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

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

3. Hadronization RHIC Strategy 20133 Rainer Fries Hadronization: Challenge or Opportunity?  HQ sector  Quark number scaling Extraction of Jet/High-PT Physics:  JET Hadronization Module Flavor conversions revisited

4. Hadrons in Heavy Ion Collisions RHIC Strategy 20134 Rainer Fries Proton/pion ratio R AA “Universal” hadronization in thermalized (low P T ) and pure fragmentation (high P T ) region. Intermediate momentum region in heavy ion collisions (2-8 GeV):  No kinetic equilibrium; Multi-particle dynamics; No microscopic description of parton dynamics.

5. Can Hadronization Tell Us About QGP? Example: Quark Number dependent phenomena Usual interpretation: quark degrees of freedom were active in the collision. RHIC Strategy 20135 Rainer Fries

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 T c. RHIC Strategy 20136 Rainer Fries

7. Heavy Quark Sector II Flavor effects in the heavy quark sector: D s vs D Changes in chemistry are often hadronization effects. RHIC Strategy 20137 Rainer Fries

8. RHIC Strategy 20138 Rainer Fries Baryon/meson ratios: “jet”: smaller than inclusive and similar to p+p ridge: similar to inclusive inclusive Au+Au: M. Lamont (STAR) SQM06 Cu+Cu: C. Nattrass (STAR), QM2008 Au+Au: J.B. (STAR), WWND07 Jana Bielcikova C. Suarez (STAR), poster, QM2008 PHENIX, arXiv:0712.3033 p T trig > 4.0 GeV/c 2.0 < p T assoc < p T trig Au+Au: 2<p T trig <3 GeV/c,Cu+Cu:3<p T trig <6 GeV/c Jana Bielcikova, Hard Probes 2008 Chemistry in Jet and Ridge

9. Recombination in Jet Showers RHIC Strategy 20139 Rainer Fries 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.

10. String Fragmentation Here: PYTHIA parton showers, will eventually work with MM showers Standard PYTHIA Lund string fragmentation: RHIC Strategy 201310 Rainer Fries Lund String String Decay

11. Recombination + Remnant Strings Here: PYTHIA parton showers, will eventually work with MM showers Standard PYTHIA Lund string fragmentation: Our approach: RHIC Strategy 201311 Rainer Fries Lund String Force gluon decay Recombine String Decay Remnant strings String Decay

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, a 1, K, K *, and K 1  Baryons N, N’, Δ, and Δ’ Reconnect remnant quarks by short strings that fragment. RHIC Strategy 201312 Rainer Fries

13. Event-By-Event Vacuum Fragmentation RHIC Strategy 201313 Rainer Fries Reproduction of vacuum fragmentation compares favorably to PYTHIA string fragmentation. Lessons learnt:  Resonances important.  Event-by-event calculation important. [K. Han, C.M. Ko, R.J.F., arxiv:1209.1141] 100 GeV light quark jets in e + +e -

14. Adding Medium Partons Sampling thermal partons from a blastwave model (T=170 MeV, = 0.6 (0.65)). Allow recombination of thermal partons RHIC Strategy 201314 Rainer Fries Recombine Remnant strings

15. Shower-Thermal Recombination Pions and protons at RHIC. Thermal-thermal added. Baryon production clearly enhanced by shower-thermal recombination. RHIC Strategy 201315 Rainer Fries

16. Recover Baryon Enhancement Proton/pion ratio is enhanced by shower-thermal recombination. RHIC Strategy 201316 Rainer Fries

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 v 2 ? RHIC Strategy 201317 Rainer Fries

18. RHIC Strategy 201318 Rainer Fries 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 N rare. 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 jet photon g s Conversions [RJF, Müller, Srivastava] [Srivastava, Gale, RJF] [Zakharov], ….. [Zhang, Vitev] [Renk] [W. Liu, RJF, PRC 77 (2008)] [W. Liu, RJF, PRC 78 (2008)]

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 201319 Rainer Fries