Pion form factors in holographic QCD

Using a holographic dual model of QCD, we compute the pion electromagnetic form factor F _π(Q ²) in the spacelike momentum transfer region, as well as pion couplings to vector mesons g _ρ(n)ππ. Spontaneous and explicit chiral symmetry breaking are intrinsic features of this particular holographic model. We consider variants with both ''hard-wall'' and ''soft-wall'' infrared cutoffs, and find that the F _π(Q ²) data tend to lie closer to the hard-wall model predictions, although both are too shallow for large Q ². By allowing the parameters of the soft-wall model (originally fixed by observables such as m _ρ) to vary, one finds fits that tend to agree better with F _π(Q ²). We also compute the pion charge radius r _π ² for a variety of parameter choices, and use the values of f ⁽ⁿ⁾ _ρ, g _ρ(n)ππ and m ⁽ⁿ⁾ _ρ to observe the saturation of F _π(0) by ρ poles.