IOPP, Wuhan China1 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)

IOPP, Wuhan China2 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, (2011) Ren, X-W and Feng, S-Q, Chinese Physics C 38, (2014) Ren, X-W and Feng, S-Q submitted to PRC Sa, Ben-Hao et al, Computer Physics Communications 183 (2012) 333–346

IOPP, Wuhan China3 1 、 Motivation

IOPP, Wuhan China4 1 、 Motivation The investigation of strange hadron productions is an important ingredient in understanding the nature of QGP 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.

IOPP, Wuhan China5 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 collisions at sqrt(s) = 0.9 TeV has been selected with triggers combining several fast detectors. 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: Strange Particle Production in pp Collisions at sqrt(s) = 0.9 and 7 TeV,The CMS Collaboration ， JHEP 05 (2011) 064, arXiv:

IOPP, Wuhan China6 Pb-Pb Collisions at LHC

IOPP, Wuhan China7 Strangeness suppression 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. Originally, the suppression of s quark pair production compared with u(d) pair production is assumed 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.

IOPP, Wuhan China8 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) Sa, B-H and Tai, A, Phys. Rev. C 55 (1997) 2010.

IOPP, Wuhan China9 The effective string tension was introduced in PLB 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) Sa, B-H and Tai, A, Phys. Rev. C 55 (1997) 2010.

IOPP, Wuhan China10  We use the transport model PACIAE to study the strangeness production in pp collisions:  Prediction: The relation between K/π ratio and reaction energies.

IOPP, Wuhan China11 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: SA 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: ; Yan Yu-liang, Zhou Dai-mei, Dong Bao-guo, Li Xiao-mei, Ma Hai-liang, Sa Ben- hao.Phys.Rev. C, 2012, 81: ; 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

IOPP, Wuhan China12 Remnant Initial state radiation Final state radiation Hadronization hadron rescattering Decay h p … Sketch for pp dynamic simulation (PYTHIA & PACIAE.641) p parton rescattering parton distribution function h h h

IOPP, Wuhan China13 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

IOPP, Wuhan China14 In this work, the dependence of effective string tension on increasing reaction energy introduced in PLB are used to discussed the strangeness production of p-p collisions in the RHIC and LHC energy regions

IOPP, Wuhan China15 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.

IOPP, Wuhan China16 3 、 Strangeness productions of p-p and A-A interactions

IOPP, Wuhan China17 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). Long,H-Y, Feng, S-Q, Zhou,D-M, Yan, Y-L, Ma H-L and Sa, B-H, Physical Review C 84, (2011)

IOPP, Wuhan China18 Transverse momentum distribution of strange particles in NSD (non- single-diffractive) p-p collisions at. Long,HY, Feng, S-Q, Zhou,D-M, Yan, Y-L, Ma H-L and Sa, B-H, Physical Review C 84, (2011)

IOPP, Wuhan China19 Strange 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:

IOPP, Wuhan China20 Transverse momentum distribution of strange particles in INEL pp collisions at.

IOPP, Wuhan China21 The strange particles rapidity densities at midrapidity in pp collisions at and.

IOPP, Wuhan China22 The strange particle rapidity distributions in NSD pp collisions at and.

IOPP, Wuhan China23 The strange particle transverse momentum distributions in NSD pp collisions at and.

IOPP, Wuhan China24 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.

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IOPP, Wuhan China32 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.