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Charged and Neutral Kaon correlations in Au-Au Collisions at sqrt(s_NN) = 200 GeV using the

Charged and Neutral Kaon correlations in Au-Au Collisions at sqrt(s_NN) = 200 GeV using the solenoidal tracker at RHIC (STAR) Selemon Bekele The Ohio State University for the STAR Collaboration. SQM2003 March 12-17, 2003. Outline. Motivation Charged Kaons cuts 1D correlations

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Charged and Neutral Kaon correlations in Au-Au Collisions at sqrt(s_NN) = 200 GeV using the

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  1. Charged and Neutral Kaon correlations in Au-Au Collisions at sqrt(s_NN) = 200 GeV using the solenoidal tracker at RHIC (STAR) Selemon Bekele The Ohio State University for the STAR Collaboration SQM2003 March 12-17, 2003

  2. Outline • Motivation • Charged Kaons • cuts • 1D correlations • 3D correlations • Neutral Kaons • cuts • C2 • The f0(980) problem • Summary • Outlook

  3. HBT : Probing source geometry x1 r1 p1 p source r(x) 1 m p2 r2 x2 5 fm 1-particle probability r(x,p) = U*U 2-particle probability F.T. of particle source Measurable!

  4. Motivation Physics -Kaon HBT has been suggested as a promising probe of QGP -Kaon HBT reveals information about strangeness dynamics M. Gyulassy, Phys. Lett B 286 (1992) 211 • -Kaons are less affected by decay of long lived resonances • Technical • -No distortions due to Coulomb interaction -K0s K0s HBT extends particle correlation systematics to higher pt allowing studies of Mt scaling, collective flow effects etc.

  5. No conclusive measurements so far F. Antinori et al. Nucl. Phys. A661 (1999) 130c WA97 protons kaons pions electrons K0s K0s HBT extends particle correlation systematics to higher pt

  6. Charged Kaon Cuts Main Cuts central events -0.5 < y < 0.5 for 1D correlations 0.25 GeV < kT < 0.45 GeV for 3D correlations 0.15 GeV < kT < 0.45 GeV for Mt dependence 0.15 GeV < kT < 0.35 GeV 0.35 GeV < kT < 0.45 GeV

  7. Fitting the correlation functions Standard fit Bowler/Synukov/CERES where

  8. Fits to 1D correlation functions K-K- K-K- Lambda = 0.333 +- 0.04 Rinv = 3.72 +- 0.1 fm STAR Preliminary K-K- STAR Preliminary What coulomb radius is used for the correction does not seem to make much difference .

  9. Projections of 3D fits using the standard procedure Side Out (qOut, qLong < 45 MeV) (qSide, qLong<45 MeV) (qSide, qOut < 45 MeV) Long K- K- K- K- K- K- Lambda = 0.5096 +- 0.0168 Ro = 2.942 +- 0.0685 fm Rs = 2.97 +- 0.0668fm Rl = 3.29 +- 0.764 fm

  10. Projections of 3D fits using the Bowler/Synukov procedure Side (qOut, qLong < 45 MeV) Out (qSide, qLong < 45 MeV) Long (qSide, qOut < 45 MeV) K- K- K- K- STAR Preliminary Lambda = 0.2871 +- 0.025 Ro = 3.62 +- 0.145 fm Rs = 3.21 +- 0.134 fm Rl = 3.92 +- 0.154 fm Lambda is small for the Bowler correction ! K- K- No corrections for purity and momentum resolution

  11. K0s Reconstruction decay length dca of V0 to primary vertex dca between daughters dca of daughters to primary vertex DCA – distance of closest approach Vo V0 Cuts central events 0.1 < pt < 3.5 -1.5 < y < 1.5

  12. K0s mass peak (Not Background subtracted) K0s multiplicity Mean ~ 3.79 / Event Number of events X 10 C2 Number of K0s M (GeV/C2) Fitting to a gaussian Gives the values Lambda= 0.506 0.133 Rinv = 5.765  0.691 K0sK0s Correlation Function STAR Preliminary

  13. Signal to Noise studies Signal + Background Signal Background 1) 2) Signal Lorentzian Background 1 ) a + b x 2 ) a + b xc 3 ) a/x + b/(1 + x) Needs more study 3)

  14. pions K- Ro STAR Preliminary Hydro Mt scaling seems to be obeyed for the charged pions and Kaons. Rs Rl

  15. Mt Scaling violated? pions K- K0s R Mt (Gev/c) STAR Preliminary Rinv for the neutral Kaons seems to indicate that Mt scaling is not obeyed as for the charged pions and Kaons.

  16. What is the effect of the f0(980)? Mass of f0(980) = 980 +- 10 MeV width = 40 - 100 MeV. => lifetime ranges between 1.97 fm/c and 4.93 fm/c Dominant decay mode is pions Branching ratio to kaons is unknown

  17. Ratio of f0(980) to K0s as a function of temperature f0s are selected from a Briet-wigner mass distribution Only those f0s which fall in the shaded region can decay to K0s, since the mass of a K0s is 0.498 GeV M = 0.996

  18. Correlation function for a pure K0 sample The effect of the f0 particle assuming the worst case scenario where its decay products are only kaons

  19. Results from a gaussian fit The radius changes by a small amount while the lambda seems to be affected most.

  20. Summary • 1D and 3D correlations of Charged Kaons • preliminary results • Not yet corrected for purity and momentum resolution • 1D K0sK0s correlations • preliminary results • Not corrected for purity and momentum resolution • The f0(980) effect seems to be small K- K- Lambda = 0.333 +- 0.04 Rinv = 3.72 +- 0.1 fm Lambda = 0.2871 +- 0.025 Ro = 3.62 +- 0145 fm Rs = 3.21 +- 0.134 fm Rl = 3.92 +- 0.154 fm Lambda is small for the Bowler procedure! Lambda= 0.506 0.133 Rinv = 5.765  0.691

  21. Outlook • Charged Kaon correlations • we need to do • more systematic studies • purity estimate/correction • momentum resolution • with more statistics • Multiplicity dependence Neutral Kaon correlations we need to do purity estimate/correction momentum resolution Hopefully new results in the near future

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