  The Coon amplitude is the unique solution to duality constraints with
logarithmic Regge trajectories. A striking feature of this solution is that it
interpolates between the Veneziano amplitude and a scalar particle amplitude.
However, an analytic proof of unitarity of the amplitude is not yet known. In
this short note, we explicitly compute the partial wave coefficients on the
leading Regge trajectory in D=4. We find that these coefficients always remain
positive, even though their magnitude decreases with spin. Since the
coefficients on the subleading trajectories are observed to be larger than
those on the leading ones, our result indicates the positivity of the full Coon
amplitude in D=4.
