Light scalar mesons in QCD

Abstract

I present a mini-review of the masses and couplings of the bare (unmixed) light scalar mesons : $\bar{q}q,(\overline{qq})(qq),(\bar{q}q)(\bar{q}q),gg$ from QCD spectral sum rules (QSSR) and low-energy theorems (LET) which we compare with recent lattice calculations when available. Some unbiased comments on the different scenarios are given. The possiblity for the $\sigma (0.6)$ to be mostly a gluonium/glueball with a huge violation of the OZI rule in its decay is discussed. This review complements and updates the ones presented earlier [1]. Despite some progresses, the internal structure of the light scalar mesons remain puzzling, and some further efforts are required. It will be more fun at LHC if the Higgs of the Standard Model is a $\sigma$-like resonance.

6 pages, Talk given at QCD 08 (7-12th july, Montpellier) and Scientific part of the invited talk for a tribute to Paco Yndurain at Confinement8 (3-7th september, Mainz)

References in corpus (11)

• Experimental status of the $\pi \pi$ isoscalar S wave at low energy: $f_0(600)$ pole and scattering length
• Glueball nature of the sigma/f_0(600) from pi-pi and gamma-gamma scatterings
• Amplitude Analysis of High Statistics Results on $\gamma \gamma \to {\pi }^{+}{\pi }^{-}$ and the Two Photon Width of Isoscalar States
• Improved dispersion relations for γγ\to π^0π^0
• Lightest scalar and tensor resonances in $\gamma \gamma \to \pi \pi$ after the Belle experiment
• Two photons into π^0π^0
• Location, correlation, radiation: where is the $\sigma$, what is its structure and what is its coupling to photons?
• Pole Mass, Width, and Propagators of Unstable Fermions
• Two-photon width and gluonic component of sigma/f_0(600)
• Can the gamma-gamma processes reveal the nature of the sigma ?
• In memory of Paco Yndurain: A precise determination of pion-pion scattering from experiment and dispersion relations

Cited by in corpus (3)

• Gluonium nature of the sigma/f_0(600) from its coupling to KK
• Exclusive photoproduction of $f_1(1285)$ meson off proton in the JLab kinematics
• A renormalization group invariant scalar glueball operator in the (Refined) Gribov-Zwanziger framework