1. In Medium Hadronization: Hadrons and Jets Rainer Fries Texas A&M University Jet Modifications in the RHIC and LHC Era Wayne State, August 20, 2014 With Kyongchol Han Che-Ming Ko JET Reco Working Group

2. Outline Jet Mod 20142 Rainer Fries Hadronization and in-medium hadronization The JET shower recombination module How to implement a medium Some preliminary results with medium Summary

3. Hadronization Matters Jet Mod 20143 Rainer Fries Example: Hadron chemistry  Does the B/M ratio measure phase space occupation? Example: Elliptic flow in the heavy quark sector.  Hadronization in-medium = additional interaction with the thermal medium.  More diffusion/thermalization p T trig > 4.0 GeV/c 2.0 < p T Assoc < p T trig C. Suarez et al, QM08 p+p /  + +  - Can effect be measured directly? YES Can effect be measured directly? DIFFICULT [M He, R J Fries, R Rapp, PRC 86 014903 (2012) ]

4. Hadronization Candidates Jet Mod 20144 Rainer Fries Lund string fragmentation Cluster hadronization Jet recombination

5. Why Quark Recombination? Jet Mod 20145 Rainer Fries Data indicates a dependence of several important observables on the number of valence quarks. Quark coalescence models very successful for hadron production at intermediate P T in HICs.  Large baryon/meson ratios  Elliptic flow scaling with quark number  QGP signature?

6. Hadronization Candidates Jet Mod 20146 Rainer Fries No clear strategy how to generalize strings or clusters to in-medium hadronization. Recombination did not have a working jet shower implementation. Can one get vacuum fragmentation right? Including medium effects then in principle straight forward; good track record. JET jet shower recombination module: work in progress (see yesterday’s talk) This is a project that benefits from feedback from the community.

7. Summary of JET Recombination Standard PYTHIA Lund string fragmentation: Our approach: Jet Mod 20147 Rainer Fries Lund String Force gluon decay Recombine into hadrons and resonances String Decay Remnant strings String Decay

8. Summary of JET Recombination Jet Mod 20148 Rainer Fries StringClusterRecombination GluonsKinksForced decay Large separation quarks String breakingClustersString Breaking Small separation quarks, low mass Indirectly from string breaking ClustersDirect recombination Small separation quarks, high mass Indirectly from string breaking High mass clusterResonance

9. Some Results Jet Mod 20149 Rainer Fries Longitudinal structure: dN / dz of stable particles compared to PYTHIA string fragmentation. 100 GeV jets How to tune parameters?

10. Adding Medium Partons Sampling thermal partons from a blastwave models or hydro. Allow recombination of shower partons with thermal partons. Jet Mod 201410 Rainer Fries Recombine Remnant strings

11. Space-Time Picture Space-time picture important. Situation not static: T = T c hypersurface moving. Jet Mod 201411 Rainer Fries QGP T > T c Hadronization T ~ T c Hadronic/vacuum T < T c

12. Space-Time Picture Space-time picture important. Situation not static: T = T c hypersurface moving. Jet shower partons born into QGP need to either propagate to the surface or be absorbed by the medium. How this is handled will depend strongly on the shower MC. Hadronization will only be applied to partons at or below T c. Jet Mod 201412 Rainer Fries QGP T > T c Hadronization T ~ T c Hadronic/vacuum T < T c

13. Space-Time Picture Space-time picture important. There is a range, say e.g. T = 155-175 MeV, during which recombination can happen. This translates to a finite thickness of the critical hypersurface. This should be a physical quantity but it’s not necessarily a known quantity. Jet Mod 201413 Rainer Fries QGP T > T c Hadronization T ~ T c Hadronic/vacuum T < T c

14. Space-Time Picture Eventually this space-time picture will be determined from the underlying hydro event. Here: a few very preliminary results for shower born 1 fm inside a static QGP phase. Thickness of the critical hypersurface is another fermi. Jet Mod 201414 Rainer Fries

15. Results in a Semi-Realistic Setup Modification of low- z spectra for 100 GeV jets by presence of a medium at hadronization. Showers: PYTHIA vacuum showers. Point of origin 1 fm inside the QGP Jet Mod 201415 Rainer Fries

16. Results in a Semi-Realistic Setup Modification of P T -spectra (all z ) for 100 GeV jets by presence of a medium at hadronization. Showers: PYTHIA vacuum showers. Point of origin 1 fm inside the QGP Jet Mod 201416 Rainer Fries

17. Varying the Point of Origin (Preliminary) Modification of z -spectra for 100 GeV jets by presence of a medium at hadronization. Trade some sh-sh to sh-th but almost no change in overall spectrum. Jet Mod 201417 Rainer Fries 1 fm 3 fm

18. How will Hadronization Matter? We need to get the physics of in-medium hadronization at least approximately right in simulations.  No effect? Fine, but we needed to check.  Large effects? Fine!! We need to look into the physics more closely. Explore parameter space. Generally: in-medium hadronization is just another layer of interaction with the medium  Energy and momentum exchange with the medium.  In principle interaction continues in the hadronic phase! Hadrons: hadronization will only affect small and intermediate momentum hadrons.  Chemistry effects: should be measurable; expect increased baryon/meson ratio  Momentum diffusion/broadening: size of the effect needs to be studied in simulations, maybe hard to distinguish from other sources of diffusion/broadening. Jet Mod 201418 Rainer Fries

19. How will Hadronization Matter? Inclusive jets: hadronization effects suppressed by design.  No access to chemistry  Diffusion/broadening can contribute to in-cone/out-of-cone effects. Jet-hadron correlations/fragmentation functions: most promising to see hadronization effects.  Both hadrochemistry and momentum redistribution. None of this has been investigated on the MC level. JET MCs should be able to do that within a year. Jet Mod 201419 Rainer Fries