Abstract
We present a new model for the hadronisation of multi-parton systems, in which colour correlations beyond leading $N_C$ are allowed to influence the formation of confining potentials (strings). The multiplet structure of $SU(3)$ is combined with a minimisation of the string potential energy, to decide between which partons strings should form, allowing also for "baryonic" configurations (e.g., two colours can combine coherently to form an anticolour). In $e^+e^-$collisions, modifications to the leading-colour picture are small, suppressed by both colour and kinematics factors. But in $pp$ collisions, multi-parton interactions increase the number of possible subleading connections, counteracting their naive $1/N_C^2$ suppression. Moreover, those that reduce the overall string lengths are kinematically favoured. The model, which we have implemented in the PYTHIA 8 generator, is capable of reaching agreement not only with the important $\left<p_\perp\right>(n_\mathrm{charged})$ distribution but also with measured rates (and ratios) of kaons and hyperons, in both $ee$ and $pp$ collisions. Nonetheless, the shape of their $p_\perp$ spectra remains challenging to explain.
Highlights
To describe the full event structure, several additional soft-physics effects must be accounted for, such as hadronisation, multiple parton interactions (MPI), Bose-Einstein correlation effects, and beam remnants
The question of colour reconnections (CR) — broadly, whether other string topologies than the LC one could lead to non-negligible corrections with respect to the LC picture — was studied at LEP [35,36,37,38,39,40,41,42], in the context of CR uncertainties on W mass determinations in ee → W W [43], with conclusion that excluded the very aggressive models and disfavoured the no CR scenario at 2.8 standard deviation [44]
For the models/tunes considered in this work, the resulting shift on the calibrated top mass is below 200 MeV, which is comparable with the current level of CR uncertainty on the measurements [58, 59, 63, 64] and far below some of the “devil’s-advocate” toy models considered in [71]
Summary
We present the colour-space model that we have developed, which allows strings to form between LC-connected partons, and between specific non-LCconnected ones, following combination rules that approximate the multiplet structure of full-colour QCD. The subleadingcolour effects we discuss here arise naturally in “full-colour” SU(3) and do not involve any physical exchange of colour or momentum ( explicit algorithms may still employ an iterative-reconnection scheme to find the potential-energy minimum). The term colour reconnections should be reserved to describe effects related to dynamical reconfigurations of the colour/string space that involve explicit exchange of colours and momentum, via perturbative gluon exchanges or non-perturbative string interactions. Effects of this type are not explored directly in this work, instead we refer the interested reader to the SK string-interaction models presented in [43, 66, 67]. We follow the entrenched convention in the field and use the acronym “CR” for effects of either kind here
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
