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measurement of jet properties and their modification in heavy-ion collisions

Jan Rak for the PHENIX collaboration Department of Physics and Astronomy. measurement of jet properties and their modification in heavy-ion collisions. Partonic degree of freedom in HI. Highlights from RHIC AuAu program: high-p T particle yield suppression – jet quenching

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measurement of jet properties and their modification in heavy-ion collisions

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  1. Jan Rak for the PHENIX collaboration Department of Physics and Astronomy measurement of jet properties and their modification in heavy-ion collisions

  2. Partonic degree of freedom in HI • Highlights from RHIC AuAu program: • high-pT particle yield suppression – jet quenching • disappearance of the back-to-back jet in central collisions • exceedingly large azimuthal anisotropy v2 • Detailed analysis of parton/jet properties like: • shape of the fragmentation D(z) and parton distribution function fq(pTq) • parton transverse momentum kT2 • and their modification is vital for understanding of the mechanism of parton interaction with QCD medium formed at RHIC

  3. Hard scattering in longitudinal plane Hard scattering in transverse plane Generally, momentum fraction x1x2. (Not in PHENIX –0.35<<0.35) Point-like partons  elastic scattering Partons have intrinsic transverse momentum kT Hard scattering

  4. jet fragmentation transverse momentum jet Jet Fragmentation (width of the jet cone) Partons have to materialize (fragment) in colorless world jT and kT are 2D vectors. We measure the mean value of its projection into the transverse plane |jTy| and |kTy| . |jTy|is an important jet parameter. It’s constant value independent on fragment’s pT is characteristic of jet fragmentation (jT-scaling). |kTy| (intrinsic + NLO radiative corrections)carries the information on the parton interaction with QCD medium. p+p p+A A+A

  5. In Practice parton momenta are not known  Simple relation Fragmentation Function (distribution of parton momentum among fragments) jet In Principle Fragmentation function

  6. CCOR (ISR) s = 63 GeV see A.L.S. Angelis, Nucl Phys B209 (1982) Correct +- 1/xE  -5.3 xE in pp collisions PHENIX preliminary 1/xE  -4 to –5

  7. final state parton distrib. extracted from PHENIX p+p0+X FFn D(z) Slope of the fragmentation function in p+p collisions at s=200 GeV ztrigg PHENIX preliminary z extracted from pp data xTtrigg=2.pTtrigg/s We measured xE and Only one unknown variable z  iterative solution

  8. pp and dAu correlation functions p+p h+- 1.0<pT<1.5 3.0<pT<6.0 • Fixed correlation: • both pTtrigg and pTassoc are in the same range • Assorted correlation: • pTtrigg and pTassoc different Away side peak Near-side peak d+Auh 1.5<pT<2.0 5.0<pTtrigg <16.0 GeV/c d+Au Jet function assumed to be Gaussian 1.0<pT<1.5 Fit = const + Gauss(0)+Gauss()

  9. However, inspired by Feynman, Field, Fox and Tannenbaum (see Phys. Lett. 97B (1980) 163) we derived more accurate equation xh = pT,assoc / pT,trigg N, A , |jTy|, |kTy| relations Knowing N and A it is straightforward to extract |jTy| and ztrigg|kTy| In the high-pT limit (pT >>|jTy| and pT >>|kTy|) See poster P07, P. Constantin

  10. N ,A |jTy|, |kTy| in pp data PHENIX preliminary PHENIX preliminary |jTy| = 35911 MeV/c |kTy| = 96449 MeV/c Both |jTy| and |kTy| in very good agreement with previous measurements: PLB97 (1980)163 PRD 59 (1999) 074007 A

  11. pp From pp to dAu |kTy|carries the information on the parton interaction with cold nuclear matter. |jTy| should be the same as in pp – systematic cross check

  12. I.Vitev nucl-th/0306039 I.Vitev |kTy| from pp and dAu No significant kT-broadening seen in dAu data z=0.75 value taken from pp data See poster P03 J. Jia and P05 N. Grau

  13. (3.0pTtrigg5.0)(1.5pTassoc3.0) pp <z><|kTy|> pp <|jTy|> There seems to be significant broadening of the away-side correlation peak which persists also at somewhat higher pT range. AuAu |jTy|and z |kTy| from CF (2.5pTtrigg4.0)(1.0pTassoc2.5)

  14. Subtracted dN/d integrating from 0-90, 90-180 to remove the v2 component. AuAu (60-90%) correlation function (2.5pTtrigg4.0)(1.0pTassoc2.5) GeV/c AuAu yield

  15. Cartoon Jet Func. = Correl Func - flow Note pT is rather low; associated particle yields increase with centrality See poster C10, N.N. Ajitanand AuAu associated yields (2.5pTtrigg4.0)(1.0pTassoc2.5) GeV/c

  16. Summary and conclusions • Jet production and fragmentation in pp, dAu and AuAu collisions: • the slope of the fragmentation function in pp • N , A , |jTy| and |kTy| in pp, dAu, AuAu • Variation of the conditional yield of back-to-back particles with Npart in AuAu • We found: • Good agreement of the jet properties in pp collisions with other experiments • dAu jT and kT consistent with pp • In AuAu significant kT - broadening with centrality • Yield of away side associated particles shows rising trend with Npart • Next step: • map out this trend to explore whether this is a hint of jet-quenching balance • Explore the AuAu fragmentation function

  17. Backup slides

  18. “flow” pairs : [1+2v22 cos(2)] Intra-jet pairs angular width : N |jTy| Inter-jet pairs angular width : A |jTy|  |kTy| CARTOON flow+jet flow N A Method – azimuthal correlation function Now we know the z - let us measure NandN. Two particle azimuthal correlation function Unavoidable source of two particle correlations in HI – elliptic flow

  19. Comparison to outside world PHENIX preliminary Add the legend – experiment names Larger markers and legends

  20. yeilds

  21. CF’s

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