Laying the groundwork at the AGS: Recent results from E895 Mike Lisa, for the E895 Collaboration

Mike Lisa, Quark Matter 2001 1E895

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


Reminder: why AGS is (still) interesting

sets baseline systematics“your systematics deviate from what?”

the “other” extreme condition - maximum baryon density probe medium & bulk effects

transition region for bulk properties

before E895pp

Fy

v2

T

Ebeam


This talkNot a “final wrap-up” of E895, which is still alive. Since QM99:

• PRL 83 1295 (1999) Transition from out-of-plane to in-plane elliptic flow• PRL 84 2798 (2000) Bombarding energy dependence of - HBT at the

AGS• PRL 84 5488 (2000) Sideward flow in Au+Au collisions at 2-8 AGeV• PRL 85 940 (2000) Anti-flow of K0 mesons in 6 AGeV Au+Au collisions• PLB 496 1 (2000) Azimuthal dependence of pion interferometry• PRL accepted (2000) flow in 2-6AGeV Au+Au collisions•Published E895 flow

•Beyond proton flow - collective flow of strange particles

•Geometrical dependence of flow

•HBT Beyond “R = 5 fm”

•geometric aspects of collective flow•6D phasespace density-p correlations

•Summary


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)

“Grandfather of STAR TPC”


The Four Fundamental Corners of E895

space-time geometry& dynamics

PRL 84 2798 (2000)

pre-equilibrium dynamicscollective bulk response

equation of statePRL 83 1295 (1999)PRL 84 5488 (2000)

thermal/chemicalproperties

poster by J. Klay

talk by C. Pinkenburg

early thermochemistrystrange potentials

strange/nonstrangeradial flow

distinct freezeout?talk by C. Pinkenburg

tilted sourcesgeometry of

anisotropic flowPLB 496 1 (2000)poster by U. Heinz

phasespace density

poster by D. Cebra

thermal population?multiparticle effects?

p correlationsbaryon source geometry

two-hadron potential

, K0 flow

PRL 85 940 (2000)PRL, in press

strange potentials

talk by C. Pinkenburg


Reminder from QM99: Proton Flow

Elab (AGeV)1 101 10

F (

GeV

/c)

0

0.1

0.2

0.3

PRL 83 1295 (1999)PRL 84 5488 (2000)

n

x

dy

pdFsideward flow

elliptic flow 2cosv2

(Beam)Reaction plane

px

py

pz

F

Momentum space

Transition region for flow mappedF drops as resonances dominateStrong sensitivity to medium contributions to pressureNo single parameterization reproduces flow detailsNo sudden drops in pressure (flow) signaling phase transition

Elab (AGeV)

0.04

-0.08

-0.04

0

1 10

v 2


Beyond protons...

see talk of Chris Pinkenburg today

neural networks identifydecays of neutral strange

particles

• (p+p)•179

1.08 1.10 1.12 1.14Minv (GeV/c2)

0sK

Minv (GeV/c2)

p

production excitation function


flow

PRL accepted (2000) see talk of Chris Pinkenburg today

•“positive” flow

•decreases with Eb (more than

p)

•RQMD (without potential) underpredicts effect

•probe potential at high (complements hypernuclei studies) astrophysical models

“quark counting”

NNN32

p

x

(G

eV

/c)

y/ycm

2 AGeV

6 AGeV

4 AGeV


K0S (anti-)flow

PRL 85 940 (2000) see talk of Chris Pinkenburg today

0-0.5-1.0 0.5 1.0

6 GeV

0

0.1

-0.1

px

(GeV

/c)

RQMD (2.3)data

4 GeV data

y/ycm

Surprise— strong antiflow•grows with collision energy

Transport models:•rescattering insufficient (results in positive flow)

•strong repulsive vector potential required

S. Pal et al, PR C62 061903 (2000)


proton elliptic flow - varying the geometry

“min-bias” flow measurements do not constrain models

geometry provides another handle on flow

increasing spatial asymmetry produces larger signal

Can HBT give geometrical information on flow??

2 AGeV

4 AGeV

6 AGeV

2 4 6 80

0

.02

-.02

-.01

.01

0

-.02

-.04

v2

b (fm)


HBT: probing freeze-out space-time structure I - Cylindrical sources

K

Kt~x~KR

Kx~KR

Kt~x~KR

2llong

2l

2side

2s

2out

2o

xxx~

)K,x(Sxd

)x(f)K,x(Sxdf

4

4

RoutRside

y,xx,x sideout

HBT @ AGS mappedby E895 (QM99)

PRL 84, 2798 (2000)NPA 661, 444c (1999)


HBT: probing freeze-out space-time structure II - Collisions at b0

•Source in b-fixed system: (x,y,z)•Space/time entangled in

pair system (xO,xS,xL)

out

b

K

side

x

y

U. Wiedemann, PRC 57, 266 (1998)MAL, U. Heinz, U. Wiedemann PLB 489, 287 (2000)See Poster by U. Heinz

(several terms vanish @ pT = y = 0)

sinz~x~R

cosz~x~R

t~z~R

2sinx~y~R

x~y~2cosx~y~R

t~x~y~2cosx~y~R

2sl

2ol

22L

22l

22212

os

222122

212

s

22222122

212

o


1st-harmonic oscillations: spatial tilt

angle S

(Beam)

Coordinate space!

x

y

z

s

2nd-harmonic oscillations fromelliptical transverse shape

b

2y~

2x~

x

y

sinz~x~R

cosz~x~R

t~z~R

2sinx~y~R

x~y~2cosx~y~R

t~x~y~2cosx~y~R

2sl

2ol

22L

22l

22212

os

222122

212

s

22222122

212

o

First-order information in HBT()


Data: - correlation functionsAu(4 AGeV)Au, b4-8 fm

• 6 components to radius tensor: i, j = o,s,l

1D projections, =45°

2D projections

2ijji Rqqe1),q(C

lines: projections of 3D Gaussian fit

out side long

C(q

)

E895, PLB 496 1 (2000)


Cross-term radii Rol, Ros, Rsl quantify “tilts” in correlation functions

fit results to correlation functions

Lines: Simultaneous fit to HBT radiito extract underlying geometry


Images of --emitting sources (scaled ~ x1014)

3 fm

x ’

y

2 AGeV

x

zS=47°

x ’

y

4 AGeV

x

zS=37°

x ’

y

6 AGeV

x

zS=33°

Large, positivetilt angles

35.1x~

y~

2

2

similar to naïveoverlap: b~5 fm


Opposing average tilts in p, x and the physics of

flow• “antiflow” (negative tilt in p-space)

• x-space tilt in positive direction non-hydro nature of flow

B. Caskey

RQMD transport model:•Antiflow reflects dense region z~0•(dilute large-|z| show positive flow)

RQMD Au(2GeV)Au

z (f

m)

x (fm)

+ 6 AGeV

pion momentum anisotropies due toreflection from flowing baryons

(N N)

tilt reflects x-space structureof proton flowBass et al [PLB 302 381 (93)]:


Tomography in 6 Dimensions

y

x’

z

x

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

py

px

pz

px

Momentum Space (Flow) Coordinate Space (HBT)

6 AGeV

Tiny flow angle positive v2 Large tilt Out-of-plane


f = occupation of 6-D positionmomentum cell, volume h3

•determines magnitude of multi-particle correlations (lasers)•provides a test of thermalization/consistency

1e

1)p,x(f

)x(T/)x(up

T determines number of , as well as spectral shape

More on position - momentum space relationshipthe phasespace density

G. Bertsch, PRL 72 2349 (94)D. Ferenc et al, PL B457 347 (99)

Experimental access to spatially averaged density

longsideout

TT

3

3T RRR

ddppdyNd

E1

y,pf

volume in p-space

volume in x-space

•observation @ SPS, AGS: “Universal” freeze-out density

• breaks down at lower energies?

Mike Lisa, Quark Matter 2001 20E895 midrapidity

central collisions

•non-universal growth of f with collision energy

•f<1 no condensate

preliminary

Measured phasespace densities


central collisions



•low-pT saturation of f as Ebeam 8 AGeV

•same occupancy as STAR!

preliminary



central collisions





•Rough agreement with thermal Bose-Einstein

•high-pT excess @ high Eb

preliminary



central collisions





•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

preliminaryalso see poster of D. Cebra



Baryon correlations

2 AGeV 4 AGeV 6 AGeVO 8 AGeV

k (GeV/c)0 0.4 0.8 0.12

0

0.6

0.8

1.0

1.2

0.2

0.4

C2

pp correlation function(central collisions, yycm)

• pp correlations ~ Ebeam independent

• another handle on baryon source?k (MeV/c)

0 20 40

0.8

0.2

0.6

0.4

1.0

1.2

1.6

1.4

1.0

1.2

1.8

C2

F. Wang & S. Pratt PRL 83 3139 (1999)

• p more sensitive than pp?• Correct p potential?

-p

p-p


Another E895 first: -p correlation function

•positive correlation observed

•qualitatively different shape than expected from Urbana p- potential

input to the particle physics

•work in progress… 100806040200

C(k

)

1.4

1.0

0.6

1.4

1.0

0.6

k (MeV/c)


Summary I•continuing to push the envelope…

•directed and elliptic flow excitation function•continue input to bulk parameterization

•strange particle flow•positive flow

• does not scale with proton flow (naïve 2/3 rule broken)

• 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


Summary II•azimuthally-sensitive HBT

• almond-shaped source, (~ entrance-channel geometry)• large positive spatial tilt angles• non-hydro nature of flow• coordinate-space structure of proton flow

•6-D phasespace density• non-universal growth of <f> with energy• saturation to “universal” behaviour at 8 AGeV• after 8 AGeV, increased yield pushed to high pT flow

• first p- signal observed• significant positive correlation• inconsistent with shape expected by Urbana potential


More E895 @ QM01

Production & Collective Behaviour of Strange Particles Parallel session today: Chris Pinkenburg

Phasespace Density & Source Charge DensityP063 Dan Cebra

Directed, Elliptic, Radial, & Longitudinal FlowP069 Jenn Klay

Azimuthally-sensitive HBT and the Tilt of the Source

P018 Ulrich Heinz*

* honorary E895 member


Pion and proton elliptic flow

• Ellitpic flow of both positive and negative pions follows the trends of the protons

W. C

askey,

DN

P98

Laying the groundwork at the AGS: Recent results from E895 Mike Lisa, for the E895 Collaboration

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Transcript of Laying the groundwork at the AGS: Recent results from E895 Mike Lisa, for the E895 Collaboration