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 (46)

• Big Bang Nucleosynthesis (in "The Review of Particle Properties" 2004)
• ππscattering
• Glueballs, Hybrids, Multiquarks. Experimental facts versus QCD inspired concepts
• Mass and width of the lowest resonance in QCD
• Is $f_0(1500)$ a Scalar Glueball?
• Masses, decays and mixings of gluonia in QCD
• Short-distance tachyonic gluon mass and 1/Q^2 corrections
• Static potentials and glueball masses from QCD simulations with Wilson sea quarks
• Heavy quarkonia mass-splittings in QCD: test of the $1/m$-expansion and estimates of $<{\alpha }_s{G}^2>$ and ${\alpha }_s$
• The K^*_0(800) scalar resonance from Roy-Steiner representations of pi K scattering
• QCD tests from $e^+e^- \rar I=1~$ hadrons data and implication on the value of ${\alpha }_s$ from $\tau$-decays
• Production of $f_0(1710)$, $f_0(1500)$, and $f_0(1370)$ in $J/\psi$ hadronic decays
• K-matrix analysis of the (IJ^{PC}=00^{++})-wave in the mass region below 1900 MeV
• QCD sum rule approach for the light scalar mesons as four-quark states
• Scalar Particles in Lattice QCD
• Experimental status of the $\pi \pi$ isoscalar S wave at low energy: $f_0(600)$ pole and scattering length
• Light quark masses from scalar sum rules
• QCD Tests of the Puzzling Scalar Mesons
• Strange quark mass from e+e- revisited and present status of light quark masses
• A lattice study of the masses of singlet 0++ mesons
• On the glueball spectrum in O(a)-improved lattice QCD
• Target Independence of the Emc-SMC Effect
• 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
• Near-Maximal Mixing of Scalar Gluonium and Quark Mesons: A Gaussian Sum-Rule Analysis
• Light Quark Masses 99
• Topological Charge Screening and the `Proton Spin' Beyond the Chiral Limit
• Gluonia, Scalar and Hybrid Mesons in QCD
• Exotic mesons, locking states and their role in the formation of the confinement barrier
• Gluon Condensate from Superconvergent QCD Sum Rule
• Location, correlation, radiation: where is the $\sigma$, what is its structure and what is its coupling to photons?
• Scalar Mesons in QCD
• Pole Mass, Width, and Propagators of Unstable Fermions
• Masses, decays and mixings of gluonia in QCD
• Scalar mesons and the muon anomaly
• Scalar mesons: in search of the lightest glueball
• On the scalar nonet lowest in mass
• Scalar mesons in QCD and tests of the gluon content of the sigma
• Two-photon width and gluonic component of sigma/f_0(600)
• Can the gamma-gamma processes reveal the nature of the sigma ?
• On concise hypotheses for the interpretation of a wide scalar resonance as gauge boson binary in QCD - some new analyses
• On the low energy end of the QCD spectrum
• In memory of Paco Yndurain: A precise determination of pion-pion scattering from experiment and dispersion relations

Cited by in corpus (24)

• The Status of Glueballs
• On the size of the sigma meson and its nature
• Gluonium nature of the sigma/f_0(600) from its coupling to KK
• The sigma and f_0(980) from Ke4 + pi-pi scatterings data
• sigma and f_0(980) substructures from gamma-gamma to pi-pi, J/psi, phi radiative and D_s semi-leptonic decays
• On meson dominance in the `second class' tau \to eta pi nu_tau decay
• Two-gluon and trigluon glueballs from dynamical holography QCD
• On the branching ratio of the "second class" tau --> eta' pi nu_tau decay
• Exclusive photoproduction of $f_1(1285)$ meson off proton in the JLab kinematics
• Spectra of glueballs and oddballs and the equation of state from holographic QCD
• A renormalization group invariant scalar glueball operator in the (Refined) Gribov-Zwanziger framework
• Di-Gluonium Sum Rules, I = 0 Scalar Mesons and Conformal Anomaly
• Holographic cold dense matter constrained by neutron stars
• Low-lying Scalars in an extended Linear $\sigma$ Model
• Investigating the composition of the K${}_0^{\ast }(700)$ state with ${\pi }^{\pm }$K${}_{\mathrm{S}}^0$ correlations at the LHC
• Generalized linear sigma model with two glueballs
• A purely algebraic construction of a gauge and renormalization group invariant scalar glueball operator
• Spinless mesons and glueballs mixing patterns in SU(3) flavor limit
• Scalar Mesons and glueballs in $Dp-Dq$ hard-wall models
• Quark and glue spectroscopy of scalars and pseudoscalars in SU(3) flavor limit
• Chiral phase transition with mixing between scalar quarkonium and tetraquark
• Scalar mesons in ${\eta }^{\prime }\to 3{\pi }^0,{\pi }^0{\pi }^{+}{\pi }^{-}$ decays
• Decays of the f0(1370) scalar glueball candidate in pp Central Exclusive Production (CEP) and in antiproton annihilations at rest
• K${}_{\mathrm{S}}^0$K${}_{\mathrm{S}}^0$ and K${}_{\mathrm{S}}^0$K${}^{\pm }$ femtoscopy in pp collisions at $\sqrt{s}=$ 5.02 and 13 TeV