Bounds on the spacelike pion electromagnetic form factor from   analyticity and unitarity
  We use the recently measured accurate BaBaR data on the modulus of the pion electromagnetic form factor, $F_\pi(t)$, up to an energy of 3 GeV, the I=1 $P$-wave phase of the $\pi\pi$ scattering amplitude up to the $\omega-\pi$ threshold, the pion charge radius known from Chiral Perturbation Theory, and the recently measured JLAB value of $F_\pi$ in the spacelike region at $t=-2.45 {\rm GeV}^2$ as inputs in a formalism that leads to bounds on $F_\pi$ in the intermediate spacelike region. We compare our constraints with experimental data and with perturbative QCD along with the results of several theoretical models for the non-perturbative contributions proposed in the literature. 
I. Sentitemsu Imsong, B.Ananthanarayan, Irinel Caprini
hep-ph