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,

Marek Bombara 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 (K 0 ) - various quark compositions correlations with identified particles: helpful for understanding particle production mechanism at intermediate p T (recombination and fragmentation) practical: for high/intermediate p T region in STAR experiment the purity/statistics ratio is best in comparison to others particles

Marek Bombara 5  associated) -  trigger)  associated) -  trigger) How do we make correlations? 1)Pick up track (for h-h) or V0 (for strange particle-h) with p T in 2-6 GeV/c (trigger particle) - we assume that track/V0 is related to jet leading particle 2)Pick up tracks from the same event with pt 1.5<p Tasso < p Ttrig (associated particle) 3)Calculate angular (azimuthal,  and polar,  correlations associated

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

Marek Bombara 7 What causes the ridge and jet broadening? 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/ ) Anisotropic QGP (P. Romatschke, Phys.Rev. C 75, , 2007) In vacuo (pp) fragmentation static medium broadening flowing medium anisotropic shape

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 The position and depth of the dip depends on p T and helicity of trigger and associated particle Could be more pronounced for V0- h correlations (3 tracks for merging) How to correct? 1)Anti-merging cut - calculation of fraction of merged hits of two tracks 2)Mirror image method - replacement of dip region on one side (for specific helicities combination) with unaffected region from other side (used in this analysis) 3)Calculation of pair reconstruction efficiency with MC simulations h_tr = -1 h_as = 1 h_tr = 1 h_as = 1 h_tr = -1 h_as = -1 genuine merging, most visible for low pt triggers h_tr = 1 h_as = -1 Closer look at the dip…. 5 dips! h_tr - helicity of trigger h_as - helicity of associated

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

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

Marek Bombara 12 ∆  projections p Ttrigger h-h  -h  -h K 0 -h GeV/c GeV/c GeV/c GeV/c GeV/c

Marek Bombara 13 ∆  projections p Ttrigger h-h  -h  -h K 0 -h GeV/c GeV/c GeV/c GeV/c GeV/c

Marek Bombara 14 ∆  projections p Ttrigger h-h  -h  -h K 0 -h GeV/c GeV/c GeV/c GeV/c GeV/c

Marek Bombara 15 ∆  projections p Ttrigger h-h  -h  -h K 0 -h GeV/c GeV/c GeV/c GeV/c GeV/c

Marek Bombara 16 Jet widths Jet is broadening in ∆  with decreasing p Ttrig Smaller broadening is seen for ∆  ∆  projection  projection

Marek Bombara 17 P Ttrig dependence Jet yield is increasing with p Ttrig Ridge yield dependence? No trigger species dependence Jet Ridge J. Bielcikova, QM’06

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

Marek Bombara 19 P T distribution of associated particles Ridge p T distribution similar to medium Jet distribution harder STAR preliminary “jet” slope ridge slope inclusive slope J. Putschke, QM’06 h-h correlations p T associated >2GeV/c J. Bielcikova, QM’06

Marek Bombara 20 Conclusions No observation of strange baryon/meson trigger differencies in angular correlations Jet peak broadened in ∆ , increasing with p Ttrig, 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%