422 research outputs found
A model of non-perturbative gluon emission in an initial state parton shower
We consider a model of transverse momentum production in which
non-perturbative smearing takes place throughout the perturbative evolution, by
a simple modification to an initial state parton shower algorithm. Using this
as the important non-perturbative ingredient, we get a good fit to data over a
wide range of energy. Combining it with the non-perturbative masses and cutoffs
that are a feature of conventional parton showers also leads to a reasonable
fit. We discuss the extrapolation to the LHC.Comment: 14 pages, 6 figures; version accepted by JHE
The Process \gamma^{*}_L+ q \to q\bar{q}g + q: Real Corrections to the Virtual Photon Impact Factor
We calculate, for the longitudinally polarized virtual photon, the cross
section of the process \gamma^{*}+q\to (q\bar{q}g)+q at high energies with a
large rapidity gap between the fragmentation system q\bar{q}g and the other
quark. This process provides the real corrections of the virtual photon impact
factor in the next-to leading order. Evidence is given for the appearance of a
new q\bar{q}g Fock-component of the photon state.Comment: 17 pages, 4 figures, revte
Spray nozzle designs for agricultural aviation applications
Techniques of generating monodisperse sprays and information concerning chemical liquids used in agricultural aviation are surveyed. The periodic dispersion of liquid jet, the spinning disk method, and ultrasonic atomization are the techniques discussed. Conceptually designed spray nozzles for generating monodisperse sprays are assessed. These are based on the classification of the drops using centrifugal force, on using two opposing liquid laden air jets, and on operating a spinning disk at an overloaded flow. Performance requirements for the designs are described and estimates of the operational characteristics are presented
Angular ordering and parton showers for non-global QCD observables
We study the mismatch between a full calculation of non-global
single-logarithms in the large-N_c limit and an approximation based on free
azimuthal averaging, and the consequent angular-ordered pattern of soft gluon
radiation in QCD. We compare the results obtained in either case to those
obtained from the parton showers in the Monte Carlo event generators HERWIG and
PYTHIA, with the aim of assessing the accuracy of the parton showers with
regard to such observables where angular ordering is merely an approximation
even at leading-logarithmic accuracy and which are commonly employed for the
tuning of event generators to data.Comment: 20 pages, 8 figure
NLO corrections to the photon impact factor: Combining real and virtual corrections.
In this third part of our calculation of the QCD NLO corrections to the
photon impact factor we combine our previous results for the real corrections
with the singular pieces of the virtual corrections and present finite analytic
expressions for the quark-antiquark-gluon intermediate state inside the photon
impact factor. We begin with a list of the infrared singular pieces of the
virtual correction, obtained in the first step of our program. We then list the
complete results for the real corrections (longitudinal and transverse photon
polarization). In the next step we define, for the real corrections, the collinear
and soft singular regions and calculate their contributions to the impact factor.
We then subtract the contribution due to the central region. Finally, we
combine the real corrections with the singular pieces of the virtual corrections
and obtain our finite results
Herwig++ 2.0 Release Note
A new release of the Monte Carlo program Herwig++ (version 2.0) is now
available. This is the first version of the program which can be used for
hadron-hadron physics and includes the full simulation of both initial- and
final-state QCD radiation.Comment: Source code and additional information available at
http://hepforge.cedar.ac.uk/herwig
Die „Sammlung Kriegsberichte (1. Weltkrieg)“ der Kriegsnachrichten-Sammelstelle des VII. Armeekorps an der Universität Münster
Die Arbeit untersucht Feldpostbriefe, die von der Kriegsnachrichten-Sammelstelle des VII Armeekorps am Historischen Seminar der Universität Münster für zukünftige (Wissenschaftler)-Generationen ausgewählt und archiviert wurden. Die Arbeit fragt einerseits nach den Kriegserlebnissen und Kriegsdeutungen der Briefeschreiber, andererseits aber auch nach dem Kriegsbild, das die Sammelstelle durch ihre Auswahl der Briefe der Nachwelt vermitteln wollte
Implications of non-linearities between cumulative CO2 emissions and CO2-induced warming for assessing the remaining carbon budget
To determine the remaining carbon budget, a new framework was introduced in the Intergovernmental Panel on Climate Change's Special Report on Global Warming of 1.5 °C (SR1.5). We refer to this as a 'segmented' framework because it considers the various components of the carbon budget derivation independently from one another. Whilst implementing this segmented framework, in SR1.5 the assumption was that there is a strictly linear relationship between cumulative CO2 emissions and CO2-induced warming i.e. the TCRE is constant and can be applied to a range of emissions scenarios. Here we test whether such an approach is able to replicate results from model simulations that take the climate system's internal feedbacks and non-linearities into account. Within our modelling framework, following the SR1.5's choices leads to smaller carbon budgets than using simulations with interacting climate components. For 1.5 °C and 2 °C warming targets, the differences are 50 GtCO2 (or 10%) and 260 GtCO2 (or 17%), respectively. However, by relaxing the assumption of strict linearity, we find that this difference can be reduced to around 0 GtCO2 for 1.5 °C of warming and 80 GtCO2 (or 5%) for 2.0 °C of warming (for middle of the range estimates of the carbon cycle and warming response to anthropogenic emissions). We propose an updated implementation of the segmented framework that allows for the consideration of non-linearities between cumulative CO2 emissions and CO2-induced warming
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