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F.S.N., V.P. Gonçalves and E. Cazaroto

Charm production in the dipole approach. Introduction. Charm structure function. Charm pt distribution in eA. Charm production in pp and pA. Summary. (focus on saturation effects). F.S.N., V.P. Gonçalves and E. Cazaroto. IFUSP / BRAZIL. Introduction.

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F.S.N., V.P. Gonçalves and E. Cazaroto

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  1. Charm production in the dipole approach Introduction Charm structure function Charm pt distribution in eA Charm production in pp and pA Summary (focus on saturation effects) F.S.N., V.P. Gonçalves and E. Cazaroto IFUSP / BRAZIL

  2. Introduction Heavy enough for perturbative QCD Light enough to be abundant Why charm ? more important at low x saturation effects ? How to calculate ? Collinear factorization + DGLAP evolution KT factorization + unintegrated gluon densities Zotov´s talk Color dipole + dipole cross section Dipoles: easy inclusion of saturation effects Nikolaev, Zakharov (1991), A. Müller (1994)

  3. ep: boson-gluon fusion pp: gluon-gluon fusion color (singlet) dipole color (octet) dipole p A A

  4. Charm structure function in eA Albacete´s talk Stasto´s talk Armesto (2002) QCD input: in the dipole – proton cross section ! A A

  5. Dipole – proton cross section Golec-Biernat - Wüsthoff GBW (1998) Bartels – Golec-Biernat - Kowalski BGK (2002) Kowalski - Teaney IPsat (2003) Iancu – Itakura - Munier IIM (2004) Kharzeev - Kovchegov -Tuchin KKT (2004) Kowalski - Motyka - Watt bCGC (2006) Dumitru - Hayashigaki – Jalilian-Marian DHJ (2006) Gonçalves – Kugeratski – Machado – Navarra GKMN (2006) Marquet - Peshanski - Soyez MPS (2007) Boer - Utermann - Wessels BUW (2008) Albacete – Armesto – Milhano - Salgado rcBK (2009) (and others...sorry for omissions)

  6. Linear limit with dipoles dp GBW KKT linear IIM saturation full rcBK (all numerical)

  7. dA Mixed description: Color transparency (CT) from GRV98 Color transparency + Shadowing (CT + Shad) from EKS98 Linear - p: linear

  8. Charm structure function in eA Pb Pb Linear - p Gonçalves, Kugerastski, Navarra (2010) Saturation: reduction by a factor 3 to4 at Almost no reduction Gonçalves, Kugerastski, Navarra (2005)

  9. Linear limit without dipoles Saturation: reduction by a factor ~ 2 Stasto´s talk

  10. Linear limit without dipoles Collinear factorization approach: Coefficient function from pQCD DS: de Florian, Sassot (2004) Cazaroto, Gonçalves, Carvalho, Navarra (2009) EPS: Eskola, Paukkunen, Salgado (2008) Difficult to see saturation

  11. eA Heavy quark pt distribution Flöter, Kopeliovich, Pirner, Raufeisen (2007) A A

  12. eA 3 - 4 5 - 8 1.5 - 2 charm Gonçalves, Kugerastski, Navarra (2010) ~2 ~3 bottom ~1.5

  13. eA charm 2 3 - 4 5 Gonçalves, Kugerastski, Navarra (2010) ~3 ~4 ~1.5 bottom

  14. eA D meson pt distribution Peterson fragment. Gonçalves, Kugerastski, Navarra (2010)

  15. Charm production in pA collisions Kopeliovich, Tarasov (2002) GRV 98

  16. pp Merino et al. (2009) C-Rays PHENIX KT fac NLO QCD UA2 C-Rays nucl-ex/0607015 KT factorization Cazaroto, Gonçalves, Navarra in progress Merino,Pajares,Ryzhinskiy, Shabelski,Shuvaev, arXiv:0910.2364

  17. pA Total cross section linear p Saturation: reduction by 10 %with x going down to

  18. Rapidity distribution Saturation: reduction by 1.7 at y = 6

  19. Summary Well established dipole model for charm production in ep, eA, pp and pA Different ways to estimate the linear predictions in eA and pA: CT (overestimates linear regime) CT+Shad Linear p (underestimates linear regime) F2c: almost no suppression with (linear-p) F2c: large suppression factors (3 – 4) with (CT , CT+Shad) Rc: no sign of saturation F2c: large suppression factors (2) in other approaches eA @ 1TeV: large suppression factors (1.5 – 8) in dN/d pt (CT , CT+Shad) Dipole models reproduce well the data on pA @ 10 TeV: reduction by 10 % (or 1.1) in the total cross section (linear-p) pA @ 10 TeV: reduction by 1.7 in dN/dy at large y (linear–p)

  20. pp Not so small r Very small r GBW rcBK (?)

  21. Discussion Merino,Pajares,Ryzhinskiy, Shabelski,Shuvaev, arXiv:0910.2364 On charm production in pp and AA : STAR data KT factorization NLO QCD NLO QCD FONLL KT factorization Will we have data on total cross section from Tevatron? Disagreement between PHENIX and STAR is gone ?

  22. Tevatron data KT factorization NLO QCD Fragmentation ? If STAR was right enhanced production might have non-pert. origin: strong fields Should we prefer KT factorization?

  23. pp Merino et al. (2009) C-Rays Merino et al. (2009) PHENIX UA2 Cazaroto, Gonçalves, Navarra in progress

  24. NLO QCD Merino,Pajares,Ryzhinskiy, Shabelski,Shuvaev, arXiv:0910.2364 KT factorization

  25. F2 R = full / linear

  26. Charm structure function in the KLN model Glück, Reya, Stratmann (1994) Glück, Reya, Vogt (1995) Coefficient function from pQCD saturation linear Kharzeev, Levin, Nardi (2001)

  27. ep Carvalho, Durães Navarra, Szpigel (2009)

  28. eA

  29. Charm production in pA collisions Kopeliovich, Tarasov (2002)

  30. Back ups

  31. Introduction NLO collinear factorization Fixed Order plus Next to Leading Log (FONLL)

  32. KT factorization

  33. Color dipole formalism

  34. pA

  35. pA Rapidity distribution Saturation: reduction by 1.7 at y = 6

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