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Strangeness production in jets from p+p 200 GeV collisions

Strangeness production in jets from p+p 200 GeV collisions. Motivation Analysis Results Summary Outlook. Anthony Timmins for the STAR Collaboration.  Modified Leading Log (MLLA). Eur. Phys. J. C55 (2008) 293 Phys. Rev. Lett. 52 (1984) 577. FF variable.

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Strangeness production in jets from p+p 200 GeV collisions

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  1. Strangeness production in jets from p+p 200 GeV collisions • Motivation • Analysis • Results • Summary • Outlook Anthony Timmins for the STAR Collaboration

  2.  Modified Leading Log (MLLA) Eur. Phys. J. C55 (2008) 293 Phys. Rev. Lett. 52 (1984) 577 FF variable MotivationStrangeness fragmentation functions… • Strange particle fragmentation functions (FFs) for p+p at RHIC energies lacking… • Understand the species dependance of fragmentation • Compare to Pythia, MLLA etc… • Understand trends behind p+p inclusive spectrum measurements • Soft vs hard production….

  3. STAR preliminary pT (GeV/c) MotivationMedium modification of jet chemistry… Eur. Phys. J. C55 (2008) 293 Y Xu, Paralell Session 6 • Modification in HI jet chemistry observed in inclusive measurements and predicted… • p+p FFs essential baseline for HI jet-finding studies

  4. AnalysisThe Experiment… • p+p 200 GeV data taken in 2006… • Full installation of calorimeter • TPC -> charged particlesCalorimeters -> neutrals • Calorimeter based jet patch trigger used.. • Neutral Ejet > 8 GeV •  x  = 1 x 1 • ~ 8 million events

  5. Recoil jet (used for FFs) K0S  h+ STAR Preliminary Triggered online jet AnalysisJet finding… • 3 jet finders used to measure FFs • FastJet, (Cacciari, Soyez, arXiv:0704.0292) • Seedless Cone SIS • KT • Anti-kt • Jets cuts • Recoil WRT trigger • Resolution parameter (~radius) < 0.4 • || < 0.6 • Charged track, Tower Energy • pT > 200 MeV/c • Corrections applied • Double counting • Corrections we’re working on… • Energy resolution • Missing jet energy….

  6. AnalysisStrangeness PID… STAR Preliminary • ,  and K0S identified via decay products…. • Place topological cuts • Reduce background… pT > 1 GeV/c

  7. ResultsCharged Hadron FFs… Helen Caines QM2009

  8. pT cut pT cut pT cut ResultsStrange particle FFs… STAR Preliminary • Measured data not corrected for tracking efficiency/jet energy uncertainties • Errors statistic + systematic (different jet finders) • V0 pT > 1 GeV/c • Pythia 6.4 ran through STAR reconstruction chain • Describes K0S OK, some deviations for strange baryons

  9. Phys. Rev. C 75 (2007) 064901 STAR Preliminary STAR Preliminary ResultsStrange particle ratios in jets… • Strange baryon asymmetry observed in jets… • Jet like process give larger baryon/meson ratios than all processes • Jet /K0S ratio appears consistent with inclusive spectra at higher pT…

  10. Eur. Phys. J. C13 (2000) 573 ResultsJets with leading strange particles… • Do strange particle tagging baryon/meson select on quark/gluon jets? • Quark jets -> h FF suppressed at large  • Gluon jets -> h FF enhanced at large 

  11. STAR Preliminary pT cut pT cut pT cut Eur. Phys. J. C13 (2000) 573 ResultsJets with leading strange particles… • Measure charged hadron FF where leading particle is , K0S or h • Fragmentation function of non-leading charged hadrons • Expect gluon jets to have more softer particles • Charged hadron FF invariant upon strange particle tagging…

  12. ResultsJets with leading strange particles… • Invariance due to jets coming from one type of parton • Jets gluon dominated? • Or jets quark dominated? • Measured jet pT range 10-40 GeV…. • Calculations indicate mixed of quark and gluon jets in this range…

  13. ResultsMean  of particle FF… • MLLA predicts mass ordering of 0 • Z. Phys. C 27 (1985) 65 • FF corrected for tracking efficiency • Fit Gaussian in peak region to extract 0

  14. e+e- CM energy ResultsMean  of particle FF… F Anulli, arXiv:0804.2021v1 STAR Preliminary • Mass ordering observed to first order • 0 (h) > 0 (K0S), 0 () • 0 (K0S) ~ 0 () • Similar patterns observed in e++e- collisions…

  15. Summary • What we have learnt so far… • Pythia describes charged hadron fragmentation functions • OK for strange mesons, deviations for strange baryons • Baryon asymmetries observed in ~0 p+p jets • Jet-like processes give /K0S ratios ~0.5-0.6 • Jets with leading baryon and mesons • Show same charged hadron fragmentation functions • Predicted MLLA mass ordering observed to first order…

  16. Outlook • What we intend to do… • Correct strange particle FFs for jet resolution and missing energy • Further models comparisons… • Extend study to heavy-ion jets? • Need to get p+p under control first!

  17. Thanks Christine!!

  18. Mean Xi extraction…

  19. Strangeness production in jets from p+p 200 GeV collisions STAR Preliminary • Pythia reproduces K0S fragmentation functions, deviations observed for strange baryons… • Larger /K0S ratios observed for jet-like processes compared to inclusive (integrated spectra) STAR Preliminary

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