Center of mass integral in canonical general relativity

For a two-surface B tending to an infinite--radius round sphere at spatial infinity, we consider the Brown--York boundary integral H_B belonging to the energy sector of the gravitational Hamiltonian. Assuming that the lapse function behaves as N \sim 1 in the limit, we find agreement between H_B and the total Arnowitt--Deser--Misner energy, an agreement first noted by Braden, Brown, Whiting, and York. However, we argue that the Arnowitt--Deser--Misner mass--aspect differs from a gauge invariant mass--aspect by a pure divergence on the unit sphere. We also examine the boundary integral H_B corresponding to the Hamiltonian generator of an asymptotic boost, in which case the lapse N \sim x^k grows like one of the asymptotically Cartesian coordinate functions. Such an integral defines the kth component of the center of mass for a Cauchy surface \Sigma bounded by B. In the large--radius limit, we find agreement between H_B and an integral introduced by Beig and O'Murchadha. Although both H_B and the Beig--O'Murchadha integral are naively divergent, they are in fact finite modulo the Hamiltonian constraint. Furthermore, we examine the relationship between H_B and a certain two--surface integral linear in the spacetime Riemann curvature tensor. Similar integrals featuring the curvature appear in works by Ashtekar and Hansen, Penrose, Goldberg, and Hayward. Within the canonical 3+1 formalism, we define gravitational energy and center--of--mass as certain moments of Riemann curvature.Comment: 52 pages, revtex4, uses amsmath and amssym

Intestinal helminths of four species of skinks (Mabuya) (Sauria: Scincidae) from southern Africa

Intestinal helminths are reported from four species of scincid lizards from southern Africa: Mabuya occidentalis, Mabuya spilogaster, Mabuya striata and Mabuya variegata. The helminth fauna consisted of one species of Cestoda, Oochoristica truncata and five species of Nematoda, Abbreviata paradoxa, Maxvachonia dimorpha, Parapharyngodon rotundatus, Spauligodon petersi and Thubunaea fitzsimonsi. All findings represent new host records. Ascarid larvae were also found. It appears that Mabuya is infected by generalist helminths that occur in other species of African lizards.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat v.9 was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.mn201

Measurement of the Michel Parameters in Leptonic Tau Decays

The Michel parameters of the leptonic tau decays are measured using the OPAL detector at LEP. The Michel parameters are extracted from the energy spectra of the charged decay leptons and from their energy-energy correlations. A new method involving a global likelihood fit of Monte Carlo generated events with complete detector simulation and background treatment has been applied to the data recorded at center-of-mass energies close to sqrt(s) = M(Z) corresponding to an integrated luminosity of 155 pb-1 during the years 1990 to 1995. If e-mu universality is assumed and inferring the tau polarization from neutral current data, the measured Michel parameters are extracted. Limits on non-standard coupling constants and on the masses of new gauge bosons are obtained. The results are in agreement with the V-A prediction of the Standard Model.Comment: 32 pages, LaTeX, 9 eps figures included, submitted to the European Physical Journal

A Measurement of the Product Branching Ratio f(b->Lambda_b).BR(Lambda_b->Lambda X) in Z0 Decays

The product branching ratio, f(b->Lambda_b).BR(Lambda_b->Lambda X), where Lambda_b denotes any weakly-decaying b-baryon, has been measured using the OPAL detector at LEP. Lambda_b are selected by the presence of energetic Lambda particles in bottom events tagged by the presence of displaced secondary vertices. A fit to the momenta of the Lambda particles separates signal from B meson and fragmentation backgrounds. The measured product branching ratio is f(b->Lambda_b).BR(Lambda_b->Lambda X) = (2.67+-0.38(stat)+0.67-0.60(sys))% Combined with a previous OPAL measurement, one obtains f(b->Lambda_b).BR(Lambda_b->Lambda X) = (3.50+-0.32(stat)+-0.35(sys))%.Comment: 16 pages, LaTeX, 3 eps figs included, submitted to the European Physical Journal

First Measurement of Z/gamma* Production in Compton Scattering of Quasi-real Photons

We report the first observation of Z/gamma* production in Compton scattering of quasi-real photons. This is a subprocess of the reaction e+e- to e+e-Z/gamma*, where one of the final state electrons is undetected. Approximately 55 pb-1 of data collected in the year 1997 at an e+e- centre-of-mass energy of 183 GeV with the OPAL detector at LEP have been analysed. The Z/gamma* from Compton scattering has been detected in the hadronic decay channel. Within well defined kinematic bounds, we measure the product of cross-section and Z/gamma* branching ratio to hadrons to be (0.9+-0.3+-0.1) pb for events with a hadronic mass larger than 60 GeV, dominated by (e)eZ production. In the hadronic mass region between 5 GeV and 60 GeV, dominated by (e)egamma* production, this product is found to be (4.1+-1.6+-0.6) pb. Our results agree with the predictions of two Monte Carlo event generators, grc4f and PYTHIA.Comment: 18 pages, LaTeX, 5 eps figures included, submitted to Physics Letters

Search for Higgs Bosons in e+e- Collisions at 183 GeV

The data collected by the OPAL experiment at sqrts=183 GeV were used to search for Higgs bosons which are predicted by the Standard Model and various extensions, such as general models with two Higgs field doublets and the Minimal Supersymmetric Standard Model (MSSM). The data correspond to an integrated luminosity of approximately 54pb-1. None of the searches for neutral and charged Higgs bosons have revealed an excess of events beyond the expected background. This negative outcome, in combination with similar results from searches at lower energies, leads to new limits for the Higgs boson masses and other model parameters. In particular, the 95% confidence level lower limit for the mass of the Standard Model Higgs boson is 88.3 GeV. Charged Higgs bosons can be excluded for masses up to 59.5 GeV. In the MSSM, mh > 70.5 GeV and mA > 72.0 GeV are obtained for tan{beta}>1, no and maximal scalar top mixing and soft SUSY-breaking masses of 1 TeV. The range 0.8 < tanb < 1.9 is excluded for minimal scalar top mixing and m{top} < 175 GeV. More general scans of the MSSM parameter space are also considered.Comment: 49 pages. LaTeX, including 33 eps figures, submitted to European Physical Journal

Morphological divergence and reduced ectoparasite prevalence in an introduced population of a Caribbean anole

As biological invasions become increasingly common understanding what factors drive a species’ ability to rapidly colonize new habitats will be important for future conservation management. Theoretical models predict that spatial sorting of an invasive population will select for enhanced dispersal-related traits and lower prevalence of parasitic infections. Supporting these, there is a growing body of evidence that demonstrates both features are common in invasive populations, although, these observations stem from mainland systems, over larger spatial scales. Here, we investigated the morphology and ectoparasite prevalence of Maynard\u27s anole (Anolis maynardi) in its native range Little Cayman, and across its introduced range Cayman Brac where it invaded 31 years ago. We tested for morphological divergence, ectoparasite prevalence between the native population and the core, intermediate and range edge populations within the introduced range. In addition, we compared the overall body condition of lizards from each sex between islands using the scaled-mass index. Our results suggest that spatial sorting could have selected for less parasitized individuals on the range edge of the introduced population, across an area of just 39 km2. However, there was no difference in hind-limb length, the character that is expected to enhance dispersal ability, across the range of the introduced population. Instead, the greatest variation in morphology across the introduced range was found in fore-limb length. Finally, both males and females from the introduced population were of significantly higher body condition than the native population, yet ectoparasite intensity had no effect on the body condition of infested hosts. These results highlight the rapid change in forelimb length and overall morphology has occurred rapidly since the species’ first introduction and a clear reduction in parasite prevalence on the range edge of the introduced population. Together these attributes have likely contributed to the successful colonization of Cayman Brac by A. maynardi

A description of parasites from mountain wolf snakes, Lycodon ruhstrati ruhstrati (Serpentes: Colubridae), from two localities in western Taiwan

Non

A search for neutral Higgs bosons in the MSSM and models with two scalar field doublets

A search is described for the neutral Higgs bosons h^0 and A^0 predicted by models with two scalar field doublets and, in particular, the Minimal Supersymmetric Standard Model (MSSM). The search in the Z^0 h^0 and h^0 A^0 production channels is based on data corresponding to an integrated luminosity of 25 pb^{-1} from e^+e^- collisions at centre-of-mass energies between 130 and 172GeV collected with the OPAL detector at LEP. The observation of a number of candidates consistent with Standard Model background expectations is used in combination with earlier results from data collected at the Z^0 resonance to set limits on m_h and m_A in general models with two scalar field doublets and in the MSSM. For example, in the MSSM, for tan(beta) > 1, minimal and maximal scalar top quark mixing and soft SUSY-breaking masses of 1 TeV, the 95% confidence level limits m_h > 59.0 GeV and m_A > 59.5 GeV are obtained. For the first time, the MSSM parameter space is explored in a detailed scan.A search is described for the neutral Higgs bosons h^0 and A^0 predicted by models with two scalar field doublets and, in particular, the Minimal Supersymmetric Standard Model (MSSM). The search in the Z^0 h^0 and h^0 A^0 production channels is based on data corresponding to an integrated luminosity of 25 pb^{-1} from e^+e^- collisions at centre-of-mass energies between 130 and 172 GeV collected with the OPAL detector at LEP. The observation of a number of candidates consistent with Standard Model background expectations is used in combination with earlier results from data collected at the Z^0 resonance to set limits on m_h and m_A in general models with two scalar field doublets and in the MSSM. For example, in the MSSM, for tan(beta) > 1, minimal and maximal scalar top quark mixing and soft SUSY-breaking masses of 1 TeV, the 95% confidence level limits m_h > 59.0 GeV and m_A > 59.5 GeV are obtained. For the first time, the MSSM parameter space is explored in a detailed scan

Measurement of the B+B^{+} and B0B^{0} lifetimes and search for CP(T) violation using reconstructed secondary vertices

The lifetimes of the B+ and B0 mesons, and their ratio, have been measured in the OPAL experiment using 2.4 million hadronic Z0 decays recorded at LEP. Z0 -> b bbar decays were tagged using displaced secondary vertices and high momentum electrons and muons. The lifetimes were then measured using well-reconstructed charged and neutral secondary vertices selected in this tagged data sample. The results are tau(B+) = 1.643 +- 0.037 +- 0.025 ps tau(B0) = 1.523 +- 0.057 +- 0.053 ps ratio tau(B+)/tau(B0) = 1.079 +- 0.064 +- 0.041 where in each case the first error is statistical and the second systematic. A larger data sample of 3.1 million hadronic Z0 decays has been used to search for CP and CPT violating effects by comparison of inclusive b and bbar hadron decays. No evidence for such effects is seen. The CP violation parameter Re(epsilon_B) is measured to be Re(epsilon_B) = 0.001 +- 0.014 +- 0.003 and the fractional difference between b and bbar hadron lifetimes is measured to be -0.001 +- 0.012 +- 0.00