23,267 research outputs found
Radiative return at NLO and the measurement of the hadronic cross-section in electron-positron annihilation
Electron-positron annihilation into hadrons plus an energetic photon from
initial state radiation allows the hadronic cross-section to be measured over a
wide range of energies. The full next-to-leading order QED corrections for the
cross-section for e^+ e^- annihilation into a real tagged photon and a virtual
photon converting into hadrons are calculated where the tagged photon is
radiated off the initial electron or positron. This includes virtual and soft
photon corrections to the process e^+ e^- \to \gamma +\gamma^* and the emission
of two real hard photons: e^+ e^- \to \gamma + \gamma + \gamma^*. A Monte Carlo
generator has been constructed, which incorporates these corrections and
simulates the production of two charged pions or muons plus one or two photons.
Predictions are presented for centre-of-mass energies between 1 and 10 GeV,
corresponding to the energies of DAPHNE, CLEO-C and B-meson factories.Comment: 13 pages, 15 figure
Kinetic Monte Carlo simulations of oscillatory shape evolution for electromigration-driven islands
The shape evolution of two-dimensional islands under electromigration-driven
periphery diffusion is studied by kinetic Monte Carlo (KMC) simulations and
continuum theory. The energetics of the KMC model is adapted to the Cu(100)
surface, and the continuum model is matched to the KMC model by a suitably
parametrized choice of the orientation-dependent step stiffness and step atom
mobility. At 700 K shape oscillations predicted by continuum theory are
quantitatively verified by the KMC simulations, while at 500 K qualitative
differences between the two modeling approaches are found.Comment: 7 pages, 6 figure
Electroweak Sudakov Logarithms and Real Gauge-Boson Radiation in the TeV Region
Electroweak radiative corrections give rise to large negative,
double-logarithmically enhanced corrections in the TeV region. These are partly
compensated by real radiation and, moreover, affected by selecting
isospin-noninvariant external states. We investigate the impact of real gauge
boson radiation more quantitatively by considering different restricted final
state configurations. We consider successively a massive abelian gauge theory,
a spontaneously broken SU(2) theory and the electroweak Standard Model. We find
that details of the choice of the phase space cuts, in particular whether a
fraction of collinear and soft radiation is included, have a strong impact on
the relative amount of real and virtual corrections.Comment: 20 pages, 4 figure
Computing in Additive Networks with Bounded-Information Codes
This paper studies the theory of the additive wireless network model, in
which the received signal is abstracted as an addition of the transmitted
signals. Our central observation is that the crucial challenge for computing in
this model is not high contention, as assumed previously, but rather
guaranteeing a bounded amount of \emph{information} in each neighborhood per
round, a property that we show is achievable using a new random coding
technique.
Technically, we provide efficient algorithms for fundamental distributed
tasks in additive networks, such as solving various symmetry breaking problems,
approximating network parameters, and solving an \emph{asymmetry revealing}
problem such as computing a maximal input.
The key method used is a novel random coding technique that allows a node to
successfully decode the received information, as long as it does not contain
too many distinct values. We then design our algorithms to produce a limited
amount of information in each neighborhood in order to leverage our enriched
toolbox for computing in additive networks
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