Pomeron intercepts at colliders

A method allowing for a direct comparison of data with theoretical predictions is proposed for forward jet production at HERA and Mueller-Navelet jets at Tevatron and LHC. An application to the determination of the effective Pomeron intercept in the BFKL-LO parametrization from d sigma/dx data at HERA leads to a good fit with a significantly higher effective intercept, $\alpha_P= 1.43 \pm 0.025 (stat.) \pm 0.025 (syst.),$ than for proton (total and diffractive) structure functions. It is however less than the value of the pomeron intercept using dijets with large rapidity intervals obtained at Tevatron. We also evaluate the rapidity veto contribution to the higher order BFKL corrections. We suggest to measure the dependence of the dijet cross-sections as a function of the jet transverse energies as a signal for BFKL pomeron at LHC.Comment: 10 pages, workshop on physics at lhc, similar to hep-ph/0002057, completed for lh

The Diffractive Interactions Working Group Summary

Diffractive interactions represent a lively domain of investigations, as confirmed by the progresses reported during the conference. We summarize the diffractive interactions session and put the new experimental data (section 1), developments in modeling diffraction (section 2) and the theoretical relations with Quantum Chromodynamics (section 3) in perspective.Comment: Summary report at DIS200

Gaps between jets in double-Pomeron-exchange processes at the LHC

The possibility to measure jet-gap-jet final states in double-Pomeron-exchange events at the LHC is presented. In the context of the ATLAS experiment with additional forward physics detectors, cross sections for different experimental settings and gap definitions are estimated. This is done in the framework of the Forward Physics Monte Carlo interfaced with a perturbative QCD model that successfully reproduces standard jet-gap-jet cross sections at the Tevatron. The extrapolation to LHC energies follows from the Balitsky-Fadin-Kuraev-Lipatov dynamics, implemented in the model at next-to-leading logarithmic accuracy.Comment: 8 pages, 5 figures, version to appear in PR

Threshold scans in Central Diffraction at the LHC

We propose a new set of measurements which can be performed at the LHC using roman pot detectors. The method exploits excitation curves in central diffractive pair production, and is illustrated using the examples of the W boson and top quark mass measurements. Further applications are mentioned.Comment: 11 page

Summary of Working Group I: Hadron Structure

A summary is given on the main aspects which were discussed by the working group. They include new results on the deep inelastic scattering structure functions $F_2, xF_3, F_L$ and $F_2^{c\bar{c}}$ and their parametrizations, the measurement of the gluon density, recent theoretical work on the small $x$ behavior of structure functions, theoretical and experimental results on $\alpha_s$, the direct photon cross section, and a discussion of the event rates in the high $p_T$ range at Tevatron and the high $Q^2$ range at HERA, as well as possible interpretations.Comment: 22 pages latex, including 8 figures (ps,eps), to appear in the Proceedings of the International Conference on Deep Inelastic Scattering, Chicago, April 1997, AI

Uncertainties on exclusive diffractive Higgs and jets production at the LHC

Two theoretical descriptions of exclusive diffractive jets and Higgs production at the LHC were implemented into the FPMC generator: the Khoze, Martin, Ryskin model and the Cudell, Hern\'andez, Ivanov, Dechambre exclusive model. We then study the uncertainties. We compare their predictions to the CDF measurement and discuss the possibility of constraining the exclusive Higgs production at the LHC with early measurements of exclusive jets. We show that the present theoretical uncertainties can be reduced with such data by a factor of 5

Decisive test for the Pomeron at Tevatron

We propose a new measurement to be performed at the Tevatron which can be decisive to distinguish between Pomeron-based and soft color interaction models of hard diffractive scattering.Comment: 5 pages, 3 figures, 1 tabel revtex forma

Hard diffraction and the nature of the Pomeron

We ask the question whether the quark and gluon distributions in the Pomeron obtained from QCD fits to hard diffraction processes at HERA can be dynamically generated from a state made of ``valence-like'' gluons and sea quarks as input. By a method combining backward Q^2-evolution for data exploration and forward Q^2-evolution for a best fit determination, we find that the diffractive structure functions published by the H1 collaboration at HERA can be described by a simple ``valence-like'' input at an initial scale of order mu^2 ~ 2.3-2.7 GeV^2. The parton number sum rules at the initial scale mu^2 for the H1 fit gives 2.1\pm .1\pm .1 and .13\pm .01 \pm .02 for gluon and sea quarks respectively, corresponding to an initial Pomeron state made of (almost) only two gluons. It has flat gluon density leading to a plausible interpretation in terms of a gluonium state.Comment: 14 pages, 9 figure