Exploring the structure of a possible light scalar nonet

We first review the work of the Syracuse group, which uses an effective chiral Lagrangian approach, on meson-meson scattering. An illustration providing evidence for the existence of a strange scalar resonance of mass around 900 MeV is given. An attempt to fit this $\kappa (900)$ together with a similarly obtained $\sigma (560)$ and the well known $a_0(980)$ and $f_0(980)$ into a nonet pattern suggests that the underlying structure is closer to a dual quark-dual antiquark than to a quark-antiquark. A possible mechanism to explain a next higher-in mass scalar meson nonet is also discussed. This involves mixing between $q{\bar q}$ and $qq{\bar q} {\bar q}$ states.Comment: 8 pages, 4 figures, invited talk at workshop "Possible Existence of the Light Sigma Resonance and its Implications to Hadron Physics", Yukawa Institute for Theoretical Physics, Kyoto, Japan, June 200

Light Scalar Mesons

We review how a certain effective chiral Lagrangian approach to pi pi scattering, pi K scattering and eta-prime decay to eta pi pi provides evidence for the existence of light scalars sigma(550) and kappa(900) as well as describing the f0(980) and the a0(980). An attempt to fit these into a nonet suggests that their structure is closer to a dual quark-dual antiquark than to a quark-antiquark. A possible mechanism to explain the next higher mass scalar nonet is also proposed.Comment: 10 pages, 4 figures, talk given at Hadron Physics: Effective Theories of Low Energy QCD, Coimbra, Portugal, Sept. 199

Mechanism for a Next-to-Lowest Lying Scalar Meson Nonet

Recent work suggests the existence of a non-conventional lowest-lying scalar nonet containing the a0(980). Then the a0(1450) and also the K0*(1430) are likely candidates to belong to a conventional p-wave q \bar q nonet. However a comparison of their properties with those expected on this basis reveals a number of puzzling features. It is pointed out that these puzzles can be resolved in a natural and robust way by assuming a ``bare\u27\u27 conventional p-wave scalar q \bar q nonet to mix with a lighter four quark qq \bar q \bar q scalar nonet to form new ``physical\u27\u27 states. The essential mechanism is driven by the fact that the isospinor is lighter than the isovector in the unmixed qq \bar q \bar q multiplet

Effects of Light Scalar Mesons in η\to 3π Decay

We study the role of a possible nonet of light scalar mesons in the still interesting \eta \to 3\pi decay process, with the primary motivation of learning more about the scalars themselves. The framework is a conventional non-linear chiral Lagrangian of pseudoscalars and vectors, extended to include the scalars. The parameters involving the scalars were previously obtained to fit the s-wave \pi\pi and \piK scatterings in the region up to about 1 GeV as well as the strong decay \eta\u27 \to \eta \pi\pi. At first, one might expect a large enhancement from diagrams including a light \sigma(560). However there is an amusing cancellation mechanism which prevents this from occurring. In the simplest model there is an enhancement of about 13 per cent in the \e3p decay rate due to the scalars. In a more complicated model which includes derivative type symmetry breakers, the cancellation is modified and the scalars contribute about 30 percent of the total decay rate (although the total is not significantly changed). The vectors do not contribute much. Our model produces a reasonable estimate for the related a_0(980)-f_0(980) mixing strength, which has been a topic of current debate. Promising directions for future work along the present line are suggested

The Scalar Sector and the Eta -\u3e 3 Pi Problem

First, recent work on light scalar mesons, which is of possible interest in connection with the strong coupling region of QCD is briefly discussed. Then a very short highlighting of a paper concerned with an application to the eta -\u3e 3 pi problem is presented

Markov Processes, Hurst Exponents, and Nonlinear Diffusion Equations with application to finance

We show by explicit closed form calculations that a Hurst exponent H that is not 1/2 does not necessarily imply long time correlations like those found in fractional Brownian motion. We construct a large set of scaling solutions of Fokker-Planck partial differential equations where H is not 1/2. Thus Markov processes, which by construction have no long time correlations, can have H not equal to 1/2. If a Markov process scales with Hurst exponent H then it simply means that the process has nonstationary increments. For the scaling solutions, we show how to reduce the calculation of the probability density to a single integration once the diffusion coefficient D(x,t) is specified. As an example, we generate a class of student-t-like densities from the class of quadratic diffusion coefficients. Notably, the Tsallis density is one member of that large class. The Tsallis density is usually thought to result from a nonlinear diffusion equation, but instead we explicitly show that it follows from a Markov process generated by a linear Fokker-Planck equation, and therefore from a corresponding Langevin equation. Having a Tsallis density with H not equal to 1/2 therefore does not imply dynamics with correlated signals, e.g., like those of fractional Brownian motion. A short review of the requirements for fractional Brownian motion is given for clarity, and we explain why the usual simple argument that H unequal to 1/2 implies correlations fails for Markov processes with scaling solutions. Finally, we discuss the question of scaling of the full Green function g(x,t;x',t') of the Fokker-Planck pde.Comment: to appear in Physica

The increasing trend in preterm birth in public hospitals in northern Argentina

Objective: To identify factors associated with the increasing incidence of preterm birth in northern Argentina. Methods: In an observational study, data were reviewed from a prospective, population-based registry of pregnancy outcomes in six cities in 2009-2012. The primary outcome was preterm birth (at 20-37 weeks). Bivariate tests and generalized estimating equations were used within a conceptual hierarchical framework to estimate the cluster-corrected annual trend in odds of preterm birth. Results: The study reviewed data from 11 433 live births. There were 484 (4.2%) preterm births. The incidence of preterm births increased by 38% between 2009 and 2012, from 37.5 to 51.7 per 1000 live births. Unadjusted risk factors for preterm birth included young or advanced maternal age, normal body mass index, nulliparity, no prenatal care, no vitamins or supplements during pregnancy, multiple gestation, and maternal hypertension or prepartum hemorrhage. The prevalence of many risk factors increased over the study period, but variations in these factors explained less than 1% of the increasing trend in preterm birth. Conclusion: The incidence of preterm births insix small cities in northern Argentina increased greatly between 2009 and 2012. This trend was unexplained by the risk factors measured. Other factors should be assessed in future studies.Fil: Weaver, Emily H.. University of North Carolina School at Chapel Hill; Estados UnidosFil: Gibbons, Luz. Instituto de Efectividad Clínica y Sanitaria; ArgentinaFil: Belizan, Jose. Instituto de Efectividad Clínica y Sanitaria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Althabe, Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto de Efectividad Clínica y Sanitaria; Argentin

Scalar mesons in three-flavor linear sigma models

The three flavor linear sigma model is studied in order to understand the role of possible light scalar mesons in the pi-pi, pi-K and pi-eta elastic scattering channels. The K-matrix prescription is used to unitarize tree-level amplitudes and, with a sufficiently general model, we obtain reasonable ts to the experimental data. The effect of unitarization is very important and leads to the emergence of a nonet of light scalars, with masses below 1 GeV. We compare with a scattering treatment using a more general non-linear sigma model approach and also comment upon how our results t in with the scalar meson puzzle. The latter involves a preliminary investigation of possible mixing between scalar nonets