Inside the SU(3) quark-antiquark QCD flux tube: screening versus quantum widening

In lattice QCD, colour confinement manifests in flux tubes. We compute in detail the quark-antiquark flux tube for pure gauge SU(3) dimension $D=3+1$ for quark-antiquark distances R ranging from 0.4 fm to 1.4 fm. To increase the signal over noise ratio, we apply the improved multihit and extended smearing techniques. We detail the gauge invariant squared components of the colour electric and colour magnetic fields both in the mediator plane between the static quark and static antiquark and in the planes of the sources. We fit the field densities with appropriate ansatze and we observe the screening of the colour fields in all studied planes together with the quantum widening of the flux tube in the mediator plane. All components squared of the colour fields are non-vanishing and are consistent with a penetration length lambda ~ 0.22 to 0.24 fm and an effective screening mass mu ~ 0.9 to 0.8 GeV. The quantum widening of the flux tube is well fitted with a logarithmic law in R.