Strange Baryon/Meson Correlations in STAR

1. Is there a strange baryon/meson dependence in correlations in STAR? Marek Bombara for the STAR Collaboration (University of Birmingham) Strangeness in Quark Matter, Levoča, Slovakia, 24.06. 2007

2. Outline • Introduction • Why correlations? • Why a strange baryon/meson correlations? • How do we make correlations? • Results • Conclusions Marek Bombara

3. Why correlations? • angular correlations: info about jet-like structures (jet and ridge) • practical: jets are indistinguishable from the bulk (in STAR TPC) Marek Bombara

4. Why a strange baryon/meson correlations? • good source of baryons (), antibaryons () and mesons (K0) - various quark compositions • correlations with identified particles: helpful for understanding particle production mechanism at intermediate pT (recombination and fragmentation) • practical: for high/intermediate pT region in STAR experiment the purity/statistics ratio is best in comparison to others particles Marek Bombara

5. How do we make correlations? • Pick up track (for h-h) or V0 (for strange particle-h) with pT in 2-6 GeV/c (trigger particle) - we assume that track/V0 is related to jet leading particle • Pick up tracks from the same event with pt 1.5<pTasso< pTtrig (associated particle) • Calculate angular (azimuthal, and polar, correlations associated associated) - trigger) associated) - trigger) Marek Bombara

6. AuAu     sameside awayside Results What we have seen in unidentified h-h correlations: dAu Sameside peak broader in and peak sits atop a ridge! Marek Bombara

7. Radiated gluon contributes to ridge and broadening (N. Armesto, C.A. Salgado, U.A. Wiedemann, Phys. Rev.Lett. 93, 2004) Coalescence of quarks from the medium (C.B. Chiu, R.C. Hwa, Phys. Rev. C 72, 2005) Collective flow combined with jet-quenching (S.A. Voloshin, Nucl. Phys. A749, 2005) Turbulent color fields (A. Majumder, B. Mueller, S.A.Bass, hep-ph/0611135) Anisotropic QGP (P. Romatschke, Phys.Rev. C 75, 014901, 2007) In vacuo (pp) fragmentation flowing medium anisotropic shape static medium broadening What causes the ridge and jet broadening? Marek Bombara

8. Dip in the centre of the jet peak ∆ projection ∆ projection Intensive analysis showed that dip is a consequence of missing pairs whose tracks are crossed in TPC. Those pairs are instead probably reconstructed as merged tracks. Marek Bombara

9. Closer look at the dip…. 5 dips! h_tr = -1 h_as = 1 h_tr = 1 h_as = -1 • The position and depth of the dip depends on pT and helicity of trigger and associated particle • Could be more pronounced for V0-h correlations (3 tracks for merging) • How to correct? • Anti-merging cut - calculation of fraction of merged hits of two tracks • Mirror image method - replacement of dip region on one side (for specific helicities combination) with unaffected region from other side (used in this analysis) • Calculation of pair reconstruction efficiency with MC simulations h_tr = 1 h_as = 1 genuine merging, most visible for low pt triggers h_tr = -1 h_as = -1 h_tr - helicity of trigger h_as - helicity of associated Marek Bombara

10. Study of jet and ridge with identified strange trigger particles Input • Pair-wise detector acceptance • Single particle reconstruction efficiency • Combinatorial background modulated by elliptic flow • Track merging • 16 million central AuAu (√sNN = 200 GeV) events Correlations corrected for Marek Bombara

11. Yields definition  R1 Assumption: Ridge is flat in all  region! R=R1+R2 JR R2  Jet+Ridge region (JR) = || < 1 Ridge region (R) = 1<||<2 Jet yield =  (JR) -  (R) Ridge yield = 2* (R) Marek Bombara

12. ∆ projections pTtrigger h-h -h -h K0-h 2.0-2.5GeV/c 2.5-3.0GeV/c 3.0-3.5GeV/c 3.5-4.5GeV/c 4.5-6.0GeV/c Marek Bombara

13. ∆ projections pTtrigger h-h -h -h K0-h 2.0-2.5GeV/c 2.5-3.0GeV/c 3.0-3.5GeV/c 3.5-4.5GeV/c 4.5-6.0GeV/c Marek Bombara

14. ∆ projections pTtrigger h-h -h -h K0-h 2.0-2.5GeV/c 2.5-3.0GeV/c 3.0-3.5GeV/c 3.5-4.5GeV/c 4.5-6.0GeV/c Marek Bombara

15. ∆ projections pTtrigger h-h -h -h K0-h 2.0-2.5GeV/c 2.5-3.0GeV/c 3.0-3.5GeV/c 3.5-4.5GeV/c 4.5-6.0GeV/c Marek Bombara

16. Jet widths ∆ projection  projection • Jet is broadening in ∆ with decreasing pTtrig • Smaller broadening is seen for ∆ Marek Bombara

17. Ridge Jet PTtrig dependence • Jet yield is increasing with pTtrig • Ridge yield dependence? • No trigger species dependence J. Bielcikova, QM’06 J. Bielcikova, QM’06 Marek Bombara

18. Ridge Jet System size dependence • Jet yield doesn’t depend on centrality • Ridge yield increases with centrality J. Bielcikova, QM’06 J. Bielcikova, QM’06 Marek Bombara

19. J. Putschke, QM’06 “jet” slope ridge slope inclusive slope STAR preliminary h-h correlations pTassociated>2GeV/c PT distribution of associated particles J. Bielcikova, QM’06 • Ridge pT distribution similar to medium • Jet distribution harder Marek Bombara

20. Conclusions • No observation of strange baryon/meson trigger differencies in angular correlations • Jet peak broadened in ∆, increasing with pTtrig, constant with centrality • Ridge (long ranged ∆ correlation) increasing with centrality, associated spectra similar to inclusive Marek Bombara

21. Backup slides Marek Bombara

22. No anti-merging cut h-h, 2.25<p_tr<2.50, 1.5<p_as<p_tr, 0-10% Marek Bombara

23. Anti-merging cut applied h-h, 2.25<p_tr<2.50, 1.5<p_as<p_tr, 0-10% Marek Bombara

24. Mirror image h-h, 2.5<p_tr<3.0, 1.5<p_as<p_tr, 0-10% Marek Bombara