0 dai-mei zho u (iopp/ccnu) collaboration with: yun cheng (ccnu) xu cai (ccnu) yu-liang yan (ciae)...
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Dai-Mei Zhou (IOPP/CCNU)
Collaboration with: Yun Cheng (CCNU)Xu Cai (CCNU)Yu-Liang Yan (CIAE)Bao-Guo Dong (CIAE)Ben-Hao Sa (CIAE)
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3 Roughly fitting model parameters to dNch/dy
1 Motivation
2 Physical ingredients in PACIAE
)(2 v4 Results of & )(2 TPv
Au+Au @ 0.2 TeV Pb+Pb @ 2.76 TeV p+Au @ 0.2 TeV and p+Pb @ 5.02 TeV p+p @ 7 TeV
Conclusions 5
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Motivation 1
Two-particle cumulant
Four-particle cumulant
Six-particle cumulant
Event plane method
Lee-Yang zero point method
Cumulant method
is important observable relevant to the exploring of sQGP2v
measurement is such hard that (10-100)% discrepancy may exist among methods2v
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In order to meet with data, they have to update AMPT_def to AMPT_sm, for instance, by
(B) enlarge parton cross section from 3 mb to 10 mb
(A)Melting hadrons (strings) from HIJING to partons to amplify parton rescattering (generates the large enough pressure)
(C) parton hadronized with coalescence rather than string fragmentation
conventional hadronic transport (cascade) models underestimated experimental data: UrQMD, AMPT(def) , & PACIAE 2.0 etc.,
2v
(a lack of pressure in the model may be the reason and that the partonic interactions have to be taken into account )
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final momentum space asymmetry:
t
pT
yx
p p
ppvel
2
22
2arg
)1(
)1(
rA
rA
Rb
Ra
Half minor axis of the ellipse
Half major axis of the ellipse
Dynamical evolution of asymmetry
Initial spatial space asymmetry:
Almond-like
(ellipse)
the radius of nucleusAR
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However, in PYTHIA (PACIAE2.0) particle momentum from SF (string fragmentation)
This symmetry arrange strongly cancels the final hadronic state transverse momentum asymmetry
)sin(),cos( TyTx pppp
sampled according to exponential/Gaussian distribution
arranged on the circle withradius of Tp
azimuthal angle of particle transverse momentum
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We modify it by
)sin()1(),cos()1( pTypTx pppp
With extra deformation parameter , experimental data are then able to be better described.
p 2v
Comput. Phys. Commun., 184(2013)1476.
On the circumference of an ellipse
half major axis half minor axis
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rp C
Parameter of can be related to the deformation parameter of in the initial spatial phase space as
pr
pan extra model parameter instead of
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22
xy
xyrp
222
222 ,
yy
xx
y
x
Spatial reaction plane eccentricity:
the average over the nucleon spatial distribution
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2
22
bab
grp
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2rp
r
geometrical eccentricity of the initial spatial overlap zone
p
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The participant eccentricity
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2222 4
xy
xyxypa
2
22 122
pa
papar
yxxyxy
pfor the p+p and p+A collisions one can only regard itself as an extra model parameter
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The Fourier expansion of particle transverse momentum azimuthal distribution reads
,...2,1
2
3
3
cos2121
nrn
TT
nvdydppNd
pdNd
E
:r
: the azimuthal angle of particle transverse momentum
azimuthal angle of reaction plane
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In the theoretical study,
zx pp the reaction plane is the plane
the beam direction
impact parameter vector
:zp
:xp
0rreaction plane angle
xpbetween the reaction plane and the axis.
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,...2,1
2
3
3
cos2121
nn
TT
nvdydppNd
pdNd
E
......,
,,cos
2
22
2
1
pT
yx
p
pT
x
pppn
p
ppv
pp
vnv
p Denotes the particle-wise average, i.e. the
average over all particles in all events
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2 Physical ingredients in PACIAE
PACIAE is based on PYTHIA(A) Initiation
(i) Distributing nucleons according to Woods Saxon,
(iii) spectator nucleons outside OLZ but inside nucleus- nucleus collision system
(ii) participant nucleons inside OLZ
OLZ
y
x
p T
z
b
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beamzyx pppp ,0(iv) Construct nucleon collision time list with NN total cross section & straight trajectory
(v) Each NN collision performed by PYTHIA with switching-off SF & breaking diquark .
(vi) Resulted initial state ,consist of partons after all of the NN collision pairs are exhausted
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(B) Parton re-scattering (parton evolution)
(C) Parton hadronization with SF or CM
(D) Hadron re-scattering coalescence model
(i) Construct hadron collision time list with hh total cross section
(ii) Perform each hh collision by differential hh cross section
Ben-Hao Sa, Dai-Mei Zhou, et.al.,Comput. Phys. Commun. 183(2012)333, 184(2013) 1476
(i) Construct parton collision time list with parton-parton total cross section(ii) Perform each parton-parton collision by 22 pQCD differential cross section
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Roughly fitting model parameters to dNch/dy3
The model parameters are all fixed as the same as default Values given in PYTHIA, except the K factor, tand
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4 Results of & )(2 v )(2 TPv
PHENIX, PRC80 (2003) 024909 event-plane
As for the best model parameter C~2 in the left panal but 1 in the right panel, which should be attributed to the particle transverse asymmetry may be difference among the different centrality and and/or Tp
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Charged particle in the Pb+Pb collisions at
Tpvandv 22 TeVsNN 76.2
CMS, PRC87(2013)014902
Lee-Yang zero point Event-plane
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Predicted charge particle in the p+Aucollisions at
Tpvandv 22 TeVsNN 2.0
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Predicted charge particle in the p+Pbcollisions at
Tpvandv 22 TeVsNN 7
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Predicted charge particle in the p+pcollisions at
Tpvandv 22 TeVsNN 7
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5 Conclusions
(2) The calculated charge particle in the Au+Au/Pb+Pb collisions at describe the corresponding experimental data fairly well
Tpvandv 22 TeVsNN 76.2/2.0
(3) The charged particle in the p+Au/p+Pb collisions at and in the p+p collisions at are predicted. The elliptic flow parameter in these reactions reaches a measurable amount.
Tpvandv 22 TeVsNN 02.5/2.0
TeVsNN 7
(1) Model parameters are first fitted to the experimental data of charged particle pseudo-rapidity and used in all of the simulations.
Thanks for your attention!