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Stopping net proton rapidity spectra pbar/p vs s Kaon production K/  vs pbar/p

Energy dependence of stopping and the K/  ratio (BRAHMS data). Stopping net proton rapidity spectra pbar/p vs s Kaon production K/  vs pbar/p Kaon slopes vs pbar/p. Dieter Roehrich UiB. BRAHMS. NA49. AGS. From SPS to RHIC. Particle production increases ...

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Stopping net proton rapidity spectra pbar/p vs s Kaon production K/  vs pbar/p

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  1. Energy dependence of stopping and the K/ ratio (BRAHMS data) • Stopping • net proton rapidity spectra • pbar/p vs s • Kaon production • K/ vs pbar/p • Kaon slopes vs pbar/p Dieter Roehrich UiB

  2. BRAHMS NA49 AGS From SPS to RHIC • Particle production increases ... • Projectile fragmentation region and central region • overlap at SPS • are well separated at RHIC • Antiproton/proton ratio at midrapidity resp. net-proton rapidity density change drastically with s

  3. (Net)-proton rapidity distribution • AGS energies • centrality dependence • energy dependence B. Back et al., E917 Collaboration. Phys. Rev. Lett. 86 (2001) 1970

  4. (Net)-proton rapidity distribution • SPS, 158 GeV/nucl., NA49- central collisions

  5. Rapidity distributions of produced hadrons at SPS • Rapidity distributions of both produced hadrons and net-protons peak at (or near) midrapidity

  6. Net-proton rapidity distribution dN dy • RHIC • central Au+Au • Npart=3578 BRAHMS, submitted to PRL, nucl-ex/0312023

  7. Stopping (1)

  8. Gaussians in pz: 2.03  0.16 2.00  0.10 Stopping (2) Net-baryon after feed-down & neutron corrections Gaussians in pz: 6 order polynomial Rapidity loss: (Npart= 357  10)

  9. Rapidity distributions at RHIC Rapidity distributions of • produced hadrons peak at midrapidity • net-protons peak at forward midrapidity

  10. SPS vs RHIC dn/dy net-protons pions RHIC: 35-40 80 forward rapidity (y4) at 200 GeV SPS: 41 100 midrapidity at 40 AGeV/c

  11. How to compare SPS and RHIC data? • use the antiproton/proton ratio: ratios at midrapidity (SPS) and at different rapidities (RHIC)

  12. Kaon production • K/ vs pbar/p • Kaon slopes vs pbar/p

  13. Fit: exponential Kaon spectra at RHIC AuAu 200 GeV AuAu 63 GeV BRAHMS preliminary Top 5% central collisions

  14. Kaon inverse slopes Top 5% central collisions

  15. K-/K+ vs pbar/p 62.4 GeV

  16. K/ vs rapidity at 200 GeV BRAHMS • Indication of divergence at large y

  17. K/ vs rapidity at 62.4 GeV BRAHMSpreliminary • Clear splitting of the ratio for positive and negative particles

  18. K/ vs s • The Horn

  19. RHIC 62.4 GeV BRAHMS preliminary K- - SPS- NA49 RHIC 200 GeV BRAHMS K-/- vs pbar/p • SPS data and RHIC data agree at same pbar/p ratio

  20. K+ + RHIC 62.4 GeV BRAHMS preliminary SPS- NA49 RHIC 200 GeV BRAHMS K+/+ vs pbar/p • SPS data and RHIC data agree at same pbar/p ratio

  21. Kaon slopes vs s • The Step

  22. Kaon slopes vs pbar/p SPS - NA49 RHIC 62.4 GeV BRAHMS preliminary T [MeV] RHIC 200 GeV BRAHMS 300 200 100

  23. Summary • Projectile fragmentation region and central region overlap at SPS and are well separated at RHIC • Antiproton/proton ratio at midrapidity changes drastically with s • Antiproton/proton ratio changes with rapidity at RHIC energies • Local systems (y1), characterized by the same pbar/p ratio, show identical K-/K+ and K/ ratios and kaon inverse slopes • The right side of the ’horn’ seems to be reproduced by going to forward rapidities at RHIC

  24. Pions: power law Kaons: exponential Protons: Gaussian Identified particle spectra Top 5% central collisions

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