Thermal Dileptons from Hot and Dense Strongly Interacting Matter

The NA60 experiment at the CERN SPS has studied muon-pair production in 158A GeV In-In collisions. The unprecedented precision of the data has allowed to isolate a strong excess of pairs above the known sources in the whole invariant mass region 0.2<M<2.6 GeV. The (mostly) Planck-like shape of the mass spectra, exponential m_T spectra, zero polarization and the general agreement with thermal-model results allow for a consistent interpretation of the excess dimuons as thermal radiation from a randomized system. For M<1 GeV, the process pi+pi- -> rho -> mu+mu- dominates. The associated space-time averaged rho spectral function shows a nearly diverging width in approaching chiral symmetry restoration, but essentially no shift in mass. Some in-medium effects are also seen for the omega, but not for the phi. For M>1 GeV, the average temperature associated with the mass spectrum is about 200 MeV, considerably above T_c=170 MeV, implying a transition to dominantly partonic emission sources in this region. The transition itself is mirrored by a large jump-like drop in the inverse slope of the transverse mass spectra around 1 GeV.Comment: 10 pages, 6 figures, Proceedings of Chiral 2010 (Valencia, June 21-24, 2010

Period, epoch and prediction errors of ephemeris from continuous sets of timing measurements

Space missions such as Kepler and CoRoT have led to large numbers of eclipse or transit measurements in nearly continuous time series. This paper shows how to obtain the period error in such measurements from a basic linear least-squares fit, and how to correctly derive the timing error in the prediction of future transit or eclipse events. Assuming strict periodicity, a formula for the period error of such time series is derived: sigma_P = sigma_T (12/( N^3-N))^0.5, where sigma_P is the period error; sigma_T the timing error of a single measurement and N the number of measurements. Relative to the iterative method for period error estimation by Mighell & Plavchan (2013), this much simpler formula leads to smaller period errors, whose correctness has been verified through simulations. For the prediction of times of future periodic events, the usual linear ephemeris where epoch errors are quoted for the first time measurement, are prone to overestimation of the error of that prediction. This may be avoided by a correction for the duration of the time series. An alternative is the derivation of ephemerides whose reference epoch and epoch error are given for the centre of the time series. For long continuous or near-continuous time series whose acquisition is completed, such central epochs should be the preferred way for the quotation of linear ephemerides. While this work was motivated from the analysis of eclipse timing measures in space-based light curves, it should be applicable to any other problem with an uninterrupted sequence of discrete timings for which the determination of a zero point, of a constant period and of the associated errors is needed.Comment: Astronomy and Astrophysics, accepte

Specification and estimation of spatial econometric models : A discussion of alternative strategies for spatial economic modelling

The semantical insufficiency of (spatial) economic theories necessitates the making of additional assumptions — thereby introducing substantial specification uncertainty — in order to arrive at a fully specified econometric model. The traditional or current approach to econometric modelling treats specification uncertainty inadequately. This proposition is illustrated by two well-known examples from the spatial economic literature. Two alternative specification strategies for spatial economic modelling — designed to improve the current spatial econometric modelling approach — are proposed. One of these strategies is used for a specification analysis of agricultural output in Eire

Experimental Conference Summary

Experimental summary talk given at International Conference on Ultrarelativistic Nucleus-Nucleus Collisions (QM2001), Stony Brook, New York, 15-20 Jan 2001.Comment: Proceedings of a summary talk given at International Conference on Ultrarelativistic Nucleus-Nucleus Collisions (QM2001), Stony Brook, New York, 15-20 Jan 200