Saturation in diffractive deep inelastic eA scattering

In this paper, we investigate the saturation physics in diffractive deep inelastic electron-ion scattering. We estimate the energy and nuclear dependence of the ratio σ^diff/σ^tot and predict the x_ℙ and β behavior of the nuclear diffractive structure function F_2,A^D(3)(Q²,β,x_ℙ). Moreover, we analyze the ratio R^diff_A1,A2(Q²,β,x_ℙ)=F_2,A1^D(3)/F_2,A2^D(3), which probes the nuclear dependence of the structure of the pomeron. We show that saturation physics predicts that approximately 37% of the events observed at eRHIC should be diffractive.     

Dijet production in diffractive deep inelastic scattering at HERA

The production of dijets in diffractive deep inelastic scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 61 pb^-1. The dijet cross section has been measured for virtualities of the exchanged virtual photon, 5 < Q² < 100 GeV², and γ^*p centre-of-mass energies, 100 < W < 250 GeV. The jets, identified using the inclusive k_T algorithm in the γ^*p frame, were required to have a transverse energy E^* _T,jet > 4 GeV and the jet with the highest transverse energy was required to have E^* _T,jet > 5 GeV. All jets were required to be in the pseudorapidity range -3.5<η^* _jet<0. The differential cross sections are compared to leading-order predictions and next-to-leading-order QCD calculations based on recent diffractive parton densities extracted from inclusive diffractive deep inelastic scattering data.     

Predictions for the forward cone in diffractive deep inelastic scattering

We calculate the diffraction slope B _D for diffractive deep inelastic scattering. We find a counterintuitive rise of B _D in going from exclusive diffractive excitation of vector mesons to excitation of continuum states with M ²∼Q ². For the small-mass continuum we predict a rapid variation of B _D with M ² on a scale of m _V ² and a sharp drop of B _D for a small-mass continuum above the vector meson excitation. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 8, 604–609 (25 October 1998) Published in English in the original Russian journal. Edited by Steve Torstveit.     

The triple regge limit of diffractive dissociation in deep inelastic scattering

We derive, within perturbative QCD, a formula for the inclusive cross section of the diffractive dissociation of the deep inelastic photon γ^*+q→X+q in the triple Regge limits?M ²?Q ²?Λ ². We use the leading ln(s/M ², ln(M ²/Q ²) approximation and derive an, expression for the triple Pomeron vertex. The Pomeron above this vertex is found to be of higher order than the BFKL Pomeron. The resulting formula for the cross section is infrared finite. We show that the Abramovsky-Gribov-Kanchelli cutting rules are satisfied, and we discuss implications for the Pomeron structure function.     

Measurement of the diffractive structure function in deep inelastic scattering at HERA

This paper presents an analysis of the inclusive properties of diffractive deep inelastic scattering events produced inep interactions at HERA. The events are characterised by a rapidity gap between the outgoing proton system and the remaining hadronic system. Inclusive distributions are presented and compared with Monte Carlo models for diffractive processes. The data are consistent with models where the pomeron structure function has a hard and a soft contribution. The diffractive structure function is measured as a function ofx , the momentum fraction lost by the proton, of , the momentum fraction of the struck quark with respect tox , and ofQ ² in the range 6.3·10^–4x <>^–2, 0.1<0.8 and=">Q ²<100>². The dependence is consistent with the formx wherea=1.30±0.08(stat) _–0.14 ^+0.08 (sys) in all bins of andQ ². In the measuredQ ² range, the diffractive structure function approximately scales withQ ² at fixed . In an Ingelman-Schlein type model, where commonly used pomeron flux factor normalisations are assumed, it is found that the quarks within the pomeron do not saturate the momentum sum rule.supported by Worldlab, Lausanne, Switzerland     

Core polarisation effects in inelastic pion-nucleus scattering

Pion-nucleus inelastic processes are analysed within the framework of Glauber theory and the possibility of expressing the effects of core polarisation by means of a renormalising constant is explored. Estimates are made of the size of the polarisation effects and the results are used to interpret the recent data of ¹⁸O(π^±, π^±)¹⁸O(2⁺.     

Measurement of the diffractive cross section in deep inelastic scattering using ZEUS 1994 data

The DIS diffractive cross section, ds^diff_{g^* p ? XN}/dM_Xd\sigma^{di\!f\!f}_{\gamma^* p \to XN}/dM_X, has been measured in the mass range M_X < 15M_X < 15 GeV for g^*p\gamma^*p c.m. energies 60 < W < 20060 < W < 200 GeV and photon virtualities Q² = 7Q^2 = 7 to 140 GeV²^2. For fixed Q²Q^2 and M_XM_X, the diffractive cross section rises rapidly with WW, ds^diff_{g^*p ? XN}(M_X,W,Q²)/dM_X μ W^adiffd\sigma^{di\!f\!f}_{\gamma^*p \to XN}(M_X,W,Q^2)/dM_X \propto W^{a^{diff}} with a^diff = 0.507 ±0.034 (stat)^+0.155_-0.046(syst)a^{diff} = 0.507 \pm 0.034 (stat)^{+0.155}_{-0.046}(syst) corresponding to a t-averaged pomeron trajectory of [`( a<sub>\mathbb P</sub> )] = 1.127 ±0.009 (stat)<sup>+0.039</sup><sub>-0.012</sub> (syst)\overline{ \alpha_{_{{\mathbb P}}} } = 1.127 \pm 0.009 (stat)^{+0.039}_{-0.012} (syst) which is larger than [`( a_{\mathbb P} )]\overline{ \alpha_{_{{\mathbb P}}} } observed in hadron-hadron scattering. The W dependence of the diffractive cross section is found to be the same as that of the total cross section for scattering of virtual photons on protons. The data are consistent with the assumption that the diffractive structure function F^D(3)₂F^{D(3)}_2 factorizes according to x_{\mathbb P} F^D(3)₂ (x_{\mathbb P},b,Q²) = (x₀/ x_{\mathbb P})ⁿ F^D(2)₂(b,Q²)x_{_{{\mathbb P}}} F^{D(3)}_2 (x_{_{{\mathbb P}}},\beta,Q^2) = (x_0/ x_{_{{\mathbb P}}})^n F^{D(2)}_2(\beta,Q^2). They are also consistent with QCD based models which incorporate factorization breaking. The rise of x_{\mathbb P} F^D(3)₂x_{_{{\mathbb P}}} F^{D(3)}_2 with decreasing x_{\mathbb P}x_{_{{\mathbb P}}} and the weak dependence of F^D(2)₂F^{D(2)}_2 on Q²Q^2 suggest a substantial contribution from partonic interactions.     

Pion fluctuation in deep inelastic scattering

The forward neutron production in the ep collisions at 300GeV measured by H1 and ZEUS Collaborations at DESY has been used to estimate the total probability for proton fluctuation into nπ⁺ and pπ⁰. The probability found is on the order of 30%. This number is compared with the numbers obtained for the probability of quark fluctuation into π⁺ from several alternative DIS processes (Gottfried sum rule, polarized structure function) and the axial-vector coupling constant, where the pion fluctuation is believed to play an important role.     

Coherence effects in deep inelastic scattering

A superfield action for the relativistic massless superparticle as a spinning particle is presented in the new gauge. The symmetries in the relativistic superparticle theory, that is to say, the invariances under, the reparametrization and the local supersymmetry-transformation in the parameter space, are manifest in this formalism. It is clear how these two kinds of transformations descend from a unified origin to be called “super-reparametrization”, which is a restricted form of the general coordinate transformation in the superspace. The action is manifestly invariant under these transformation by its constructions The minimal coupling with electromagnetic field is also constructed in the superfield formalism, and a manifestly invariant superfield action for the interacting superparticle is presented in our gauge. The formalism is extended to the construction of an action for theN=2 superparticle.     

Jets in neutrino deep inelastic scattering

Jet cross sections are calculated to first order in QCD for neutrino production. We give thrust and spherocity distributions and calculate angular correlations between jet and leptonic planes.