We extract diffractive parton densities from data on diffractive deep inelastic scattering ͑DIS͒ and on diffractive photoproduction of jets. We explore the results of several Ansätze for the functional form of the parton densities. Then we use the fitted parton densities to predict the diffractive production of jets and of W's and Z's in pp collisions at the Fermilab Tevatron. To fit the photoproduction data requires a large gluon density in the Pomeron. The predictions for the Tevatron cross sections are substantially higher than data; this signals a breakdown of hard-scattering factorization in diffractive hadron-hadron collisions. ͓S0556-2821͑99͒00309-4͔

We apply the method of principal value resummation of large momentum-dependent radiative corrections to the calculation of the Drell Yan cross section. We sum all nextto-leading logarithms and provide numerical results for the resummed exponent and the corresponding hard scattering function.1 A precise definition of this range will be discussed below, and in section 4.

The FELIX collaboration had proposed the construction of a full-acceptance detector for the LHC. The primary mission of FELIX was the study of QCD: to provide comprehensive and definitive observations of a very broad range of strong-interaction processes. This document contains an extensive discussion of this physics menu. In a further paper the FELIX detector will be reviewed. Contents HISTORYWith the advent of the large hadron collider (LHC), we are on the threshold of a new era in high-energy physics. With instrumentation in the form of dedicated experiments of unprecedented precision and complexity, the LHC will move significantly beyond the current high-energy frontier, and dramatically improve our understanding of particle physics at the highest energies and shortest distances accessible to man.As currently planned, however, the LHC experimental programme is incomplete. Moreover, these deficiencies continue and extend what has been a gap in the experimental programme of all hadron colliders. The problem lies in the design of the detectors instrumenting hadron colliders: they are all optimized for rare, high-pt events. These 'general purpose' detectors are anything but that. Rather, they are designed to explore extreme shortdistance phenomena. Without intending to demean the efforts of the collaborations which have built or are building these detectors, it is nevertheless these events in which the theorists are most confident that they understand the physics, and are in many ways experimentally most accessible.While there is no doubt that such physics and such detectors should be the centrepiece of any programme of hadron collider physics, it seems much less clear that they should be the only item on the agenda. Indeed, it can be argued that a full-acceptance detector, capable of detecting and measuring each particle in an event well, may have the greatest discovery potential. Alas, the absence of any experimental effort in this direction in the collider era has meant that both theoretical investigations and experimental design of such detectors has languished, to the point that many in the community have come to think of high-pt physics as the last frontier in particle physics.The FELIX collaboration sought to rectify this situation. With support from the CERN administration, some 160 physicists collaborated in preparing the FELIX LoI. Many of these could not officially join the collaboration, and so their help could only be acknowledged. While the FELIX proposal was never officially killed, it was nevertheless effectively killed without the collaboration making a formal presentation to the LHC committee.All of this, of course, is history, and not very pleasant history at that. The motivation for a full-acceptance detector remains, however, and interest on the part of the broader community, despite the implications of this history, remains high. Because of this, the FELIX collaboration, together with those who helped but were not members, believes that it is important to document the physics of a ...

We evaluate nuclear shadowing of the total cross section of charm particles production in DIS within the framework of Gribov theory of nuclear shadowing generalized to account for the QCD evolution. We use as an input the recent QCD Pomeron parton density analysis of the HERA diffractive data. Assuming that the QCD factorization theorem is applicable to the charm production off nuclei we also calculate shadowing of the gluon densities in nuclei and find it sufficiently large for heavy nuclei: G A∼200 (x, Q 2 )/AG N (x, Q 2 ) ∼ 0.45 − 0.5 · (A/200) −0.15 for x ∼ 10 −3÷−4 , Q 2 ∼ 20 ÷ 40GeV 2 to influence significantly the physics of heavy ion collisions at LHC. We evaluate also suppression of minijet and hidden charm production in the central AA collisions. We also discuss some * On leave of absence from PSU.

Using a recent calculation of the perturbative hard part for dilepton production that sums large threshold corrections to all orders in perturbative QCD, we compute the corresponding cross sections. The hard part has been evaluated using principal value resummation and contains all singular momentum-dependent corrections. We also include a resummation of large Sudakov terms, which are independent of parton momenta. We give predictions for the dilepton-mass distribution, the rapidity distribution and the rapidity-integrated K-factor at fixed-target energies and compare with various experimental results in several kinematic regimes. We find that principal value resummation produces cross sections that are finite and well-behaved. For both protons and anti-protons on fixed targets, the resummed cross sections are, in general, in excellent agreement with the data. †Present