kaon freeze-out dynamics in √s nn =200gev au+au collisions at rhic
DESCRIPTION
Michal Šumbera NPI ASCR, Prague (for the Pas: Paul Chung, Petr Chaloupka , Richard Lednický , Robert Vertesi ). Kaon Freeze-out Dynamics in √s NN =200GeV Au+Au Collisions at RHIC . 1. Outline. Why and how to extract the source shape? - PowerPoint PPT PresentationTRANSCRIPT
November 6, 2012M.Š. STAR regional mtg.,
Warsaw 11
Kaon Freeze-out Dynamics in √sNN=200GeV Au+Au Collisions at RHIC
Michal ŠumberaNPI ASCR, Prague(for the Pas: Paul Chung, Petr Chaloupka, Richard Lednický, Robert Vertesi)
22
Outline Why and how to extract the source shape?
1D source extraction: previous and recent results
Kaon data analysis details
3D source function extraction via Cartesian surface – spherical harmonic decomposition technique: correlation moments fitting
Comparison to thermal blast wave model
mT- dependence of the Gaussain radii in LCMS
ConclusionsM.Š. STAR regional mtg.,
WarsawNovember 6, 2012
33
Technique devised by
D. Brown and P. DanielewiczPLB398:252, 1997 PRC57:2474, 1998 Emitting source
Kernel is independent of freeze-out conditions
ÞModel-independent analysis of emission shape(goes beyond Gaussian shape assumption)
Source imagingInversion of linear integral equation
to obtain source function
Source function(Distribution of pair separations in pair
rest frame)
Encodes FSI
Correlationfunction
1D Koonin-Pratt equation
M.Š. STAR regional mtg., WarsawNovember 6, 2012
44
Inversion procedure
Freeze-out occurs after last scattering. Þ Only Coulomb & quantum statistics effects included the kernel.
Expansion into B-spline basis
M.Š. STAR regional mtg., WarsawNovember 6, 2012
5
Particle correlations at low relative momenta:How far we can go and what it means for the source function.(1D example)
M.Š. STAR regional mtg., WarsawNovember 6, 2012
6
Particle correlations at low relative momenta:How far we can go and what it means for the source function.(1D example)
M.Š. STAR regional mtg., WarsawNovember 6, 2012
7
Particle correlations at low relative momenta:How far we can go and what it means for the source function.(1D example)
M.Š. STAR regional mtg., WarsawNovember 6, 2012
8
Particle correlations at low relative momenta:How far we can go and what it means for the source function.(1D example)
M.Š. STAR regional mtg., WarsawNovember 6, 2012
9
Particle correlations at low relative momenta:How far we can go and what it means for the source function.(1D example)
M.Š. STAR regional mtg., WarsawNovember 6, 2012
10
Previous 1D source imaging results PHENIX, PRL 98:132301,2007 PHENIX, PRL 103:142301,2009
Observed long non-gaussian tails attributed to non-zero particle emision duration and contribution of long-lived resonances
M.Š. STAR regional mtg., WarsawNovember 6, 2012
11
Pions: STAR Run 4 vs PHENIX
Excellent point by point agreement!!!November 6, 2012
M.Š. STAR regional mtg., Warsaw
TPC
12
Kaon data analysis20% most central Au+Au @ √sNN=200 GeV Run 4: 4.6 Mevts, Run 7: 16 Mevts30% most central Au+Au @ √sNN=200 GeV Run 4: 6.6 Mevts
Particle ID selection via TPC dE/dx: NSigmaKaon<2.0 && NSigmaPion>3.0 && NSigmaElectron>2.0
|y| < 0.5 & 0.2 < pT < 0.4 GeV/c
dE/dx vs rigidity: before
after PID cuts
M.Š. STAR regional mtg., WarsawNovember 6, 2012
13
Kaon PID @ 0.2<pT<0.36 GeV/c Au+Au (0-30%)
-1.5<Number of Sigma<2.0
Rigidity (GeV/c)
Rigidity (GeV/c)
dE/dx
No PID selection
STAR PRELIMINARY STAR PRELIMINARY
M.Š. STAR regional mtg., WarsawNovember 6, 2012
14
Kaon PID @ 0.36<pT<0.48 GeV/cAu+Au (0-30%)
-0.5<Number of Sigma<2.0
Rigidity (GeV/c)Rigidity (GeV/c)
dE/dx
No PID selection
STAR PRELIMINARYSTAR PRELIMINARY
M.Š. STAR regional mtg., WarsawNovember 6, 2012
STAR kaon 1D source shape result
15
PHENIX, PRL 103:142301,2009
34M+83M=117M K+K+ & K-K- pairs
STAR data arewell described by Gaussian.Contrary toPHENIX no non-gaussiantails are observed.
May be due to a differentkT-range:STAR bin is4x narrower.
M.Š. STAR regional mtg., WarsawNovember 6, 2012
3D source shape analysis:Spherical Harmonics basis
The disadvantage of expansion in the spherical harmonics Yℓm: connection between the geometric features of the real source function S(r) and the complex valued projections Sℓm(r) is not transparent.
The Yℓm harmonics are convenient for analyzing quantum angular momentum, but are clumsy for expressing anisotropies of real-valued functions.
16November 6, 2012M.Š. STAR regional mtg.,
Warsaw
Cartesian harmonics basis• Based on the products of unit vector components, nα1 nα2 ,
…, nαℓ . Unlike the spherical harmonics they are real.• Due to the normalization identity n2
x + n2y + n2
z = 1, at a given ℓ ≥ 2, the different component products are not linearly independent as functions of spherical angle.
• At a given ℓ, the products are spanned by spherical harmonics of rank ℓ′ ≤ ℓ, with ℓ′ of the same evenness as ℓ.
17M.Š. STAR regional mtg.,
WarsawNovember 6, 2012
18
3D Koonin-Pratt:
Plug (1) and (2) into (3)
Invert (1)
Invert (2)
Danielewicz and Pratt, Phys.Lett. B618:60, 2005
Þ
Þ
Þ
x = out-directiony = side-directionz = long-direction
ai = x, y or z
M.Š. STAR regional mtg., WarsawNovember 6, 2012
3D source shape analysis:Cartesin Harmonics basis
19
C0(qinv) vs. C(qinv): comparison
K+K+ & K-K- l=0 moment
C0(qinv)
C(qinv)
M.Š. STAR regional mtg., WarsawNovember 6, 2012
20
Run4 Kaon CF: l=0 moment
l=0 moment in agreement with 1D C(q)M.Š. STAR regional mtg.,
WarsawNovember 6, 2012
• Fit to the 3D correlation function with a trial functional form for S(r).
• Trial function: 4-parameter ellipsoid (3D Gaussian)
• Since the 3D correlation function has been decomposed into its independent moments, this is equivalent to a simultaneous fit of 6 independent moments with the trial functional form.
21
Extracting 3D source function S(r)
M.Š. STAR regional mtg., WarsawNovember 6, 2012
22
Independent correlation moments Rl
α1…αl , 0≤l≤4Extracted 3D Gaussianfit parameters:λ = 0.48 ± 0.01rx = (4.8 ± 0.1) fmry = (4.3 ± 0.1) fmrz = (4.7 ± 0.1) fm
N.B. Contributionsdecrese with increasing ℓ. For ℓ > 4 are zero.
M.Š. STAR regional mtg., WarsawNovember 6, 2012
23
Independent correlation moments Rl
α1…αl , 0≤l≤4With two 3D Gaussiansfit gets even worse:λ1 = 0.48 ± 0.01rx1 = (4.7 ± 0.1) fmry1 = (4.4 ± 0.1) fmrz1 = (4.6 ± 0.1) fmλ2 = 0.16 ± 0.10rx2 = (38 ± 17) fmry2 = (0.6 ± 0.6) fmrz2 = (46 ± 31) fm
M.Š. STAR regional mtg., WarsawNovember 6, 2012
24
Kaon 3D Gaussian Fits 0<cent.<30%
3D Gaussian shape provides an adequate representation at both kT binsM.Š. STAR regional mtg.,
WarsawNovember 6, 2012
0.20<kT<36 GeV/c 0.36<kT<48 GeV/c
25
Kaon correlation function profilesC(qx) C(qx,0,0)
C(qy) C(0,qy,0)
C(qz) C(0,0,qz)
M.Š. STAR regional mtg., WarsawNovember 6, 2012
P. Chung, STAR, arXiv:1012.5674 [nucl-ex]
26
Kaon vs. pion 3D source shape
Pion and kaon 3D source shapes are very different: Is this due to the different dynamics?
PRL 98:13230
Very good agreement on 3D pion source shape between PHENIX and STAR
PRL 98:13230
M.Š. STAR regional mtg., WarsawNovember 6, 2012
Comparison to thermal BW model
27
Therminator (A. Kisiel et al., Phys. Rev. C 73:064902 2006) basic ingredients:
1. Longitudinal boost invariance.
2. Blast-wave expansion with transverse velocity profile semi-linear in transverse radius ρ: vr(ρ)=(ρ/ρmax)/(ρ/ρmax+vt). Value of vt =0.445 comes from the BW fits to particle spectra from Au+Au @ 200GeV: STAR, PRC 79:034909, 2009.
3. Thermal emission takes place at proper time t, from a cylinder of infinite longitudinal size and finite transverse dimension ρmax.
Freeze-out occurs at t = t0 +aρ. Particles which are emitted at (z, ρ) have LAB emission time t2 = (t0 +aρ)2+z2 .
Emission duration is included via Δt.
STAR preliminary
M.Š. STAR regional mtg., WarsawNovember 6, 2012
28
And to the HYDJET++ modelTherminator: Comp.Phys.Com. 174, 669 (2006) HYDJET++: Comp.Phys.Com. 180, 779 (2009)
HYDJET++ gives larger source lifetime than TerminatorM.Š. STAR regional mtg., WarsawNovember 6, 2012
29
mT-dependence of the radii in LCMS
M.Š. STAR regional mtg., WarsawNovember 6, 2012
Buda-Lund: arXiv:0801.4434v2HKM: PRC81, 054903 (2010)
Rout=Rx/γ , Rside=Ry , Rlong=Rz
Buda-Lund describes mT–dependence of Rout & Rside but fails for Rlong at low mT Þ violation of mT -scaling between pion and kaon Gaussian radii.
HKM is more representative of fireball expansion dynamics than the simpler perfect fluid hydrodynamics.
30
Conclusions First model-independent extraction of kaon 3D source shape. Source function of mid-rapidity, low-momentum kaons from
central Au+Au collisions at √sNN=200 GeV is Gaussian – no significant non-Gaussian tail is observed.
Comparison with Therminator model indicates kaon emission from a fireball with transverse dimension and lifetime which are consistent with values from two-pion interferometry.
3D source function shapes for kaons and pions are very different. The narrower shape observed for the kaons indicates a much smaller role of resonance decays and/or of the exponential emission duration width ∆τ on kaon emission.
M.Š. STAR regional mtg., WarsawNovember 6, 2012
31
Conclusions The Gaussian radii for the kaon source function display
monotonic decrease with increasing transverse mass mT over the interval of 0.55≤ mT ≤ 1.15 GeV/c2.
In the outward and sideward directions this decrease is adequately described by the mT –scaling. However, in the longitudinal direction the scaling is broken, favoring the HKM model as more representative of the expansion dynamics of the fireball than the simpler perfect fluid hydrodynamics.
M.Š. STAR regional mtg., WarsawNovember 6, 2012
32
Backup slides
M.Š. STAR regional mtg., WarsawNovember 6, 2012
33
Momentum resolution correction1D C(q) Corrected vs C(q)
UnSmeared1D C(q) UnSmeared vs C0 (q) UnSmeared)
STAR preliminary
STAR preliminary
M.Š. STAR regional mtg., WarsawNovember 6, 2012
Two-pion Correlation Function from Run4 Au+Au 200GeV:Run4 Tracker vs ITTF
Paul ChungNuclear Physics Institute ASCR
Prague
BulkCorr PWG29.06.2011 34
Run4 vs Run4 P10ik: Tracker Effect
29.06.2011 BulkCorr PWG 35
Tracker ITTF significantly underestimates CF Essentially no effect of centrality definition
Run4 P10ik vs Run7 & Run10
29.06.2011 BulkCorr PWG 36
Run4 P10ik agrees with Run7 P10ik Run4 P10ik disagrees with Run10 P10ik
BulkCorr PWG 37
Conclusion
Run 4 CF significantly different from Run 4 P10ik => Direct effect of tracker change
Run 4 P10ik in reasonable agreement with Run 7 P10ik => Use of same tracker gives same result
Run 4 P10ik in sharp disagreement with Run 10 P10ik => very confusing state of affairs
=> Need to check effect of Run 4 tracker on Run 10 data
29.06.2011 37
38
Buda-Lund and HKM Comparison
M.Š. STAR regional mtg., WarsawNovember 6, 2012
Buda-Lund: arXiv:0801.4434v2HKM: PRC81, 054903 (2010)
Rout=Rx/γ , Rside=Ry , Rlong=Rz
Buda-Lund describes mT–dependence of Rout & Rside but fails for Rlong at low mT Þ violation of mT -scaling between pion and kaon Gaussian radii.
HKM is more representative of fireball expansion dynamics than the simpler perfect fluid hydrodynamics.