Energy dependence of p and p production in central Pb Pb collisions from NA49

1
Energy dependence of p and p production in
central PbPb collisions from NA49

• Ewelina Kornas
• IFJ PAN Krakow, Poland
• for the collaboration
• Hot Quarks 2006

2
StoppingEnergy dependence of p - p

• AGS ?SPS ? RHIC
• Stopping ? Transparency
• 
  
• Phys.Rev.Lett.93,102301(2
  004)
• The shape of the distributions changes with
  energy

3
158 AGeV data from NA49

• Rather large
• but not complete stopping
• The rapidity loss
• dy1.75-0.05 for PbPb
• Central PbPb 158 AGeV
• Phys.Rev.Lett.82,2471(99)

4
The NA49 experiment

• large acceptance hadron spectrometer
• tracking (TPCs)
• particle identification by dE/dx (3-6 res.)
• and TOF (60 ps res.) around midrapidity
• centrality determination Veto calorimeter

5
Mid-rapidity p, p mt-spectra in central PbPb
from NA49
Phys.Rev.C73,044910
(2006) the shape of mT spectra hardly changes
the shape can be described by in
the SPS energy region
hydro-inspired models
(temperature plus collective radial
flow)
Ebeam/AGeV 20 30 40 80 158
dn/dy p 46.1 2.1 42.1 2.0 41.3 1.1 30.1 1.0 29.6 0.9
dn/dy p 0.06 0.01 0.16 0.02 0.32 0.03 0.87 0.07 1.66 0.17
6
Mid-rapidity central PbPb _at_ 20-158 AGeV

• Phys.Rev.C73,044910(2006)
• The increase of the p/p ratio reflects the
  decrease of
• the baryochemical potential towards higher energy

7
Analysis of the MTPC data

• Advantage larger acceptance
• Particle identification dE/dx
• MTPC has been optimized for
• the best dE/dx resolution
• dE/dx
• p14 GeV
• pt0.3GeV

8
Geometrical acceptance of the MTPC for protons

• 40 AGeV central PbPb data
• f lt300

9
40 AGeV central PbPb data from NA49
the preliminary results are

• corrected for
• geometrical acceptance
• reconstruction efficiency

• not yet corrected for
• feeddown

10
dN/dy distribution for 40AGeV data

• data
  PRELIMINARY
• ? reflected

11
dN/dy distribution for 40 AGeV data

• data
  PRELIMINARY
• ? reflected
• ? TOF analysis (corrected for feeddown)

12
Summary

• NA49 published p and p yields at midrapidity
• for the SPS energy range
• Preliminary results have been shown for the
  rapidity distributions of p and p at 40AGeV
• Outlook
• 4p yields of p and p at all SPS energies
• Results provide interesting information in the
  energy range where transparency develops in
  nuclear collisions