41 research outputs found
The Interest of Large-t Elastic Scattering
Existing data for large- elastic-scattering differential
cross-sections are energy-independent and behave as . This has been
explained in terms of triple-gluon exchange, or alternatively through
triple-singlet exchange. A discussion is given of the problems raised by each
of these explanations, and of the possibility that at RHIC or LHC energies the
exchange of three BFKL pomerons might result in a rapid rise with energy.Comment: 6 pages, plain tex, 3 figures embedded with eps
Pomeron physics: an update
Key issues in pomeron physics include whether the hard and soft pomerons are
distinct objects, and whether the hard pomeron is already present in amplitudes
at . It is urgent to learn how to combine perturbative and
nonperturbative concepts, and to construct a sound theory of perturbative
evolution at small . Other questions are whether screening corrections are
small, and gap survival probabilities large. Finally, do diffractive processes
present a good way to discover the Higgs?Comment: 12 pages, 23 figures embedded with epsf Summary talk at
Diffraction2000, Calabria, September 200
Proton-Proton Near-Forward Hard Elastic Scattering
We calculate the leading twist contribution to near-forward proton-proton
(and proton-antiproton) elastic scattering with large momentum transfer, in the
multiple scattering (Landshoff) mechanism. The amplitude in the near-forward
region is dominated by singlet exchange for all three valence quark-quark
scatterings. We assume the existence of a hard singlet quark-quark amplitude,
which we estimate to be . For a three-quark state whose
transverse size is less than , Sudakov resummation
accounts for both approximate \d \sigma^{pp}/ \d t \sim t^{-8} at moderate
, and \d \sigma^{pp}/ \d t \sim t^{-10} at larger . The transition from
approximate to behavior is strongly correlated with the
transverse size of the valence three-quark state in the proton.Comment: 34 pages, LaTe
Canine Models of Inherited Musculoskeletal and Neurodegenerative Diseases
Mouse models of human disease remain the bread and butter of modern biology and therapeutic discovery. Nonetheless, more often than not mouse models do not reproduce the pathophysiology of the human conditions they are designed to mimic. Naturally occurring large animal models have predominantly been found in companion animals or livestock because of their emotional or economic value to modern society and, unlike mice, often recapitulate the human disease state. In particular, numerous models have been discovered in dogs and have a fundamental role in bridging proof of concept studies in mice to human clinical trials. The present article is a review that highlights current canine models of human diseases, including Alzheimer\u27s disease, degenerative myelopathy, neuronal ceroid lipofuscinosis, globoid cell leukodystrophy, Duchenne muscular dystrophy, mucopolysaccharidosis, and fucosidosis. The goal of the review is to discuss canine and human neurodegenerative pathophysiologic similarities, introduce the animal models, and shed light on the ability of canine models to facilitate current and future treatment trials
Eikonal profile functions and amplitudes for and scattering
The eikonal profile function obtained from the Model of the Stochastic
Vacuum is parametrized in a form suitable for comparison with experiment. The
amplitude and the extended profile function (including imaginary and real
parts) are determined directly from the complete pp and p elastic
scattering data at high energies. Full and accurate representation of the data
is presented, with smooth energy dependence of all parameters. The changes
needed in the original profile function required for description of scattering
beyond the forward direction are described.Comment: Latex, 28 pages and 16 figure
Evidence for eikonal zeros in the momentum transfer space
We present the results of fitting elastic differential cross section
data at 23.5 62.5 GeV with a novel analytic
parametrization for the scattering amplitude. Making use of a fitting method,
the errors from the free parameters are propagated to the imaginary part of the
eikonal in the momentum transfer space. A novel systematic study of the effects
coming from data at large momentum transfer is also performed. We find
statistical evidence for the existence of eikonal zeros in the interval of
momentum transfer 5-9 .Comment: Text with 9 pages in Revtex (preprint form), 8 figures in PostScript.
Replaced with small changes. Final version to be published in Physical Review
The practical Pomeron for high energy proton collimation
We present a model which describes proton scattering data from ISR to Tevatron energies, and which can be applied to collimation in high energy accelerators, such as the LHC and FCC. Collimators remove beam halo particles, so that they do not impinge on vulnerable regions of the machine, such as the superconducting magnets and the experimental areas. In simulating the effect of the collimator jaws it is crucial to model the scattering of protons at small momentum transfer t, as these protons can subsequently survive several turns of the ring before being lost. At high energies these soft processes are well described by Pomeron exchange models. We study the behaviour of elastic and single-diffractive dissociation cross sections over a wide range of energy, and show that the model can be used as a global description of the wide variety of high energy elastic and diffractive data presently available. In particular it models low mass diffraction dissociation, where a rich resonance structure is present, and thus predicts the differential and integrated cross sections in the kinematical range appropriate to the LHC. We incorporate the physics of this model into the beam tracking code MERLIN and use it to simulate the resulting loss maps of the beam halo lost in the collimators in the LHC