recent results from E895
Mike Lisa, for the E895 Collaboration
N.N. Ajitanand, J. Alexander, D. Best, P. Brady, T. Case, B. Caskey, D. Cebra,
J. Chance, P. Chung, 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, 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 St. Mary’s College - OSU - Purdue - Stony Brook
E895
Mike Lisa, Quark Matter 2001
1
Reminder: why AGS is
(still) interesting
spp
 sets baseline systematics
“your systematics deviate
from what?”
Fy
before E895
v
 the “other” extreme condition 2
- maximum baryon density
 probe medium & bulk
b
effects
 transition region for bulk
properties
E895
T
Mike Lisa, Quark Matter 2001
Ebeam
2
This talk
Not a “final wrap-up” of E895, which is still alive. Since QM99:
•
•
•
•
•
•
PRL 83 1295 (1999)
PRL 84 2798 (2000)
PRL 84 5488 (2000)
PRL 85 940 (2000)
PLB 496 1 (2000)
PRL accepted (2000)
E895
Transition from out-of-plane to in-plane elliptic flow
Bombarding energy dependence of p- HBT at the AGS
Sideward flow in Au+Au collisions at 2-8 AGeV
Anti-flow of K0 mesons in 6 AGeV Au+Au collisions
Azimuthal dependence of pion interferometry
L flow in 2-6AGeV Au+Au collisions
• Published E895 flow
• Beyond proton flow - collective flow of strange particles
• Geometrical dependence of flow
• HBT Beyond “Rp = 5 fm”
• geometric aspects of collective flow
• 6D phasespace density
• L-p correlations
• Summary
Mike Lisa, Quark Matter 2001
3
Measurement with the EOS TPC
• Up to ~350 particles/event
measured over large phase space
• Good reaction plane resolution
• p/p  3% (dominated by MCS)
E895
“Grandfather of STAR TPC”
Mike Lisa, Quark Matter 2001
4
p phasespace density
The Four Fundamental
Corners of E895
thermal population?
multiparticle effects?
poster by D. Cebra
space-time geometry
& dynamics
thermal/chemical
properties
PRL 84 2798 (2000)
poster by J. Klay
tilted sources
geometry of
anisotropic flow
L-p correlations
baryon source geometry
two-hadron potential
PLB 496 1 (2000)
poster by U. Heinz
pre-equilibrium dynamics
collective bulk response
equation of state
PRL 83 1295 (1999)
PRL 84 5488 (2000)
E895
strange/nonstrange
radial flow
distinct freezeout?
talk by C. Pinkenburg
L, K0 flow
strange potentials
PRL 85 940 (2000)
PRL, in press
talk
byQuark
C. Pinkenburg
Mike
Lisa,
Matter 2001
early thermochemistry
strange potentials
talk by C. Pinkenburg
5
d px
sideward flow
dyn
v2  cos2
elliptic flow
F
F (GeV/c)
Reminder from
QM99: Proton Flow
0.3
0.2
0.1
0
0.04
10
1
10
Elab (AGeV)
v2
 Transition region for flow mapped
Momentum
space
 F drops as presonances
dominate
y
0
px
 Strong sensitivity to medium
contributions to pressure qF
 No single parameterization p
z
reproduces flow details
(Beam)
-0.04
plane
 No sudden drops Reaction
in pressure
(flow) signaling phase transition
-0.08
E895
1
1
Elab (AGeV)
10
Mike Lisa, Quark Matter 2001
PRL 83 1295 (1999)
PRL 84 54886(2000)
K s0  p  p-
Beyond protons...
neural networks identify
decays of neutral strange particles
L production excitation function
L  p  pL
Minv (GeV/c2)
• (p+p)•179
E895
1.08
1.10
1.12
1.14
2)
see 2001
talk of Chris Pinkenburg7 today
MMike
Lisa, Quark
Matter
inv (GeV/c
L flow
• “positive” L flow
• decreases with Eb (more than p)
2 AGeV
 px  (GeV/c)
• RQMD (without L potential)
underpredicts effect
• probe L potential at high r
(complements hypernuclei
studies)  astrophysical models
4 AGeV
“quark counting”
6 AGeV
E895
NL  23 NN
y/ycm
PRL accepted (2000)
see 2001
talk
Mike Lisa, Quark Matter
of Chris Pinkenburg8 today
K0S (anti-)flow
Surprise— strong antiflow
• grows with collision energy
px (GeV/c)
0.1
S. Pal et al, PR C62 061903 (2000)
0
-0.1
6 GeV
-1.0
data
RQMD (2.3)
4 GeV data
-0.5
0
y/ycm
0.5
1.0
Transport models:
• rescattering insufficient
(results in positive flow)
• strong repulsive vector
potential required
E895
PRL 85 940 (2000)
see 2001
talk
Mike Lisa, Quark Matter
of Chris Pinkenburg9 today
proton elliptic flow - varying the geometry
0
-.02
2 AGeV
-.04
D
.02
v2
“min-bias” flow
measurements do not
constrain models
 geometry provides
another handle on flow
4 AGeV
0
increasing spatial
asymmetry produces
larger signal
-.02
6 AGeV
.01
-.01
0
E895
Can HBT give geometrical
information on flow??
2
4
b (fm)
6
8
Mike Lisa, Quark Matter 2001
10
HBT: probing freeze-out space-time structure I
- Cylindrical sources
 
 
  

~2
K  ~
x out - b t 

2 
2
~
R s K  x side K

~2
2
Rl K  ~
x long - bl t
R o2
 
  
K
Rside
E895
 

K

K
~
xx- x
d 4 x  S( x, K )  f ( x )

f 
4
d
 x  S( x, K)
x out , x side   x, y 
Rout HBT @ AGS mapped
by E895 (QM99)
PRL 84, 2798 (2000)
NPALisa,
661,
444c
(1999)
Mike
Quark
Matter
2001
11
HBT: probing freeze-out space-time structure II
- Collisions at b0
side
y
•Source in b-fixed system: (x,y,z)
•Space/time entangled in
pair system (xO,xS,xL)
R o2
R s2
2
R os

   ~y
   ~y

- 12
1
2
1
2


cos2   ~y
sin 2
2
- ~
x2
- ~
x2
1
2
2
 ~
x2
out



~
~y 2 - ~
x 2 cos 2  12 ~y 2  ~
x 2  b2 t 2
2
K
x
b
~
R l2  ~z 2  b2L t 2
2
R ol
 ~
x  ~z cos
R2  - ~
x  ~z sin 
sl
E895
(several terms vanish @ pT = y = 0)
U. Wiedemann, PRC 57, 266 (1998)
MAL, U. Heinz, U. Wiedemann PLB 489, 287 (2000)
Poster
by U. Heinz
Mike Lisa, QuarkSee
Matter
2001
12
First-order information in HBT()
y
2nd-harmonic oscillations from
elliptical transverse shape

   ~y
   ~y


cos2   ~y
sin 2
~
x2
~y 2
b

1
x
~
R o2  - 12 ~y 2 - ~
x 2 cos 2  12 ~y 2  ~
x 2  b2 t 2
R s2
2
R os
1
2
1
2
2
2
- ~
x2
- ~
x2
~
R l2  ~z 2  b2L t 2
1
2
2
 ~
x2
st-harmonic
oscillations:
spatial tilt angle qS
y
x
qs
2
R ol
 ~
x  ~z cos
R2  - ~
x  ~z sin 
z
(Beam)
sl
E895
Coordinate space!
Mike Lisa, Quark Matter 2001
13
Data: p- correlation functions
Au(4 AGeV)Au, b4-8 fm
2D projections  
C(q)
1D projections, =45°
out
side
long
lines: projections of 3D Gaussian fit

- q i q j R ij2  
C(q, )  1     e
• 6 components to radius tensor: i, j = o,s,l
E895
E895, PLB 496 1 (2000)
Mike Lisa, Quark Matter 2001
14
Cross-term radii Rol, Ros, Rsl
quantify “tilts” in correlation functions
 
 fit results to correlation functions
Lines: Simultaneous fit to HBT radii
to extract underlying
Mike Lisa, Quarkgeometry
Matter 2001
E895
15
Images of p--emitting sources (scaled ~ x1014)
~y 2
 1.35
2
~
x
y
similar to naïve
overlap: b~5 fm
y
x’
x’
2 AGeV
3 fm
z
y
qS=47°
x’
4 AGeV
z
6 AGeV
qS=37°
z
qS=33°
Large, positive
tilt angles
E895
x
Mike Lisa, Quark Matter 2001
x
x
16
Opposing average tilts in p, x
and the physics of p flow
p+ 6 AGeV
• p “antiflow” (negative tilt in p-space)
• x-space tilt in positive direction
 non-hydro nature of p flow
z (fm)
RQMD transport model:
• Antiflow reflects dense region z~0
• (dilute large-|z| show positive flow)
B. Caskey
pion momentum anisotropies due to
reflection from flowing baryons
(pND pN)
p tilt reflects x-space structure
of proton flow
E895
Bass et al
[PLB 302 381 (93)]: Mike Lisa, Quark Matter 2001
RQMD Au(2GeV)Au
x (fm)
17
Tomography in 6 Dimensions
Flow analysis and HBT relative to the reaction plane
allow a complete characterization of the final state in
phase space, get space-momentum correlations
6 dimensional Tomography of proton flow
6 AGeV
Momentum Space (Flow)
pz
py
Tiny flow angle px
E895
Coordinate Space (HBT)
z
positive v2
px
y
Large tilt
Mike Lisa, Quark Matter 2001
x
Out-of-plane x’
18
More on position - momentum space relationship
the phasespace density
f = occupation of 6-D positionmomentum cell, volume h3
• determines magnitude of multi-particle correlations (lasers)
• provides a test of thermalization/consistency
f ( x , p) 
1
e pu ( x ) / T ( x ) - 1
T determines number of p,
as well as spectral shape
Experimental access to spatially averaged density
1
d3 N

E dy  pT dpT  d
f pT , y   p3 
R out  R side  R long
volume in p-space
volume in x-space
G. Bertsch, PRL 72 2349 (94)
D. Ferenc et al, PL B457 347 (99)
• observation @ SPS, AGS: “Universal” p freeze-out density
E895
• breaks down at lower
Mike energies?
Lisa, Quark Matter 2001
19
Measured phasespace densities
• non-universal growth of f
with collision energy
• f<1  no condensate
E895
preliminary
Mike Lisa, Quark Matter 2001
midrapidity
central collisions
20
Measured phasespace densities
• non-universal growth of f
with collision energy
• f<1  no condensate
• low-pT saturation of f as
Ebeam  8 AGeV
• same occupancy as STAR!
E895
preliminary
Mike Lisa, Quark Matter 2001
midrapidity
central collisions
21
Measured phasespace densities
• non-universal growth of f
with collision energy
• f<1  no condensate
• low-pT saturation of f as
Ebeam  8 AGeV
• same occupancy as STAR!
• Rough agreement with
thermal Bose-Einstein
• high-pT excess @ high Eb
E895
preliminary
Mike Lisa, Quark Matter 2001
midrapidity
central collisions
22
Measured phasespace densities
• non-universal growth of f
with collision energy
• f<1  no condensate
• low-pT saturation of f as
Ebeam  8 AGeV
• same occupancy as STAR!
• Rough agreement with
thermal Bose-Einstein
• high-pT excess @ high Eb
• Better description by
inclusion of radial flow
[B. Tomasik, Ph.D. thesis]
• Substantial experimental &
theoretical uncertainties
E895
preliminary
also see poster of D. Cebra Mike Lisa, Quark Matter 2001
midrapidity
central collisions
23
Baryon correlations
C2
• Lp more sensitive than pp?
1.2
• Correct Lp potential?
1.8
1.0
1.6
0.8
1.4
 2 AGeV
 4 AGeV
 6 AGeV
O 8 AGeV
0.6
1.2
1.0
C2
0.4
pp correlation function
(central collisions, y<ycm)
0.2
0
L-p
0
0.4
0.8
0.12
k (GeV/c)
• pp correlations ~ Ebeam independent
• another handle on baryon source?
E895
1.2
p-p
1.0
0.8
0.6
0.4
0.2
0
20
40
k (MeV/c)
Wang & S. Pratt PRL 83 3139
Mike Lisa, Quark MatterF.
2001
24 (1999)
Another E895 first: L-p correlation function
• positive correlation
observed
1.4
• work in progress…
E895
1.0
C(k)
• qualitatively different
shape than expected
from Urbana p-L
potential
 input to the particle
physics
0.6
1.4
1.0
0.6
0
20
Mike Lisa, Quark Matter 2001
40
60
80
100
k (MeV/c)
25
Summary I
• continuing to push the envelope…
• directed and elliptic flow excitation function
• continue input to bulk parameterization
• strange particle flow
• positive L flow
• does not scale with proton flow (naïve 2/3 rule broken)
• L potential important to describe flow
• strong antiflow of K0’s
• strong, repulsive vector potential indicated
• Varying geometry (impact parameter): another handle
• increased x asymmetry  larger p asymmetry
E895
Mike Lisa, Quark Matter 2001
26
Summary II
• azimuthally-sensitive p- HBT
• almond-shaped source, (~ entrance-channel geometry)
• large positive spatial tilt angles
• non-hydro nature of p flow
• coordinate-space structure of proton flow
• 6-D p phasespace density
• non-universal growth of <f> with energy
• saturation to “universal” behaviour at 8 AGeV
• after 8 AGeV, increased p yield pushed to high pT flow
• first p-L signal observed
• significant positive correlation
• inconsistent with shape expected by Urbana potential
E895
Mike Lisa, Quark Matter 2001
27
More E895 @ QM01
 Production & Collective Behaviour of Strange Particles
Parallel session today:
Chris Pinkenburg
 p Phasespace Density & Source Charge Density
P063
Dan Cebra
 Directed, Elliptic, Radial, & Longitudinal Flow
P069
Jenn Klay
 Azimuthally-sensitive HBT and the Tilt of the p Source
P018
Ulrich Heinz*
E895
Mike Lisa, Quark Matter 2001
* honorary E895 member
28
Pion and proton elliptic flow
E895
Mike Lisa, Quark Matter 2001
W. Caskey, DNP98
• Ellitpic flow of both
positive and negative
pions follows the
trends of the
protons
29