17028127
Coulomb effects in W+W- production.
We calculate the Coulomb effects on the cross section for e+ e- --> W+ W- taking into account the instability of the W bosons. We carefully explain the consequences of instability throughout the energy range which will be accessible at LEP2. We present a formula which allows these effects to be easily implemented.
15108358
Off-diagonal parton distributions and their evolution
We construct off-diagonal parton distributions defined on the interval 0 ≤ X ≤ 1 starting from the off-forward distributions defined by Ji. We emphasize the particular role played by the symmetry relations in the “ERBL-like” region. We find the evolution equations for the off-diagonal distributions which conserve these symmetries. We present numerical results of the evolution, and verify that the analytic asymptotic forms of the parton distributions are reproduced. We also compare the constructed off-diagonal distributions with the non-forward distributions defined by Radyushkin and comment on the singularity structure of the basic amplitude written in terms of the off-diagonal distributions.
126229857
Structure Function Analysis and psi, Jet, W, Z Production: Pinning Down the Gluon
118665854
Diffraction and correlations at the LHC: definitions and observables
We note that the definition of diffractive events is a matter of convention. We discuss two possible “definitions”: one based on unitarity and the other on Large Rapidity Gaps (LRG) or Pomeron exchange. LRG can also arise from fluctuations and we quantify this effect and some of the related uncertainties. We find care must be taken in extracting the Pomeron contribution from LRG events. We show that long-range correlations in multiplicities can arise from the same multi-Pomeron diagrams that are responsible for LRG events, and we explain how early LHC data can illuminate our understanding of ‘soft’ interactions.
117807416
Diffractive deep inelastic scattering
A new approach to the analysis of diffractive deep inelastic data is presented. We show that the collinear factorisation theorem, which holds for diffractive DIS, has important modifications in the sub‐asymptotic HERA regime, which can be quantified by using perturbative QCD. In fact the diffractive parton densities are shown to satisfy an inhomogeneous evolution equation. Moreover it is necessary to include both the gluonic and sea‐quark t‐channel components of the perturbative Pomeron.
123328618
Proton-proton scattering and the pomeron
Abstract We describe various attempts to fit the data on pp and p p elastic scattering and total cross sections, including the recent ISR data, with a variety of Regge pole and cut models. Only two types of model are able to explain the data over the whole energy range satisfactorily. The simplest of these has no cuts, but a pomeron pole with trajectory α p(0) = 1.06 + 0.25 t , and a non-shrinking “core” term at large | t |. The other has a flat trajectory, α p( t ) = 1.06 for all t , and strong eikonal-model cuts which explain both the shrinkage at low | t |, and the lack of it at larger | t |. We also briefly review various speculations which relate the fact that α p(0) > 1 to the small triple-pomeron coupling.
20265396
E3 transition probabilities in the platinum, mercury, and lead isotopes.
Spectroscopical properties of the platinum, mercury, and lead isotopes are studied within the Hartree-Fock plus BCS framework with the finite range density-dependent Gogny force. These properties are also studied beyond mean-field theory by combining the use of generator-coordinate-method-like wave functions with the angular momentum projection technique as to generate many-body correlated wave functions that are at the same time eigenstates of the angular momentum operator. We apply this formalism to the calculation of reduced transition probabilities {ital B}({ital E}3) from the lowest-lying octupole collective state to the ground state of several isotopes of the platinum, mercury, and lead nuclei whose experimental {ital B}({ital E}3) values present a peculiar behavior. The projected calculations show a large improvement over the unprojected ones when compared with the experimental data. The unprojected calculations are unable to predict any structure in the {ital B}({ital E}3). {copyright} {ital 1996 The American Physical Society.}
17649647
Variational approximation for two-time correlation functions in Phi 4 theory: Optimization of the dynamics.
We apply the time-dependent variational principle of Balian and Veneroni to {Phi}{sup 4} theory. An appropriate parametrization for the variational objects allows us to write coupled dynamical equations from which we derive approximations for the two-time correlation functions involving two, three, or four field operators. {copyright} 1995 The American Physical Society.
5751474
Implications of supersymmetric models with natural R-parity conservation.
In the minimal supersymmetric standard model, the conservation of {ital R} parity is phenomenologically desirable, but is {ital ad} {ital hoc} in the sense that it is not required for the internal consistency of the theory. However, if {ital B}{minus}{ital L} is gauged at very high energies, {ital R} parity will be conserved automatically and exactly, provided only that all order parameters carry even integer values of 3({ital B}{minus}{ital L}). We propose a minimal extension of the supersymmetric standard model in which {ital R}-parity conservation arises naturally in this way. This approach predicts the existence of a very weakly coupled, neutral chiral supermultiplet of particles with electroweak-scale masses and lifetimes which may be cosmologically interesting. Neutrino masses arise via an intermediate-scale seesaw mechanism, and a solution to the {mu} problem is naturally incorporated. The apparent unification of gauge couplings at high energies is shown to be preserved in this approach. We also discuss a next-to-minimal extension, which predicts a pair of electroweak-scale chiral supermultiplets with electric charge 2. {copyright} {ital 1996 The American Physical Society.}
14821065
Some simple criteria for gauged R parity.
Some simple conditions which are sufficient to guarantee that R- parity survives as an unbroken gauged discrete subgroup of the continuous gauge symmetry in certain supersymmetric extensions of the standard model are presented.
33800044
Finite-size and dynamical effects in pair production by an external field.
We evaluate the rate of pair production in a uniform electric field confined to a bounded region in space. Using the Balian-Bloch expansion of Green's functions we obtain explicit expressions for finite-size corrections to Schwinger's formula. The case of a time-dependent boundary, relevant to describe energy deposition by quark-antiquark pair production in ultrarelativistic collisions, is also investigated. We find that finite-size effects are important in nuclear collisions. They decrease when the strength of the chromoelectric field between the nuclei is large. As a result, the rate of energy deposition increases sharply with the mass number {ital A} of the colliding nuclei.