Presentation on theme: "Recombination for JET Shower MC: Status and Discussion Rainer Fries Texas A&M University JET NLO & MC Meeting Wayne State University, August 23, 2013 On."— Presentation transcript:
Recombination for JET Shower MC: Status and Discussion Rainer Fries Texas A&M University JET NLO & MC Meeting Wayne State University, August 23, 2013 On Behalf Of Kyongchol Han Che-Ming Ko
Hadronization JET NLO&MC Rainer Fries 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, hadronization system-dependent.
Hadrons in Heavy Ion Collisions JET NLO&MC Rainer Fries Proton/pion ratio R AA Intermediate momentum region in heavy ion collisions (2-8 GeV): No kinetic equilibrium Multi-particle dynamics No microscopic description of parton dynamics.
Why Quark Recombination? JET NLO&MC 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?
Quark Recombination Start from a distribution of quarks Instantaneous approximation: 2 1, 3 1 Finite time: recombination rate equations JET NLO&MC Rainer Fries ?
Recombination in Jet Showers JET NLO&MC Rainer Fries 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, (2004); (2004)]
Formalism: Overview JET NLO&MC Rainer Fries 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 Perturbative parton shower (PYTHIA, HERWIG, JET MCs) Apply instantaneous quark recombination w/ phenomenological meson and baryon Wigner functions. Sample quarks from thermal medium in which jet is embedded. Recombine into full hadronic resonance spectrum and decay; treat remnant partons.
String Fragmentation Extract PYTHIA parton showers evolved to a scale Q 0. Standard PYTHIA Lund string fragmentation: JET NLO&MC Rainer Fries Lund String String Decay
Recombination + Remnant Strings Extract PYTHIA parton showers evolved to a scale Q 0. Standard PYTHIA Lund string fragmentation: Our approach: JET NLO&MC Rainer Fries Lund String Force gluon decay Recombine String Decay Remnant strings String Decay
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 Rainer Fries
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, a 1, K, K *, and K 1 Baryons N, N’, Δ, and Δ’ Reconnect remnant quarks by short strings that fragment. JET NLO&MC Rainer Fries
Adding Medium Partons Sampling thermal partons from a blastwave model (T=170 MeV, = 0.6 (0.65)). Allow recombination of thermal partons JET NLO&MC Rainer Fries Recombine Remnant strings
Adding Shower-Thermal Recombination Pions and protons at RHIC. Thermal-thermal added. Baryon production clearly enhanced by shower-thermal recombination. JET NLO&MC Rainer Fries
Baryon Enhancement Proton/pion ratio is enhanced by shower-thermal recombination. JET NLO&MC Rainer Fries
Baryon Enhancement Very similar picture for LHC. JET NLO&MC Rainer Fries
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 + reco vs data Protocol for interface with parton shower MCs. Role of spatial coordinates? Replace blastwave by hydro. JET NLO&MC Rainer Fries
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 < T c. Partons that “stop” inside QGP will be propagated to the critical hypersurface by the hadronization module. Recombination + remnant fragmentation applied to partons at T = T c and T > T c. JET NLO&MC Rainer Fries
Backup JET NLO&MC Rainer Fries
Recombination in Equilibrium JET NLO&MC Rainer Fries [He, RJF & Rapp, [nucl-th]] Realistic hadronization hypersurface : Extract equal-time quark phase space distributions f q along from hydro or kinetic model. Apply RRM cell-by-cell meson phase space distribution f M along . Compute meson current across a la Cooper-Frye: Result for charm-light system using AZHYDRO: t = const.