1,345 research outputs found
The enforcement of speeding: should fines be higher for repeated offences?
Speed limits are a well-known instrument to improve traffic safety. However, speed limits alone are not enough; there is need for enforcement of these limits. When one observes fine structures for speed offences one often finds two characteristics. First, the fine increases with the severity of the violation. Secondly, the fine depends on the speeders' offence history. We focus on this last point and confront two fine structures, both increasing with speed: a uniform fine and a differentiated fine, which depends on the offence history. Drivers differ in their propensity to have an accident and hence in their expected accident costs. Literature then prescribes that the fine for bad drivers should be higher than for good drivers. However, the government does not know the type of the driver. We develop a model where the number of previous convictions gives information on the type of the driver. We find that the optimal fine structure depends on the probability of detection and on the strength of the relationship between the type and having a record. We illustrate this by means of a numerical example.
Relativistic Unitarized Quark/Meson Model in Momentum Space
An outline is given how to formulate a relativistic unitarized constituent
quark model of mesons in momentum space, employing harmonic quark confinement.
As a first step, the momentum-space harmonic-oscillator potential is solved in
a relativistically covariant, three-dimensional quasipotential framework for
scalar particles, using the spline technique. Then, an illustrative toy model
with the same dynamical equations but now one and one meson-meson
channel, coupled to one another through quark exchange describing the
mechanism, is solved in closed form on a spline basis. Conclusions are
presented on how to generalize the latter to a realistic multichannel
quark/meson model.Comment: Plain LaTeX, 12 pages, 2 EPS figures. Contribution to the Second
International Workshop on Hadron Physics, Effective Theories of Low Energy
QCD, 25-29 September, 2002 (Coimbra, Portugal
Comment on "Study of D(sJ) decays to D(*)K in inclusive e(+)e(-) interactions"
We comment on the recent observation of the decay mode D(sJ)(*)(2860)-->D(*)K
by the BABAR Collaboration [arXiv:0908.0806], and contest their peremptory
conclusion that the data exclude a 0(+) assignment for the D(sJ)(*)(2860). In
particular, we argue that the observed branching fraction
B(D(sJ)(*)(2860)-->D(*)K)/B(D(sJ)(*)(2860)-->DK)=1.1 pm 0.15 pm 0.19 supports
the existence of two largely overlapping resonances at about 2.86 GeV, namely a
pair of radially excited tensor 2(+) and scalar 0(+) c-sbar states. This
scenario is further justified by comparing with the corresponding excited
charmonium states. Also other aspects of the charm-strange spectrum are
discussed.Comment: regular LaTeX, 4 page
Modified Breit-Wigner formula for mesonic resonances describing OZI decays of confined states and the light scalar mesons
A general expression resembling Breit-Wigner formulae is derived for the
description of resonances which appear in meson-meson scattering. Starting
point is a unitarised meson model, but reduced to a simpler form and freed from
the specific assumption about the confining force. The parameters of the
resulting ``Resonance-Spectrum Expansion'' are directly related to the
confinement spectrum and the mechanism of valence-quark-pair creation
for OZI-allowed hadronic decay, and not to the central positions and widths of
resonances. The method also provides a straightforward explanation for the
origin of the light scalar mesons without requiring extra degrees of freedom.Comment: 21 pages, 6 figures included. v2, new figures with respect to the
movement of singularities in the complex energy plane. Discussion on model
dependence included. More references included. v3/4 extension
acknowledgements. v5, correction misspelling in citation to Karabarbounis and
Shaw's wor
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