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Energy dependence of stopping

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Presentation on theme: "Energy dependence of stopping"— Presentation transcript:

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 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 BRAHMS NA49 AGS

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/

7 Stopping (1)

8 Stopping (2) Rapidity loss: Net-baryon after
Gaussians in pz: Net-baryon after feed-down & neutron corrections Gaussians in pz: 2.03  0.16 2.00  0.10 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: 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 Kaon spectra at RHIC AuAu 200 GeV AuAu 63 GeV BRAHMS preliminary
Fit: exponential 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 BRAHMS preliminary
Clear splitting of the ratio for positive and negative particles

18 K/ vs s The Horn

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

20 K+/+ vs pbar/p K+ + SPS- NA49 RHIC 62.4 GeV BRAHMS preliminary RHIC 200 GeV BRAHMS 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

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


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