14,010 research outputs found
Generalized Parton Distributions and Transversity in Nucleons and Nuclei
We present an exploratory study using generalized parton distributions of
several observables related to transverse degrees of freedom in hadronic
structure -- the nucleon transverse momentum, the transverse radius, or impact
parameter, and the momentum transfer, , dependence of the longitudinal
variable -- in both nucleons and nuclei.Comment: 6 pages, 3 figures, Talk presented at "Baryons 04", October
25th-30th, 2004, Palaiseau, Franc
Recommended from our members
Tyre curve estimation in slip-controlled braking
Progress in reducing actuator delays in pneumatic brake systems creates an opportunity for advanced anti-lock braking algorithms to be used on heavy goods vehicles. However, these algorithms require knowledge of variables that are impractical to measure directly. This paper introduces a braking force observer and road surface identification algorithms to support a sliding-mode slip controller for air-braked heavy vehicles. Both the force observer and the slip controller are shown to operate robustly under a variety of conditions in quarter-car simulations. A non-linear least-squares algorithm was found to be capable of performing regressions on all the parameters of the tyre model from the University of Michigan Transportation Research Institute when used ‘in the loop’ with the controller and the observer. A recursive least-squares algorithm that is less computationally expensive than the non-linear algorithm was also investigated but gave only reasonable estimates of the tyre model parameters on high-friction smooth roads. The authors would like to thank the members of the Cambridge Vehicle Dynamics Consortium (CVDC), and the Gates Cambridge Trust for their parts in funding this work.This is the author accepted manuscript. The final version is available from Sage via http://dx.doi.org/10.1177/095440701558593
Optical studies of the ultraluminous X-ray source NGC1313 X-2
NGC1313 X-2 was among the first ultraluminous X-ray sources discovered, and
has been a frequent target of X-ray and optical observations. Using the HST/ACS
multi-band observations, this source is identified with a unique counterpart
within an error circle of 0\farcs2. The counterpart is a blue star on the
edge of a young cluster of years amid a dominant old stellar
population. Its spectral energy distribution is consistent with that for a
Z=0.004 star with 8.5 about years old, or for an O7 V
star at solar metallicity. The counterpart exhibited significant variability of
mag between two F555W observations separated by
three months, reminiscent of the ellipsoidal variability due to the orbital
motion of this ULX binary.Comment: 21 pages, 7 figures, scheduled for the ApJ June 10, 2007, v662n 1
issu
Overview of nucleon structure studies
A brief overview of the recent activity in the measurement of the elastic
electromagnetic proton and neutron form factors is presented. It is discussed
how the quality of the data has been greatly improved by performing double
polarization experiments, and the role of two-photon exchange processes will be
highlighted. The spatial information on the quark charge distribibutions in the
nucleon resulting from the form factors measurements will be discussed, as well
as the steady rate of improvements made in the lattice QCD calculations. It is
discussed how generalized parton distributions have emerged as a unifying theme
in hadron physics linking the spatial densities extracted from form factors
with the quark momentum distribution information residing in quark structure
functions. The recent progress in the electromagnetic excitation of the
resonance will also briefly be discussed.Comment: prepared for Proceedings of International Nuclear Physics Conference
(INPC07), typos corrected + references adde
Nucleon Generalized Parton Distributions and Holographic Models
Using ideas from Light Front Holography, we discuss the calculation of the
nucleon helicity-independent generalized parton distributions of quarks in the
zero skewness case.Comment: Prepared for LIGHTCONE 2011, 23 - 27 May, 2011, Dalla
Generalized parton distributions for dynamical equation models
We show how generalized parton distributions (GPDs) can be determined in the
case where hadrons are described in terms of their partonic degrees of freedom
through solutions of dynamical equations. We demonstrate our approach on the
example of two-quark bound states described by the Bethe-Salpeter equation, and
three-quark bound states described by three- and four-dimensional Faddeev-like
equations. Within the model of strong interactions defined by the dynamical
equations, all possible mechanisms contributing to the GPDs are taken into
account, and all GPD sum rules are satisfied automatically. The formulation is
general and can be applied to determine generalized quark distributions,
generalized gluon distributions, transition GPDs, nucleon distributions in
nuclei, etc. Our approach is based on the gauging of equations method.Comment: 23 pages, 9 figures, revtex4, feynm
- …