June 2009 CPOD09 H. StröbeleGoethe-Universität Frankfurt
Baryon Stopping at 40 and 158 A GeV
Net proton spectra in pp, peripheral and central PbPb
collisions
June 2009 CPOD09 H. StröbeleGoethe-Universität Frankfurt
outline
• energy loss and baryon transport• (normalized) rapidity and Feynman x• net protons, net baryons, baryochemical potential (Anti-
L/Anti-p)• rapidity loss: scaling in “fragmentation” and mid-rapidity
regions ??• sqrt(s) dependence of rapidity shape and ~ loss, • sqrt(s) dependence of chem.-temperature and <p_T>• centrality dependence of rapidity shape and ~ loss at 40
& 158 GeV/nucleon• centrality dependence of chem.-temperature(?) and
<p_T> at 40 & 158 GeV/nucleon• model comparison: HSD, UrQMD, core corona
June 2009 CPOD09 H. StröbeleGoethe-Universität Frankfurt
energy loss and baryon transport
• In particle collisions part of the cm-energy of the incident particles is diverted into:– Thermal motion– Radial or transverse flow– Mass (particle production)
• The remaining energy stays in the longitudinal motion
• => plong ∙c = (√s – Ethermal – Eflow – ∑mi∙c2)/2
June 2009 CPOD09 H. StröbeleGoethe-Universität Frankfurt
energy loss and baryon transport
• => plong ∙c = (√s – Ethermal + Eflow + ∑mi∙c2)/2
• Plong is commonly represented by– rapidity: y = ln((E+plong)/mT) (energy loss causes
rapidity shift (e.g. ΔEcm=0.5 ≈> Δy=0.7)).
• or– Feynman x: xF = plong/pbeam (energy loss is mapped
directly on xF (e.g. ΔE=0.5 ≈> xF= 1 – 0.5)).
June 2009 CPOD09 H. StröbeleGoethe-Universität Frankfurt
• We will compare proton rapidity distributions from 40 and 158 A GeV PbPb collisions at different centralities to nucleon-nucleon (NN) data (as a base line).
• First get the base line, i.e. NN
June 2009 CPOD09 H. StröbeleGoethe-Universität Frankfurt
energy loss and baryon transportexample: p+p =>p + X at 158 GeVnew from NA49 [arXiv:0904.2708v1 [hep-ex]
• rapidity XF distribution
June 2009 CPOD09 H. StröbeleGoethe-Universität Frankfurt
energy loss and baryon transportexample: p+p =>p + X at 158 GeV
• Neutron complication
– dn/dx of net neutrons must be converted into dn/dy
June 2009 CPOD09 H. StröbeleGoethe-Universität Frankfurt
energy loss and baryon transportexample: p+p =>p + X at 158 GeV
• hyperon complication
June 2009 CPOD09 H. StröbeleGoethe-Universität Frankfurt
energy loss and baryon transportexample: p+p =>p + X at 158 GeV
• Base line for centrality dependend Pb+Pb collisions at 158 A GeV: – pp => p + X– pp => n + X– pp => Y+ X
• What about 40 A GeV (no data on elementary collisions )
June 2009 CPOD09 H. StröbeleGoethe-Universität Frankfurt
energy loss and baryon transportexample: p+p =>p + X at 12 & 24 GeV (Blobel data)
June 2009 CPOD09 H. StröbeleGoethe-Universität Frankfurt
energy loss and baryon transportexample: p+p =>p + X at 40 GeV/c
June 2009 CPOD09 H. StröbeleGoethe-Universität Frankfurt
energy loss and baryon transportparametrization
June 2009 CPOD09 H. StröbeleGoethe-Universität Frankfurt
energy loss and baryon transportparametrization
June 2009 CPOD09 H. StröbeleGoethe-Universität Frankfurt
energy loss and baryon transportrapidity shift in nuclear collisions
June 2009 CPOD09 H. StröbeleGoethe-Universität Frankfurt
Results on Pb+Pb at SPS
158 A GeV
June 2009 CPOD09 H. StröbeleGoethe-Universität Frankfurt
Results on Pb+Pb at SPS
158 A GeV
net protons
June 2009 CPOD09 H. StröbeleGoethe-Universität Frankfurt
Results on Pb+Pb at SPS
158 A GeV
Normalized to
Nw
June 2009 CPOD09 H. StröbeleGoethe-Universität Frankfurt
Results on Pb+Pb at SPS
158 A GeV
net protons
peripheral
versus pp.
normalisation?
June 2009 CPOD09 H. StröbeleGoethe-Universität Frankfurt
Results on Pb+Pb at SPS
40 A GeV
June 2009 CPOD09 H. StröbeleGoethe-Universität Frankfurt
Results on Pb+Pb at SPS
40 A GeV
peripheral
versus
pp
June 2009 CPOD09 H. StröbeleGoethe-Universität Frankfurt
Results on Pb+Pb at SPS
40 A GeV
extrapolation
to y_beam??
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