Florix, an index to assess plant species in floodplains for nature conservation – Developed and tested along the river Danube

Natural floodplains are ecosystems with a diverse mosaic of habitats and site conditions, but also highly threatened due to anthropogenic pressures. Plant species occur in all habitat types and can indicate their value for nature conservation. To improve sustainable management of rivers and floodplains, several indices such as the River Ecosystem Service Index (RESI) have been developed. However, there are so far no assessment schemes for the entire range of floodplain plants. The common assessment approaches like biological integrity, achievement rates or threatened species (Red list), applying to other species groups or other ecosystems, are not appropriate in floodplains. Legal obligations and the need to restore floodplains clearly call for an index assessing the ecological value in a reference area which can be combined with a 5-scale assessment in accordance to established assessments like RESI or the Water Framework Directive. Five typical characteristics describing vascular plants’ adaptation to floodplain habitats were identified. These can be derived from published data sets available for all species in Germany. We checked these indicators for multicollinearity and selected three of them: species number, hydrodynamic indicators, nature conservation indicators. Species number highly correlate with habitat indicators and geographic occurrence. For the selected three indicators we determined thresholds to group habitats and their indicator rate to five classes (very low to very high value for nature conservation). These thresholds are valid for the river Danube and for the habitat types scrutinized in this study. The Florix approach was sensitive in data sets testing active against former floodplains and protected against unprotected areas: For the entire reference region ‘Danube floodplain’, Florix values were higher in the active floodplain and in the protected areas. Only the habitat type ‘water bodies’ showed better scores for habitats in the former floodplain, for ‘softwood forests’ the status of being part of a protected area had no effect. Florix results were validated in two case studies differing in land use intensity. The region with dominant agricultural use showed significantly lower values than that with a higher portion of forests and grasslands. Florix can be used for a floristic conservation status assessment at single habitat level or for the entity of a study region in comparison to a reference region. It allows to identify main pressures and to complement a habitat-type based evaluation. To achieve higher comparability, we should strive for a generalized monitoring in Europe like it is common in aquatic ecosystem monitoring

Modeling the Space Debris Environment with MASTER-2009 and ORDEM2010

Spacecraft analysis using ORDEM2010 uses a high-fidelity population model to compute risk to on-orbit assets. The ORDEM2010 GUI allows visualization of spacecraft flux in 2-D and 1-D. The population was produced using a Bayesian statistical approach with measured and modeled environment data. Validation of sizes 1mm is on-going

A simplified approach to analyze the space debris evolution in the low earth orbit

During the past 60 years the number of objects on Earth orbits has increased. So has the risk of collisions, which is likely to be the main driver for space debris generation in the future. This is important, for example, in densely populated regions like the sun-synchronous orbit at around 800 km altitude. In order to predict the future development of the debris environment numerical simulations can be used. These simulations are usually based on initial assumptions like the launch rate, the probability distribution of success of post mission disposal measures and the likelihood for catastrophic collisions. The computationally expensive Monte-Carlo method is employed for the random sampling of the defined events. Additionally, a propagator needs to process the objects to determine potential collision partners, increasing the demand for computing power even further. In this paper an analytical model is presented, which is based on source and sink mechanisms, like launches, collisions and explosions. In this approach different altitude shells and diameter bins, as well as four different object classes for intact objects and fragments, each on circular and eccentric orbits are considered. By using pre-computed tables for orbital lifetimes and decay rates, both the computational effort and complexity of the model are decreased. The model can be adjusted to reflect different forecasts by altering the decay and collision rates. The paper concludes by showing preliminary results and a discussion of the generic approach, which allows the model to be fitted against more computationally expensive Monte-Carlo simulations

Search for R-parity violating supersymmetry via the LLE couplings lambda_{121}, lambda_{122} or lambda_{133} in ppbar collisions at sqrt(s)=1.96 TeV

A search for gaugino pair production with a trilepton signature in the framework of R-parity violating supersymmetry via the couplings lambda_121, lambda_122, or lambda_133 is presented. The data, corresponding to an integrated luminosity of L~360/pb, were collected from April 2002 to August 2004 with the D0 detector at the Fermilab Tevatron Collider, at a center-of-mass energy of sqrt(s)=1.96 TeV. This analysis considers final states with three charged leptons with the flavor combinations eel, mumul, and eetau (l=e or mu). No evidence for supersymmetry is found and limits at the 95% confidence level are set on the gaugino pair production cross section and lower bounds on the masses of the lightest neutralino and chargino are derived in two supersymmetric models.Comment: 9 pages, 4 figures (fig2 includes 3 subfigures

Measurement of the Lifetime Difference in the B_s^0 System

We present a study of the decay B_s^0 -> J/psi phi We obtain the CP-odd fraction in the final state at time zero, R_perp = 0.16 +/- 0.10 (stat) +/- 0.02 (syst), the average lifetime of the (B_s, B_sbar) system, tau (B_s^0) =1.39^{+0.13}_{-0.16} (stat) ^{+0.01}_{-0.02} (syst) ps, and the relative width difference between the heavy and light mass eigenstates, Delta Gamma/Gamma = (Gamma_L - Gamma_H)/Gamma =0.24^{+0.28}_{-0.38} (stat) ^{+0.03}_{-0.04} (syst). With the additional constraint from the world average of the B_s^0$lifetime measurements using semileptonic decays, we find tau (B_s^0)= 1.39 +/- 0.06 ~ps and Delta Gamma/\Gamma = 0.25^{+0.14}_{-0.15}. For the ratio of the B_s^0 and B^0 lifetimes we obtain tau(B_s^0)/tau(B^0)} = 0.91 +/- 0.09 (stat) +/- 0.003 (syst).Comment: submitted to Phys. Rev. Lett. FERMILAB-PUB-05-324-

Measurement of Semileptonic Branching Fractions of B Mesons to Narrow D** States

Using the data accumulated in 2002-2004 with the DO detector in proton-antiproton collisions at the Fermilab Tevatron collider with centre-of-mass energy 1.96 TeV, the branching fractions of the decays B -> \bar{D}_1^0(2420) \mu^+ \nu_\mu X and B -> \bar{D}_2^{*0}(2460) \mu^+ \nu_\mu X and their ratio have been measured: BR(\bar{b}->B) \cdot BR(B-> \bar{D}_1^0 \mu^+ \nu_\mu X) \cdot BR(\bar{D}_1^0 -> D*- pi+) = (0.087+-0.007(stat)+-0.014(syst))%; BR(\bar{b}->B)\cdot BR(B->D_2^{*0} \mu^+ \nu_\mu X) \cdot BR(\bar{D}_2^{*0} -> D*- \pi^+) = (0.035+-0.007(stat)+-0.008(syst))%; and (BR(B -> \bar{D}_2^{*0} \mu^+ \nu_\mu X)BR(D2*0->D*- pi+)) / (BR(B -> \bar{D}_1^{0} \mu^+ \nu_\mu X)\cdot BR(\bar{D}_1^{0}->D*- \pi^+)) = 0.39+-0.09(stat)+-0.12(syst), where the charge conjugated states are always implied.Comment: submitted to Phys. Rev. Let

Search for right-handed W bosons in top quark decay

We present a measurement of the fraction f+ of right-handed W bosons produced in top quark decays, based on a candidate sample of $t\bar{t}$ events in the lepton+jets decay mode. These data correspond to an integrated luminosity of 230pb^-1, collected by the DO detector at the Fermilab Tevatron $p\bar{p}$ Collider at sqrt(s)=1.96 TeV. We use a constrained fit to reconstruct the kinematics of the $t\bar{t}$ and decay products, which allows for the measurement of the leptonic decay angle $\theta^*$ for each event. By comparing the $\cos\theta^*$ distribution from the data with those for the expected background and signal for various values of f+, we find f+=0.00+-0.13(stat)+-0.07(syst). This measurement is consistent with the standard model prediction of f+=3.6x10^-4.Comment: Submitted to Physical Review D Rapid Communications 7 pages, 3 figure

Measurement of the ppbar to ttbar production cross section at sqrt(s)=1.96 TeV in the fully hadronic decay channel

A measurement of the top quark pair production cross section in proton anti-proton collisions at an interaction energy of sqrt(s)=1.96 TeV is presented. This analysis uses 405 pb-1 of data collected with the D0 detector at the Fermilab Tevatron Collider. Fully hadronic ttbar decays with final states of six or more jets are separated from the multijet background using secondary vertex tagging and a neural network. The ttbar cross section is measured as sigma(ttbar)=4.5 -1.9 +2.0 (stat) -1.1 +1.4 (syst) +/- 0.3 (lumi) pb for a top quark mass of m(t) = 175 GeV/c^2.Comment: 10 pages, 10 figures, submitted to Phys. Rev.

Search for Neutral Higgs Bosons Decaying to Tau Pairs in p-pbar Collisions at sqrt(s) = 1.96 TeV

A search for the production of neutral Higgs bosons Phi decaying into tau^+tau^- final states in p-pbar collisions at a center-of-mass energy of 1.96 TeV is presented. The data, corresponding to an integrated luminosity of up to 348 pb^-1, were collected by the D0 experiment at the Fermilab Tevatron Collider. Since no excess compared to the expectation from standard model processes is found, limits on the production cross section times branching ratio are set. The results are combined with those obtained from the D0 search for Phi b(b) to b-bbar-b(bbar) and are interpreted in the minimal supersymmetric standard model.Comment: Version accpeted by Phys. Rev. Lett. (minor changes

Measurement of the Bs0B^{0}_{s} Lifetime Using Semileptonic Decays

We report a measurement of the $B^0_{s}$ lifetime in the semileptonic decay channel $B^0_{s}\to D^-_s \mu^{+}\nu X$ (and its charge conjugate), using approximately 0.4 fb$^{-1}$ of data collected with the D0 detector during 2002 -- 2004. We have reconstructed 5176 $D^-_s \mu^{+}$ signal events, where the $D_s^-$ is identified via the decay $D_s^-\to \phi\pi^-$, followed by $\phi\to K^+ K^-$. Using these events, we have measured the $B^0_s$ lifetime to be $\tau(B^0_{s}) = 1.398 \pm 0.044$ $({stat}) ^{+0.028}_{-0.025}$ $({syst}) {ps}$. This is the most precise measurement of the $B_s^0$ lifetime to date.Comment: To appear in Phys. Rev. Lett., 7 pages, 2 figure