centrality determination and reaction plane reconstruction with mpd d.dryablov, v. zhezher,...
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Centrality Determination and Reaction plane reconstruction with MPD
D.Dryablov, V. Zhezher, M.Kapishin, G.Musulmanbekov
XIV GDRE Workshop, Dubna 12 - 14 December 2012
TopicsMotivation
Event Generators
MPD Layout
Reaction Plane Reconstruction with ExtZDC
Definitions
MC estimation of efficiency of ExtZDC
Determination of Centrality
by TPC
by ExtZDC
Results of RP reconstruction
Plans for the Future
XIV GDRE Workshop, Dubna 12 - 14 December 2012
Motivation: Why do we need RP reconstruction?
Physics Tasks at semi-central nucleus-nucleus collisions:
Elliptic Flow of mesons, nucleons and hyperons, hypernuclei
Direct Flow of nucleons, hyperons and hypernuclei
Femtoscopy Correlations w.r.t. RP
Global polarization (w.r.t. RP) of hyperons (Λ, Ξ, Ω)
Vector mesons alightment w.r.t. RP , measured by dilepton yield asymmety
Charge asymmetry w.r.t. RP, CME
Selection ofSemi-central collisions Centrality Determination
XIV GDRE Workshop, Dubna 12 - 14 December 2012
Event Generators: UrQMD vs LAQGSM
QGSMUrQMD
UrQMD QGSM
XIV GDRE Workshop, Dubna 12 - 14 December 2012
Event Generators
LAQGSM K. Gudima et al. LA-UR-01-6804
• minbias events: 105 for √s = 3, 5, 7, 9, 11 GeV
• semi-central events: 105 for √s = 7 GeV
GLISSANDO – GlauberMC W. Broniowski et al., CPC, 2008
• any statistics at any energy
In prospect:
UrQMD add-on: A. Polanski, G. Musulmanbekov, ISHEPP’2012• residual nucleus• evaporation• multifragmentation
XIV GDRE Workshop, Dubna 12 - 14 December 2012
Length of TPC -340 cm, D=300cm
ExtZDCExtZDC
Last MPD layout
XIV GDRE Workshop, Dubna 12 - 14 December 2012
“Old” and Extended ZDC
cell 10 x 10 (cm x cm)XIV GDRE Workshop, Dubna 12 - 14 December 2012
Extended ZDC detector
XIV GDRE Workshop, Dubna 12 - 14 December 2012
Simulation of Extended ZDC within mpdroot:
• L ≈ 120 cm
• 5 < R < 61 cm (radius of the inscribe circle)
• dcell = 10x10 cm
• z0 = 365 cm (distance from the int. point to ZDC)
• 0.8o < θ < 9.3o (covered zenith angle)
• 2.5 < η < 5.0 (covered pseudorapidity range)
x
yExtZDC
Reaction Plane: Definitions
initial spatial anisotropy anisotropy in momentum spacex
y z
py
px
y 2 x 2
y 2 x 2
v2 px
2 py2
px2 py
2
-/4
y
x
/43/4
-3/4
“In-plane” region
“Out-of-plane” region
Reaction plane defined by (1) beam direction and (2) impact parameter
XIV GDRE Workshop, Dubna 12 - 14 December 2012
Definitions: Flows
1-st Fourier harmonics → directed flow
2-nd Fourier harmonics → elliptic flow
))-cos(φ2v +(12πφ Rn∑ totN
d
dN
ψR
XIV GDRE Workshop, Dubna 12 - 14 December 2012
Definitions: Reaction Plane reconstruction
Reactio
n plane
x
y
Reactio
n plane
x
y
Σ wi*sin(2i) tan(22) =
Σ wi*cos(2i)
21
Σ wi*sin(i) tan(1) =
Σ wi*cos(i)
plane with the directed moment
plane with the elliptic moment
(wi: 1 or pT)
i
i
ShinIchi Esumi
XIV GDRE Workshop, Dubna 12 - 14 December 2012
Method 1:
2222,
,φcos;φsin;
φcos
φsinarctanφ
∑∑
ii
ii
ii
ii
iivis
iivisLR
xy
x
xy
y
E
E
Method 2:
;
∑∑
,
,arctanφ
iivis
iivisLR
xE
yE
Reaction Plane reconstruction with ExtZDC
x
yExtZDC
XIV GDRE Workshop, Dubna 12 - 14 December 2012
Problem of identification:directed flows of pions and nucleons have opposite signs !
So are orientations of RPs defined by them!
XIV GDRE Workshop, Dubna 12 - 14 December 2012
ΔΨR vs impact parameter
200 GeV
Selection of Semi-Central Events XIV GDRE Workshop, Dubna 12 - 14
December 2012
Reaction Plane Reconstruction
3 GeV
ExtZDC acceptance
XIV GDRE Workshop, Dubna 12 - 14 December 2012
Extended ZDC detector
5 GeV
ExtZDC acceptance
XIV GDRE Workshop, Dubna 12 - 14 December 2012
Extended ZDC detector
7 GeV
ExtZDC acceptance
XIV GDRE Workshop, Dubna 12 - 14 December 2012
Extended ZDC detector
9 GeV
ExtZDC acceptance
XIV GDRE Workshop, Dubna 12 - 14 December 2012
Extended ZDC detector
11 GeV
ExtZDC acceptance
XIV GDRE Workshop, Dubna 12 - 14 December 2012
Selection of events by centrality in TPC
Impact parameter b: 0 - 3 fm 3 – 6 fm 6 – 9 fm 9 – 12 fm
Fraction of σincltot : 0 - 5% 5 – 15% 15 – 30% 30 – 60%
Total multiplicity of charged tracks is a measure of impact parameter b (and centrality of nucleus-nucleus interaction)
Semi-Central Events XIV GDRE Workshop, Dubna 12 - 14
December 2012
Selection of events by centrality in TPC
LAQGSM Minbias events, √s = 9 GeV
XIV GDRE Workshop, Dubna 12 - 14 December 2012
Selection of events by centrality in TPC
LAQGSM Minbias events, √s = 9 GeV
- 5 – 9 fm, semi-central eventsXIV GDRE Workshop, Dubna 12 - 14
December 2012
Selection of centrality: Nparticipants
GlauberMC Minbias events, √s = 9 GeV
- 5 – 9 fm, semi-central eventsXIV GDRE Workshop, Dubna 12 - 14
December 2012
Selection of events by centrality in ExtZDC
LAQGSM Minbias events, √s = 9 GeV
- 5 – 9 fm, semi-central eventsXIV GDRE Workshop, Dubna 12 - 14
December 2012
Selection of events by centrality in ExtZDC
LAQGSM Minbias events, √s = 9 GeV
XIV GDRE Workshop, Dubna 12 - 14 December 2012
Selection of events by centrality in ExtZDC
LAQGSM Minbias events, √s = 9 GeV
- 5 – 9 fm, semi-central eventsXIV GDRE Workshop, Dubna 12 - 14
December 2012
RP reconstruction by Extended ZDC detector
• No particle identification
• Geant 4 , QGSP_BIC physics model
• Systematic effect of magnetic field:
~1o at 9 AGeV increases to
~3o at 3 AGeV
x
yExtZDC
∑∑
,
,arctanφ
iivis
iivisLR
xE
yE
XIV GDRE Workshop, Dubna 12 - 14 December 2012
Resolution δφRP and <cos δφRP> vs b
M. Kapishin 2012
RP reconstruction by Extended ZDC detector
XIV GDRE Workshop, Dubna 12 - 14 December 2012
• Extended ZDC detector (2.2<η<4.8) provides RP measurement at medium b (4<b<10 fm) with resolution of δφRP~22-35o in AuAu collisions at energies 5-9 AGeV, RP resolution deteriorates to δφRP~45-65o at 3 AGeV
• Sensitivity of extended ZDC to RP azimuthal angle in central (b<3 fm) and peripheral collisions (b>12 fm) is much weaker
• QGSM and UrQMD models give consistent results for RP resolution of extended ZDC, model dependence increases at low beam energies
• ZDC cell size and length is not critical: dcell=10x10cm, L=60cm are sufficient for RP measurement. ZDC length is more crucial for energy flow measurement
• Magnetic field systematics to φRP is ~1o at 9 AGeV which increases to ~3o at 3 AGeV. Reduced magnetic field at the lowest energy would decrease systematics
Summary
M. Kapishin 2012
XIV GDRE Workshop, Dubna 12 - 14 December 2012
7 GeV
Protons + neutrons +pionsprotons + neutrons
7 GeV
no particle identification
RP reconstruction by MC in Extended ZDC acceptance
7 GeV
<Δψ1> = 34o<Δψ1> = 33.8o R = 0.83 R = 0.83
RP resolution, R = <cos(Δψ1)>
XIV GDRE Workshop, Dubna 12 - 14 December 2012
Dependence of RP resolution on size of Extended ZDC
XIV GDRE Workshop, Dubna 12 - 14 December 2012
Protons + neutrons
Dependence of RP resolution on size of Extended ZDC
XIV GDRE Workshop, Dubna 12 - 14 December 2012
Protons + neutrons+pions
Plans for RP reconstruction:
1. Include ExtZDC channel-by-channel Eloss in DST,
2. Estimate the resolutions needed for the physical tasks.
XIV GDRE Workshop, Dubna 12 - 14 December 2012
Thank You!
XIV GDRE Workshop, Dubna 12 - 14 December 2012
Reaction plane resolution vs. numbers of particle and value of the flow
XIV GDRE Workshop, Dubna 12 - 14 December 2012
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