The emergence of a heavy quark family on a lattice (original) (raw)
2012
In this thesis, we focus on some aspects concerning hadronic phenomena at low energy, below 1 GeV, under which the spontaneous breaking of chiral symmetry takes place. Under this scale, the spectrum of Quantum Chromodynamics reduces to an octet of light pseudo-scalar mesons (π, K and η). But because of the confinement property, QCD under 1 GeV is highly non-perturbative, it is thus not possible to describe at low energy the dynamics of these mesons in terms of gluons and quarks (in that case the three light quarks u,d, and s). Two main alternatives exist to circumvent this major obstacle: Lattice QCD and Effective Field Theories. Lattice QCD is concerned with the numerical computations of various hadronic observables, while Effective Field Theories correspond to analytical frameworks adapted to a particular energy scale. In the case of QCD at low energy, this role is devoted to Chiral Perturbation Theory (ChiPT). This theory can be built either from two quark flavours (u and d), or ...
Composite models of quarks and leptons and strong-coupling lattice gauge theories
Physical Review D, 1982
We extend a previous variational block spin analysis of the realization of chiral symmetry in a strong coupling lattice gauge theory to models which have been suggested as possibly describing massless composite fermions. In all cases we find massive fermioncomposites and spontaneous breaking of chiral symmetry.
Physics of Heavy Quarks from Lattice QCD
2020
In the last few years, lattice QCD has made a dramatic progress in understanding the physics of hadrons containing heavy quarks, from the first principle. This review summarises the major achievements. I. INTRODUCTION Heavy quarks play a dominant role in the understanding of the weak interactions as well as of what may lie beyond the standard model. Since quarks are always bound into hadrons, and we do not understand the strong interactions rigorously, the results of these phenomena are often expressed in terms of non-perturbative parameters (also called matrix elements) that reflect our knowledge/ignorance of the strong interaction effects. Lattice QCD offers the best route to a non-perturbative determination of these parameters. The field of lattice gauge theories has nowadays achieved a maturity level where statistical errors are beaten down enough to expose systematic effects. This control over systematic effects has helped reliable extraction of matrix elements that allow us to...
Chiral dynamics with strange quarks in the light of recent lattice simulations
Journal of High Energy Physics, 2011
Several lattice collaborations performing simulations with 2+1 light dynamical quarks have experienced difficulties in fitting their data with standard N f = 3 chiral expansions at next-to-leading order, yielding low values of the quark condensate and/or the decay constant in the N f = 3 chiral limit. A reordering of these expansions seems required to analyse these data in a consistent way. We discuss such a reordering, known as Resummed Chiral Perturbation Theory, in the case of pseudoscalar masses and decay constants, pion and kaon electromagnetic form factors and K ℓ3 form factors. We show that it provides a good fit of the recent results of two lattice collaborations (PACS-CS and RBC/UKQCD). We describe the emerging picture for the pattern of chiral symmetry breaking, marked by a strong dependence of the observables on the strange quark mass and thus a significant difference between chiral symmetry breaking in the N f = 2 and N f = 3 chiral limits. We discuss the consequences for the ratio of decay constants F K /F π and the K ℓ3 form factor at vanishing momentum transfer.
Heavy Quarks: Effective Theories, Lattice and Models
Arxiv preprint hep-ph/0301138, 2003
Heavy-light mesons, heavy quarkonium and doubly heavy baryons are briefly discussed. Effective field theories (EFTs) of QCD based on the heavy quark mass expansion 1/mQ provide a unified frame-work to describe all three systems. They produce a number of model-independent ...
Chiral symmetry breaking in lattice QCD at finite temperature
Physics Letters B, 1984
A hamiltonian with continuous chiral symmetries is formulated using Kogut-Susskind fermions in lattice QCD. The finite temperature chiral symmetry breaking transition is discussed at strong coupling. Current algebra relation is derived for the mass of the Goldstone bosons. The effective hamiltonian is shown to reproduce a lattice version of the Nambu-Jona-Lasinio model.
Further discussions on a possible lattice chiral gauge theory
Physics Letters B, 1997
In a possible SU L (2) lattice chiral gauge theory with a large multifermion coupling, we try to further clarify the threshold phenomenon: the possibility that the right-handed three-fermion state turns into the virtual states of its constituents (free chiral fermions) in the low-energy limit. Provided this phenomenon occurs, we discuss the chiral gauge coupling, Ward identities and the gauge anomaly within the gauge-invariant prescription of the perturbative chiral gauge theory.
The heavy-quark hybrid meson spectrum in lattice QCD
2003
Recent findings on the spectrum of heavy-quark mesons from computer simulations of quarks and gluons in lattice QCD are summarized, with particular attention to quark-antiquark states bound by an excited gluon field. The validity of a Born-Oppenheimer treatment for such systems is discussed. Recent results on glueball masses, the light-quark 1-+ hybrid meson mass, and the static three-quark potential are
Journal of Physics: Conference Series, 2006
I present our recent results on the critical end point in the µ B -T phase diagram of QCD with two flavours of light dynamical quarks and compare them with similar results from other groups. Implications for a possible energy scan at the RHIC are discussed. I also comment briefly on the new results of great relevance to heavy ion collisions from finite temperature lattice QCD simulations on speed of sound, specific heat and on the fate of J/ψ.