115 research outputs found
Novel Approach to Confront Electroweak Data and Theory
A novel approach to study electroweak physics at one-loop level in generic
theories is introduced. It separates the 1-loop
corrections into two pieces: process specific ones from vertex and box
contributions, and universal ones from contributions to the gauge boson
propagators. The latter are parametrized in terms of four effective form
factors , , and corresponding to the , , and
propagators. Under the assumption that only the Standard Model contributes to
the process specific corrections, the magnitudes of the four form factors are
determined at and at q^2=\mmz by fitting to all available precision
experiments. These values are then compared systematically with predictions of
theories. In all fits \alpha_s(\mz) and
\bar{\alpha}(\mmz) are treated as external parameters in order to keep the
interpretation as flexible as possible. The treatment of the electroweak data
is presented in detail together with the relevant theoretical formulae used to
interpret the data. No deviation from the Standard Model has been identified.
Ranges of the top quark and Higgs boson masses are derived as functions of
\alpha_s(\mz) and \bar{\alpha}(\mmz). Also discussed are consequences of
the recent precision measurement of the left-right asymmetry at SLC as well as
the impact of a top quark mass and an improved mass measurement.Comment: 123 pages, LaTeX (33 figures available via anonymous ftp),
KEK-TH-375, KEK preprint 93-159, KANAZAWA-94-19, DESY 94-002, YUMS 94-22,
SNUTP 94-82, to be published in Z.Phys.
Contracting on litigation
Two risk‐averse litigants with different subjective beliefs negotiate in the shadow of a pending trial. Through contingent contracts, the litigants can mitigate risk and/or speculate on the trial outcome. Contingent contracting decreases the settlement rate and increases the volume and costs of litigation. These contingent contracts mimic the services provided by third‐party investors, including litigation funders and insurance companies. The litigants (weakly) prefer to contract with risk‐neutral third parties when the capital market is transaction‐cost free. However, contracting with third parties further decreases the settlement rate, increases the costs of litigation, and may increase the aggregate cost of risk bearing.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149242/1/rand12274.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149242/2/rand12274_am.pd
Neutral weak currents in pion electroproduction on the nucleon
Parity violating asymmetry in inclusive scattering of longitudinally
polarized electrons by unpolarized protons with or meson
production, is calculated as a function of the momentum transfer squared
and the total energy of the -system. This asymmetry, which is
induced by the interference of the one-photon exchange amplitude with the
parity-odd part of the -exchange amplitude, is calculated for the
processes ( is a virtual photon and
a virtual Z-boson) considering the -contribution in the channel,
the standard Born contributions and vector meson ( and )
exchanges in the channel. Taking into account the known isotopic properties
of the hadron electromagnetic and neutral currents, we show that the P-odd term
is the sum of two contributions. The main term is model independent and it can
be calculated exactly in terms of fundamental constants. It is found to be
linear in . The second term is a relatively small correction which is
determined by the isoscalar component of the electromagnetic current. Near
threshold and in the -region, this isoscalar part is much smaller (in
absolute value) than the isovector one: its contribution to the asymmetry
depend on the polarization state (longitudinal or transverse) of the virtual
photon.Comment: 30 pages 9 figure
Precision Measurement of the Proton and Deuteron Spin Structure Functions g2 and Asymmetries A2
We have measured the spin structure functions g2p and g2d and the virtual
photon asymmetries A2p and A2d over the kinematic range 0.02 < x < 0.8 and 0.7
< Q^2 < 20 GeV^2 by scattering 29.1 and 32.3 GeV longitudinally polarized
electrons from transversely polarized NH3 and 6LiD targets. Our measured g2
approximately follows the twist-2 Wandzura-Wilczek calculation. The twist-3
reduced matrix elements d2p and d2n are less than two standard deviations from
zero. The data are inconsistent with the Burkhardt-Cottingham sum rule if there
is no pathological behavior as x->0. The Efremov-Leader-Teryaev integral is
consistent with zero within our measured kinematic range. The absolute value of
A2 is significantly smaller than the sqrt[R(1+A1)/2] limit.Comment: 12 pages, 4 figures, 2 table
Measurements of the -Dependence of the Proton and Neutron Spin Structure Functions g1p and g1n
The structure functions g1p and g1n have been measured over the range 0.014 <
x < 0.9 and 1 < Q2 < 40 GeV2 using deep-inelastic scattering of 48 GeV
longitudinally polarized electrons from polarized protons and deuterons. We
find that the Q2 dependence of g1p (g1n) at fixed x is very similar to that of
the spin-averaged structure function F1p (F1n). From a NLO QCD fit to all
available data we find at
Q2=5 GeV2, in agreement with the Bjorken sum rule prediction of 0.182 \pm
0.005.Comment: 17 pages, 3 figures. Submitted to Physics Letters
Measurement of the Charged Multiplicities in b, c and Light Quark Events from Z0 Decays
Average charged multiplicities have been measured separately in , and
light quark () events from decays measured in the SLD experiment.
Impact parameters of charged tracks were used to select enriched samples of
and light quark events, and reconstructed charmed mesons were used to select
quark events. We measured the charged multiplicities:
,
, from
which we derived the differences between the total average charged
multiplicities of or quark events and light quark events: and . We compared
these measurements with those at lower center-of-mass energies and with
perturbative QCD predictions. These combined results are in agreement with the
QCD expectations and disfavor the hypothesis of flavor-independent
fragmentation.Comment: 19 pages LaTex, 4 EPS figures, to appear in Physics Letters
Spatial representation for navigation in animats
This article considers the problem of spatial representation for animat navigation systems. It is proposed that the global navigation task, or "wayfinding, " is best supported by multiple interacting subsystems, each of which builds its own partial representation of relevant world knowledge. Evidence from the study of animal navigation is reviewed to demonstrate that similar principles underlie the wayfinding behavior of animals, including humans. A simulated wayfinding system is described that embodies and illustrates several of the themes identified with animat navigation. This system constructs a network of partial models of the quantitative spatial relations between groups of salient landmarks. Navigation tasks are solved by propagating egocentric view information through this network, using a simple but effective heuristic to arbitrate between multiple solutions
Measurement of the Bottom-Strange Meson Mixing Phase in the Full CDF Data Set
We report a measurement of the bottom-strange meson mixing phase \beta_s
using the time evolution of B0_s -> J/\psi (->\mu+\mu-) \phi (-> K+ K-) decays
in which the quark-flavor content of the bottom-strange meson is identified at
production. This measurement uses the full data set of proton-antiproton
collisions at sqrt(s)= 1.96 TeV collected by the Collider Detector experiment
at the Fermilab Tevatron, corresponding to 9.6 fb-1 of integrated luminosity.
We report confidence regions in the two-dimensional space of \beta_s and the
B0_s decay-width difference \Delta\Gamma_s, and measure \beta_s in [-\pi/2,
-1.51] U [-0.06, 0.30] U [1.26, \pi/2] at the 68% confidence level, in
agreement with the standard model expectation. Assuming the standard model
value of \beta_s, we also determine \Delta\Gamma_s = 0.068 +- 0.026 (stat) +-
0.009 (syst) ps-1 and the mean B0_s lifetime, \tau_s = 1.528 +- 0.019 (stat) +-
0.009 (syst) ps, which are consistent and competitive with determinations by
other experiments.Comment: 8 pages, 2 figures, Phys. Rev. Lett 109, 171802 (2012
Inclusive hadron photoproduction from longitudinally polarized protons and deuterons.
We report measurements of the asymmetry A_parallel for inclusive hadron production on longitudinally polarized proton and deuteron targets by circularly polarized photons. The photons were produced via internal and external bremsstrahlung from an electron beam of 48.35 GeV. Asymmetries for both positive and negative signed hadrons, and a subset of identified pions, were measured in the momentum range 1
Measurements of the dependence of the proton and neutron spin structure functions and
he structure functions g1p and g1n have been measured over the range 0.014 < x < 0.9 and 1 < Q2 < 40 GeV2 using deep-inelastic scattering of 48 GeV longitudinally polarized electrons from polarized protons and deuterons. We find that the Q2 dependence of g1p (g1n) at fixed x is very similar to that of the spin-averaged structure function F1p (F1n). From a NLO QCD fit to all available data we find at Q2=5 GeV2, in agreement with the Bjorken sum rule prediction of 0.182 \pm 0.005
- …