Small x: two pomerons!

Regge theory provides a very simple and economical description of data for (i) the proton structure function with x<0.7 and all available Q2 values, (ii) the charm structure function, and (iii) γ p→J/ψ p. The data are all in agreement with the assumption that there is a second pomeron, with intercept about 1.4 . They suggest also that the contribution from the soft pomeron is higher twist.