Bear presence attracts avian predators but does not impact lesser snow goose daily nest attendance

The presence of foraging bears in Arctic breeding bird colonies has been increasingly reported in the literature, and these may constitute disturbance events which cause incubating birds to leave their nest. Avian predators may associate with bears during such events, likely to capitalize on unattended nests in the presence of bears. Here, we estimated changes in daily nest attendance of lesser snow geese Anser caerulescens caerulescens in the presence of foraging bears, and estimated the association between foraging bears and avian predators. We predicted decreased nest attendance by geese on days with bears, and close associations between avian predators and bears. We monitored snow goose nests with cameras from 2013 to 2018 to assess nest attendance behaviours on days when bears were in the colony compared to control days without bears. When bears were present in colonies, we estimated the probability of avian predator occurrence compared to control periods. When controlling for day of incubation and camera placement types, we found no significant effects of bears on daily nest attendance behaviours of snow geese (n = 85). We found a significantly higher probability of observing avian predators when bears were present (0.72) compared to control periods without bears (0.11). We show that snow geese do not alter daily nest attendance in the presence of foraging bears, and suggest this is due to the presence of avian predators

Improved W boson mass measurement with the D0 detector

We have measured the W boson mass using the D0 detector and a data sample of 82 pb^-1 from the Tevatron collider. This measurement used W -> e nu decays, where the electron is close to a boundary of a central electromagnetic calorimeter module. Such 'edge' electrons have not been used in any previous D0 analysis, and represent a 14% increase in the W boson sample size. For these electrons, new response and resolution parameters are determined, and revised backgrounds and underlying event energy flow measurements are made. When the current measurement is combined with previous D0 W boson mass measurements, we obtain M_W = 80.483 +/- 0.084 GeV. The 8% improvement from the previous D0 measurement is primarily due to the improved determination of the response parameters for non-edge electrons using the sample of Z bosons with non-edge and edge electrons.Comment: submitted to Phys. Rev. D; 20 pages, 18 figures, 9 table

Measurement of the Top Quark Mass in the Dilepton Channel

We report a measurement of the top quark mass using six candidate events for the process pbarp->ttbar->l^+ nu l^- nubar b bbar + X, observed in the D0 experiment at the Fermilab ppbar collider. Using maximum likelihood fits to the dynamics of the decays, we measure a mass for the top quark of m(top) = 168.4 +- 12.3 (stat) +- 3.6 (syst) GeV/c^2. We combine this result with our previous measurement in the ttbar->l+jets channel to obtain m(top) = 172.1 +- 7.1 GeV/c^2 as the best value of the mass of the top quark measured by D0.Comment: 48 pages, 22 figures (encapsultaed postscript), Submitted for publication in Physical Review

High-pT jets in p¯p collisions at s=630 and 1800 GeV

Results are presented from analyses of jet data produced in pp̅ collisions at √s=630 and 1800 GeV collected with the DØ detector during the 1994–1995 Fermilab Tevatron Collider run. We discuss the details of detector calibration, and jet selection criteria in measurements of various jet production cross sections at √s=630 and 1800 GeV. The inclusive jet cross sections, the dijet mass spectrum, the dijet angular distributions, and the ratio of inclusive jet cross sections at √s=630 and 1800 GeV are compared to next-to-leading-order QCD predictions. The order αs3 calculations are in good agreement with the data. We also use the data at √s=1800 GeV to rule out models of quark compositeness with a contact interaction scale less than 2.2 TeV at the 95% confidence level