29,380 research outputs found
Diffractive Final States with the H1 Detector at HERA
Recent measurements of diffractive dijet and charm quark production in
electron-proton collisions using the H1 detector at HERA are presented, where
the exchanged photon is either almost real or highly virtual. The data are
compared with leading and next-to-leading order QCD calculations based on the
diffractive parton distributions obtained from a recent DGLAP QCD analysis of
H1 inclusive diffractive deep-inelastic scattering data, thus testing QCD
factorization in diffractive ep interactions.Comment: 3 pages, 6 figures, to appear in the proceedings of the Intl.
Europhysics Conference on High Energy Physics EPS 2003, Aachen, July 200
Measurements of the Top Quark Pair-Production Cross Section
Measurements of the inclusive and differential cross section for the
production of top quark pairs in proton-(anti)proton collision at
center-of-mass energies of 1.96, 7.0 and 8.0 TeV are presented and compared
with the latest theory predictions and Monte-Carlo models. In addition, first
measurements of the production of top quark pairs in association with
additional jets or with a boson are highlighted. All measurements are in good
agreement with the Standard Model.Comment: 6 pages, 11 figures, proceedings of HCP2012, Kyoto (Japan
Exterior and Symmetric Powers of Modules for Cyclic 2-Groups
We prove a recursive formula for the exterior and symmetric powers of modules
for a cyclic 2-group. This makes computation straightforward. Previously, a
complete description was only known for cyclic groups of prime order
Learning flexibility: the environment and a case study
This paper outlines the flexible student learning environment in the Faculty of Engineering and Surveying, before concentrating on evaluating one online learning option. This Faculty provides a variety of high quality on-campus, distance education and on-line academic programmes and various learning strategies for the heterogeneous student cohort (national and international). By accessing appropriate flexible learning and different learning experiences, students are empowered to determine learning opportunities and methodologies to suit their personal needs.
The off-campus mode study may disadvantage students since they donât have the benefit of face-to-face instructions or to participate in formative assessments delivered informally in lectures. This may lead to feelings of remoteness and isolation leading to poorer learning, lower results in assessments, and may also contribute to drop-out rates, particularly in first year courses. To overcome this inequity, the usual training materials presented for a first year course in 2005 were supplemented with PowerPoint lectures, enhanced with synchronous audio, and a series of quizzes to be used as formative assessments. The lectures and quizzes were presented online via a course web site and were designed to become an integral part of the learning experience. An evaluation of the effectiveness of these strategy demonstrated improved students' learning, a positive contribution to the learning experience, increased enjoyment of the course, and a strong learning motivator. Students reported feeling less disenfranchised with the university and having a greater affinity with the lecturer
Particle Acceleration in Gamma-Ray Burst Jets
Gradual shear acceleration of energetic particles in gamma-ray burst (GRB)
jets is considered. Special emphasis is given to the analysis of universal
structured jets, and characteristic acceleration timescales are determined for
a power-law and a Gaussian evolution of the bulk flow Lorentz factor
with angle from the jet axis. The results suggest that local power-law
particle distributions may be generated and that higher energy particles are
generally concentrated closer to the jet axis. Taking several constraints into
account we show that efficient electron acceleration in gradual shear flows,
with maximum particle energy successively decreasing with time, may be possible
on scales larger than cm, provided the jet magnetic field
becomes sufficiently weak and/or decreases rapidly enough with distance, while
efficient acceleration of protons to ultra-high energies eV may be
possible under a wide range of conditions.Comment: 11 pages, 3 figures; ApJ Letters accepted; final version: small typos
corrected in order to match published versio
HERA Diffractive Structure Function Data and Parton Distributions
Recent diffractive structure function measurements by the H1 and ZEUS
experiments at HERA are reviewed. Various data sets, obtained using
systematically different selection and reconstruction methods, are compared.
NLO DGLAP QCD fits are performed to the most precise H1 and ZEUS data and
diffractive parton densities are obtained in each case. Differences between the
Q^2 dependences of the H1 and ZEUS data are reflected as differences between
the diffractive gluon densities.Comment: Contributed to the Proceedings of the Workshop on HERA and the LHC,
DESY and CERN, 2004-200
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