Related papers: Small x: Two Pomerons!
By using the concept of duality between direct channel resonances and Regge exchanges we relate the small- and large-$x$ behavior of the structure functions. We show that even a single resonance exhibits Bjorken scaling at large $Q^2$.
The drastic rise of the proton structure function $F_2(x,Q^2)$ when the Bj\"orken variable $x$ decreases, seen at HERA for a large span of $Q^2$, may be damped when $x\to 0$ and $Q^2$ increases beyond $\sim$ several hundreds \g2. This…
The use of the differential gluon structure function of the proton ${\cal F}(x,Q^{2})$ introduced by Fadin, Kuraev and Lipatov in 1975 is called upon in many applications of small-x QCD. We report here the first determination of ${\cal…
Recent results presented in the structure functions working group are briefly summarized for the following topics: The theoretical treatment of heavy quarks in structure functions, higher-order corrections for the leading-twist evolution…
Higher-twist effects in the low-order moments of the longitudinal and transverse structure functions of proton and deuteron have been analyzed using available phenomenological fits of existing data in the Q**2 range between 1 and 20…
Deep-inelastic scattering at small x is a new field of QCD phenomenology which HERA experiments started to explore. The data show the feature expected by the perturbative Regge asymptotics. We describe the parton picture of structure…
Exclusive vector meson production from real and virtual photons is a good probe of pomeron physics. In particular, it sheds light on how the soft pomeron is related to nonperturbative QCD, and how it couples to heavy flavours. It also…
New Results on the measurement of the proton structure function F_2(x,Q^2) are reported for momentum transfers squared Q^2 >= 1.5 GeV^2 and Bjorken x >= 3.5 10^{-5} using data collected by the HERA experiments H1 and ZEUS in 1994. F_2…
The charm quark contribution to the first moment of $g_1(x,Q^2)$ is calculated using a heavy mass expansion of the divergence of the singlet axial current. It is shown to be small.
A simple application of Regge theory, with 9 free parameters, provides a good fit to elastic scattering data at small t from 13.76 GeV to 13 TeV. It yields a value for rho, the ratio of the real part of the forward amplitude to its…
We consider scattering amplitudes in string models in the Regge limit of high energies and fixed momentum transfers with the use of the unitarity in direct channels. Intermediate states are taken in the multi-Regge kinematics corresponding…
Operator definitions of diffractive parton distribution functions are given. A distinction is made between the special case of ``Regge factorization'' to the general case of ``diffractive factorization'' with explicit expressions for…
We report an odderon Regge trajectory emerging from a field theoretical Coulomb gauge QCD model for the odd signature JPC (P=C= -1) glueball states (oddballs). The trajectory intercept is clearly smaller than the pomeron and even the omega…
Measurements are reported of the proton and deuteron spin structure functions g1 at beam energies of 29.1, 16.2, and 9.7 GeV and g2 at a beam energy of 29.1 GeV. The integrals of g1 over x have been evaluated at fixed Q**2 = 3 (GeV/c)**2…
This talk reviews the latest measurements of the proton, Pomeron and photon structure functions. These measurements, especially at low $x$ and/or low $Q^2$ lead to new insight into the picture of hadronic interactions.
The structure function of the proton has been investigated and has been found to possess the power law behaviour in conformity with the empirical fits to the experimental findings. We have estimated F$_{2}$(x, Q$^{2}$)/F$_{2}$(x,…
We investigate the production of a quark-antiquark pair in diffractive photon- proton scattering, approximating soft pomeron exchange by the exchange of two nonperturbative gluons. In deep inelastic scattering at HERA, events with two jets…
Stimulated by recent progress made by the LHCb Collaboration in discoveries of new bottom baryons, e.g., the $\Xi _{b}(6227)^{-}$ and the $\Sigma_{b}(6097)^{\pm}$, we re-examine the orbitally excited spectrum of the charmed and bottom…
Coherence phenomena, the increase with energy of coherence length and the non-universality of parton structure of the effective Pomeron are explained. New hard phenomena directly calculable in QCD such as diffractive electroproduction of…
We predict the effect of the charm structure function on the longitudinal structure function at small x. In NLO analysis we find that the hard Pomeron behavior gives a good description of $F_{L}$ and $F^{c}_{k}$ (k = 2,L) at small x values.…