43 research outputs found
Does player specialization predict player actions? Evidence from penalty kicks at FIFA World Cup and UEFA Euro Cup
Penalty-kicks are analysed in the literature as `real life experiments' for assessing the use of rational mixed strategies by professional players. However, each penalty kick cannot be considered a repetition of the same event because of the varying background conditions, in particular the heterogeneous ability of different players. Consequently, aggregate statistics over datasets composed of a large number of penalty kicks mediate the behaviour of the players in \emph{different} games, and the properties of optimal mixed strategies cannot be tested directly because of \emph{aggregation bias}. In this paper we model the heterogeneous ability of players. We then test the hypothesis that differently talented players randomise over different actions. To this aim, we study a dataset that collects penalties kicked during shootout series in the last editions of FIFA World-Cup and UEFA Euro-Cup (1994-2012) where kickers are categorized as specialists and non-specialists. The results support our theoretical prediction
Pion photoproduction on nucleons in a covariant hadron-exchange model
We present a relativistic dynamical model of pion photoproduction on the
nucleon in the resonance region. It offers several advances over the existing
approaches. The model is obtained by extending our -scattering
description to the electromagnetic channels. The resulting photopion amplitude
is thus unitary in the , \ga N channel space, Watson's theorem is
exactly satisfied. At this stage we have included the pion, nucleon,
\De(1232)-resonance degrees of freedom. The and meson
exchanges are also included, but play a minor role in the considered energy
domain (up to GeV). In this energy range the model provides a
good description of all the important multipoles. We have allowed for only two
free parameters -- the photocouplings of the -resonance. These
couplings are adjusted to reproduce the strength of corresponding
resonant-multipoles and at the resonance position.Comment: 17 pages, 4 figs, version to appear in Phys. Rev. C 70 (2004
Multipole Strength Distributions in 16-O Above the Dipole Resonance Region
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Monte Carlo Simulation of the Photon-Tagger Focal-Plane Electronics at the MAX IV Laboratory
Rate-dependent effects in the electronics used to instrument the tagger focal
plane at the MAX IV Laboratory have been investigated using the novel approach
of Monte Carlo simulation. Results are compared to analytical calculations as
well as experimental data for both specialized testing and production running
to demonstrate a thorough understanding of the behavior of the detector system.Comment: 31 pages, 17 figures, modified after submission to Nuclear
Instruments and Methods in Physics Research Section
New Measurement of Compton Scattering from the Deuteron and an Improved Extraction of the Neutron Electromagnetic Polarizabilities
The electromagnetic polarizabilities of the nucleon are fundamental
properties that describe its response to external electric and magnetic fields.
They can be extracted from Compton-scattering data --- and have been, with good
accuracy, in the case of the proton. In contradistinction, information for the
neutron requires the use of Compton scattering from nuclear targets. Here we
report a new measurement of elastic photon scattering from deuterium using
quasimonoenergetic tagged photons at the MAX IV Laboratory in Lund, Sweden.
These first new data in more than a decade effectively double the world
dataset. Their energy range overlaps with previous experiments and extends it
by 20 MeV to higher energies. An analysis using Chiral Effective Field Theory
with dynamical \Delta(1232) degrees of freedom shows the data are consistent
with and within the world dataset. After demonstrating that the fit is
consistent with the Baldin sum rule, extracting values for the isoscalar
nucleon polarizabilities and combining them with a recent result for the
proton, we obtain the neutron polarizabilities as \alpha_n = [11.55 +/-
1.25(stat) +/- 0.2(BSR) +/- 0.8(th)] X 10^{-4} fm^3 and \beta_n = [3.65 -/+
1.25(stat) +/- 0.2(BSR) -/+ 0.8(th)] X 10^{-4} fm3, with \chi^2 = 45.2 for 44
degrees of freedom.Comment: 6 pages, 3 figures, comments from Physical Review Letters Referees
addresse
Report on Experiment E349: Quasifree Radiative Capture in the Deuteron
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
The (p,n) Reaction at Intermediate Energies with the Isotopes of Oxygen (16,17,18-O) and 9-Be as Part of a Unified Approach to the Study of These Nuclei
This work was supported by the National Science Foundation Grant NSF PHY 78-22774 A02 & A03 and by Indiana Universit
Chiral Dynamics in Photo-Pion Physics: Theory, Experiment, and Future Studies at the HIS Facility
A review of photo-pion experiments on the nucleon in the near threshold
region is presented. Comparisons of the results are made with the predictions
of the low energy theorems of QCD calculated using chiral perturbation theory
(ChPT) which is based on the spontaneous breaking of chiral symmetry as well as
its explicit breaking due to the finite quark masses. As a result of the
vanishing of the threshold amplitudes in the chiral limit, the experiments are
difficult since the cross sections are small. Nevertheless the field has been
brought to a mature stage of accuracy and sensitivity. The accomplishments and
limitations of past experiments are discussed. Future planned experiments at
Mainz and HIS using polarization observables are discussed as a more
rigorous test of theoretical calculations. Emphasis is given to the technical
developments that are required for the HIS facility. It is shown that
future experiments will provide more accurate tests of ChPT and will be
sensitive to isospin breaking dynamics due to the mass difference of the up and
down quarks.Comment: 61 pages, 10 figures, 2 table
Compton Scattering from the Deuteron Above Pion-Production Threshold
The electromagnetic polarizabilities of the nucleon are fundamental nucleon-structure observables that characterize its response to external electromagnetic fields. The neutron polarizabilities can be accessed from Compton-scattering data on light nuclear targets. Recent measurements of the differential cross section for Compton scattering on the deuteron below the pion-production threshold have decreased the uncertainties in the neutron polarizabilities, yet the proton polarizabilities remain known substantially more accurately. As the sensitivity of the cross section to the polarizabilities increases with incident photon energy, measurements above the pion threshold may offer a way for an improved determination of the neutron polarizabilities. In this Rapid Communiciation, the first measurement of the cross section for coherent Compton scattering on the deuteron above the pion-production threshold is presented
Field theory of nucleon to higher-spin baryon transitions
We discuss the nucleon to higher-spin - and -resonance transitions
by pions and photons. The higher-spin baryons are described by Rarita-Schwinger
fields and, as we argue, this imposes a stringent consistency requirement on
the form of the couplings. Popular and couplings
are inconsistent from this point of view. We construct examples of consistent
interactions with the same nonrelativistic limit as the conventional ones.Comment: 5 pages, Revtex, 1 PostScript figure; published versio