$s_{P}\approx 2.25\;\!{\rm{GeV}}^2$, see [@Belyaev:1982sa]. It is advantageous to use the whole sum rule [@Braun:2006hz] instead of a fixed number for $|\lambda_{P}|^2$. This will decrease the dependence of our LCSR on the value of the quark condensate and thus improve stability and reduce errors. We are left with the choice for the Borel window.

The Borel window is determined by two competing requirements. On the one hand, $t$ must be large enough to ensure that severing the twist expansion after twist 4 is valid, as the contributions of twist 5 and 6 are suppressed by an additional factor $\frac{1}{t}$ compared to the twist 3 and 4 contributions. On the other hand, a small Borel parameter is necessary to assure an adequate exponential suppression of the continuum and guarantees the validity of the quark-hadron duality. This suggests the interval $$\label{Borelwindow}
1{\rm{GeV}}^2 \; \leq t \leq 2 \; {\rm{GeV}}^2  \mbox{ .}$$

In Fig.\[ProtonGraph\] we plotted the sum rule for different values of $\varphi(1/2)$. The comparison with the experimental value [@PDG] $\mu_P\approx2.793$ favours a value $\varphi(1/2)=5.25 \pm 0.15 \;{\rm GeV^{-2}}$. This corresponds to $\chi(\mu=1\;{{\rm GeV}})=3.5\pm 0.1 \;{\rm GeV}^{-2}$, assuming one uses the asymptotic expression for the DAs. This agrees rather well with the result 