Caractéristiques non-perturbatives des hadrons sur le cône de lumière – DIAM

In spite of its success in explaining strong interaction between elementary constituents of matter, Quantum Chromodynamics does not provide the non-perturbative description of the proton and other hadrons as composites of confined, relativistic quark and gluon quanta. A particularly powerful tool to analyse this issue consists in parton distribution amplitudes (DAs) of hadrons on the light cone. Indeed, these non-perturbative, gauge- and process-independent quantities can be defined theoretically in a clean way and provide information relevant to the transition from energetic quarks to hadrons, i.e. hadronisation. In particular, the shape of meson and baryon valence-quark DAs describes in a very useful and intuitive way how a hadron shares its longitudinal momentum among its valence quarks. Applications of DAs range from nuclear physics (nucleon structure) and hadronic physics (transition form factors,) to flavour physics (B-decays). Unfortunately, these non-perturbative universal functions remain poorly known. The DIAM project (DIstribution Amplitudes of Mesons) aims at determining some of these DAs on a sound theoretical basis. For this reason, we will focus on valence-quark of DAs for pseudoscalar mesons, combining lattice simulations and effective field theories. In the case of light mesons (pion, kaon), the twist-2 and twist-3 valence-quark DAs will be considered : their first positive moments will be computed on the lattice using publicly available gauge configurations (with two dynamical flavours). We will control ultraviolet physics (renormalisation of operators on the lattice) through lattice perturbation theory, and infrared aspects (light-quark mass extrapolation, finite-volume effects) through chiral perturbation theory. In the case of heavy-light mesons (B-meson), higher-twist DAs will be investigated : their renormalisation-scale dependence will be determined through Renormalisation Group Equations in HQET (Heavy Quark Effective Theory), allowing us to provide models for these DAs and to determine their role in the estimation of form factors through light-cone sum rules. The previous steps will provide strong constraints on the DAs of the mesons that we will exploit to tackle several cognate issues : pion electromagnetic form factor, models of generalised parton distributions for pions and kaons, form factors involved in B decays, extension of the method for baryons.