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Identified particle spectra and jet interactions with the medium

Quark Matter 2005 - Budapest. Identified particle spectra and jet interactions with the medium. Paul Sorensen — Lawrence Berkeley National Lab. Heavy Ion Goals and QCD. Create a system of quasi-free quarks and gluons: Learn about the EOS Study the deconfined-to-confined transition:

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Identified particle spectra and jet interactions with the medium

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  1. Quark Matter 2005 - Budapest Identified particle spectra and jet interactions with the medium Paul Sorensen — Lawrence Berkeley National Lab

  2. Heavy Ion Goals and QCD • Create a system of quasi-free quarks and gluons: • Learn about the EOS • Study the deconfined-to-confined transition: • hadronization of the matter • development of mass • Determine properties of the matter: • energy density • gluon density • temperature T • coupling s(Q, T) Lattice QCD for finite temperature Tc~170 MeV PDG s(Q)s(Q,T/Tc) Quark Matter — Budapest — August 2005

  3. Chiral symmetry is broken, but the confining forces are still modified: Are these hadrons, dressed quarks, proto-hadrons, resonances? Varying the coupling behavior allows us to study confinement, hadronization, and these intermediate objects. chiral symmetry breaking limit s,c=0.43(hep-ph/0302011) Modifications to s heavy quark-antiquark coupling at finite T from lattice QCD O.Kaczmarek, hep-lat/0503017 high Q2 low Q2 heating the vacuum modifies soft/long-wave-length processes (like hadronization): At RHIC we’re trying to probe these modifications Quark Matter — Budapest — August 2005

  4. k’ k’ ? ? k ? intermediate low pT high pT ? * * * * * * * * *        * * * * * *                                                      probing the fireball We can’t perform scattering experiments with the fireball so we rely on internally created probes. This only tells us half the story. But can we learn enough from the information we have: pT, , y? For example, can we determine the dof from different pT regions? ≈1 fm ≈10 fm 0 fm << 1 fm ≈0 fm Quark Matter — Budapest — August 2005

  5. review nucl-ex/0412003 • First a large proton excess is observed. • These measurements could be interpreted several ways: flow, scaling with N-binary (i.e. absence of jet quenching), etc. • Enhancement is noted to be related to the number of constituent quarks rather mass • also an upper pT limit is placed on the baryon excess. • Finally elliptic flow is found to scale with the number of quarks • also the large baryon v2 excluded scenarios involving less energy loss for protons. PHENIX PRC69, 0304909 (2004) STAR Phys. Rev. C 72 (2005) 014904 Evidence gathered for modifications to hadronization at intermediate pT Quark Matter — Budapest — August 2005

  6. cross talk between the matter, the probes, and hadronization invalidates factorization. We see lots of evidence for this cross-talk Baryon to Meson How might the B/M ratio be related to modifications to hadronization? Phenix: PRL 91, 172301 Factorization is not likely to hold for these collision at this pT: fragmentation functions become energy and system-size dependent Quark Matter — Budapest — August 2005

  7. Outline Azimuthal dependence of spectra Centrality dependence of spectra Jet interactions with the medium Quark Matter — Budapest — August 2005

  8. x z Non-central Collisions Event anisotropies Azimuthal momentum-space anisotropy: a self quenching probe of early interactions out-of-plane y Au nucleus in-plane Au nucleus sensitivity to the system geometry can arise through secondary rescattering, soft-gluon radiation, etc. Quark Matter — Budapest — August 2005

  9. v2 vs. pT Large values indicate strong sensitivity to the system geometry for production at all measured pT v2 at intermediate pT is grouped by quark number Intermediate pT PRL 92 (2004) 052302; PRL 91 (2003) 182301 Quark Matter — Budapest — August 2005

  10. Extended pT Year 4 data gives RHIC higher statistics and greater coverage for identified particle v2 Quark Matter — Budapest — August 2005

  11. Extended pT Year 4 data gives RHIC higher statistics and greater coverage for identified particle v2 Quark Matter — Budapest — August 2005

  12. Extended pT PHENIX/STAR comparison shows consistency Consistent with no particle type dependence at 7 GeV/c But why not earlier? PHENIX Preliminary  Charged Hadrons Quark Matter — Budapest — August 2005

  13. PRL 92 (2004) 052302; PRL 91 (2003) 182301 Quark-number scaling • Since hadronization is a soft process, it should be modified by changes to the shape of the running coupling at low Q2. • In one simple hadronization model quark v2 is approximately related to hadron v2 through • v2q = v2h(pT/n)/n, • where n is the number of quarks in the hadron • implies v2 is developed before hadronization • model implies deconfinement Quark Matter — Budapest — August 2005

  14. Run IV update The observed scaling does not appear to follow the simple 3 vs. 2 constituent quark number relationship Is this related to a jet component, a breakdown of simple approximations, or something new? Numerical approximations give a 1% relative error Imperfect v2/n was also anticipated within models incorporating more realistic assumptions. STAR Preliminary (Talk by M.Oldenburg) Quark Matter — Budapest — August 2005

  15. Inclusion of gluons in recombination was predicted to lead to a larger meson v2/n than baryon v2/n: B.Müller, et al. nucl-th/0503003 To 1st order: the constituents look like massive valence quarks with no sub-structure  g Probing more deeply reveals substructure in the form of sea quarks or gluons g qq Further daughter partons are revealed as the scale Q2 is increased Including contributions from sea quarks and gluons should cause deviations from v2/n a closer look STAR Preliminary Quark Matter — Budapest — August 2005

  16. comparison to predictions Inclusion of gluons in recombination was predicted to lead to a larger meson v2/n than baryon v2/n: B.Müller, et al. nucl-th/0503003 Tantalizing indication for the fate of gluons and the nature of the constituents Systematic errors on the data and calculations need to be carefully addressed Quark Matter — Budapest — August 2005

  17. 0 1 2 pT/n (GeV/c) comparison to predictions MPC + Coalescence/Jetset: jet fragmentation contribution + spatial correlations also can spoil the scaling of v2/n: D. Molnar nucl-th/0406066 pT/n (GeV/c) Original quark v2 is not recovered by v2/n. The trend is correct but deviations are larger than what’s seen in the data Calculations will also miss the Baryon to Meson ratio but the fragmentation component appears to show up in correlation measurements Quark Matter — Budapest — August 2005

  18. The multi-strange hadrons Even the (ss), and (sss) have large v2 values and appear to follow baryon vs. meson systematics • (in)dependence of v2 on hadronic x-sections or flavor/mass: • can phi and Omega v2 be understood without prehadronic flow? Quark Matter — Budapest — August 2005

  19. v2 at intermediate pT Constituent quarks appear to be the relevant degrees-of-freedom just prior to hadronization With sufficient precision we can address questions about the nature of the constituents and the microscopic nature of the matter The centrality dependence of spectra compliments v2 measurements more quench (pT<0) v2 RCP more flow (pT>0) v2 RCP Quark Matter — Budapest — August 2005

  20. the centrality dependence v2 and RCP: complimentary measures to probe flow vs. energy loss. RCP is a better than RAA for many studies because it’s not sensitive to the change in chemistry from p+p to Au+Au Baryon production increases more quickly with collision overlap density than meson production more evidence of constituent quark number instead of mass Quark Matter — Budapest — August 2005

  21. 2 . 5 R d A u R ( 6 0 ~ 8 0 / p p ) 2 . 0 A A R ( 0 5 / p p ) A A Ratio 1 . 5 1 . 0 0 . 5 S T A R P r e l i m i n a r y 0 . 0 0 . 0 0 . 5 1 . 0 1 . 5 2 . 0 2 . 5 3 . 0 3 . 5 4 . 0 2 P ( G e V / c ) PHENIX Preliminary: Talk by D. Pal T Update on fRCP STAR Preliminary Talk by Xiangzhou Cai The  RCP is well below proton or lambda RCP. Consistent with NCQ scaling expectations. a discrepancy arises between PHENIX and STAR RAA (RAA ≠ RCP) Quark Matter — Budapest — August 2005

  22. Non-photonic electron RAA Are D’s just like other mesons? There inclusive yield scales with Nbin but the RAA is similar to meson RAA. At intermediate pT, do we see evidence for flow + coalescence or do we only see energy loss? v2 distinguishes between these scenarios. Comparing PHENIX and STAR electron RAA to charged hadrons we note a similar and surprisingly large suppression! Quark Matter — Budapest — August 2005

  23. electron v2: dE/dx or flow See talk by F. Laue • Collisional energy loss can give us charm RAA ~ 0.3 and v2 ~ 5% • A push from below (flow) is likely needed to get a larger charm v2. • D v2~5% can come from v2c=0 + coalescence or v2c=5% + no coal. Quark Matter — Budapest — August 2005

  24. Lower energy Features of the particle-type dependence are common to different energies. But the underlying behavior changes between 17.2 and 200 GeV At low energy RCP is larger but v2 is smaller. Reveals what’s happening to the spectra: change in underlying spectrum, more energy loss (pT<0) and more flow (pT>0) Quark Matter — Budapest — August 2005

  25. f0(980): 2-quark state f0(980): 4-quark state 4-quark candidates The centrality dependence of 4-quark-state candidates (a0(980) and f0(980) for example) can be used to probe their quark content. accessible through +- minv cocktail analysis Quark Matter — Budapest — August 2005

  26. Jet-like correlation structures J. Adams et al, Phys. Rev. Lett. 91 (2003) 072304 Dihadron correlations at intermediate pT indicate the presence of jet-like correlations Can these measurements be reconciled with the apparent non-fragmentation nature suggested by other measurements? Notice the enhanced near-side peak in AuAu: we’ll see more of this. Quark Matter — Budapest — August 2005

  27. identified trigger particles PHENIX; arXiv:nucl-ex/0408007 PHENIX; arXiv:nucl-ex/0408007 • Baryons and mesons have similar probabilities to have an associated hadron • But why do both of them have a higher probability to have an associated hadron in Au+Au collisions than in p+p collisions? • This may arise from interactions between soft matter and hard partons. What indications do we have for this? Quark Matter — Budapest — August 2005

  28. identified trigger particles PHENIX; arXiv:nucl-ex/0408007 PHENIX; arXiv:nucl-ex/0408007 • Mesons have a greater probability to have an associated hadron (thanks Barbara) • But why do both of them have a higher probability to have an associated hadron in Au+Au collisions than in p+p collisions? • This may arise from interactions between soft matter and hard partons. What indications do we have for this? Quark Matter — Budapest — August 2005

  29. data-peak mediums response to jets Correlations from fluctuations Subtract elliptic flow and the near-side jet-peak Mediums response to an impinging jet is revealed The fluctuation bin-size dependences are related to two-particle correlations Fluctuations are inverted to autocorrelations pick gluons from the vacuum gluon density dNg/dy ~ 1000 STAR Preliminary: see posters by Duncan Prindle look for modifications to particle composition in the away-side/recoil region Quark Matter — Budapest — August 2005

  30. Near- and away-side B/M away-side: comoving partons enhance the probability for baryon production near-side like p+p • The larger B/M ratio in the away side is also suggestive of recombination: • wherever the density of comoving constituents is larger (in-plane, central vs. peripheral, and now in the wake of quenched jets), it becomes easier to produce baryons. • We already knew that it was partons losing energy in a dense medium, this may help us determine if the matter is hadronic or not (dAu?). Quark Matter — Budapest — August 2005

  31. Conclusions • Production is highly sensitive to the fireball geometry. Either from: • - hadronization — a long-wave-length/soft process or • soft pushes (i.e. flow) • quenching in medium (soft gluon radiation) • Quark degrees of freedom are apparent from RCP, and v2: • the flavor dependence is apparently not from mass, quark vs. gluon, or hadronic cross-section. Rather, particles are grouped by constituent quark number. • Measurements of large collectivity developed for  and  challenge any non-QGP or hadronic scenario • Significant modification to s at low and intermediate Q2 are demonstrated through modifications to hadronization Quark Matter — Budapest — August 2005

  32. QUARK GLUON PLASMA It’s highly interacting It doesn’t appear to be hadronic What do we call it? chiral symmetry breaking limit s,c=0.43(hep-ph/0302011) Quark Matter — Budapest — August 2005

  33. the end Thanks to the organizers and S. Blyth, J. Chen, X. Dong, H. Huang, Y. Lu, H-G. Ritter, A. Rose, M. Oldenburg, K. Schweda, and N. Xu Quark Matter — Budapest — August 2005

  34. SOFTENING BROADENING Jet remnants (thermalization) What happens to a hard probe that traverses a colored medium? Can we observe effects of dissipation or thermalization? Trigger pT: 4–6 GeV/c STAR Preliminary: F. Wang, J.Phys.G30:S1299-S1304,2004 Quark Matter — Budapest — August 2005

  35. Anti-baryon to baryon ratio Also, notice that the pbar/p ratios don’t yet reach pQCD predictions PHENIX PRC69, 0304909 (2004) Quark Matter — Budapest — August 2005

  36. Baryon/anti-baryon ratios Au Au Central Some indication of gluon vs. quark jet dependence Quark Matter — Budapest — August 2005

  37. year 4 ratios Au+Au Central Quark Matter — Budapest — August 2005

  38. year 4 RCP Quark Matter — Budapest — August 2005

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