Chiral symmetry breaking in QCD-like gauge theories with a confining propagator and dynamical gauge boson mass generation

We study chiral symmetry breaking in QCD-like gauge theories introducing a confining effective propagator, as proposed recently by Cornwall, and considering the effect of dynamical gauge boson mass generation. The effective confining propagator has the form $1/(k^2+m^2)^2$ and we study the bifurcation equation finding limits on $m$ below which a satisfactory fermion mass solution is generated. Since the coupling constant and gauge boson propagator are damped in the infrared, due to the presence of dynamically massive gauge bosons, the major part of the chiral breaking is only due to the confining propagator. We study the asymptotic behavior of the gap equation containing confinement and massive gauge boson exchange, and find that the symmetry breaking can be approximated at some extent by an effective four-fermion interaction generated by the confining propagator. We compute some QCD chiral parameters as a function of $m$, finding values compatible with the experimental data. Within this approach we expect that lattice simulations should not see large differences between the confinement and chiral symmetry breaking scales independent of the fermionic representation and we find a simple approximate relation between the fermion condensate and dynamical mass for a given representation as a function of the parameters appearing in the effective confining propagator.Comment: 32 pages, 9 figures, new references added, matchs published versio

Chiral symmetry breaking with a confining propagator and dynamically massive gluons

Chiral symmetry breaking in QCD is studied introducing a confining effective propagator, as proposed recently by Cornwall, and considering the effect of dynamically massive gluons. The effective confining propagator has the form $1/(k^2+m^2)^2$ and we study the bifurcation equation finding limits on the parameter $m$ below which a satisfactory fermion mass solution is generated. Since the coupling constant and gluon propagator are damped in the infrared, due to the presence of a dynamical gluon mass, the major part of the chiral breaking is only due to the confining propagator and related to the low momentum region of the gap equation. We study the asymptotic behavior of the gap equation containing this confinement effect and massive gluon exchange, and find that the symmetry breaking can be approximated by an effective four-fermion interaction generated by the confining propagator. We compute some QCD chiral parameters as a function of $m$, finding values compatible with the experimental data. We find a simple approximate relation between the fermion condensate and dynamical mass for a given representation as a function of the parameters appearing in the effective confining propagator.Comment: 12 pages, 2 figures. Talk presented at the International Workshop on QCD Green's Functions, Confinement, and Phenomenology - QCD-TNT II, September 05-09 2011, ECT* Trento, Italy; ANN.PHYS.(NY, 2011

Geometric scaling in ultrahigh energy neutrinos and nonlinear perturbative QCD

It is shown that in ultrahigh energy inelastic neutrino-nucleon(nucleus) scattering the cross sections for the boson-hadron(nucleus) reactions should exhibit geometric scaling on the single variable tau_A =Q2/Q2_{sat,A}. The dependence on energy and atomic number of the charged/neutral current cross sections are encoded in the saturation momentum Q_{sat,A}. This fact allows an analytical computation of the neutrino scattering on nucleon/nucleus at high energies, providing a theoretical parameterization based on the scaling property.Comment: 5 pages, 4 figure

Geometric scaling in ultrahigh energy neutrinos and nonlinear perturbative QCD

The ultrahigh energy neutrino cross section is a crucial ingredient in the calculation of the event rate in high energy neutrino telescopes. Currently there are several approaches which predict different behaviors for its magnitude for ultrahigh energies. In this contribution is presented a summary of current predictions based on the non-linear QCD evolution equations, the so-called perturbative saturation physics. In particular, predictions are shown based on the parton saturation approaches and the consequences of geometric scaling property at high energies are discussed. The scaling property allows an analytical computation of the neutrino scattering on nucleon/nucleus at high energies, providing a theoretical parameterization.Comment: 6 pages, one figure. Presented at First Caribbean Symposium on Nuclear and Astroparticle Physics - STARS2011, La Habana, Cuba, 2011. arXiv admin note: substantial text overlap with arXiv:1011.2718 by different author