Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · hep-ph/0306040

Light Scalar Mesons in the Improved Ladder Approximation of QCD with Strong $U_A(1)$ Breaking

Toru Umekawa
View original source ↗Read source document ↗Export metadata ↓

Abstract

The spectrum and the mixing angle of the light scalar nonet mesons are studied using the extended Nambu-Jona-Lasinio (NJL) model as well as the improved ladder approximation (ILA) of QCD with U_A(1) symmetry breaking interaction. The U_A(1) breaking is represented by the Kobayashi-Maskawa-'t Hooft (KMT) interaction. The strength of the KMT interaction in the NJL model is determined so as to reproduce the electromagnetic decays of the ηmeson. That in the ILA approach is determined so as to reproduce the pseudoscalar meson spectrum. In the extended NJL model, we study the qualitative features of the scalar meson spectrum. In the scalar nonet spectrum, the KMT interaction is found to give the right ordering of σ- a_0 masses and a few hundred MeV mass difference between the σand a_0 mesons. We also find that the strangeness content in the σmeson is about 15%. In the ILA approach, we confirm the qualitative features of the results from the extended NJL. We obtain the mass spectra of the light pseudoscalar nonet mesons and the σ, a_0 mesons which are consistent with current experimental data. On the other hand, we show that the obtained f_0 and K_0^* state can not be identified directly with the experimental data. It may suggest that the f_0(980) and κ(700-900) states may not be explained only by the quark-anti quark state. We also find that the strangeness content in the σmeson is about 5%. We obtain the result that the U_A(1) breaking interaction reproducing the mass spectrum of the pseudoscalar meson gives large effects on the scalar meson mass spectrum.

Explore related subjects

hep-ph

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Toru Umekawa. 2003-06-05. Light Scalar Mesons in the Improved Ladder Approximation of QCD with Strong $U_A(1)$ Breaking. https://arxiv.org/abs/hep-ph/0306040

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Axionic Wormholes in Metric-Affine Gravity

The axion is a promising candidate for solving the strong CP problem. To solve this problem, the global U(1) symmetry must be preserved to a high degree of accuracy. However, it is well known that global symmetries are explicitly violated by quantum gravity effects, giving rise to what is referred to as the axion quality problem. In this paper, we investigate axionic wormholes as a source of explicit U(1) violation in Metric-Affine Gravity. This framework allows for spacetime torsion and non-metricity, which accommodate additional curvature-like and topological terms, such as the Holst and Nieh--Yan terms, that are absent from the metric and Palatini formalisms. We show that non-minimal couplings to these terms modify the wormhole dynamics and enhance the Euclidean wormhole action, thereby alleviating the axion quality problem. We also find that the viable parameter space is enlarged when two of these couplings are simultaneously present. We further identify representative parameter regions where the alleviation of the axion quality problem is compatible with inflationary constraints.

hep-ph↗
arXiv2026

Qubit-Qutrit Quantum Tomography of hadronic $\Lambda\phi$ and $\Lambda K^{\ast 0}$ systems

Quantum-information observables have emerged in recent years as new tools in nuclear and particle physics, from entanglement in top-quark pairs to spin correlations in $\Lambda\bar{\Lambda}$ production. Extending these studies to unequal-spin hadronic final states poses a fundamental challenge: the $6\times6$ density matrix of a qubit-qutrit system contains 35 independent spin parameters, but the decays of $\Lambda V$ pairs, with $V=\phi$ or $K^{*0}$, provide access to only 23 due to the hidden vector polarization from the strong decay. In this Letter, we formulate a qubit-qutrit quantum tomography (QQQT) technique for these spin-$\tfrac{1}{2}\otimes1$ systems and establish exact criteria for entanglement certification from the \textit{incomplete} density matrix. Compared with the $\Lambda\bar{\Lambda}$ system, QQQT of $\Lambda\phi$ and $\Lambda K^{*0}$ provides a new probe of nonperturbative QCD hadronization, enabling a direct comparison of the spin evolution of entangled quark pairs produced from the vacuum as they hadronize into a baryon or a vector meson.

hep-ph↗
arXiv2026

Twist decomposition of exclusive heavy meson production cross sections

We study the twist decomposition of the total cross sections for exclusive heavy vector meson electroproduction and photoproduction in the $\gamma^\ast p$ processes, within the leading logarithmic $1/x$ BFKL formalism. The Mellin transforms of the impact factors of the vector meson are calculated. We show that the higher twist contributions are strongly suppressed in the low-$x$ kinematical regime. Possible enhancement of the higher twists effects for nuclei targets is discussed.

hep-ph↗