### Speaker

Dr
Bachir Moussallam
(IPN Orsay)

### Description

Some properties of the scalar mesons sigma(600) and f0(980) are
discussed using the Roy integral equations to control continuations in the complex energy plane.
On the real axis, firstly, high precision numerical solutions of the equations are constructed for energies up to the K-Kbar threshold.
Fits to the data by such solutions are performed and constrained by the recent measurements of the S-wave scattering lengths by the
NA48/2 collaboration.
These results are combined with recent measurements of photo-photon scattering to two pions by the Belle collaboration. From a chirally constrained analytic representation of the amplitudes, the values of the couplings of the sigma(600) and f0(980) to two photons are deduced.
As a second application, the question of the gluon and q-qbar "contents" of the scalar mesons is reconsidered. These may be defined using analytic extensions to the second sheet of two-point correlators of GG and q-qbar operators. The pole residues involve pion-pion matrix elements of these operators. A numerical evaluation is made using dispersion relations and low-energy constraints.

### Primary author

Dr
Bachir Moussallam
(IPN Orsay)