Energy dependence of p and p production in central Pb+Pb

collisions from NA49

Ewelina Kornaś

IFJ PAN Krakow, Poland

for the collaboration

Hot Quarks 2006

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StoppingEnergy dependence of p - p

AGS →SPS → RHIC :Stopping → Transparency

Phys.Rev.Lett.93,102301(2004)

The shape of the distributions changes with energy

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158 AGeV data from NA49

Rather large but not complete stopping

The rapidity loss δy~1.75+-0.05 for Pb+Pb

Central Pb+Pb 158 AGeVPhys.Rev.Lett.82,2471(99)

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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

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Mid-rapidity p, p mt-spectra in central Pb+Pb 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

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Mid-rapidity central Pb+Pb @ 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

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Analysis of the MTPC data

Advantage – larger acceptance

Particle identification – dE/dx MTPC has been optimized for the best dE/dx resolution

dE/dx p=14 GeV pt=0.3GeV

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Geometrical acceptance of the MTPC for protons

40 AGeV central Pb+Pb data|φ| <300

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40 AGeV central Pb+Pb data from NA49

the preliminary results are

corrected for geometrical acceptance reconstruction efficiency

not yet corrected for feeddown

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dN/dy distribution for 40AGeV data

■ data PRELIMINARY□ reflected

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dN/dy distribution for 40 AGeV data

■ data PRELIMINARY□ reflected▲ TOF analysis (corrected for feeddown)

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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 4π yields of p and p at all SPS energies Results provide interesting information in the energy

range where transparency develops in nuclear collisions