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Colour reconnection and Bose-Einstein effects

B. R. Webber

TL;DR

This paper surveys how final-state interactions in fully hadronic WW decays at LEP2—specifically colour reconnection and Bose-Einstein correlations—could bias the reconstructed W mass. It contrasts perturbative colour reconnection (found to be highly suppressed) with non-perturbative hadronization models, including colour-singlet (string and cluster) scenarios and non-singlet (colour-full) approaches, highlighting mass-shift predictions from each. In BE correlations, multiple grafting strategies (redistribution, reweighting with clustering or limited permutations, and other space-time-based methods) are reviewed, with results showing model-dependent, generally modest mass shifts. The paper calls for updated, data-titted studies and cross-model comparisons to better quantify potential biases and identify robust observables that correlate with W-mass shifts.

Abstract

Final-state interactions and interference phenomena that could affect the value of the W mass reconstructed from hadronic WW decays at LEP2 are reviewed, and possible areas for future investigation are identified.

Colour reconnection and Bose-Einstein effects

TL;DR

This paper surveys how final-state interactions in fully hadronic WW decays at LEP2—specifically colour reconnection and Bose-Einstein correlations—could bias the reconstructed W mass. It contrasts perturbative colour reconnection (found to be highly suppressed) with non-perturbative hadronization models, including colour-singlet (string and cluster) scenarios and non-singlet (colour-full) approaches, highlighting mass-shift predictions from each. In BE correlations, multiple grafting strategies (redistribution, reweighting with clustering or limited permutations, and other space-time-based methods) are reviewed, with results showing model-dependent, generally modest mass shifts. The paper calls for updated, data-titted studies and cross-model comparisons to better quantify potential biases and identify robust observables that correlate with W-mass shifts.

Abstract

Final-state interactions and interference phenomena that could affect the value of the W mass reconstructed from hadronic WW decays at LEP2 are reviewed, and possible areas for future investigation are identified.

Paper Structure

This paper contains 12 sections, 2 equations, 5 figures.

Table of Contents

  1. Introduction
  2. Perturbative colour reconnection
  3. Non-perturbative reconnection
  4. Colour singlet models
  5. Non-singlet models
  6. Modelling Bose-Einstein effects
  7. Redistribution method
  8. Reweighting methods
  9. Clustering.
  10. Limited permutation.
  11. Other methods
  12. Summary

Figures (5)

  • Figure 1: Lowest-order colour reconnection in WW decay.
  • Figure 2: Hadronization region for WW final state.
  • Figure 3: HERWIG model for colour reconnection. Solid: usual clustering. Dashed: possible alternative clustering.
  • Figure 4: Mean charged multiplicity as a function of the angle $\theta$ defined in fig. \ref{['fig_WWtubes']}.
  • Figure 5: Charged multiplicity and rapidity distributions.