1 / 21

Recombination for JET Shower MC: Status and Discussion

JET NLO & MC Meeting Wayne State University , August 23, 2013. Recombination for JET Shower MC: Status and Discussion. Rainer Fries Texas A&M University. On Behalf O f Kyongchol Han Che -Ming Ko. Hadronization. Hadronization = difficult, non- perturbative problem

haracha
Download Presentation

Recombination for JET Shower MC: Status and Discussion

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. JET NLO & MC Meeting Wayne State University, August 23, 2013 Recombination for JET Shower MC:Status and Discussion Rainer Fries Texas A&M University On Behalf Of Kyongchol Han Che-Ming Ko

  2. Hadronization • Hadronization = difficult, non-perturbative problem • Sometimes we can apply one of two extreme limits in which hadronization becomes simpler: • Universality at large momentum  single-particle fragmentation: fragmentation functions can be measured. • Universality at low momenta  thermalization: equation of state, can be calculated on the lattice. • In between: universality broken, hadronizationsystem-dependent. JET NLO&MC 2013

  3. Hadrons in Heavy Ion Collisions • Proton/pion ratio • RAA • Intermediate momentum region in heavy ion collisions (2-8 GeV): • No kinetic equilibrium • Multi-particle dynamics • No microscopic description of partondynamics. JET NLO&MC 2013

  4. Why Quark Recombination? • Data indicates a dependence of several important observables on the number of valence quarks. • Quark coalescence models very successful for hadron production at intermediate PT in HICs. • Large baryon/meson ratios • Elliptic flow scaling with quark number  QGP signature? JET NLO&MC 2013

  5. Quark Recombination • Start from a distribution of quarks • Instantaneous approximation: 2  1, 3  1 • Finite time: recombination rate equations ? JET NLO&MC 2013

  6. Recombination in Jet Showers • JET goal related to NSAC Performance Measures: Complete realistic calculations of jet production in a high energy density medium for comparison with experiment. (DM7) • This includes chemical composition • Well-established hadronization models for vacuum shower Monte-Carlo’s • Lund string fragmentation • Cluster hadronization • How to generalize to jets in a medium? • Recombination: some early work on vacuum showers. • Challenge: get vacuum fragmentation right. • Advantage: medium effects are straight forward to implement; does well with heavy ion single particle spectra. [R. Migneron, M. E. Jones, K. E, Lassila, PLB 114, 189 (1983)] [R.C. Hwa and C.B. Yang, PRC 70, 024904 (2004); 024905 (2004)] JET NLO&MC 2013

  7. Formalism: Overview • Challenges: • Calculate parton showers in a controlled way; vacuum or medium modified. • Need event-by-event formalism; momentum and energy conservation in each shower are important. • Want to include space-time information. • Established work flow: • Here: We use parton and hadron showers from PYTHIA as a testing ground. • No space-time information. Add minimum non-perturbative effects: gluon splitting Perturbativeparton shower (PYTHIA, HERWIG, JET MCs) Apply instantaneous quark recombination w/ phenomenological meson and baryon Wigner functions. Recombine into full hadronic resonance spectrum and decay; treat remnant partons. Sample quarks from thermal medium in which jet is embedded. JET NLO&MC 2013

  8. String Fragmentation • Extract PYTHIA parton showers evolved to a scale Q0. • Standard PYTHIA Lund string fragmentation: Lund String String Decay JET NLO&MC 2013

  9. Recombination + Remnant Strings • Extract PYTHIA parton showers evolved to a scale Q0. • Standard PYTHIA Lund string fragmentation: • Our approach: Lund String Force gluon decay String Decay Recombine Remnant strings String Decay JET NLO&MC 2013

  10. Recombine Quarks • Use instantaneous recombination model by Greco, Ko, Levai: • Baryon and meson Wigner functions • Here M = 0.24 GeV, B = 0.35 GeV JET NLO&MC 2013

  11. Recombine Quarks • In absence of space-time information integrate out spatial coordinates in the Wigner functions. • 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. JET NLO&MC 2013

  12. Results • PYTHIA 100 GeV jets: • Recombination probability: JET NLO&MC 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] JET NLO&MC 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 JET NLO&MC 2013

  15. Adding Shower-Thermal Recombination • Pions and protons at RHIC. • Thermal-thermal added. • Baryon production clearly enhanced by shower-thermal recombination. JET NLO&MC 2013

  16. Baryon Enhancement • Proton/pion ratio is enhanced by shower-thermal recombination. JET NLO&MC 2013

  17. Baryon Enhancement • Very similar picture for LHC. JET NLO&MC 2013

  18. Plans for the Near Future • Additional tests … • E.g. broadening variables • Similar tests done for parton shower MCs? • So far tested against PYTHIA. Next step: new shower MC + recovs data • Protocol for interface with parton shower MCs. • Role of spatial coordinates? • Replace blastwave by hydro. JET NLO&MC 2013

  19. Merging of Modules • First step: take vacuum showers from “HT-MC” including space-time information. • Need access to a database of vacuum events. • Hadronization module assumes that full space-time information x is available. • This will allow us to test recombination with space-time information. • List of items to agree on for medium shower: • Shower MC needs to provide identifier of hydro event used. • Hadronization expects full information on space-time point x. • Space-time point = point of last splitting? • Shower medium effects restricted to T< Tc. • Partons that “stop” inside QGP will be propagated to the critical hypersurface by the hadronization module. • Recombination + remnant fragmentation applied to partons at T=Tc and T> Tc. JET NLO&MC 2013

  20. Backup JET NLO&MC 2013

  21. Recombination in Equilibrium • Realistic hadronizationhypersurface: • Extract equal-time quark phase space distributions fq along  from hydro or kinetic model. • Apply RRM cell-by-cell  meson phase space distribution fM along . • Compute meson current across  a la Cooper-Frye: • Result for charm-light system using AZHYDRO: t = const. [He, RJF & Rapp, 1106.6006 [nucl-th]] JET NLO&MC 2013

More Related