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Cronin Effect at RHIC - from d+Au Collisions at 200 GeV

This study examines the Cronin Effect in d+Au collisions at 200 GeV at RHIC. The physics results and discussions show the enhancement of hadron production and the centrality dependence. The conclusions highlight the significance of initial multiple parton scattering and recombination models in understanding the Cronin Effect.

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Cronin Effect at RHIC - from d+Au Collisions at 200 GeV

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  1. Cronin Effect at RHIC - from d+Au Collisions at 200 GeV Ming SHAO, Lijuan RUAN USTC/LBNL Outline: • Introduction and Motivation • Physics Results and Discussions • Conclusions • For STAR Collaboration ISMD 2005, Kromeriz, Czech

  2. Cronin Data at Lower Energy J.W. Cronin et al., PRD 11, 3105 (1975); • Enhancement of hadron production in proton-nucleus collisions. • R>1 at high pT. Cronin effect larger for protons compared to pions ISMD 2005, Kromeriz, Czech

  3. Cronin Effect at Lower Energy P.B. Straub et al., PRL 68, 452 (1992) Cronin effect decrease with energy ISMD 2005, Kromeriz, Czech

  4. STAR, Phys. Rev. Lett. 91 (2003) 072304 A. Accardi, hep-ph/0212148 Px~1 GeV/c 1 <RM<2 , 2.5<PM<4.5 GeV/c Model Prediction:Initial Multiple Parton Scattering X.N. Wang, Phys. Lett. B565(2003) 116-122 Initial multiple parton scattering can reproduce Cronin Effect of the charge hadron. IMPS+jet quenching can reproduce the suppression of the charge hadron in Au+Au collisions. ISMD 2005, Kromeriz, Czech

  5. Centrality Dependence: RCP in Au+Au Phys. Rev. Lett. 92(2004)052302, STAR Collaboration IMPS+jet quenching will result in the same suppression of baryon/meson in Au+Au collisions. Baryons () increase faster than mesons (Ks, K) from peripheral to central collisions; Baryon:~ Nbin scaling ISMD 2005, Kromeriz, Czech

  6. Centrality Dependence: RCP in Au+Au R.J. Fries et al., Phys. Rev. C68 (2003) 044902 Recombination: q q proton q q Ks qbar Recombination models predict that a scale according to the number of constituent quarks in a hadron seems to govern the particle production at intermediate pT. ISMD 2005, Kromeriz, Czech

  7. Measure the Cronin effect of pion/proton. • Compare with recombination model • How about the eta asymmetry of Cronin effect? • Cronin effect is initial state or final state effect? Motivation • Initial multiple parton scattering can reproduce Cronin Effect of the charge hadron. • IMPS+independent Fragmentation will result in the same Cronin Effect of pion and proton. • IMPS predict that the Cronin effect on deuteron side is larger than that on Au side at forward rapidity. • X.N. Wang, Phys. Lett. B565 (2003) 116 Recombination models can produce the RCP of baryon/meson at intermediate pT in Au+Au collisions ISMD 2005, Kromeriz, Czech

  8. MRPC-TOF PID Hadron PID pion/proton:3GeV/c kaon: 1.6GeV/c PLB 616, 9 (2005) • A prototype detector of time-of-flight (TOF) was installed in year3. • Just one tray: ~0.3% of TPC coverage ( coverage ~(-1.0, 0.0),coverage 1/60 of 2, in the forward Au beam outgoing direction) • Intrinsic timing resolution: 85 psin year3 ISMD 2005, Kromeriz, Czech

  9. Spectra from 200GeV d+Au, p+p STAR Collaboration, PLB 616, 9 (2005) d+Au MinBias: 95%3% of total nuclear cross section p+p NSD : 30.0 3.5 mb, spectra correction <5% to inelastic ISMD 2005, Kromeriz, Czech

  10. Cronin Effect:  K p RdAu • Low pT, RdAu <1 • High pT, RdAu >1 • Px~=1 GeV/c • RdAu(p)> RdAu(,K) • RdAu of protons rises • faster than those of • pions and kaons. • Proton spectra at • intermediate pT : no • binary scaling STAR Collaboration, PLB 616, 9 (2005) Characteristic Cronin Effect ISMD 2005, Kromeriz, Czech

  11. The Ratios between p+pbar and h STAR Collaboration, PLB 616, 9 (2005) • d+Au: (pbar+p)/h=0.240.01 0.01 (2<PT<3 GeV/c) • p+p: (pbar+p)/h=0.210.02 0.01 (2<PT<3 GeV/c) • p-=0.048 0.012 0.006 (1.2<PT<3 GeV/c), • lower energy sqrt(s)~30 GeV/c, p-=0.0810.005 • (pbar+p)/h=0.24,A factor of 2 smaller than that in Au+Au  AuAu baryon excess due to Final State Effect. ISMD 2005, Kromeriz, Czech

  12. Model Comparison: recombination Recombination model can reproduce the  and p spectra in d+Au collisions R.C. Hwa et al., Phys. Rev. Lett. 93(2004)082302; R.C. Hwa et al., nucl-th/0406066 Great Thanks to C.B. Yang (CCNU)! ISMD 2005, Kromeriz, Czech

  13. RdAu and RCP in d+Au collisions STAR Preliminary X. Cai at QM05 It seems that the RdAu at 200 GeV is baryon/meson dependent. STAR Preliminary ISMD 2005, Kromeriz, Czech

  14. Integral Yield RdAu • Integral yield RdAu is smaller than 1: • - Shadowing effect ? • - Mass dependent ? • The integral yield RdAu is bigger for proton than for pion. ISMD 2005, Kromeriz, Czech

  15. Cronin Effect  Asymmetry STAR,Phys. Rev. C 70 (2004) 064907 Initial multiple parton scattering alone can’t reproduce the  asymmetry of Cronin effect. X.N. Wang, Phys. Lett. B565(2003)116-122 ISMD 2005, Kromeriz, Czech

  16. Conclusions • RdAu of protons rises faster than those of pions and kaons at 200 GeV d+Au collisions, Characteristic Cronin Effect. • The mass dependence of Cronin effect at RHIC energy is much smaller than that at lower energy. • Recombination model can reproduce the Cronin Effect of , p Final State Effect. • Baryon enhanced p/h (dAu/pp)=1.19 0.05 0.03. In Au+Au, the ratio is about a factor of 2 higher Final State Effect. • Initial multiple parton scattering can reproduce Cronin Effect of the charge hadron. • IMPS + independent fragmentation will result in the same Cronin Effect of pion and proton. • Model based on initial multiple parton scattering can NOT reproduce the measured rapidity asymmetry. Cronin Effect is not the initial-state effect only, the final-state effect plays an important role. ISMD 2005, Kromeriz, Czech

  17. Thank You!!! ISMD 2005, Kromeriz, Czech

  18. Some Definitions Initial-state effect: The effect happens before the hard scattering. Final-state effect: The effect happens after or at the hard scattering. ISMD 2005, Kromeriz, Czech

  19. Extended PID at STAR Combine TPC (n,K,p(dE/dx)) and TOF (m2) information, the PID range could be greatly extended ISMD 2005, Kromeriz, Czech

  20. Spectra in 3 centrality bin central peripheral • The spectra in d+Au collisions are harder than those in p+p collisions ISMD 2005, Kromeriz, Czech

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