# Presentation: 598633

## Forward Identified Particle Production in d+Au and p+p collisions at √sNN=200 GeV

- 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**

- DNP2004 Oct. 27-30 Hyatt Regency Chicago IL

## 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

## Use of the BRAHMS RICH to  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

## Using ratios to obtain the RdAu of identified negative particles.

- DNP2004 Oct. 27-30 Hyatt Regency Chicago IL

## Ratios:  pion over charged (negatives)

**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

## Anti-proton/negative charged particles in d+Au at 4 degrees

- DNP2004 Oct. 27-30 Hyatt Regency Chicago IL

## 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

## 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

## 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

## d+Au positives

**Same information as above but this time we show how h****+ ****is composed of protons, pions, and kaons.**

**d+Au positives**

- DNP2004 Oct. 27-30 Hyatt Regency Chicago IL

## 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

## 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

## 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

## 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