5,335 research outputs found
Soft Colour Interactions in Non-perturbative QCD
Improved understanding of non-perturbative QCD dynamics can be obtained in
terms of soft colour exchange models. Their essence is the variation of colour
string-field topologies giving a unified description of final states in high
energy interactions. In particular, both events with and without large rapidity
gaps are obtained in agreement with data from ep at HERA and ppbar at the
Tevatron, where also the surprisingly large production rate of high-p_T
charmonium and bottomonium is reproduced.Comment: 4 pages, contribution to PANIC 99 conference proceedings, to appear
in Nucl. Phys. A. Uses espcrc1.st
Rapidity Gaps from Colour String Topologies
Diffractive deep inelastic scattering at HERA and diffractive W and jet
production at the Tevatron are well described by soft colour exchange models.
Their essence is the variation of colour string-field topologies giving both
gap and no-gap events, with a smooth transition and thereby a unified
description of all final states.Comment: 3 pages, 6 eps figures, contribution to the DIS 99 workshop
proceedings, uses npb.st
A model for parton distributions in hadrons
The non-perturbative parton distributions in hadrons are derived from simple
physical arguments resulting in an analytical expression for the valence parton
distributions. The sea partons arise mainly from pions in hadronic
fluctuations. The model gives new insights and a good description of structure
function data.Comment: 3 pages, 4 figures, LaTeX. Contribution to DIS 99 worksho
Diffractive deep inelastic scattering from multiple soft gluon exchange in QCD
Diffractive hard scattering is interpreted as the effect of soft gluon
exchanges between the emerging energetic quarks and the nucleon's color field,
resulting in an overall color singlet exchange. Summing multiple gluon
exchanges to all orders leads to exponentiation and an amplitude in analytic
form. Numerical evaluation reproduces the precise HERA data and gives new
insights on the density of gluons in the proton.Comment: 6 pages, 2 figures. Minor change to conventions in Eqs. (4-6), some
discussion clarified. Version to appear in PL
Assessing the bias due to non-coverage of residential movers in the German microcensus panel: an evaluation using data from the socio-economic panel
The German Microcensus (MC) is a large scale rotating panel survey over three years. The MC is attractive for longitudinal analysis over the entire participation duration because of the mandatory participation and the very high case numbers (about 200 thousand respondents). However, as a consequence of the area sampling that is used for the MC , residential mobility is not covered and consequently statistical information at the new residence is lacking in theMCsample. This raises the question whether longitudinal analyses, like transitions between labour market states, are biased and how different methods perform that promise to reduce such a bias. Based on data of the German Socio-Economic Panel (SOEP), which covers residential mobility, we analysed the effects of missing data of residential movers by the estimation of labour force flows. By comparing the results from the complete SOEP sample and the results from the SOEP, restricted to the non-movers, we concluded that the non-coverage of the residential movers can not be ignored in Rubins sense. With respect to correction methods we analysed weighting by inverse mobility scores and loglinear models for partially observed contingency tables. Our results indicate that weighting by inverse mobility scores reduces the bias to about 60 percent whereas the official longitudinal weights obtained by calibration result in a bias reduction of about 80 percent. The estimation of loglinear models for nonignorable nonresponse leads to very unstable results. --Panel survey,labour market analysis,residential mobility,non-coverage bias,log-linear modelling,inverse probability weighting
A new functional observer to estimate velocity, acceleration and disturbance for motion control systems
This paper presents a novel functional observer which can observe the velocity, acceleration and disturbance information of a motion control system with higher accuracy and less noise in comparison to classical observers. The observer uses the input current and position information and the nominal parameters of the plant. The novelty of the observer is based on its functional structure that can intrinsically estimate and compensate the un-measured inputs (like disturbance acting on the system) using the measured input current. The experimental results of the proposed estimator verifies its success in estimating the velocity,
acceleration and disturbance with better precision than classical observers
Swimming with the tide: solidarity wage policy and the gender earnings gap
The purpose of this paper is to examine the role of wage compression for the gender wage gap in Sweden during the period 1968-1991. We find that the effects of changes in the wage structure on women's wages have varied over time and have had partly counteracting effects. Changes in industry wage differentials have systematically worked against women, while the changes in the returns to human capital and unobserved characteristics have contributed to reductions in the gender wage gap. Changes in the wage structure were particularly important between 1968 and 1974, when the reduction of overall wage inequality was dramatic. In 1981, however, the wage compression effect accounted only for a minor proportion of women's relative wage gains, as compared to 1974. At this time, women gained in relative wages mainly because discrimination was mitigated and/or the gender gap in unobserved skills was reduced. Between 1981 and 1991 there is a small increase in the gender wage gap. This small increase seems to have been driven by changed inter-industry wage differentialsGender wage gap; Wage structure
Rapidity Gaps in DIS through Soft Colour Interactions
We present a new mechanism for the creation of large rapidity gaps in DIS
events at HERA. Soft colour interactions between perturbatively produced
partons and colour-charges in the proton remnant, modifies the colour structure
for hadronization giving colour singlet systems that are well separated in
rapidity. An explicit model is presented that, although the detailed results
depend on the initial state parton emission, can describe both the observed
rapidity gaps and, in addition, the forward energy flow in an inclusive event
sample.Comment: 4 pages Latex, 4 encapsulated Postscript figures, uses qcdparis.sty,
tar-compressed and uuencoded with uufiles, Presented by GI at workshop `DIS
and QCD', Paris, April 1995, minor Postscript problem fixe
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