1

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)

2

5

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

3

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

4

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 )

5

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

6

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

7

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

8

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

22

22

xy

xyrp

222

222 ,

yy

xx

y

x

Spatial reaction plane eccentricity:

the average over the nucleon spatial distribution

9

2

22

bab

grp

4

2rp

r

geometrical eccentricity of the initial spatial overlap zone

p

10

The participant eccentricity

22

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

11

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

12

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.

13

,...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

14

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

15

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

16

(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

17

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

18

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

19

Charged particle in the Pb+Pb collisions at

Tpvandv 22 TeVsNN 76.2

CMS, PRC87(2013)014902

Lee-Yang zero point Event-plane

20

Predicted charge particle in the p+Aucollisions at

Tpvandv 22 TeVsNN 2.0

21

Predicted charge particle in the p+Pbcollisions at

Tpvandv 22 TeVsNN 7

22

Predicted charge particle in the p+pcollisions at

Tpvandv 22 TeVsNN 7

23

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！