Determination of the b quark mass at the M_Z scale with the DELPHI detector at LEP

TL;DR

This paper measures the b quark mass at the Z boson energy scale using jet algorithms at LEP, providing the most precise high-energy b mass measurement and confirming QCD predictions on mass evolution.

Contribution

It presents a novel high-precision measurement of the b quark's running mass at the Z scale using three-jet rates and jet algorithms, aligning with theoretical QCD predictions.

Findings

Measured m_b(M_Z) = 2.85 GeV/c^2 with uncertainties

Results favor the running mass over the pole mass

Confirms QCD's prediction of mass evolution and flavor independence

Abstract

An experimental study of the normalized three-jet rate of b quark events with respect to light quarks events (light= \ell \equiv u,d,s) has been performed using the CAMBRIDGE and DURHAM jet algorithms. The data used were collected by the DELPHI experiment at LEP on the Z peak from 1994 to 2000. The results are found to agree with theoretical predictions treating mass corrections at next-to-leading order. Measurements of the b quark mass have also been performed for both the b pole mass: M_b and the b running mass: m_b(M_Z). Data are found to be better described when using the running mass. The measurement yields: m_b(M_Z) = 2.85 +/- 0.18 (stat) +/- 0.13 (exp) +/- 0.19 (had) +/- 0.12 (theo) GeV/c^2 for the CAMBRIDGE algorithm. This result is the most precise measurement of the b mass derived from a high energy process. When compared to other b mass determinations by experiments at lower energy scales, this value agrees with the prediction of Quantum Chromodynamics for the energy evolution of the running mass. The mass measurement is equivalent to a test of the flavour independence of the strong coupling constant with an accuracy of 7 permil.