Precise determination of αS( $ m_{Z^0 } $ ) from a global fit of energy-energy correlations to NNLO+NNLL predictions

A Kardos,S Kluth,Z Tulipánt,G Somogyi,A Verbytskyi

doi:10.1051/epjconf/201920605002

A Kardos, S Kluth + Show 3 more

Open Access

https://doi.org/10.1051/epjconf/201920605002

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Abstract

We present a determination of the strong coupling constant αS( $ m_{Z^0 } $ ) using a global fit of theory predictions in next-to-next-next-leading-order (NNLO) combined with resummed predictions at the next-to-next-leading-log level (NNLL) [bibrR11]. The predictions are compared to distributions of energy-energy correlations measured in e+e−annihilation to hadronic final states by experiments at the e+e−colliders LEP, PETRA, TRISTAN and PEP. The predictions are corrected for hadronisation eﬀects using the modern generator programs Sherpa 2.2.4 and Herwig 7.1.1.

Highlights

Data from experiments at e+e− colliders have been used since a long time to investigate the theory of strong interactions, Quantum Chromo Dynamics (QCD) and in particular to measure its only free parameter the strong coupling constant αS(mZ0 ) at the reference scale mZ0, see e.g.[2]
There are several recent determinations of αS(mZ0 ) using data of e+e− annihilation to hadronic final states using NNLO QCD predictions combined with resummed calculations and different approaches to treat non-perturbative effects, see [3]
We have shown a determination of the strong coupling constant αS(mZ0 ) using the event shape observable EEC using NNLO combined with next-leading-log level (NNLL) resummed QCD predictions

Summary

Introduction

Data from experiments at e+e− colliders have been used since a long time to investigate the theory of strong interactions, Quantum Chromo Dynamics (QCD) and in particular to measure its only free parameter (in the absence of quark mass effects) the strong coupling constant αS(mZ0 ) at the reference scale mZ0 , see e.g.[2]. There are several recent determinations of αS(mZ0 ) using data of e+e− annihilation to hadronic final states using NNLO QCD predictions combined with resummed calculations and different approaches to treat non-perturbative effects (hadronisation), see [3]. The theoretical predictions are at the level of the partons (quarks and gluons) of QCD and are known to not give an adequate description of the data This is due to the presence of nonperturbative corrections connected with the transition of partons to hadrons, i.e. the hadronisation process. The hadronisation corrections are calculated as the ratio of EEC distributions at parton and hadron level in the simulations using the weighted events. These corrections are applied to the perturbative predictions before they are compared with the data.

Fits to the data

Truncated parton shower bias

Summary