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Baryon/Meson Ratios for Intermediate p T

Baryon/Meson Ratios for Intermediate p T. Eun-Joo Kim University of Kansas For the BRAHMS collaboration. Motivation. PRC 69 (2004)034909. (0-10%)/(60-92%). At p T > 1.5GeV/c, ratios are from p/ p 0. Baryon Anomaly at RHIC.

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Baryon/Meson Ratios for Intermediate p T

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  1. Baryon/Meson Ratios for Intermediate pT Eun-Joo Kim University of Kansas For the BRAHMS collaboration

  2. Motivation PRC69(2004)034909 (0-10%)/(60-92%) At pT > 1.5GeV/c, ratios are from p/p0 Baryon Anomaly at RHIC • In pQCD approach, p/p ratios at high pT are determined by the fragmentation of • energetic partons, independent of the initial colliding systems. However… • The clear increase in p/p ratios from peripheral to central collisions is observed. • Rcp for p, pbar is close to 1 below 4GeV/c, while it is about 0.3 for pions.

  3. Theoretical Models PHENIX p/p ratio (0-10% central) R.J. Fries et al. (Duke) PRL90(2003)202303, PRC68(2003) 044902 - recombination dominates over fragmentation for an exponentially falling parton spectrum, but the fragmentation wins out, when the spectrum takes the form of a power law. - strictly separates soft and hard physics, allowing only the soft partons to recombine and only the hard partons to fragment. ReCombination Parton Coalescence R. Hwa et al. (Oregon) PRC70(2004)024904, PRC67(2003)034902 replaces fragmentation functions by a scenario where mini-jet partons develop a shower which subsequently recombines, i.e. recombination of soft partons with shower partons. V. Greco et al. (TAMU) PRL90(2003)202302, PRC68(2003)034904 added assumption that soft partons in QGP can coalesce with comoving hard partons from a mini-jet.

  4. New for Run IV AuAu sNN=200GeV MRS 90o, 40o, 45o 20% data only processed!

  5. C4 performance

  6. C4 Efficiency

  7. PID at TFW2

  8. pT Spectra : p BRAHMS Preliminary 0-10% 10-20% 20-40% 40-60% We are still working on…

  9. pT Spectra : p, pbar BRAHMS Preliminary 0-10% 10-20% 20-40% 40-60% We are still working on…

  10. p-/p+, pbar/p ratios BRAHMS Preliminary • No significant pT dependence up to 3GeV/c • Similar behavior at y~0 and y~1

  11. p/p ratios BRAHMS Preliminary Hwa et.al, PRC70(2004)024905 Greco et.al.,PRL90(2003)202302 p/p ratios increase with pT up to 3GeV/c. L feed down correction applied.

  12. Summary & Outlook • The new BRAHMS Cherenkov detector functions well at high pT, and we are currently working on the efficiency and background estimates. • With upgraded Cherenkov and Time-of-Flight detectors, BRAHMS has measured the identified hadron transverse momentum spectra and particle ratios up to 4GeV/c. • With our complete data (a factor 5 increase), BRAHMS can extend the pT coverages up to 5-6 GeV/c at y~0. • p/p ratios increase with pT up to 3GeV/c. • Striking similarity between y~0 and y~1. • The recombination and parton coalescence models seem to give reasonable explanation of the data at intermediate pT.

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