arXiv subjects
Publications and source records attributed to Nora Brambilla.
I discuss effective field theories for heavy bound systems, particularly bound systems involving two heavy quarks. The emphasis is on the relevant concepts and on interesting physical applications and results.
We derive and discuss the constraints induced by Poincare' invariance on the form of the heavy-quark potential up to order 1/m^2. We present two derivations: one uses general arguments directly based on the Poincare' algebra and the other follows from an explicit calculation on the expression of the potential in terms of Wilson loops. We confirm relations from the literature, but also clarify the origin of a long-standing false statement pointed out recently.
Heavy quark bound states are used as significative probes of the QCD vacuum and the mechanism of confinement.
In the framework of the QCD effective field theory called potential Non-Relativistic QCD, we explore quark-antiquark bound systems that may be dominated by the perturbative interaction and we discuss the extent of validity of such a picture. Some phenomenological implications are outlined.
We evaluate in perturbative QCD, up to order $α_s^4$, the mass of the $B_c$. We use the so-called 1S-mass in order to improve the convergence of the perturbative series. Our result is $E(B_c)_{pert} = 6326^{+29}_{-9}$ MeV. Non-perturbative effects are discussed. A comparison with potential models seems to be consistent with non-perturbative contributions of the order $ - (40÷100)$ MeV.
Heavy quark bound state systems, mesons and hybrids, are discussed in the framework of the QCD effective field theory called potential Non-Relativistic QCD.
We discuss heavy quarkonium in the framework of pNRQCD, a QCD effective theory appropriate for the study of heavy quark bound systems.
We present model independent predictions on the short range behavior of the energies of the gluonic excitations between static quarks (hybrid potentials) in an effective field theory framework (pNRQCD).
These lectures contain an introduction to the following topics: 1) Phenomenology of the hadron spectrum; 2) The static Wilson loop in perturbative and in lattice QCD. Confinement and the flux tube formation; 3) Non static properties: effective field theories and relativistic corrections to the quarkonium potential; 4) The QCD vacuum: minimal area law, Abelian projection and dual Meissner effect, stochastic vacuum.
I discuss the bound state quark dynamics focusing on the nonperturbative interaction and the flux tube structure.
Starting from the NRQCD Lagrangian the heavy quark-antiquark potential is written in terms of field strength insertions on a static Wilson loop. The relevant matching coefficients are given at the present status of knowledge. The short-range, perturbatively dominated, behaviour of the spin-dependent terms is discussed.
We establish a relation between the two-point field strength correlator in QCD and the dual field propagator of the effective dual Abelian Higgs model describing the infrared behaviour of QCD.
We study field strength correlators in presence of a static quark-antiquark pair by use of lattice methods. The lattice data have been acquired recently in the context of a determination of relativistic corrections to the static interquark potential. We extract independent estimates of the form factors of two point correlation functions and investigate the effect of higher order correlators. Our results confirm the dominance of the two point correlators in the regions of intermediate and large quark separations, and are compatible with correlation length values obtained from different approaches.
We obtain the non-perturbative interaction kernel of the heavy-light quark system in a gauge-invariant approach. The potential and the sum rules limit are discussed. Some insight is given in the light quark interaction.
The complete $ q\bar{q}$ semirelativistic interaction is obtained as a gauge-invariant function of the Wilson loop and its functional derivatives. The approach is suitable for analytic evaluations as well as for lattice calculations. Here we consider three different models for the Wilson loop non-perturbative behaviour and discuss the related semirelativistic dynamics.
We study the $q \bar{q}$ relativistic interaction starting from the Feynman-Schwinger representation of the gauge-invariant quark-antiquark Green function. We focus on the one-body limit and discuss the obtained non-perturbative interaction kernel of the Dirac equation.
Starting from the relativistic gauge-invariant quark-antiquark Green function we obtain the relevant interaction in the one-body limit, which can be interpreted as the kernel of a non-perturbative Dirac equation. We study this kernel in different kinematic regions, reproducing, in particular, for heavy quark the potential case and sum rules results. We discuss the relevance of the result for heavy-light mesons and the relation with the phenomenological Dirac equations used up to now in the literature.
We write the 4-point Green function in QCD in the Feynman-Schwinger representation and show that all the dynamical information are contained in the Wilson loop average. We work out the QED case in order to obtain the usual Bethe-Salpeter kernel. Finally we discuss the QCD case in the non-perturbative regime giving some insight in the nature of the interaction kernel.