Results from BRAHMS from y=0 to y=3 I. G. Bearden Niels Bohr Institute University of Copenhagen, Denmark. Champaigne Workshop, Seattle, 13 Dec.

Transcription

1 Results from from y=0 to y=3 I. G. Bearden Niels Bohr Institute University of Copenhagen, Denmark Champaigne Workshop, Seattle, 13 Dec. 2002

2 The Collaboration I.G. Bearden 7, D. Beavis 1, C. Besliu 10, Y. Blyakhman 6, J.Brzychczyk 4, B. Budick 6, H. Bøggild 7,C. Chasman 1, C. H. Christensen 7, P. Christiansen 7,J.Cibor 4, R.Debbe 1, J. J. Gaardhøje 7,M. Germinario 7,K. Grotowski 4, K. Hagel 8, O. Hansen 7, A.K. Holme 12, H. Ito 11, E. Jacobsen 7, A. Jipa 10, J. I. Jordre 10, F. Jundt 2, C.E.Jørgensen 7, T. Keutgen 9, E. J. Kim 5, T. Kozik 3, T.M.Larsen 12, J. H. Lee 1, Y. K.Lee 5, G. Løvhøjden 2, Z. Majka 3, A. Makeev 8, B. McBreen 1, M. Murray 8, J. Natowitz 8, B.S.Nielsen 7, K. Olchanski 1, D. Ouerdane 7, R.Planeta 4, F. Rami 2, D. Roehrich 9, B. H. Samset 12, S. J. Sanders 11, I. S. Sgura 10, R.A.Sheetz 1, Z.Sosin 3, P. Staszel 7, T.S. Tveter 12, F.Videbæk 1, R. Wada 8 and A.Wieloch 3 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, Blegdamsvej 17, 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 2

3 The Experiment

4 Determination of Collision Vertex, Centrality Strips? tsilicon in BBC measurements (σ 0.7 cm) Plastic Scintillator Tiles 4

5 Ratios are (relatively) easy o 8 o 4 o Ratios could vary in pt, and in y Narrow y bins, look vs pt geometric acceptance same for particles and antiparticles, so correction is not needed. For given B field, angular setting, compare (+) and (-) polarity Normalize to number of triggers, and --bingo!-- ratios... No dependence on transverse momentum or centrality (at least for top ~25%) has been observed 5

6 How consistent are the models? 130 GeV data... 6

7 acceptance 7

8 Particle/Particle vs rapidity, submitted to PRL 12/07/02 nucl-ex/

9 How does this compare to p+p? ISR R803 s=63 s=23 9

10 p+p: Ratios vs Y ISR extrapolation 10

11 Ratios vs. S ISR Data A. Rossi et al. Nucl. Phys. B 84 (1975)

12 Spectra 12

13 The spectra can be fit... 13

14 Flow T eff =T fo +mβ 2 T fo~ 200MeV β 0.41 β 0.34 T fo too high, β too low β indicates less flow at y 3. y 2 anxiously anticipated! 14

15 15

16 K/π vs. rapidity 16

17 K/π vs. Beam energy 17

18 Comparison to PREdictions Points scaled by 2 QM

19 PRELIMINARY Fritiof 1.7 Venus 4.02 Fritiof 7.2 Now, all fits in mt, as is proper. Λ corrections: Scale HIJING to STAR at y=0, use same scaling factor at other rapidities. Shown here are (net protons) x 2. RQMD 19

20 Net protons vs. HIJING models 20

21 Net protons AGS,SPS, RHIC 21

22 Net protons: From stopping to transparency Peter Christiansen, J.H. Lee, QM

23 Summary Ratios for p+p similar to Au+Au at mid rapidity, begin to diverge y>2. K-/p- decreases from 0.18 (y=0) to 0.1(y=3) Inverse slope decreases with rapidity, larger decrease for p than K than p Net baryon central plateau (y=0 to almost y=2) Significant transparency 23