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C$_{20}$ ( t ) form factors. 

Similarly to the pion case we have tried to deduce some information from the high-energy region, t ∼ − 1 . 2 GeV $^{2}$, by attempting the Regge form 

Unfortunately, again the large errors in the data do not allow to fix the b parameter unambiguously, and it is compatible with b = 2. Thus we stick to the simple monopole form, 

Since most of the lattice data are accumulated at pion masses significantly above the physical value, extrapola- tion to the physical point is necessary. At low values of the pion mass and t the chiral corrections are expected to be significant. 4 Not entering these intricacies, we assume, following many lattice studies, the simple dependence of m$_{σ}$ on m$_{π}$ : 

Hence m$_{σ}$ (without an argument) denotes the value at the physical point. Similarly, 

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We use simultaneously the form factors (77) for the six pion masses from LHPC [73]. There are several ways one can perform the fit, all leading to similar but not identical results. Our procedure is as follows: We first normalize the form factors to unity at t = 0, by dividing a data set at a particular m$_{π}$ by the value of the point at t = 0. That way we get rid of the dependence on 〈 x 〉 N u + d and can carry out a two-parameter fit, with the parameters of Eq. (81). The χ 2 method yields 

with χ $^{2}$/ DOF = 5 . 2 / (87 − 2). The resulting correlation plot is shown in Fig. 6 

One may perform separately the fit to the normalized form factors at each value of m$_{π}$ . An example for the two lowest pion masses, 356 and 352 MeV, is shown in Fig. 5. The band indicates the uncertainty in m$_{σ}$ obtained with the χ 2 method. The result of the procedure at all values of m$_{π}$ is shown in Fig. 7, together with the best fit curve with parameters (83). The point at the physical value of 

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m$_{π}$ indicates the resulting extrapolation for the physical value of m$_{σ}$ , Eq. (83). 

Taking the values of the unnormalized form factors at t = 0 we may compute the momentum fraction carried by the quarks as a function of m$_{π}$ . The result of the χ 2 fit is 

In the case of the lattice calculations of the QCDSF Collaboration [72], five points have been provided at val- ues ranging between 0 ≤ − t ≤ 3 GeV 2 for the pion masses m$_{π}$ = 930, 760, and 550 MeV, then extrapolated to the physical pion mass. The corresponding nucleon masses are M$_{N}$ = 1724, 1519, and 1308 MeV. The A , B , and C form factors have been parametrized in Ref. [72] 

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