Top quark production cross-section at the Tevatron Run 2

The top quark pair production cross-section ${\sigma}_{t\bar{t}}$ has been measured in $p\bar{p}$ collisions at center of mass energies of 1.96 TeV using Tevatron Run 2 data. In the begining of Run 2 both CDF and D\O\ $\sigma_{t\bar{t}}$ measurements in the {\it dilepton} channel $t\bar{t}{\to}WbW\bar{b}{\to}\bar{\ell}{\nu}_{\ell}b{\ell}^{'}\ bar{\nu}_{{\ell}^{'}}\bar{b}$and in the {\it lepton plus jets} channel$t\bar{t}{\to}WbW\bar{b}{\to}q\bar{q}^{'}b{\ell}\bar{\nu}_{\ell }\bar{b}+\bar{\ell}{\nu}_{\ell}bq\bar{q}^{'}\bar{b}$ agree with the NLO (Next-to-Leading-Order) theoretical predictions. The presence of a top signal in Tevatron data has been reestablished.Comment: 4 pages, 3 figure

On a static charged fluid around a magnetized mass

We show that any magnetostatic axially symmetric solution of the Einstein-Maxwell equations can be endowed with a specific charged fluid source of the Polanco et al type via a simple procedure requiring the knowledge of exclusively the magnetostatic seed spacetime. Using this procedure we construct yet another exact solution for a massive magnetic dipole surrounded by a static charged fluid which is different from the Polanco et al metric.Comment: 5 pages, no figures, submitted to Physical Review

Remarks on the mass-angular momentum relations for two extreme Kerr sources in equilibrium

The general analysis of the relations between masses and angular momenta in the configurations composed of two balancing extremal Kerr particles is made on the basis of two exact solutions arising as extreme limits of the well-known double-Kerr spacetime. We show that the inequality M^2 >= |J| characteristic of an isolated Kerr black hole is verified by all the extremal components of the Tomimatsu and Dietz-Hoenselaers solutions. At the same time, the inequality can be violated by the total masses and total angular momenta of these binary systems, and we identify all the cases when such violation occurs.Comment: 11 pages, 4 figure

A combined Majumdar-Papapetrou-Bonnor field as extreme limit of the double-Reissner-Nordstrom solution

The general extreme limit of the double-Reissner-Nordstrom solution is worked out in explicit analytical form involving prolate spheroidal coordinates. We name it the combined Majumdar-Papapetrou-Bonnor field to underline the fact that it contains as particular cases the two-body specialization of the well-known Majumdar-Papapetrou solution and Bonnor's three-parameter electrostatic field. To the latter we give a precise physical interpretation as describing a pair of non-rotating extremal black holes with unequal masses and unequal opposite charges kept apart by a strut, the absolute values of charges exceeding the respective (positive) values of masses.Comment: 10 pages, 3 figures, title changed, the result extended, matching the published versio

Utility analysis : current trends and future directions.

Utility analysis procedures offer organizational decision-makers useful information regarding the relative values of different interventions. Years of research have resulted in a number of practically viable utility models and extensions. There is a continued need for research to examine the accuracy of utility estimates and to further compare the different models. A more recent research concern is that of low levels of acceptance of utility analysis results by practitioners. Many researchers are turning their attention to ways in which this acceptance may be increased. This article reviews different utility models as well as a number of important extensions. It then discusses current utility analysis issues, such as the aforementioned acceptance problem and the introduction of a multi-attribute utility model. The article concludes with suggestions for future utility analysis researchUtility theory; Mathematical models; Decision making;

Experimental determination of the b quark mass in DELPHI

The running mass of the b quark as defined in the MS-bar renormalization scheme, m_b, was measured at the M_Z scale using 2.8 million hadronic Z^0 decays collected by the DELPHI experiment at LEP. The result is m_b(M_Z) = 2.67 +- 0.25 (stat.) +- 0.34 (frag.) +- 0.27(theo.) GeV/c^2 which differs from that obtained at the Upsilon scale, by m_b(M_\Upsilon/2)-m_b(M_Z) = 1.49 +- 0.52 GeV/c^2. This measurement, performed far from the $b\bar{b}$ production threshold, provides the first experimental observation of the running of the quark masses.Comment: Talk given at the QCD 97 conference held in Montpellier, July 1997. Also available here http://hep.ph.liv.ac.uk/~martis