Oct23-2008 論文セミナー

1. Oct23-2008 論文セミナー

2. Abstract

3. 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

4. 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

5. 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

6. 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

7. 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

8. vertex p • ex • a<0.5cm • b>2.85cm • c>0.90cm • d>5cm b Λ π d a c

9. mT spectra & integrated yield • mT distribution • corrections • geometrical acceptance • detector inefficiency • anti-proton absorption • NOTcontained weak decays of multi-strange particles • fitting • assuming flat rapidity distribution (|y|<0.5)

10. mT spectra & integrated yield

11. 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

12. 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

13. 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