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Suppression of high P T hadron spectra in p+A collisions

arXiv:1204.1998. Suppression of high P T hadron spectra in p+A collisions. Wei- Tian Deng In Collaboration with: Rong Xu & Xin-Nian Wang. Nuclear Modification Factor:. Phys.Lett. B696 (2011) 30-39. If R = 1 here, no any nuclear modification. Suppression at High p T. Final state?.

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Suppression of high P T hadron spectra in p+A collisions

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  1. arXiv:1204.1998 Suppression of high PT hadron spectra in p+A collisions Wei-Tian Deng In Collaboration with: RongXu & Xin-Nian Wang

  2. Nuclear Modification Factor: Phys.Lett. B696 (2011) 30-39 If R = 1 here, no any nuclear modification Suppression at High pT

  3. Final state? Initial state? + Only initial cold nuclear effect RHIC d+Au 200GeV LHC p+Pb 4.4TeV within HIJING

  4. Initial Cold Nuclear Effect in p+A • Cronin effect • Shadowing • Energy-Momentum conservation • Parton flavor composition • Fragmentation • …… parton level Final hadron

  5. Cronin effect Nuclear modification: Cronin Effect If no nuclear modification P.R.L. 91, 072303 PHENIX P.R.L. 91, 072304 STAR

  6. KT Broadening in HIJING kT kick in p+A collisions: KT broadening of initial and final partons, with Gaussian distribution Multiple inelastic scattering Energy dependence of the width in Gaussian distribution

  7. Shadowing in HIJING Nuclear shadowing: Gluon, fit to the RHIC Gluon uncertainty in EPS09 Quark, fixed on DIS Phys.Lett.B 527, 85(2002) S.Y. Li & X.N. Wang arXiv: 1205.5359

  8. RpA on Parton level Cronin Effect at fix PT Shadowing suppress RpA at low pT region (small x region) There is suppression on large pT, why?

  9. Momentum Correlation 1st Hard Scattering 1st Hard Scattering 2nd Hard Scattering 2nd Hard Scattering 1st Soft Scattering 2nd Soft Scattering …… 1st Soft Scattering 2nd Soft Scattering …… De-coherent Hard Collision (DHC) means: Soft-Hard is de-coupled in multiple scattering in HIJING ……

  10. RpA on Parton level For DHC without shadowing, RpA is 1 at large pT Soft-Hard coupling suppress RpA at large pT

  11. Flavor Correlation in projectile Valence Quark Number Conservation Quark availability is less in multiple scattering … In HIJING, we push to the limit: If a quark has been scattered once, only gluon available for latter scattering

  12. Flavor Correlation the Q/G ratio in p+A is smaller at large pT. More gluon give softer hadron spectrum

  13. RpA for Final Hadron This flavor correlation suppress RpA of final hadron at large pT Lund Fragmentation

  14. Lund Frg Vs. Inde Frg Hard gluons are attached on the excited participants as a kink Hard gluons fragment into hadron independently Projectile in p+p Projectile in p+A

  15. RpA for Final Hadron hadron spectra in Lund frag. is softer than Independent frag.

  16. The suppression of High pT hadron comes from fragmentation mainly: • More gluon jets • Multiple gluon fragmentation model

  17. Summary We studied the p+A collision within HIJING model. • Cronin effect at intermediate pT due to KT broadening through multiple scattering. • High pT suppression from initial nuclear effects: • parton shadowing, • soft-hard coupling, • enhanced gluon jets due to valence quark conservation • Fragmentation method • Such effects in AA collisions need to be investigated

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