oct23-2008 論文セミナー. abstract au+au √s nn =62.4gev mid-rapidity, 7 centrality classes ...
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Au+Au √s NN =62.4GeV mid-rapidity, 7 centrality classes m T spectra dN/dy energy dependence (SPS, AGS data) yield (anti-Λ)/Λ ratioTRANSCRIPT
Oct23-2008論文セミナー
Abstract
Abstract
Au+Au √sNN=62.4GeV
mid-rapidity, 7 centrality classes mT spectra dN/dy
energy dependence (SPS, AGS data) yield (anti-Λ)/Λ ratio
Introduction
strange particle production →collision でできた matter の情報
Why 62.4GeV? ->energy scan b/w SPS & RHIC 130,200GeV SPS : baryon dominated RHIC : net-baryon free
hope excitation function の情報 constrains to the thermal model predictions
STAR experiment TPC (|y|<1.8):charged track SVT (|y|<1.) ,SSD (|y|<1.) :primary/secondary vertex SVT ,TPC : dE/dx を使用して PID
experimental setup
Au+Au √sNN=62.4GeV (Run4)
mid-rapidity STAR detector(|y|<0.5) 6.5×106 events 7 different centrality classes
# of primary tracks(0-5% ~ 60-80%)
charged particle track : TPC -> PID
reconstruction
neutral particle reconstruction : V0 decay topology method
K0(s)->π++π-
(anti-)Λ->(anti-)proton+(π+)π-
S/N improvement dE/dx information (daughter tracks) distance of closest approach (b/w daughter
tracks) some topological cuts
vertex
ex a<0.5cm b>2.85cm c>0.90cm d>5cm
Λ
π
p
b
c
a d
mT spectra & integrated yield
mT distribution
corrections geometrical acceptance detector inefficiency anti-proton absorption NOT contained weak decays of multi-strange
particles
fitting assuming flat rapidity distribution (|y|<0.5)
mT spectra & integrated yield
integrated yield integrated yield
〈 Npart 〉 ← Glauber model
integrated yield / 〈 Npart 〉 enhancement of strangeness
production as a function of centrality
normalized @ most peripheral bin
same enhancement pattern with SPS experiment
earlier saturation point
Energy dependence of yield & ratio
yield of mid-rapidity anti-Λ : monotonic increase Λ : constant Λ : different b/w SPS & RHIC
anti-Λ/Λ ratio @RHIC energy ratio~1
conclusions
strange hyperon production @62.4GeV new point in excitation function
integrated yield / ratio relatively smooth behavior with energy non-identical particle ratio に重要 (Λ/π, K/π)
typical strangeness enhancement