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 $q\bar{q}$ and one meson-meson channel, coupled to one another through quark exchange describing the $^3P_0$ 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 qqˉq\bar{q} 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 $^3P_0$ 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