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Ramiro Debbe for the BRAHMS collaboration Physics Department

Forward Identified Particle Production in d+Au and p+p collisions at √s NN =200 GeV. 2004 Fall Meeting Division of Nuclear Physics. Ramiro Debbe for the BRAHMS collaboration Physics Department. Outline of the presentation.

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Ramiro Debbe for the BRAHMS collaboration Physics Department

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  1. Forward Identified Particle Production in d+Au and p+p collisions at √sNN=200 GeV 2004 Fall Meeting Division of Nuclear Physics Ramiro Debbe for theBRAHMScollaboration Physics Department DNP2004 Oct. 27-30 Hyatt Regency Chicago IL

  2. Outline of the presentation • Will show RdAu for negative identified particles using our RICH to construct anti-proton and negative pion to negative charged particle ratios. • Present a study of the composition of the positive particle pt distribution at 4 degrees using proton/pion and kaon/pion ratios. • Compare particle ratios extracted from p+p data collected at 4 degrees with PYTHIA simulation. • Summarize DNP2004 Oct. 27-30 Hyatt Regency Chicago IL

  3. Use of theBRAHMSRICHto identify particles We make use of already produced spectra and RdAu factors and use the RICH at high momentum to bypass the long process of invariant yield extraction. 17 GeV/c Above the selected momentum threshold the RICH is ~94% efficient. DNP2004 Oct. 27-30 Hyatt Regency Chicago IL

  4. Using ratios to obtain the RdAu of identified negative particles. DNP2004 Oct. 27-30 Hyatt Regency Chicago IL

  5. Ratios: pion over charged (negatives) d + Au p +p The conversion from RdA(h-) to RdAu(-) is done point by point. DNP2004 Oct. 27-30 Hyatt Regency Chicago IL

  6. Anti-proton/negative charged particles in d+Au at 4 degrees DNP2004 Oct. 27-30 Hyatt Regency Chicago IL

  7. Ratio of anti-proton to negative particles in p+p at 4 degrees The conversion from RdAu(h-) to RdAu(p) makes use of fits to the ratios of anti-proton to negative charged hadrons. Error propagation includes all parameter correlations. DNP2004 Oct. 27-30 Hyatt Regency Chicago IL

  8. RdAu for anti-protons and pions at ~3 (min bias) This will not be the first time baryons show a different nuclear modification factor. PHENIX reported such difference at y=0 in AuAu and dAu systems DNP2004 Oct. 27-30 Hyatt Regency Chicago IL

  9. The difference between positive and negative hadrons in dAu at 4 degrees This measured difference (≥2 at 3GeV/c) is not easily explained if pion production is dominant. (NLO pQCD) It has been early dubbed as “beam fragmentation” DNP2004 Oct. 27-30 Hyatt Regency Chicago IL

  10. d+Au positives As seen in the figure on the right there are roughly as many protons as pions at high pt at forward rapidities (y~3) in d+Au Same information as above but this time we show how h+ is composed of protons, pions, and kaons. DNP2004 Oct. 27-30 Hyatt Regency Chicago IL

  11. The composition of h+ yields in dAu at ~3 Isospin considerations set: + = - We make use of the measured ratio -/h-~0.8 Independent of momentum to write: h+ = 0.8h-( 1 + p/+ + K/+) DNP2004 Oct. 27-30 Hyatt Regency Chicago IL

  12. Comparison of particle ratios extracted from p+p data at 4 degrees and PYTHIA 6.303 For protons we find a remarkable difference that may indicate other processes besides parton fragmentation. We measure a small excess of kaons and see an emerging trend that suffers from low statistics at high pt. DNP2004 Oct. 27-30 Hyatt Regency Chicago IL

  13. Summary and outlook • With the use of particle ratios obtained with our RICH we have shown that baryons and mesons have a different behavior as can be seen in the nuclear modification factors of anti-protons and pions at ~3 in d+Au collisions. • We have shown the composition of positive particles at high pt and rapidity 3 in d+Au collisions. • We compared particle ratios extracted from p+p data collected at 4 degrees and find strong disagreement with PYTHIA calculations. • BRAHMS measurements continue to show that Forward Physics in hadron colliders is fertile ground for discovery. DNP2004 Oct. 27-30 Hyatt Regency Chicago IL

  14. The BRAHMS Collaboration I. Arsene, I.G. Bearden, D. Beavis, C. Besliu, B. Budick, H. Bøggild, C. Chasman, C. H. Christensen, P. Christiansen, J. Cibor, R. Debbe, E. Enger J. J. Gaardhøje, M. Germinario, K. Hagel, O. Hansen, A. Holme, A.K. Holme, H. Ito, A. Jipa, J.I. Jørdre, F. Jundt, C.E.Jørgensen, R. Karabowicz, E.J. Kim, T. Kozik, T.M. Larsen, J.H. Lee, Y. K.Lee, S. Linda, G. Løvhøjden, R. Lystad, Z. Majka, A. Makeev, M. Mikelsen, M. Murray, J. Natowitz, B. Neumann, B.S. Nielsen, K. Olchanski, D. Ouerdane, R.Planeta, F. Rami, C. Ristea, O. Ristea, D.Roehrich, B. H. Samset, D. Sandberg, S. J. Sanders, R.A.Sheetz, P. Staszel, T.S. Tveter, F.Videbæk, R. Wada,Z. Yin and I. S. Zgura Brookhaven, Strasbourg, Krakov, Johns Hopkins, NYU, Niels Bohr. Texas A&M, Bergen, Bucharest, Kansas, Oslo DNP2004 Oct. 27-30 Hyatt Regency Chicago IL

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