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Elementary Process and d+Au Collision at RHIC Energy @ 大阪大学 RCNP, 28 Oct., 2003

Elementary Process and d+Au Collision at RHIC Energy @ 大阪大学 RCNP, 28 Oct., 2003. 北大理 　一瀬 昌嗣 ( M.Isse) ☆共同研究　　　　　　　　　　　　　　　　　　 原研東海研　 大塚 直彦 ( N.Otuka) インド物理学研 Ｐ．Ｋ．サフ ( P.K.Sahu) 北大理 　 　大西 明 ( A. Ohnishi) Introduction Additional Jets study (Au+Au)

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Elementary Process and d+Au Collision at RHIC Energy @ 大阪大学 RCNP, 28 Oct., 2003

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  1. Elementary Process and d+Au Collision at RHIC Energy@ 大阪大学 RCNP, 28 Oct., 2003 北大理　一瀬 昌嗣 (M.Isse) ☆共同研究　　　　　　　　　　　　　　　　　　 原研東海研　 大塚 直彦 (N.Otuka) インド物理学研 Ｐ．Ｋ．サフ (P.K.Sahu) 北大理　 　大西 明 (A. Ohnishi) • Introduction • Additional Jets study (Au+Au) • Elliptic flow with two analysis method • Elementary Process study (p+p, d+Au) • pt-spectrum and Azimuthal Correlation • Summary

  2. Introduction • p+p and d+Au collision has been done at RHIC (√s =200 AGeV). • d+Au collision dose not show signature of QGP formation seen in Au+Au (√s =130, 200 AGeV), like Jet Quenching. • d+Au collision is not expected to form QGP. • Then, Hadronic Cascade should reproduce d+Au collisions. • We would like to estimate how the Jet events occur in each event at RHIC.

  3. Today’s Two Topic • Additional Jets study ->Au+Au • High pT hadrons, underestimated in hadronic cascade, seems to come from jets in both Au+Au, d+Au collisions. • Elliptic flow v2 of Au+Au (130,200 AGeV) collision at RHIC is available, which may be a sensitive probe to see jet effect. • We introduce jets additionally in Hadronic Cascade model JAM 1.010 and study elliptic flow v2. • Elementary Process study ->d+Au

  4. Additional Jets study Au+Au

  5. Final State Interaction and Jet production • Final State Interaction • Hadron multiple scattering • Resonance and String production and decay • Soft process is dominant. • Jet production • Hard process. • QCD based scenario has to be considered. • Jet-quenching or Cronin effect or shadowing are not considered in this result, but we include independent jets.

  6. Glauber geometry (h++h-) 2 Additional Jets Additional Jets Ncentral • Au+Au pT- spectrum produced by JAM1.010 is not enough at high-pT. • Add some (Ncentral=7 (Au+Au), 1.5(d+Au)) jets of p+p collision by PYTHIA 6.2 to reproduce high-pT hadrons in central events. • Additional jet number is determined by Njet(b)= Ncentral*<Nbin>/<Nbin>max, proportional to the number of binary collision assuming Glauber geometry.

  7. Analysis Methods of Elliptic Flow • Reaction Plane Method The R.P. is initially known in the simulation. vn(pT,h)=<cos(n(f-F))> • Correlation Method Calculate the angle of each particles Df. vn(pT,h)=<cos(nDf)> (pT,h) / √<cos(nDf)> (h) squared

  8. Elliptic flow v2 (Nch/Nmax) Au+Au √s =130AGeV h± • Jetsdo not affect so much on v2 • Two Analysis Methods (Reac. and Corr.) do not have significant differences. Corr. Reac.

  9. Elliptic flow v2 (pT) Au+Au √s =130AGeV h± • Additional Jets reduce v2 at high-pT . Including additional Jets make v2 reduce!! Both in Reaction Plane Method and Correlation Method.

  10. Summary of Additional Jets study • We have investigated Au+Au collision at RHIC by using hadron-string cascade model JAM 1.010 with additional jets by using PYTHIA 6.2. They are determined to fit experimental pT-spectra. • We calculate elliptic flow v2 by JAM with additional jets. In Nch/Nmax distribution, v2 change little. While, in pT distribution, v2 at high-pT is largely suppressed, both in Reaction Plane and Correlation method.

  11. Elementary process study p+p, d+Au

  12. Total cross sections of p+p collision. Inelastic cross sections of p+p collision. Elementary Process

  13. Lower limit of allowed pT • We choose a parameter in JAM (i.e. PYTHIA 6.1), which give the lower limit of allowed pT value for hard 22 processes. • Here we denote it “c”. (“ckin(3)” in PYTHIA) • The default value of “c” in JAM is 2, it is same in HIJING.

  14. c=2.7 seems good p+p √s= 200 AGeV pt-spectrum (h++h-) 2

  15. Nuclear coherent thickness In nucleus-nucleus collisions, we increase thickness for hard processes. (1+a) Put a factor “a” on sjet Calculate pT–spectrum and Azimuthal Correlation of d+Au collision.

  16. d+Au √s=200 AGeV pt-spectrum (h++h-) 2 Increased thickness “a” Dose not increased thickness “a”

  17. Jet Jet d+Au M.B. Azimuthal correlation • Much far-side @high-pT • Little near-side @low&high-pT We need more consideration.

  18. Summary • We have investigated p+p, d+Au collision at RHIC by using hadron-string cascade model JAM 1.010. • When we put a factor “a” on sjet as nucleon coherent thickness, pT -spectrum of d+Au collision is reproduced. • Independent h+h collision is not suitable for A+A collisions at RHIC energies. • Df correlation should be considered more carefully. High-pT (<4GeV/c) component may not come from back-to-back jets.

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