A parametrization of σ (γ) above the resonance region for Q2⪖0

Proton structure function at smallQ 2

“…We have shown recently [7] that all total cross-sections may be parametrised as a simple sum of two Regge powers σ TOT = Xs 0.0808 + Y s −0.4525 (2) We fixed the two powers in this expression from pp andpp data, and found that the resulting expression works well also for πp and Kp. In the case of γp, the fit (2) is very similar to one we made a few years ago [1] , and it is in agreement with the published data points from HERA [8] .…”

“…Because T is a hadronic amplitude, its high-energy behaviour should involve the same Regge powers of (p − k) 2 as appear as powers of s in (2), and these reflect themselves as corresponding powers of 1/x in νW 2 . Of course the parton model is only the first term in a perturbative-QCD expansion of νW 2 ; the influence of the perturbative corrections on the Regge powers is not understood and is the reason for the great interest in small-x physics at HERA.…”

“…Strictly speaking, because x = Q 2 /2ν, the Q 2 → 0 limit of (4) is not a sum of powers of s as in (2), but rather a sum of powers of 2ν = s − m 2 N . At the lowest s-value of the data in figure 1a the difference is negligible, though if we continue to smaller s it becomes important.…”

Exclusive Production of Neutral Vector Mesons at the Electron-Proton Collider HERA

“…9 and compared to calculations using the ALLM proton structure function parametrizations [114], which exhibit consistency with the data over the entire range in Q 2 . Substantial gains in the kinematic range were achieved, and the region covered by these measurements now reaches that of the lower energy deep inelastic fixed-target experiments.…”

“…The transition region from the threshold behavior at high x to the high W region covered by [29] and H1 [35] collaborations with the 1994 data and by the NMC collaboration [30] at CERN. The curves represent calculations using the ALLM proton structure function parametrizations [114]. The dashed line connects points where x=0.1.…”