1. HAW05 18-22 Sep. 2005 Maui, Hawaii Ramiro Debbe BNL Physics Department The excess of positive charged particles measured at forward rapidities in d+Au DNP 2005

2. HAW05 18-22 Sep. 2005 Maui, Hawaii Outline of the presentation  This is a report on our ongoing dAu data analysis. I will start with a historical motivation to this presentation.  We see an unexpected abundance of protons at high rapidity and transverse momentum, I will enumerate possible explanations.  Spectra of identified pions and protons at y=3 in d+Au collisions. Compare the abundance of proton and anti-protons to that of same sign pions.  Similar studies for p+p collisions  Summary

3. HAW05 18-22 Sep. 2005 Maui, Hawaii Gusev, Strickman, Vogelsang: “At most a 10% difference with pQCD and standard PDFs and fragmentation functions” Phys. Lett. B603 173 (2004) Preliminary results of charged hadron distributions shown at QM2004 Oakland At DNP 2004 we showed that the bulk of the excess in h + is in the protons Historical Motivation

4. HAW05 18-22 Sep. 2005 Maui, Hawaii EPOS K. Werner et al. hep-ph/0506232 Some possible descriptions of the physics close to projectile rapidity High p T ? Y Baryons? N Multiple scattering Modified target wave function Coalescence final state High p T ? : Modified Baryons? N High p T ? Y Baryons? Y High p T ? N Baryons? Y

5. HAW05 18-22 Sep. 2005 Maui, Hawaii Pion Invariant Yield from d + Au at y = 3. All the spectra are fully corrected for spectrometer acceptance, tracking efficiency and PID efficiency as well as multiple scattering and absorption.

6. HAW05 18-22 Sep. 2005 Maui, Hawaii Anti-proton and proton Invariant Yields from dAu at y=3. PID done with our RICH. Proton spectra for momentum above threshold (~17 GeV/c).

7. HAW05 18-22 Sep. 2005 Maui, Hawaii Ratio proton/pion in d+Au at y=3. Protons can be as much as 80% of the pion yield at high p T. This explains the difference between h + and h -. p/  - is similar to the ratios found in e + e- collisions; DELPHI Euro. Phys. C17 207, (2000) Why that many protons at that high p T ? Systematic error 20%

8. HAW05 18-22 Sep. 2005 Maui, Hawaii Negative pion Invariant yield from p+p at y=3. NSD trigger. Integrated yield consistent with UA5 results Spectra extracted from run 5 p+p collisions

9. HAW05 18-22 Sep. 2005 Maui, Hawaii Anti-proton and proton Inv. Yields from p+p at y=3.

10. HAW05 18-22 Sep. 2005 Maui, Hawaii Ratio proton/pion from pp at y=3. The abundance of protons at y=3 and high p T is also present in p+p collisions. Above 2 GeV/c we see a factor ~4 compared to Pythia. Abundance of anti- protons is consistent with fragmentation of quark-antiquark “in vacuum”. Pythia 6.303 run in “Min. Bias QCD”

11. HAW05 18-22 Sep. 2005 Maui, Hawaii Summary  We have reanalyzed the 2003 d+Au data, this time we include PID from the RICH and a thorough treatment of efficiency corrections.  The study of the difference between charged hadron distributions has yielded an interesting result pertaining to the abundance of protons at high rapidity and transverse momentum.  We have also analyzed the dada from this year p+p run and find an equally high abundance of protons at y=3.

12. HAW05 18-22 Sep. 2005 Maui, Hawaii I.Arsene, I.G. Bearden 7, D. Beavis 1, S.Bekele 11, C. Besliu 10, B. Budick 6, H. Bøggild 7, C. Chasman 1, C. H. Christensen 7, P. Christiansen 7, R.Clarke 10, R. Debbe 1,J. J. Gaardhøje, K. Hagel 8, H. Ito 1, A. Jipa 10, J. I. Jordre 10, F. Jundt 2, E.B.Johnson 11, J.I.Jordre 9, C.Jørgensen 7, R. Karabowicz 3, E. J. Kim 11, T.M. Larsen 7, J. H. Lee 1, Y. K.Lee 5, S.Lindal 12, G. Løvhøjden 2, Z. Majka 3, M. Murray 11, J. Natowitz 8, B.S.Nielsen 7, D.Ouerdane 7, R.Planeta 4, F. Rami 2, C.Ristea 7, O.Ristea 10, D. Röhrich 9, B. H. Samset 12, S. J. Sanders 11, R.A.Sheetz 1, P. Staszel 3, T.S. Tveter 12, F.Videbæk 1, R. Wada 8, H.Yang 9, Z. Yin 9, and I. S. Zgura 10 1 Brookhaven National Laboratory, USA, 2 IReS and Université Louis Pasteur, Strasbourg, France 3 Jagiellonian University, Cracow, Poland, 4 Institute of Nuclear Physics, Cracow, Poland, 5 Johns Hopkins University, Baltimore, USA, 6 New York University, USA, 7 Niels Bohr Institute, University of Copenhagen, Denmark, 8 Texas A&M University, College Station. USA, 9 University of Bergen, Norway, 10 University of Bucharest, Romania, 11 University of Kansas, Lawrence,USA, 12 University of Oslo Norway The BRAHMS Collaboration

13. HAW05 18-22 Sep. 2005 Maui, Hawaii Backup Slides

14. HAW05 18-22 Sep. 2005 Maui, Hawaii