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Looking for intrinsic charm at RHIC and LHC

Looking for intrinsic charm at RHIC and LHC. F.S. Navarra. University of São Paulo. V.P. Gonçalves. University of Pelotas. Winter Workshop on Nuclear Dynamics. 1 - 8 feb 2009. Charm sea. charm pair comes from the QCD DGLAP evolution. “extrinsic”. Perturbative QCD OK !.

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Looking for intrinsic charm at RHIC and LHC

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  1. Looking for intrinsic charm at RHIC and LHC F.S. Navarra University of São Paulo V.P. Gonçalves University of Pelotas Winter Workshop on Nuclear Dynamics 1 - 8 feb 2009

  2. Charm sea charm pair comes from the QCD DGLAP evolution “extrinsic” Perturbative QCD OK ! “intrinsic” charm pair was there before evolution The pair knows in which hadron it is ! Strong non-perturbative effects Brodsky, Hoyer, Peterson, Sakai, (80)

  3. Bag with five quarks Brodsky, Hoyer, Peterson, Sakai, (80) Probability to find a charm – anticharmpair in theproton : momentum of the parton i Momentum distribution : integrate P over Heavy quark Light quark

  4. Navarra, Nielsen, Nunes, Teixeira (96) Charm meson cloud Paiva, Nielsen, Navarra, Durães, Barz (98) Carvalho, Durães, Navarra, Nielsen (01) proton proton both with similar momentum fraction charm quarks are hard !

  5. Can we measure IC ? Partondistributionsmeasured in DeepInelasticScattering : Gunion, Vogt, hep-ph/9706252 massless charm extrinsic intrinsic extrinsic charm Pumplin, Lai, Tung, hep-ph/0701220 fits of DIS data favor 1-2 % IC CTEQ6.5C :

  6. Hadronic collisions IC is hard and will produce charm at large momentum Standard descrition in proton-proton collisions (PYTHIA) collinear factorization formula

  7. PYTHIA fails for D´s with large longitudinal momentum ! Excess of “fast” D´s can be explained with IC large PYTHIA small

  8. 1994 – 2008: low x “revolution “ High densities: non-linear evolution gluon recombination g g -> g Saturation Color Glass Condensate Non-linear evolution equations: JIMWLK and BK Collinear factorization breaks down !

  9. Change from parton distributions to dipole cross sections: color dipole DIS

  10. saturation scale or when when Physics is in the “anomalous dimension”: Help from approximate solutions of BFKL, BK Color dipoles also in hadron-hadron collisions BRAHMS Use N to fit data: Boer, Utermann, Wessels hep-ph/0701219

  11. amplitude conjugate amplitude abstract dipole

  12. Forward hadron production at RHIC dilute dense dilute CGC formula Dumitru, Hayashigaki Jalilian-Marian (04) quark–antiquark dipole cros section gluon-gluon dipole cros section standard parton distributions in the proton: MRST, CTEQ, ... standard parton fragmentation functions: KKP, ...

  13. Forward charm production at RHIC collinear factorization formula CGC formula dilute dense dilute gluon-gluon fusion small at large D suppression quark-antiquark fusion charm from CTEQ6.5C Pumplin, Lai, Tung, hep-ph/0701220 recent fit from RHIC data Boer, Utermann, Wessels hep-ph/0701219 No new parameter!

  14. The CTEQ 6.5 C parametrizations : extrinsic charm

  15. D transverse momentum spectra p p extrinsic charm

  16. Ratio IC / No IC p p

  17. D transverse momentum spectra

  18. Ratio IC / No IC

  19. D transverse momentum spectra extrinsic charm

  20. Ratio IC / No IC

  21. IC + CGC versus “standard physics” PYTHIA: no intrinsic charm collinear factorization standard parton distributions overestimates the gluon density in the target higher cross sections ! STAR version (thanks to Thomas Ullrich!) IC + CGC: intrinsic charm fom CTEQ dipole approach: dipole cross section from BUW IC enhances the cross sections non-linear effects deplete the gluon density in the target decrease the cross sections

  22. D transverse momentum spectra

  23. D transverse momentum spectra

  24. Complementary search of IC Kniehl, Kramer, Schienbein, Spisberger, arXiv: 0901.4130 Meson Cloud IC / No-IC BHPS

  25. Summary Intrinsic charm is the non-perturbative component of the charm sea of the proton. Still to be confirmed... IC explains HERA and ISR data Best place to look for it: at RHIC at large rapidities (FPD) Intrinsic/extrinsic ~ 10 Results very sensitive to parton distributions...

  26. Qualitative prediction : Saturation reduces the number of gluons in the target and the number of produced particles at large rapidity Nuclear modification ratio:

  27. CGC visible when is large ! Saturation scale Saturation condition: target area completely filled by gluons QS : saturation scale dilute (linear) dense (saturation) LHC : x may be small eRHIC : A may be large

  28. Introduction Origin of the sea quarks the proton? valence sea

  29. IC PYTHIA Perturbative parton branching

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