Rainer Fries Texas A&M University

1. RHIC Strategy Meeting Wayne State University, August 24, 2013 Uncertainties in jet event generators due to hadronizatonscheme, Other issues with energy loss on E-by-E hydro, and the extraction of transport coefficients Rainer Fries Texas A&M University

2. RHIC Strategy Meeting Wayne State University, August 24, 2013 Hadronization, Chemistry and Other Issues Rainer Fries Texas A&M University

3. Hadronization • Hadronization: Challenge or Opportunity? • HQ sector • Quark number scaling • Extraction of Jet/High-PT Physics: • JET Hadronization Module • Flavor conversions revisited RHIC Strategy 2013

4. Hadrons in Heavy Ion Collisions • Proton/pion ratio • RAA • “Universal” hadronization in thermalized (low PT) and pure fragmentation (high PT) region. • Intermediate momentum region in heavy ion collisions (2-8 GeV): • No kinetic equilibrium; Multi-particle dynamics; No microscopic description of parton dynamics. RHIC Strategy 2013

5. Can Hadronization Tell Us About QGP? • Example: Quark Number dependent phenomena • Usual interpretation: quark degrees of freedom were activein the collision. RHIC Strategy 2013

6. Heavy Quark Sector I • Recombination forces heavy quarks to feel the collective flow. • Charm to D-meson coalescence in a recombination model with correct equilibrium limit. • Recombination rate ~ c+light quark elastic scattering rate near Tc. RHIC Strategy 2013

7. Heavy Quark Sector II • Flavor effects in the heavy quark sector: Dsvs D • Changes in chemistry are often hadronization effects. RHIC Strategy 2013

8. Chemistry in Jet and Ridge pTtrig > 4.0 GeV/c 2.0 < pTassoc< pTtrig inclusive Au+Au: M. Lamont (STAR) SQM06 Cu+Cu: C. Nattrass (STAR), QM2008 Au+Au: J.B. (STAR), WWND07 C. Suarez (STAR), poster, QM2008 Au+Au: 2<pTtrig<3 GeV/c,Cu+Cu:3<pTtrig<6 GeV/c • Baryon/meson ratios: • “jet”: smaller than inclusive • and similar to p+p • ridge: similar to inclusive PHENIX, arXiv:0712.3033 RHIC Strategy 2013 Jana Bielcikova, Hard Probes 2008 Jana Bielcikova

9. Recombination in Jet Showers • JET goal: jet shower Monte Carlo including medium-modified hadronization • Well-established hadronization models for vacuum shower Monte-Carlo’s • Lund string fragmentation • Cluster hadronization • How to generalize to jets in a medium? • Recombination • Challenge: get vacuum fragmentation right. • Advantage: medium effects are straight forward to implement; does well with heavy ion single particle spectra. • Need event-by-event formalism; momentum and energy conservation in each shower are important. • Need to include space-time information. RHIC Strategy 2013

10. String Fragmentation • Here: PYTHIA parton showers, will eventually work with MM showers • Standard PYTHIA Lund string fragmentation: Lund String String Decay RHIC Strategy 2013

11. Recombination + Remnant Strings • Here: PYTHIA parton showers, will eventually work with MM showers • Standard PYTHIA Lund string fragmentation: • Our approach: Lund String Force gluon decay String Decay Recombine Remnant strings String Decay RHIC Strategy 2013

12. Recombine Quarks • In absence of space-time information integrate out spatial coordinates in the Wigner functions. • Monte-Carlo implementation of recombination probabilities • Direct recombination produces hard spectra. • Allow recombination into resonances with subsequent decay • Mesons: π, ρ, a1, K, K*, and K1 • Baryons N, N’, Δ, and Δ’ • Reconnect remnant quarks by short strings that fragment. RHIC Strategy 2013

13. Event-By-Event Vacuum Fragmentation • Reproduction of vacuum fragmentation compares favorably to PYTHIA string fragmentation. • Lessons learnt: • Resonances important. • Event-by-event calculation important. 100 GeV light quark jets in e++e- [K. Han, C.M. Ko, R.J.F., arxiv:1209.1141] RHIC Strategy 2013

14. Adding Medium Partons • Sampling thermal partons from a blastwave model (T=170 MeV, <v> = 0.6 (0.65)). • Allow recombination of thermal partons Recombine Remnant strings RHIC Strategy 2013

15. Shower-Thermal Recombination • Pions and protons at RHIC. • Thermal-thermal added. • Baryon production clearly enhanced by shower-thermal recombination. RHIC Strategy 2013

16. Recover Baryon Enhancement • Proton/pion ratio is enhanced by shower-thermal recombination. RHIC Strategy 2013

17. Lessons So Far? • Hadronization effects in jets: too early to tell the full story • Extrapolating from heavy quarks: jet-thermal recombination adds a layer of diffusion and makes “hard” hadrons feel collective flow. • Broadening? • Larger v2? RHIC Strategy 2013

18. Conversions • Example 1: excess production of particles which are rare in the medium and rare in the probe sample • Example: photons • Need enough yield to outshine other sources of Nrare. • Example 2: chemical equilibration of a rare probe particle • Example: strangeness at RHIC • Coupling of jets (not equilibrated) to the equilibrated medium should drive jets towards chemical equilibrium. • Quark-gluon conversion  proton/pion ratio photon jet [RJF, Müller, Srivastava] [Srivastava, Gale, RJF] [Zakharov], ….. [Zhang, Vitev] [Renk] s g [W. Liu, RJF, PRC 77 (2008)] [W. Liu, RJF, PRC 78 (2008)] RHIC Strategy 2013

19. Conclusions • Chemistry: Need identified hadrons up to 8-10 GeV with good statistics. • Diffusion: • out-of-cone energy/momentum in jet measurements • near-side correlations of hadrons RHIC Strategy 2013