Download - Why transport model? Space-time (x-t) correlation: its effect on R out/ R side Extract radii from
SQM2003 March 13 Zi-wei Lin The Ohio State University
● Why transport model?
● Space-time (x-t) correlation:its effect on Rout/Rside
• Extract radii from1) emission function S(x,K) 2) Gaussian fits to 3-d C(Q,K)
non-Gaussian emission source
● Summary and Outlook
Zi-wei Lin The Ohio State Universityin collaboration with C.M. Ko
Kaon HBT at RHIC from AMPT Model
SQM2003 March 13 Zi-wei Lin The Ohio State University
Rout/Rside ~1up to Kt~1GeV
from S. Johnson at RWW02
●Inconsistent with the hydro model.
● Puzzling considering the “common” relations:
SQM2003 March 13 Zi-wei Lin The Ohio State University
Why transport model?
● HBT probes the space-time information of particles at freezeout
● In transport models, hadrons freeze out dynamically (both chemical and kinetic freezeout),
when mean-free-path is too large:
Transport models may have some advantages to address HBT
SQM2003 March 13 Zi-wei Lin The Ohio State University
HIJINGenergy in strings and minijet partons
ZPC (Zhang's Parton Cascade)
till parton freezeout
ART (A Relativistic Transport model for hadrons)
A+A
Strong-decay resonances for final particle spectra
A Multi-Phase Transport (AMPT) model with String Melting
Fragment excited strings into quarks and antiquarks (via Lund frag. to hadrons)
Nearest quark coalescence to hadrons
Z.W.L. &C.M.Ko,PRC65
SQM2003 March 13 Zi-wei Lin The Ohio State University
An central Au+Au event at 130AGeV from AMPT model(no string melting here)
SQM2003 March 13 Zi-wei Lin The Ohio State University
Definitions:
in the Pratt-Bertsch out-side-long system
xi(1-3)=xout, xside, xlong
qi(1-3)=Qout, Qside, Qlong
=> Rinv
2
=> Rout, Rside, Rlong
Pratt, PRD33
Pratt et al,PRC42
Bertsch et al,PRC37
SQM2003 March 13 Zi-wei Lin The Ohio State University
Method 1 to extract radii:From emission function S(x,K): curvature at q=0
Pratt,PRL84
Pratt,PRL84
Wiedemann,PRC57
Dx,y=<x*y>-<x><y>
.
SQM2003 March 13 Zi-wei Lin The Ohio State University
out-side out-t
Emission function (at freezeout):
positive xout-t correlation
K:200<pt<400 MeV -1<y<1
SQM2003 March 13 Zi-wei Lin The Ohio State University
(3.4fm)^2 = (35 - 2 * 22 + 20) fm^2
from the emission function:
Spatial-size
xout-t correlation
duration-time part
K:200<pt<400 MeV -1<y<1
is positive and large
reduces Rout and Rout/Rside
Complicates the extraction of the duration time from
Mangnitude of the xout-t correlation
SQM2003 March 13 Zi-wei Lin The Ohio State University
out-side out-t
also positive and large, reduces Rout/Rside
(17fm)^2 = (185 - 2*168 + 431) fm^2
pi:125<pt<225 MeV -1<y<1
Similar to the pion case: Z.W.L.,C.M.Ko&S.Pal,PRL89
from the emission function:
SQM2003 March 13 Zi-wei Lin The Ohio State University
Experimentally, from 4-parameters Gaussian fits of C(q) (w/o Coulomb effects):
Pratt,PRL84
.
Method 2 to extract radii:
If source is Gaussian in space-time, then:
and Method1= Method2
BUT
if source is non-Gaussian in space-time:e.g., see
D.Hardtke&S.Voloshin,
PRC61Method1= Method2
SQM2003 March 13 Zi-wei Lin The Ohio State University
source radii vs fitted radii
Difference is up to 30%
decays are not included in
source radii)
Source radii are much larger
if decays are included.
Fitted radii should be used for fair comparison with data, as source radii suffer from non-Gaussian source
SQM2003 March 13 Zi-wei Lin The Ohio State University
Rout/Rside from the 2 methods:
SQM2003 March 13 Zi-wei Lin The Ohio State University
● xout-t correlation from emission function from AMPT model:
is large & positive tends to reduce Rout and Rout/Rside
complicates the extraction of emission duration time same for pions
●Radius parameters extracted from 2 methods:
1) from spatial correlation of the emission source
2) from Gaussian fits to 3-d C(Q) difference is up to 30% for K (even when decays are not included) 2) should be used for comparison with data
Summary
SQM2003 March 13 Zi-wei Lin The Ohio State University
1) Need parton subdivision to avoid causality violation
2) Current approach in AMPT model with string melting:
partons coalesce when they freezeout in parton cascade
local density at hadronization controled by p (cross
section)local density is directly related with collective flow
(v2, ...)investigate coalescence when local energy density < critical value
3) Resonance abundances (K*, ) from quark coalescence need
further study (at least constrained by data) for quantitative
statements
4) Investigate the origin of the large & positive xout-t correlation
Outlook