In lattice QCD, colour confinement manifests in flux tubes. We compute in detail the quarkantiquark 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 λ ∼ 0.22 to 0.24 fm and an effective screening mass µ ∼ 0.8 to 0.9 GeV. The quantum widening of the flux tube is well fitted with a logarithmic law in R.PACS11.15. Ha, 12.38.Gc,74.25.Uv,
We discuss, how to study I = 0 quarkonium resonances decaying into pairs of heavy-light mesons using static potentials from lattice QCD. These static potentials can be obtained from a set of correlation functions containing both static and light quarks. As a proof of concept we focus on bottomonium with relative orbital angular momentum L = 0 of thebb pair corresponding to J P C = 0 −+ and J P C = 1 −− . We use static potentials from an existing lattice QCD string breaking study and compute phase shifts and T matrix poles for the lightest heavy-light meson-meson decay channel. We discuss our results in the context of corresponding experimental results, in particular for Υ(10860) and Υ(11020).
We combine techniques previously utilised to study flux tube field density profiles and to study the excited spectrum of the gluonic fields produced by a static quark-antiquark pair. Working with pure gauge SU(3) fields discretised in a lattice, we utilise Wilson loops with a large basis of gluonic spacelike Wilson lines to include different excitations of the quark-antiquark flux tube. To increase the signal over noise ratio, we use the multihit technique in the temporal Wilson lines and the APE smearing in spatial Wilson lines. The number of gluonic operators combined with the space points where we compute the flux tube densities turns out to be very large, and we resort to GPUs and to CUDA codes. Computing the effective mass plot from the diagonalized correlation matrix, we separate the excitations with different two-dimensional angular momentum, parity and radial quantum numbers. We then compute the colour field density profiles for all the components of the colour electric and colour magnetic fields. We analyse our results for the first excitations of the flux tube and search for signals of novel phenomena beyond the Nambu-Goto string model, such as a longitudinal mode or an explicit gluon.
We compute the composition of the bottomonium Υ(nS) states (including Υ(10860)) and the new Υ(10753) resonance reported by Belle in terms of quarkonium and meson-meson components. We use the Born Oppenheimer approximation, static potentials from a lattice QCD study of string breaking and the unitary emergent wave method to compute the poles of the S matrix. We focus on I = 0 bottomonium S wave bound states and resonances, where the Schrödinger equation is a set of two coupled differential equations. One of the two channels corresponds to a confined heavy quark-antiquark pair b b, the other to a pair of heavy-light mesons B ( * ) B( * ) . We confirm the new Belle resonance Υ(10753) as a dynamical meson-meson resonance with 94% meson-meson content. Moreover, we identify Υ(4S) and Υ(10860) as predominantly quarkonium states, however with sizable meson-meson contents of 30% and 41%, respectively. With these results we contribute to the clarification of ongoing controversies in the vector bottomonium spectrum.
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