Deirdre Black

Putative light scalar nonet

We investigate the {open_quotes}family{close_quotes} relationship of a possible scalar nonet composed of the a{sub 0}(980), the f{sub 0}(980) and the {sigma} and {kappa} type states found in recent treatments of {pi}{pi} and {pi}K scattering. We work in the effective Lagrangian framework, starting from terms which yield {open_quotes}ideal mixing{close_quotes} according to Okubo{close_quote}s original formulation. It is noted that there is another solution corresponding to dual ideal mixing which agrees with Jaffe{close_quote}s picture of scalars as qq{bar q}{bar q} states rather than q{bar q} states. At the Lagrangian level there is no difference in the formulation of the two cases (other than the numerical values of the coefficients). In order to agree with experiment, additional mass and coupling terms which break ideal mixing are included. The resulting model turns out to be closer to dual ideal mixing than to conventional ideal mixing; the scalar mixing angle is roughly {minus}17{degree} in a convention where dual ideal mixing is 0{degree}. {copyright} {ital 1999} {ital The American Physical Society}

Evidence for a scalar κ(900) resonance in π K scattering

Motivated by the

Complementary ansatz for the neutrino mass matrix

1/N_c

Evidence for a scalar {kappa}(900) resonance in {pi}K scattering

expansion, we study a simple model in which the pi-K scattering amplitude is the sum of a current-algebra contact term and resonance pole exchanges. This phenomenological model is crossing symmetric and, when a putative light strange scalar meson, kappa, is included, satisfies the unitarity bounds to well above 1 GeV. The model also features chiral dynamics, vector meson dominance and appropriate interference between the established scalar K*(1430) resonance and its predicted background. We briefly discuss the physical significance of the results and directions for further work.

Chiral Approach to phi radiative decays

We propose a simple ansatz for the three generation neutrino mass matrix M{sub {nu}} which is motivated from an SO(10) grand unified theory. The ansatz can be combined with information from neutrino oscillation experiments and bounds on neutrinoless double beta decay to determine the neutrino masses themselves and to reconstruct, with some assumptions, the matrix M{sub {nu}}. (c) 2000 The American Physical Society.

Two or Four: A Hint from Scalar Mesons in Radiative φ Decays?

Motivated by the 1/N{sub c} expansion, we study a simple model in which the {pi}K scattering amplitude is the sum of a {ital current-algebra} contact term and resonance pole exchange. This phenomenological model is crossing symmetric and, when a putative light strange scalar meson {kappa} is included, satisfies the unitarity bounds to well above 1 GeV. The model also features chiral dynamics, vector meson dominance and appropriate interference between the established K{sub 0}{sup {asterisk}}(1430) resonance and its predicted background. {copyright} {ital 1998 American Institute of Physics.}

Remark on pion scattering lengths

Rare decays of the φ vector meson, to ππγ and πηγ, have been measured in the last few years. We give some background about why these decays are of interest in that they may provide some insights about the puzzling light scalar mesons. We then present our approach to studying strong and radiative decays involving light scalar mesons more generally, pointing out that it has the advantage of potentially relating many radiative decays at tree‐level. Finally we discuss the rare radiative φ decays and comparison with recent experimental data in more detail.

The Scalar Sector and the Eta -> 3 Pi Problem

In this write-up, we summarize our recent analysis of radiative decays involving light scalar mesons. Our analysis using the vector meson dominance model at tree level indicates that it may be difficult to distinguish qq¯ ¯ q picture and q ¯ q picture for the light scalar nonet. Our result on the process of φ → π 0 ηγ shows that the derivative-type f0K ¯ K interaction reproduces experimental data below 950 MeV well, but gives a poor fit above 950 MeV, i.e., in the energy region around the mass of a0(980), but that the discrepancy can be compensated by the effect of the K loop.

Role of light scalar mesons in η, η' → 3π

First it is shown that the tree amplitude for pion–pion scattering in the minimal linear sigma model has an exact expression which is proportional to a geometric series in the quantity

Investigating the Light Scalar Mesons

(s-m_\pi^2)/(m_B^2-m_\pi^2)