study the particle ratio fluctuations in heavy-ion collisions
DESCRIPTION
Study the particle ratio fluctuations in heavy-ion collisions. Limin Fan ( 樊利敏 ). Central China Normal University (CCNU). Outline. Introduction. Model and calculation. Results and discussion. Summary and outlook. hadronic phase and freeze-out. QGP and hydrodynamic expansion. - PowerPoint PPT PresentationTRANSCRIPT
Study the particle ratio fluctuations in heavy-ion collisions
Limin Fan (樊利敏 )
Central China Normal University (CCNU)
1
Outline
Introduction.
Model and calculation.
Results and discussion.
Summary and outlook.2
3
Pre-equilibrium parton hard scattering.
QGP thermal and Expansion Stage: 1-10fm/cCollective expansion, Parton energy loss et al., Hadronization: Recombination and coalescence.
Freeze out Stage: ~10-15fm/cChemical freeze out: Inelastic scatt. cease.Kinetic freeze out: Elastic scatt. cease.
arxiv:0809.2482, hep-ph/0407360
Evolution of High Energy Heavy Ion Collisions
initial state
pre-equilibrium
QGP andhydrodynamic expansion
hadronization
hadronic phaseand freeze-out
QCD Phase Diagram
4
At high enough energy density ordinary matter will undergoes a transition into a plasma-like phase.
The quark/gluon to hadron phase transition may lead to significant fluctuation.
The correlation between strangeness S and baryon number B is sensitive to the state of matter created in heavy-ion collisions. and fluctuations could be related to strangeness fluctuations, baryon number fluctuations and baryon-strangeness correlations at mid-rapidity.
pk //k /p
Fluctuations Measure
5
6
PACIAE model
PACIAE is based on PYTHIA
(A) Initiation
(i) Distributing nucleons according to Woods Saxon,
(ii) participant nucleons inside OLZ
(iii)spectator nucleons outside OLZ but inside nucleus-nucleus collision system
OLZ
y
x
p T
z
bbeamzyx 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
(ii) Perform each parton-parton collision by 2→2 pQCD differential cross section
(C) Parton hadronization with SF or CM
(D) Hadron evolution (re-scattering)
(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
(B) Parton re-scattering (parton evolution)
(i) Construct parton collision time list with parton-parton total cross section
9
Calculation
21
212
2
222
1
1121 2)1()1()/(
NNNN
NNN
NNNNNdyn
The advantage of is that it does not require the creation of mixed events.A Poisson simulation also shows that provide more stable results compare
to if the statistics is limiteddyn
dyn
dyn
dynEarly measurements of particle ratio fluctuations utilized the variable
Another observable, ,is also proposed to study the deviation from Poisson behavior. the observable for particle can be written as 21,NNdyn
dyn
dynWhere is the relative width of the event-by-event particle-ratio ( k/π, p/π or k/p )distribution in either real or mixed events.
Calculation
10
Statistical fluctuation poisson distribution
0dyn The production of corresponding pairs are highly correlated
0dyn High fluctuation low correlation
0dyn
The negative value of means the cross-correlation terms dominate,whichcould be due to the proton-pion and kaon-pion correlation from resonancedecay.
dyn
If kaons and pions distribution are Poisson and independent of each other One would expect
NNNN KK
2)1( KKK NNN2)1( NNN
Identified particle numbers
11
Identified particle numbers used in the calculation,0-5% centrality, we use the PACIAE model within the STAR experimental acceptance charged kaons and pions are selected with transeverse momentum 0.2 < pt < 1.6GeV/c and pseudorapidity |η| < 1.0
dyn
The number of participating nucleons are from Au+Au collisions at = 11.5,19.6,39,62.4 and 200 GeV. NNs
Results of the charge dependent particle ratio fluctuations
12
The STAR data are compared to theoretical model predictions!
The same sign fluctuations and )/( kdyn)/( kdyn
The opposite sign fluctuations show more negative value due to neutral resonance decay
KK )892(*
Result of in 0-5% most central Au+Au collisions calculated by the PACIAE model (red stars and circles) and compared with STAR experimental results (blue triangles).
)/( kdyn
The opposite sign fluctuationsand)/( kdyn
)/( kdyn
Results of the charge dependent particle ratio fluctuations
13
Result of in 0-5% most central Au+Au collisions calculated by the PACIAE model (red stars and circles) and compared with STAR experimental results (blue triangles).
)/( pdyn
The opposite sign fluctuationsand)/( pdyn )/( pdyn
The same sign fluctuations and )/( pdyn
)/( pdyn
The experimental data show that the opposite sign fluctuations show more negative value due to neutral resonance decays
14
Results of the charge dependent particle ratio fluctuations
k/p fluctuations are related to baryon-strangeness correlations,can be used as a tool to study the deconfinement phase transition.
Results of in 0-5% most central Au+Au collisions calculated by the PACIAE model (red stars and circles) and compared with STAR experimental results (blue triangles).
)/( pkdyn
The results of are close to zero,at some energy the results are positive
)/( pkdyn
15
Results of the charge independent particle ratio fluctuations
Energy dependence of , and . model predication from PACIAE (black squares), UrQMD (blue trangles) and STAR (blank trangles),using the STAR experimental acceptance and those calculations are compared at Au+Au centrality collision with =11.5,19.6,39,62.4 and 200 GeV
)/( pkdyn)/( kdyn )/( pdyn
NNS
16
Results of the charge independent particle ratio fluctuations
)/()(/
NNNNPPP
)/()(/
NNNNKKK
)/()(/ PPKKNNNNPK
The result of dynamical k/p ratio fluctuation in the PACIAE model have the same trend withSTAR and UrQMD model.
The results calculated by the PACIAE model of and are nearly the same, and are more negative than the UrQMD and STAR results.
)/( kdyn )/( pdyn
all decay to and decay to K)1270(),892( 1* KK,p ,,
Summary
17
/K /P
1. All of the opposite sign fluctuations are larger than the same sign fluctuations.
GeVsNN 200 2. We see either a weak energy dependence or monotonic
decrease with decreasing energy At both sign fluctuations are nearly the same.
4.For dynamical and fluctuations PACIAE model results are negative and having larger fluctuation than UrQMD and STAR
3.The PACIAE model results of agree with STAR experimental results fairly well.
)/( kdyn
Thank you !
18