Transcript Centrality classification

Определение центральности столкновения ядер
с использованием калориметра cпектаторов
в эксперименте MPD@NICA
M.Golubeva, F.Guber, A.Ivashkin, A.Kurepin,
INR, Moscow
A.Litvinenko, E.Litvinenko, A.Isupov, I.Migulina,
V.Peresedov, JINR, Dubna
A.Litvinenko, [email protected]
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Outline
 Introduction
Some definitions
Spectators
 UrQMD generator
 LAQGSM generator
 UrQMD - SHIELD - LAQGSM
 Conclusions
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NICA
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MPD
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Nuclear-Nuclear collisions
 Quasi-Classical picture
b – not observable
 observables
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b
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Centrality classification
2R
 geo  2  bdb   (2 R) 2
Geometrical cross section
0
Value of impact parameter
b  2  4 fm (2  8%)
In percent from the geometrical cross section
b
σ ( b)  2π  bdb  π ( b) 2 ;
σ (bmin ) σ (bmax )


σ geo
σ geo
2
2
 b min   b max 

  
 ( %)
 2RA   2RA 
0
Corresponds to the region impact parameter
Centrality
40  50 %
bmin  0.4 (2R)  0.63(15)fm 9.5fm
bmax  0.5 (2R)  0.71(15)fm 10.6fm
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Centrality classification
1.
bmin  b  bmax (fm)
Impact parameter
2. Fraction from total cross-section
2
2
 b min   b max 

  
 ( %)
 2R A   2R A 
3. Number of participant
…. ?
N part .
Centrality classification
8
The importance of the centrality classification
Space eccentricity
Elliptic flow
dN
1

(1  2v1 cos  2v 2 cos 2  ...)
d
2
v2
A2 =
ε
Nuclear Physics A
V757, No. 1-2 , p.184,2005
elliptic flow scaling
with space eccentricity
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short equlibration time
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The importance of the centrality study
Nuclear modification factor
Nuclear Physics A
V757, No. 1-2 , p.184,2005
Jet Quenching – nuclear modification
factor vs centrality
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The importance of the centrality study
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Nucleon spectators (spectrum)
  Em  p(backward)  X
~
 Em  pX
  Pb  nX
 C  nX
R.Ammarи et al., Pisma v JETF,
V.94, No. 4, p.189, (1989)
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Yu.Bayukov et al ., YaF
V.35, No. 4, p.960, (1982)
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Spectator spectrum
d
E 3  C  e xp(-T/T0 )
dp
T0  5 - 10 МэВ
PS PF - m 2N
d
E 3  C  e xp()
dp
m N T0
(p - pb ) 2
dσ
Θ2
E 3 = C • exp() • exp(- 2 )
2
dp
2σ p
2σ Θ
p 
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EbT0
mNT0
 0.15- 0.22GeV/c;   
 0.016- 0.022
2
mN
pb
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Front view of ZDC. The squares size is 5 x 5 cm x cm
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ZDC@MPD geometrical efficiency
 (ZDC)  NS (ZDC) / NS (tot.)
central hole
2


rint/L ZDC e xp(- 2 )d )
2 
 ( ZDC) 
2

0 e xp(- 2 )d )
2 
 50  70 %
out of ZDC
ε ( ZDC) > 0.99
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Simulation
Transport – Geant3 and Geant4, generates UrQMD and LAQGSM
framework MpdRoot
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Optimistic results with UrQMD
URQMD generator, Sqrt(S)=5 GeV
Total kinetic energy of all nucleons
directed to ZDC
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Optimistic results with UrQMD
UrQMD generator, Sqrt(S)=9 GeV
ε=
ΔEZDC
( S NN - 2mN )A
= 0.78
Total kinetic energy of all nucleons
directed to ZDC
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The accuracy of impact parameter
determination for MC with UrQMD
N(b) = A • b + C ;ΔN = N ;
δN = 1/ N(b)
E(b) = Tb • N(b); ΔE = Tb • N ; δE = 1/ N(b)
N(b)
N(b) - C
1
b=
; Δb =
N(b); δb =
A
A
N(b) - C
b = 0 fm ; Δb = 0.35fm; δb =
E(b) = 114Ge V; ΔE = 20 Ge V; δE = 18 %
b = 5 fm ; Δb = 0.67fm; δb = 13 %
E(b) = 392Ge V; ΔE = 38 Ge V; δE = 10 %
b = 10 fm ; Δb = 0.87fm; δb = 9 %
E(b) = 673Ge V; ΔE = 49 Ge V; δE = 7 %
ΔE
β
=
;
E
E
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β << 150%
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The centrality resolution evaluations √S=9 AGeV
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But
The NA49 collaboration. Eur. Phys. J., A2, 383, (1998)
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But
LAQGSM high-energy event generator
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Taking into account spectator fragments
LAQGSM generator, Sqrt(S)=5 GeV
Total kinetic energy of all nucleons
and fragments directed to ZDC
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Taking into account spectator fragments
LAQGSM generator, Sqrt(S)=9 GeV
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Total kinetic energy of all nucleons
and fragments directed to ZDC
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SHIELD event generator
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LAQGSM, Sqrt(S)=5 GeV
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URQMD, Sqrt(S)=5 GeV
Total kinetic energy of all nucleons
and fragments directed to ZDC
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Experimental data : the deposited energy for different
types of spectators in dependence of the centrality
The NA49 collaboration. Eur. Phys. J., A2, 383, (1998)
At large impact parameters the most of
spectator nucleons are bound in fragments.
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All nucleons directed to the hole of ZDC
(rectangle 10x10cm2)
0 % - 60 %
60 % - 80 %
80 % - 100 %
θ ~ 0.3 • 10-3 rad = 0.3 mrad
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Experimental data : the deposited energy for different
types of spectators in dependence of the centrality
The NA49 collaboration. Eur. Phys. J., A2, 383, (1998)
At large impact parameters the most of
spectator nucleons are bound in fragments.
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The centrality resolution evaluations
√S=9 AGeV
Kinetic energy of all spectators directed to solid angle 5º
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The centrality resolution evaluations √S=9 AGeV
The centrality resolution evaluations √S=9 AGeV
The centrality resolution evaluations √S=9 AGeV
The centrality determination:
ZDC (energy) + number of charged barrel tracks
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UrQMD - SHIELD - LAQGSM
b < 3 фм (0 – 4 %)
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UrQMD - SHIELD - LAQGSM
3 фм < b < 9.5 фм (4 – 40 %)
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UrQMD - SHIELD - LAQGSM
9.5 фм < b
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(40 – 100 %)
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Centrality determination in some experiment
PHENIX
NA49
STAR
y=0
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NA49
ZDC Only
STAR
TPC only
PHENIX
BBC & ZDC
y=3
y>6
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Conclusions
• The SHIELD and LAQGSM could be used
for NICA/MPD simulations under mpdroot.
• The SHIELD and LAQGSM angular
distributions of the spectators differ from
URQMD picture.
• The experimental study of the spectator
distributions and calorimeter resolution have
to be performed on the extracted beam of
NUCLOTRON-M at the fixed target.
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Conclusions
• Работа выполнена при
поддержке грантов РФФИ
10-02-01036-а
11-02-01026-а
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Backup slides
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Fast evaluations: the movement of spectators at NICA/MPD
Y X pb

 0.3Q B z 
pT A

sin
x( z ) 
0.3Q B  p z A 


 y( z )  p T A cos 0.3Q B z  - p T A
 p A  0.3Q B

0.3
Q
B
z



Z
B 1T

 0.3Q B z  
pT A
 
(B, z )  x  y 
2 1  cos
0.3Q B 
 pz A  
2
2
 0.3QB  z 
pT
1  0.3QB  z 

  0.2   ( B, z ) 

z ;   
pz
2  pz A 
 pz A 
The conclusion:
Magnetic field of MPD will not change the polar angles
for spectators at ZDC position
 it will only slightly changes the azimutal angles
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  pT / p z
  60
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Centrality classification
C.E.Aguilar et al., Brazilian Journal of Physics, V.34,No.1,p.319,(2004)
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Calorimeter No.1
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Calorimeter No.1
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Calorimeter No.1
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Calorimeter No.1
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Linearity
Resolution
Longitudinal distribution
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Calorimeter No.1
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CONCLUSION
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Пространственное разрешение
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ZDC
N part
E ZDC (GeV )
Pz (GeV / c)
Pz (GeV / c)
N part
N part
Px (GeV / c)
Pz (GeV / c)
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Pz (GeV / c)
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ZDC + Multiplicity
N ch
1000 Min Bias
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ZDC + Multiplicity
N ch
N ch
N ch
N ch
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1000 Min Bias
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PHENIX
ZDC + BBC
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NA49
VCAL (ZDC)
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TIME = 0 fm/c,
  0.7
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TIME = 1 fm/c,
  0.6
66
TIME = 2 fm/c,
  0.5
67
TIME = 3 fm/c,
  0.3
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