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Expected nuclear modifications and pseudorapidity asymmetry at the LHC

Expected nuclear modifications and pseudorapidity asymmetry at the LHC. George Fai Kent State University. Collaborators: A. Adeluyi, Kent G.G. Barnaföldi, Kent and Budapest P. Lévai, Budapest. U.S. Department of Energy DE-FG02-86ER40251. Outline. 1. Introduction.

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Expected nuclear modifications and pseudorapidity asymmetry at the LHC

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  1. Expected nuclear modifications and pseudorapidity asymmetry at the LHC George Fai Kent State University Collaborators: A. Adeluyi, Kent G.G. Barnaföldi, Kent and Budapest P. Lévai, Budapest U.S. Department of Energy DE-FG02-86ER40251 Tokaj, March 17, 2008

  2. Outline 1. Introduction 2. Motivation: why do we insist on pA collisions? G. Fai, Workshop on pA physics at RHIC, BNL, Oct. 29, 2000 3. Pseudorapidity asymmetry and nuclear modifications 4. Calculations 4a. d+Au results at RHIC 4b. d+Pb prediction for the LHC 5. Summary and conclusions Tokaj, March 17, 2008

  3. The importance of pA measurements We expect QGP to be formed in AA, but NOT in pA Miklos Gyulassy “The deuteron-gold control experiment” Tokaj, March 17, 2008

  4. Centrality Dependence Au + Au Experiment d + Au Control Experiment • Dramatically different and opposite centrality evolution of Au+Au experiment from d+Au control. Final Data Preliminary Data Tom Hemmick: Quark Matter 04 Tokaj, March 17, 2008

  5. The importance of pA measurements The jump from pp to AA (heavy) is too large to reliably • provide baseline • (enhancement/suppression relative to what?) • separate various nuclear effects • (shadowing, multiple scattering, EMC effect,…) ? Examples: J/ψ production, Drell-Yan, strangeness “enhancement” Direct observation of asymmetry should come from forward-backward difference in pA In light of no QGP formation and difference from pp, large forward-backward asymmetry should be expected in pA Tokaj, March 17, 2008

  6. The pT distributions soften in a similar way in pp and dAu collisions BRAHMS R. Debbe, 2005 Tokaj, March 17, 2008

  7. Forward-backward asymmetry in d+Au PHOBOS, PRC72, 031901(R) (2005) around 40% effect in the central bin back/forward asymmetry ratio > 1 Tokaj, March 17, 2008

  8. Forward-backward asymmetry in d+Au BRAHMS, PRL 94, 032301 (2005) upto 40% effect back/forward asymmetry ratio > 1 Tokaj, March 17, 2008

  9. The importance of pA measurements: other reasons Peter Steinberg 2005 v1,v3! Paul Stankus Tokaj, March 17, 2008

  10. In the past at RHIC: small detectors to go to higher rapidity PHOBOS, PRC70, 061901 (2004) BRAHMS, PRL 93, 242303 (2004) Notwithstanding some additions of large-rapidity capabilities STAR, ALICE, ATLAS, CMS are big barrels … Tokaj, March 17, 2008

  11. Front view of ALICE detector Tokaj, March 17, 2008

  12. … and here are many of them, with content measured (sampled) at this conference … Tokaj, March 17, 2008

  13. Ingredients of the pQCD calculation Shadowing parameterizations (nPDF-s) EKS, FGS, HKN, HIJING Fragmentation functions (FF-s) KKP, BKK, AKK, Kretzer Particularly interested in 1. Role of multiple scattering (over and above intrinsic kT) A. Adeluyi and G. Fai, PRC74, 054904 (2006) 2. Role of the EMC effect B.A. Cole & Hungarians, hep-ph/0702101 Tokaj, March 17, 2008

  14. Calculated spectra at RHIC -- compared to data Central rapidity intrinsic kTincreases the calculation mostly at low pT need to include multiple scattering with HIJING shadowing for same D/T Tokaj, March 17, 2008

  15. Calculated spectra at RHIC Nonzero rapidity Forward and backward data averaged by STAR multiple scatt. influences d-side (forward) more than Au-side (backward) Need separated forward/backward data! Tokaj, March 17, 2008

  16. Calculated spectra at Tevatron – compared to data Central rapidity p + Be @ sqrt(s) ~ 35 GeV Tokaj, March 17, 2008

  17. Calculated spectra at Tevatron – compared to data Nonzero rapidity Tokaj, March 17, 2008

  18. Study role of multiple scattering in rapidity distributions using HIJING shadowing d+Au at RHIC Pseudorapidity distribution at fixed pT intrinsic kT turned off asymmetry disappears in the absence of shadowing gold side deuteron side Tokaj, March 17, 2008

  19. Add intrinsic transverse momentum in the nucleon No shadowing added symmetry preserved gold side deuteron side Tokaj, March 17, 2008

  20. Turn on shadowing and multiple scattering multiple scatt. increases yield further (mostly d side), reverses asymmetry intrinsic kT increases the yield, keeping asymmetry gold side deuteron side Tokaj, March 17, 2008

  21. Start from full calculation, turn off multiple scatteringand shadowing separately shadowing suppresses yield, more on deuteron side (forward) multiple scatt. contribution is large on the deuteron side gold side deuteron side Tokaj, March 17, 2008

  22. What happens with increasing transverse momentum? When pTbecomes large compared to (broadened) intrinsic kT, intrinsic transverse momentum effects become less important + we approach antishadowing gold side deuteron side Tokaj, March 17, 2008

  23. What happens with increasing transverse momentum? When pTbecomes large compared to (broadened) intrinsic kT, intrinsic transverse momentum effects become less important + we approach antishadowing Tokaj, March 17, 2008

  24. Summary so far: pseudorapidity asymmetry arises from nuclear effects in constrained geometry In an asymmetric geometry (his wine thief), if there are some physical effects (gravity here), and the conditions are carefully controlled, the medium prefers one direction over the other (here the one leading to the wine glass) Tokaj, March 17, 2008

  25. Nuclear modification factors for deuteron on gold total charged hadrons min. bias EKS intrinsic kT turned off HKN FGS Tokaj, March 17, 2008

  26. Central-to-peripheral ratio for deuteron on gold HKN Without kTand without the possibility to tune multiple scattering, RCP overpredicted at forward rapidities Tokaj, March 17, 2008

  27. Semicentral-to-peripheral ratio for deuteron on gold Tokaj, March 17, 2008

  28. Pseudorapidity asymmetry for several species in |η| < 0.5 with EKS, FGS, HKN, without kT Tokaj, March 17, 2008

  29. Pseudorapidity asymmetry in 0.5 < |η| < 1.0 with EKS, FGS, HKN, without kT HKN Tokaj, March 17, 2008

  30. Comparing the two kinds of descriptions no significant difference at small η GO TO LHC ! at high η and pT, shadowing-type differences start to show up differences at high pT and higher pseudorapidity Tokaj, March 17, 2008

  31. Expected pseudorapidity asymmetry at the LHC 2 When going to LHC: much larger < kT> is used HIJING shadowing very strong Tokaj, March 17, 2008

  32. Expected nuclear modification factor at the LHC central rapidity HKN without kT EMC effect possible effects of jet quenching Tokaj, March 17, 2008

  33. Conclusions (tentative) In the framework of a pQCD-based model, two options to describe spectra in d+Au both at y=0 and y≠0: EITHER use EKS (or FGS or HKN) shadowing forward RCPnot well reproduced OR use HIJING-type shadowing + multiscattering pseudorapidity asymmetry not reproduced unless kT broadening given rapidity dependence NEED SEPARATED FORWARD/BACKWARD DATA FOR THIS KIND OF ANALYSIS! working on it LHC will hopefully prefer one over the other at sufficiently high rapidity and transverse momentum Tokaj, March 17, 2008

  34. Intrinsic transverse momentum width in the proton Tokaj, March 17, 2008

  35. Differences in RAAbetween Au+Au and d+Au Tokaj, March 17, 2008

  36. Shadowing and EMC summary Tokaj, March 17, 2008

  37. HKM Sarcevic EKS98 Frankfurt Armesto new HIJING Shadowing parameterizations as functions of x Tokaj, March 17, 2008

  38. Rapidity evolution of the Cronin peak Deuteron side Tokaj, March 17, 2008

  39. Rapidity evolution of the Cronin peak Gold side Tokaj, March 17, 2008

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