Study of Zγ events and limits on anomalous ZZγ and Zγγ couplings in pp̄ collisions at s=1.96TeV

We present a measurement of the Zγ production cross section and limits on anomalous ZZγ and Zγγ couplings for form-factor scales of Λ=750 and 1000 GeV. The measurement is based on 138 (152) candidates in the eeγ (μμγ) final state using 320(290)pb-1 of pp̄ collisions at s=1.96TeV. The 95% C.L. limits on real and imaginary parts of individual anomalous couplings are |h10,30Z|<0.23, |h20,40Z|<0.020, |h10,30γ|<0.23, and |h20,40γ|<0.019 for Λ=1000GeV. © 2005 The American Physical Society

Search for particles decaying into a Z boson and a photon in p(p)over-bar collisions at root s=1.96 TeV

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Search for neutral supersymmetric higgs bosons in multijet events at s=1.96TeV

We have performed a search for neutral Higgs bosons produced in association with bottom quarks in pp collisions, using 260pb-1 of data collected with the D0 detector in Run II of the Fermilab Tevatron Collider. The cross sections for these processes are enhanced in many extensions of the standard model (SM), such as in its minimal supersymmetric extension at large tanâ□¡Î. The results of our analysis agree with expectations from the SM, and we use our measurements to set upper limits on the production of neutral Higgs bosons in the mass range of 90 to 150 GeV. © 2005 The American Physical Society

An environmental study of the macroinvertebrate fauna of three Hobart streams

Three adjacent streams, Cartwright Creek, Lambert Creek, and Sandy Bay Rivulet in the Hobart municipality have their upper catchments relatively unimpacted, but the lower reaches have been affected to various degrees by urban development. An investigation of their macroinvertebrate communities was undertaken to assess their potential usefulness in recognising the impact of development on these three streams. This investigation may provide baseline data and define indicator species which may be useful in the development of biological criteria for water quality assessment. Macroinvertebrate data collection was undertaken from March to November 1998. In total 59 species and 19 107 macroinvertebrate individuals from 9 sites were collected (three sites at each stream). Multivariate analysis including clustering (Two-way Indicator Species Analysis TWINSPAN) and ordination (semi-strong Hybrid Multidimentional Scaling HMDS) was used to recognise assemblages of species typical of each stream, site and season. Significant differences in species composition and diversity were found between the Sandy Bay Rivulet sites where site 1 was different from sites 2 and 3, and between the Cartwright Creek sites. No variation between the Lambert Creek sites was found. Results indicate a strong correlation between impacted sites lower in the catchment and the diversity of species as well as number of individuals. Pollution sensitive invertebrates (especially Ephemeroptera and Plecoptera) were found only at unimpacted sites in the higher reaches of the catchment, and were absent in all lower sites. No Ephemeroptera or Plecoptera were found in Lambert Creek. Two pollution tolerant species, the introduced snail Potamopyrgus antipodarum and the native crustacean Austrogammarus sp, were abundant in all lower sites. Results from this investigation therefore indicate that development has had some detrimental impact on macroinvertebrates at the three streams investigated

Measurement of gamma+b+X and gamma+c+X Production Cross Sections in pp[over ] Collisions at sqrt[s]=1.96 TeV.

First measurements of the differential cross sections d;{3}sigma/(dp_{T};{gamma}dy;{gamma}dy;{jet}) for the inclusive production of a photon in association with a heavy quark (b, c) jet are presented, covering photon transverse momenta 3015 GeV. The results are based on an integrated luminosity of 1 fb;{-1} in pp[over ] collisions at sqrt[s]=1.96 TeV recorded with the D0 detector at the Fermilab Tevatron Collider. The results are compared with next-to-leading order perturbative QCD predictions

Measurement of the tt̄ production cross section in pp̄ collisions at √s = 1.96 TeV using lepton + jets events with lifetime b-tagging

We present a measurement of the top quark pair (tt̄) production cross section (σtt̄) in pp̄ collisions at √s=1.96 TeV using 230 pb-1 of data collected by the DØ experiment at the Fermilab Tevatron Collider. We select events with one charged lepton (electron or muon), missing transverse energy, and jets in the final state. We employ lifetime-based b-jet identification techniques to further enhance the tt̄ purity of the selected sample. For a top quark mass of 175 GeV, we measure σtt̄=8.6-1.5+1.6(stat.+syst.) ±0.6(lumi.) pb, in agreement with the standard model expectation

Measurement of the inclusive jet cross section in pp̄ collisions at s=1.96TeV

We report on a measurement of the inclusive jet cross section in pp̄ collisions at a center-of-mass energy s=1.96TeV using data collected by the D0 experiment at the Fermilab Tevatron Collider corresponding to an integrated luminosity of 0.70fb-1. The data cover jet transverse momenta from 50 to 600 GeV and jet rapidities in the range -2.4 to 2.4. Detailed studies of correlations between systematic uncertainties in transverse momentum and rapidity are presented, and the cross section measurements are found to be in good agreement with next-to-leading order QCD calculations. © 2008 The American Physical Society

Search for excited electrons in ppbar collisions at sqrt(s) = 1.96 TeV

8 pages, 5 figures, submitted to Phys.Rev.D Rap.CommWe present the results of a search for the production of an excited state of the electron, e*, in proton-antiproton collisions at sqrt(s) = 1.96 TeV. The data were collected with the D0 experiment at the Fermilab Tevatron Collider and correspond to an integrated luminosity of approximately 1 fb^-1. We search for e* in the process ppbar -> e* e, with the e* subsequently decaying to an electron plus photon. No excess above the standard model background is observed. Interpreting our data in the context of a model that describes e* production by four-fermion contact interactions and e* decay via electroweak processes, we set 95% C.L. upper limits on the production cross section ranging from 8.9 fb to 27 fb, depending on the mass of the excited electron. Choosing the scale for contact interactions to be Lambda = 1 TeV, excited electron masses below 756 GeV are excluded at the 95% C.L

Search for a scalar or vector particle decaying into Zγ in p over(p, ̄) collisions at sqrt(s) = 1.96 TeV

We present a search for a narrow scalar or vector resonance decaying into Zγ with a subsequent Z boson decay into a pair of electrons or muons. The data for this search were collected with the DØ detector at the Fermilab Tevatron p over(p, ̄) collider at a center of mass energy sqrt(s) = 1.96   TeV. Using 1.1 (1.0) fb-1 of data, we observe 49 (50) candidate events in the electron (muon) channel, in good agreement with the standard model prediction. From the combination of both channels, we derive 95% C.L. upper limits on the cross section times branching fraction (σ × B) into Zγ. These limits range from 0.19 (0.20) pb for a scalar (vector) resonance mass of 600 GeV/ c2 to 2.5 (3.1) pb for a mass of 140 GeV/ c2