1. Multiparticle Correlations and Charged Jet Studies in p+p, d+Au, and Au+Au Collisions at  s NN =200 GeV. Michael L. Miller Yale University For the STAR Collaboration

2. May 2003Mike Miller Jet Properties at RHIC Measure jets in “simple” system (p+p). Use this information to measure jets in complex system (Au+Au).

3. May 2003Mike Miller Jets in Au+Au: Angular Correlations Px (GeV/c) Py (GeV/c) -4 -3 -2 -1 0 1 2 3 4 Particles from same jet are close in angle Particles from di-jets are ~180 deg. apart Select high-p T portion of event (p T >2 GeV)

4. May 2003Mike Miller Jets in p+p: Direct Identification  Cluster final state (charged!) hadrons from a common “parent” quark/gluon.  Reconstruct momentum of quark/gluon  Implemented, tested, using 4 jet-finding algorithms Remember: only charged particles!

5. May 2003Mike Miller Di-jet Angular Distributions Increase jet p T, tighten di-jet peak Measure Nuclear k T in d+Au Raw STAR Preliminary

6. May 2003Mike Miller Jet-Event Shape and Size Raw STAR Preliminary (Arbitrary Units) Within away side jetWithin lead jetTransverse region Raw STAR Preliminary

7. May 2003Mike Miller Raw STAR Preliminary “Fragmentation” of Charged Jets Selecting Jets with large Fragmentation Bias! Events with p T >4 GeV track All jets with at least one 2<p T <6 GeV track What about “Correlation” jets? Slope depends on jet- algorithm

8. May 2003Mike Miller What Does this Mean? 1.At high jet-p T, leading particle collinear with jet axis 2.Correlation jets: leading particle carries ~80% of reconstructed charged particle jet p T. Leading particle is a good approximation of jet direction Leading particle is easily related to jet p T Mean trigger fragmentation Defines the pQCD scale Defines jet p T of away-side partner!

9. May 2003Mike Miller Jets In d+Au Collisions  No background subtraction  Central: top 20% of -3.8<η<-2.8 uncorrected multiplicity Back-to-back jets are not suppressed in central d+Au underlying event: p+p  d+Au minbias  d+Au central near-side: correlation strength and width similar away-side: d+Au peak broader but with little centrality dependence p+p: Adler et al., PRL90:082302 (2003), STAR

10. May 2003Mike Miller Au+Au, p+p: Adler et al., PRL90:082302 (2003), STAR Jets In Least Violent Au+Au Collisions “Near side” jet: consistent in all 3 systems “away side” jet: consistent in all 3 systems  Au+Au: Subtract background from combinatorics, flow  d+Au: no suppression in central collisions  use min. bias.  d+Au: subtract underlying event.

11. May 2003Mike Miller Au+Au, p+p: Adler et al., PRL90:082302 (2003), STAR Jets In Most Violent Au+Au Collisions “Near side” jet: consistent in all 3 systems “away side” jet: p+p  d+Au  Au+Au  Au+Au: Subtract background from combinatorics, flow  d+Au: no suppression in central collisions  use min. bias.  d+Au: subtract underlying event.

12. May 2003Mike Miller Conclusions 1.p+p: p T >4 GeV particles are good approximation of jet direction, momentum 2.d+Au: no suppression of away-side jet in central collisions 3.Au+Au: strong suppression of away-side jet in central collisions. Combined: Strong back-to-back suppression in central Au+Au cannot be fully explained by initial state physics

13. May 2003Mike Miller What’s Coming from STAR? 1.p+p: Run III data with E.M. Calorimeter 0<  <1. Identified jets including  0. 2.d+Au: Same! 3.Au+Au: Run IV with expanded calorimeter and extensive high-p T triggered data. Measure vacuum, in-medium “fragmentation” functions!

14. May 2003Mike Miller Backup slides

15. May 2003Mike Miller The STAR Detector

16. May 2003Mike Miller ZDCW FTPCE Au d d+Au “Centrality” Tagging  FTPCE multiplicity: -3.8<  <-2.8 (Au fragmentation direction)  ZDCW: single deuteron spectator Uncorrected FTPCE multiplicity minbias single deuteron spectator FTPCE multiplicity: defines “centrality” in d+Au events

17. May 2003Mike Miller Raw STAR Preliminary Jet-Event Shape and Size (Arbitrary Units) Within away side jetWithin lead jetTransverse region

18. May 2003Mike Miller Why Jets? Energy Loss in Dense Matter Strong dependence of energy loss on gluon density  glue  measure   measure gluon density at early hot, dense phase Thick plasma (Baier et al.): Thin plasma (Gyulassy et al.): Gluon Bremsstrahlung

19. May 2003Mike Miller “Fragmentation” of Charged Jets Raw STAR Preliminary Fragmentation slope scales with jet p T beyond 6 GeV How does the slope change as a function of jet p T ?

20. May 2003Mike Miller “Fragmentation” of Charged Jets Raw STAR Preliminary Slope depends on jet- algorithm What fraction of (reconstructed) jet p T does each particle carry?

21. May 2003Mike Miller Di-jet Angular Distributions Increase jet p T, tighten di-jet peak Measure Nuclear k T in d+Au Raw STAR Preliminary