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Reduction of strange quark suppression and strange hadron production in p-p and A-A collisions at RHIC and LHC. Sheng-Qin Feng China Three Gorges University (CTGU). Outline. 1 、 Motivation 2 、 PACIAE and strangeness production mechanisms - PowerPoint PPT Presentation
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IOPP, Wuhan China 1
Reduction of strange quark suppression and strange hadron production in p-p and A-A collisions at RHIC and LH
C
Sheng-Qin Feng
China Three Gorges University (CTGU)
IOPP, Wuhan China 2
Outline 1、Motivation
2、 PACIAE and strangeness production mechanisms
3、 strangeness productions of p-p and A-A interactions
4、 Summary
Based on:Long,HY, Feng, S-Q, Zhou,D-M, Yan, Y-L, Ma H-L and Sa, B-H, Physical Review C 84, 034905 (2011)Ren, X-W and Feng, S-Q, Chinese Physics C 38, 054102 (2014)Ren, X-W and Feng, S-Q submitted to PRCSa, Ben-Hao et al, Computer Physics Communications 183 (2012) 333–346
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1、Motivation
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1、Motivation
The investigation of strange hadron productions is an i
mportant ingredient in understanding the nature of QG
P in relativistic heavy ion collisions .
As the strange quark is heavier than up and down quarks,
production of strange hadrons is generally suppressed
relative to hadrons containing only up and down quarks. The
amount of strangeness suppression is an important research
topics.
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The differential transverse momentum yields ( spectra) and integrated yields at
central rapidity of have been measured by the
ALICE experiment during the commissioning phase of the LHC (December 2009)
with the very first proton-proton collisions. A sample of 250 k minimum bias pp c
ollisions at sqrt(s) = 0.9 TeV has been selected with triggers combining several fast
detectors .
Tp
0SK
LHC new experimental results
Strange particle production in proton-proton collisions at sqrt(s) = 0.9 TeV with ALICE at the LHC. ALICE collaboration, , Eur.Phys.J.C71,2011:1594, arXiv:1012.3257
Strange Particle Production in pp Collisions at sqrt(s) = 0.9 and 7 TeV,The CMS Collaboration, JHEP 05 (2011) 064 , arXiv:1102.4282
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Pb-Pb Collisions at LHC
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Strangeness suppression
As the strange quark is heavier than up and down qua
rks, production of strange hadrons is generally suppre
ssed relative to hadrons containing only up and down
quarks. Originally, the suppression of s quark pair pr
oduction compared with u(d) pair production is assum
ed to be a ‘constant’ in the LUND string fragmentation
scheme (PYTHIA).
B. Andersson, G. Gustafson, G. Ingelman and T. Sjiistrand, Phys. Rep. 97 (1983) 31.
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Strangeness suppression
The mechanism of reduction of strange quark suppression has been studied in the early paper.
Later experiments during SPS have shown this suppression decreases with increasing collision energy.
Tai,A and Sa, B-H PLB409(1997)393-397
Sa, B-H and Tai, A, Phys. Rev. C 55 (1997) 2010.
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The effective string tension was introduced in PLB409-393 and assumed it to be increased with increasing reaction energy. Hence the strange quark production increases with increasing reaction energy.
It was assumed further that the effective string tension varies with reaction energy can be considered by the effective string tension as a function of the number and hardening of gluons in the string.
Tai,A and Sa, B-H PLB409(1997)393-397
Sa, B-H and Tai, A, Phys. Rev. C 55 (1997) 2010.
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We use the transport model PACIAE to study the strangeness production in pp collisions:
STAR@
ALICE@
CMS@ Prediction:
ALICE@
GeVs 200
GeVs 900
TeVs 7,9.0
TeVs 14,7,36.2
The relation between K/π ratio and reaction energies.
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2、 PACIAE and strangeness production mechanisms
References:Sa Ben-hao, Zhou Dai-mei, Yan Yu-liang, LI Xiao-mei, Feng Sheng-qin, CAI Xu. Comput. Phys. Commun, 2012,183: 333-346SA Ben-hao, ZHOU Dai-mei, DONG Bao-guo, YAN Yu-liang, MA Hai-liang, LI Xiao-mei. J. Phys. G: Nucl. Part.Phys., 2009, 36: 025007; Yan Yu-liang, Zhou Dai-mei, Dong Bao-guo, Li Xiao-mei, Ma Hai-liang, Sa Ben-hao.Phys.Rev. C, 2012, 81: 044914; Zhou Dai-mei, Yan Yu-liang, Dong Bao-guo, Li Xiao-mei, Wang Du-juan, Cai Xu, Sa Ben-hao. Nucl.Phys. A, 2011, 860: 68
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Remnant
Remnant Initial state radiation
Final state radiation
Hadronization
kf
lf
hadronrescattering
Decay
)(xf pi
)(xf pj
h
p
…
ˆd
dt
Sketch for pp dynamic simulation (PYTHIA & PACIAE.641)
p partonrescattering
parton distribution function
1
2
34
h
h
h
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The PACIAE
PACIAE is a parton and hadron cascade model which consist of four stages of the parton initiation, parton re-scattering, hadronization,and hadron re-scattering.
In the PYTHIA model it is assumed that the pair produce with probability
22
expexp Tpm
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In this work, the dependence of effective string
tension on increasing reaction energy introduc
ed in PLB409-393 are used to discussed the str
angeness production of p-p collisions in the R
HIC and LHC energy regions
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The PACIAE
where is the string tension of the pure string assumed to be 1 ~GeV/fm
represents the deviation scale of the multi-gluon string from the pure string.
0
10eff
1
20
2
0
0
2max
lnln
ln
n
j
Tj
T
ss
s
s
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3、 Strangeness productions of p-p and A-A interactions
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Strange particles rapidity densities at midrapidity (|y| <0.5) in NSD pp collisions at with adj1(31)=0.18(D=0.1), adj1(32)=0.4 (D=0.3), and adj1(33)=0.5(D=0.4).
GeVs 200
Long,H-Y, Feng, S-Q, Zhou,D-M, Yan, Y-L, Ma H-L and Sa, B-H, Physical Review C 84, 034905 (2011)
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Transverse momentum distribution of strange particles in NSD (non-single-diffractive) p-p collisions at . GeVs 200
Long,HY, Feng, S-Q, Zhou,D-M, Yan, Y-L, Ma H-L and Sa, B-H, Physical Review C 84, 034905 (2011)
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GeVs 900Strange particles rapidity densities at mid-rapidity in inelastic pp collisions at
Strange particle production in proton-proton collisions at sqrt(s) = 0.9 TeV with ALICE at the LHC. ALICE collaboration, , Eur.Phys.J.C71,2011:1594, arXiv:1012.3257
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Transverse momentum distribution of strange particles in INEL pp collisions at
.GeVs 900
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The strange particles rapidity densities at midrapidity in pp collisions at and . TeVs 7
TeVs 9.0
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The strange particle
rapidity distributions in
NSD pp collisions at and .
TeVs 9.0
TeVs 7
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The strange particle transverse momentum distributions in NSD pp collisions at and .
TeVs 9.0
TeVs 7
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The PACIAE results at =2.36, 7, and 14 TeV indicate that the K/π ratio as a function of first grows up from 0.2TeV to 0.9TeV and then turns to saturation.
s
s
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Summary
In summary, these results might indicate the un-negligible effect of the reduction of strange quark suppression mechanism.
Until now, we find that PACIAE can fit well
the strangeness productions in RHIC and LHC data. but for the multi-strangeness production, we still need to improve the fit results.