6254089
QCD predictions for the behavior of the gluon distribution at small x.
The very-small-{ital x} behavior of the gluon distribution in a proton is obtained by solving the Lipatov equation with the nonlinear shadowing term incorporated. We find, with decreasing {ital x}, the emergence of an {ital x}{sup {minus}{lambda}} behavior {ital and} he eventual taming of this singular behavior by the shadowing term. We compare our dynamically generated gluon distribution with (i) the results of a recent next-to-leading order QCD structure function analysis which incorporated both a singular {ital x}{sup {minus}1/2} behavior and shadowing corrections, and (ii) the double-leading-logarithm approximation. We formulate the semiclassical approximation of the Lipatov equation, with and without shadowing contributions, in order to compare with earlier analyses based on this approximation.
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.
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
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.
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.
471847
Search for supersymmetry with a light gravitino at the Fermilab Tevatron and CERN LEP colliders.
We analyze the prospects for discovering supersymmetry at the Fermilab Tevatron and CERN LEP colliders in the scenario that the lightest supersymmetric particle is a gravitino of mass {approx_lt}1 keV. We consider in particular the case that the lightest neutralino has a nearly 100{percent} branching fraction into gravitino+photon within the detector. This implies that supersymmetric events should contain both missing (transverse) energy and two energetic photons. Therefore, one can search for supersymmetry simply through inclusive production of superpartners. We consider the exclusion and reach capabilities of the Tevatron in exploring the supersymmetric parameter space, and study the efficiencies which can be achieved in this search. We also consider the discovery reach and backgrounds at LEP with {radical}{ital s}=160, 175, and 190 GeV. {copyright} {ital 1996 The American Physical Society.}
41996012
Stability of systems of three arbitrary charges: General properties.
The stability of systems consisting of a negative charge {minus}{ital q}{sub 1} and two positive charges {ital q}{sub 2} and {ital q}{sub 3} is discussed as a function of the values of the charges {ital q}{sub {ital i}} and of the constituent masses {ital m}{sub {ital i}}. We give general results and list some open questions of interest, which hopefully will stimulate further investigations.
11226857
Dynamical electroweak symmetry breaking with top-quark and neutrino condensates.
Recently it has been suggested that electroweak symmetry is broken by a top-quark vacuum condensate. In that model, the prediction for the top-quark mass seems to be in conflict with indirect experimental upper bounds. We propose a new scenario in which electroweak symmetry is broken by a combination of top-quark and third-generation neutrino condensates, involving a right-handed gauge-singlet neutrino. We show that the top-quark mass comes out smaller in this model and can easily lie in the experimentally favored window. The resulting neutrino spectrum is phenomenologically acceptable if we make the natural assumption that the right-handed neutrino has a large Majorana mass.
16739726
Spacings of quarkonium levels with the same principal quantum number.
The spacings between bound-state levels of the Schr{umlt o}dinger equation with the same principal quantum number {ital N} but orbital angular momenta {ital l} differing by unity are found to be nearly equal for a wide range of power potentials {ital V}={lambda}{ital r}{sup {nu}}, with {ital E}{sub {ital Nl}}{approx_equal}{ital F}({nu},{ital N}){minus}{ital G}({nu},{ital N}){ital l}. Semiclassical approximations are in accord with this behavior. The result is applied to estimates of masses for quarkonium levels which have not yet been observed, including the 2{ital P} {ital c{bar c}} states and the 1{ital D} {ital b{bar b}} states. {copyright} {ital 1996 The American Physical Society.}
10832623
Sparticle spectrum constraints.
The supersymmetric standard model with supergravity-inspired soft breaking terms predicts a rich spectrum of sparticles to be discovered at the SSC, LHC, and NLC. Because there are more supersymmetric particles than unknown parameters, one can write down sum rules relating their masses. We discuss the spectrum of sparticles from this point of view. Some of the sum rules do not depend on the input parameters and can be used to test the consistency of the model, while others are useful in determining the input parameters of the theory. If supersymmetry is discovered but the sum rules turn out to be violated, it will be evidence of new physics beyond the minimal supersymmetric standard model with universal soft supersymmetry-breaking terms.