Jet fragmentation via recombination of parton showers

We propose to model hadronization of parton showers in QCD jets through a hybrid approach involving quark recombination and string fragmentation. This is achieved by allowing gluons at the end of the perturbative shower evolution to undergo a nonperturbative splitting into quark and antiquark pairs, then applying a Monte Carlo version of instantaneous quark recombination, and finally subjecting remnant quarks (those which have not found a recombination partner) to Lund string fragmentation. When applied to parton showers from the pythia Monte Carlo event generator, the final hadron spectra from our calculation compare quite well to pythia jets that have been hadronized with the default Lund string fragmentation. Our new approach opens up the possibility to generalize hadronization to jets embedded in a quark gluon plasma.

Figure 1

Distribution $dN/dz$ of shower partons in terms of the momentum fraction $z$ of the initial jet momentum at the end of the perturbative shower evolution for a jet of 100 GeV before (upper panel) and after (lower panel) forcing gluon decays into quark-antiquark pairs.

Figure 2

Same as Fig.  1 but for the shower parton transverse momentum distribution $dN/d^2{\mathbf{p}}_T$.

Figure 3

Statistical distribution of quark-antiquark pairs in 100 GeV jet parton shower in terms of relative spatial and momentum coordinates $y$ and $k$ of the pair. The coordinates are defined in the common rest frame of the pair at the time the latter parton is created in the shower.

Figure 4

Probabilities of light and strange quarks to recombine into hadrons as functions of their momentum fraction $z$ for 100 GeV jets.

Figure 5

Longitudinal-momentum-fraction spectrum $dN/dz$ of pions (upper-left panel), kaons (upper-right panel), nucleons and antinucleons (lower-left panel), and $\mathrm{\Lambda }$ and $\overline{\mathrm{\Lambda }}$ (lower-right panel) from our calculation. Shown separately are contributions from the recombination of shower partons (stars) and fragmentation of remnant partons (circles). Also shown are the total contribution (dashed lines) and the results from pythia string fragmentation (solid lines).

Figure 6

Same as Fig. 5 but for the transverse-momentum spectra.

Figure 7

Same as Fig. 5 but for jets of energy $E_{\mathrm{jet}}=25$ GeV.

Figure 8

Same as Fig. 6 but for jets of energy $E_{\mathrm{jet}}=25$ GeV.