Carles Ayala

Is the strange quark heavy or light

Abstract The (invariant) strange quark mass, m s , and vacuum condensate, 〈ss〉 0 , are discussed in the context of SVZ-sum rules saturated by the scalar κ -meson. The value obtained for m s ( m s ≅360 MeV ) is found to approach its constituent mass value, while 〈ss〉 0 is predicted to be negligibly small. These two features, which are characteristic of the c- and b- (i.e., heavy) quarks, are new and unexpected for the s-quark. Our results strongly depend on the κ-meson parameters, for which further analyses seem of interest.

Renormalization group approach to matrix models in two-dimensional quantum gravity

Abstract We explore the implications of recent work by Brezin and Zinn-Justin, applying the renormalization group techniques from critical phenomena to the scaling limit of matrix models in two-dimensional quantum gravity. They endeavour to get the lowest order fixed points of the theory giving insight into the critical points of the theory. We show that at leading order the perturbative result is equal to the saddle-point approximation result. We calculate the next-to-leading order in the perturbative expansion exploring the goodness of the approach.

A simple π-η-gh′ mixing model for R=Γ (ψ′ → ψπ)Γ(ψ′ → ψη) and r = Γ(ψ → η′γ)Γ(ψ → ηγ)☆

Abstract A joint description of the ratios r ≡ Γ(ψ → η′γ) Γ(ψ → ηγ) and R ≡ Γ(ψ′ → ψ π) Γ(ψ′ → ψη) is achieved in the context of a simple π-η-gh′ mixing model. An η-η′ mixing angle θ ⋍ − 19.5° and a large tadpole effect for the ηπ and η′π isospinviolating transitions are required. Both requirements are in agreement with recent data for the η-meson.

Hadronic gauge coupling forρ′→ρππ

A reasonable understanding of the smallness of the ρ′→ππ to the ρ′→ρππ branching ratio in the context of the quark-pair creation model (QPCM) is achieved. Our crucial hypothesis consists in assuming that the ρ can be phenomenologically considered as a gauge particle which couples to the derivative ρ′ππ coupling through a gauge principle. This fixes unambiguously the ρ′→ρππ amplitude.

Comments on the treatment of the QCD SVZ- and FE-sum rules

Abstract Approaching SVZ (inverse Laplace transform) sum rules to finite energy sum rules we prove a conjecture recently proposed concerning the stability of the latter in their characteristic parameter. It nicely follows from the SVZ sum rules stability criteria. A critical analysis of the finite energy sum rules (taking into account the renormalization group dependence of the condensates) is made and an explanation of the large values of the non-perturbative parameters found in that framework is given.

The μ(x, β, α) function and its role in the analysis of the QCD-SVZ sum rules☆

Abstract The μ( x , β, α) function and related quantities required by QCD-SVZ sum rules are constructed as FORTRAN functions. A careful study of the behaviour of its asymptotic expansions is performed. It is stated that it does not go at the same pace of the physical expansion for renormalization group dependent quantities, such as α s , in QCD.

Strong coupling expansions in pure lattice gauge theory mixed actions

Abstract We give a general survey on the strong coupling expansions in pure SU(2) lattice gauge theory mixed actions. The most general mixed action analyzed is a mixture of the spin 1 2 , 1, 3 2 , and 2 representations. A study of the phase structure ofthis SU(2) lattice through Pade analysis of the free energy and internal energy series for space-time dimensions ranging from 3 to 6 is given.

Generation and analysis of high order strong coupling series for SU(2) lattice gauge theory

We present a package of VAX FORTRAN programs that analyze the information coming from two sets of FORTRAN routines. The first set of routines perform strong coupling series expansions in pure SU(2) lattice gauge theory mixed actions. The most general mixed action we are able to analyze is a mixing of the spin 12, 1, 32 and 2 representations. This set is a symbiosis between the use of algebraic outputs from REDUCE and its execution using the VAX FORTRAN language. The second set of FORTRAN routines perform the Pade approximants analysis of the series. Making a systematic study of the Pade table will give the mean value of the significant real (and complex) poles put together with its standard deviation. The programs perform the series analysis and graphical representation of the results for all the cases.

Contact terms in γγ→π+π−π+π− transitions

Abstract The contribution of contact terms (originated by gauge invariance) to the γγ→ϱ0π+π− transition is evaluated. They are shown to play an essential role in order to explain the large cross section of γγ → π+π−π+π− and the π+π− invariant mass distributions recently observed at PETRA and SPEAR.