16 research outputs found

    Measurement of CP observables in B-+/- -> DK +/- and B-+/- -> D pi(+/-) with D -> KS0<mml:msup>K +/-</mml:msup><mml:msup>pi -/+</mml:msup> decays

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    Measurements of CPCP observables in B±→DK±B^\pm \to D K^\pm and B±→Dπ±B^\pm \to D \pi^\pm decays are presented, where DD represents a superposition of D0D^0 and Dˉ0\bar{D}^0 states. The DD meson is reconstructed in the three-body final state KS0K±π∓K_{\rm{S}}^0K^\pm \pi^\mp. The analysis uses samples of BB mesons produced in proton-proton collisions, corresponding to an integrated luminosity of 1.0, 2.0, and 6.0 fb−1^{-1} collected with the LHCb detector at centre-of-mass energies of s=\sqrt{s} = 7, 8, and 13 TeV, respectively. These measurements are the most precise to date, and provide important input for the determination of the CKM angle γ\gamma

    Measurement of the electron reconstruction efficiency at LHCb

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    The single electron track-reconstruction efficiency is calibrated using a sample corresponding to 1.3 fb−1 of pp collision data recorded with the LHCb detector in 2017. This measurement exploits B+→ J/ψ(e+e−)K+ decays, where one of the electrons is fully reconstructed and paired with the kaon, while the other electron is reconstructed using only the information of the vertex detector. Despite this partial reconstruction, kinematic and geometric constraints allow the B meson mass to be reconstructed and the signal to be well separated from backgrounds. This in turn allows the electron reconstruction efficiency to be measured by matching the partial track segment found in the vertex detector to tracks found by LHCb's regular reconstruction algorithms. The agreement between data and simulation is evaluated, and corrections are derived for simulated electrons in bins of kinematics. These correction factors allow LHCb to measure branching fractions involving single electrons with a systematic uncertainty below 1%

    Reducing nutrient availability and enhancing biotic resistance limits settlement and growth of the invasive Australian swamp stonecrop (Crassula helmsii)

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    The Australian swamp stonecrop is invasive due to its efficient colonization of empty niches. The establishment of dense C. helmsii growth is threatening native biodiversity and functioning of freshwater ecosystems. In this study we’ve tested the competitive strength of C. helmsii in a greenhouse experiment with two native competitor species of the same habitat type, Pilularia globulifera and Littorella uniflora. After the collection of native vernation and bare soil sods we manually infested these with 60 propagules of C. helmsii. The settlement and growth of C. helmsii was assessed (by counting) after five weeks. In addition, the effect of nutrient enrichment by water bird feces on competition was studied by adding waterfowl droppings. Additionally we’ve measured nutrients in soil and water samples (by AA- and ICP analysis) collected from the sods. This gives insights in the establishment success and invasiveness of C. helmsii in absence of native competitors and eutrophication. *The data appropriate to this article may contain Dutch notes. For an English explanation, please contact the author of the data Abstract of the paper: The invasive Australian swamp stonecrop, Crassula helmsii, is a perennial amphibious herb originating from Australia and New Zealand. In freshwater wetlands of North-western Europe, this alien plant species is invasive due to its efficient colonization of empty niches. The establishment of dense C. helmsii growth is threatening native biodiversity and functioning of freshwater ecosystems, especially oligotrophic wetlands with high disturbance and nutrient enrichments. As the effects of these potential drivers of ecosystem degradation are generally difficult to determine in the field, we tested the competitive strength of C. helmsii in a greenhouse experiment with two native competitor species of the same habitat type, Pilularia globulifera and Littorella uniflora. Sods dominated by either of the native species, as well as bare soils, were collected from the field and manually infested with propagules of C. helmsii. Settlement and growth of C. helmsii was assessed after five weeks. In addition, the effect of nutrient enrichment by water bird feces on competition was studied by adding waterfowl droppings. C. helmsii was able to settle successfully in all treatments, but P. globulifera and L. uniflora dominance reduced settlement success and growth of C. helmsii. On vegetated sods, the addition of waterfowl droppings had a low effect on the performance of C. helmsii, however, this treatment significantly increased biomass production on bare soils with low nutrient availability. We conclude that both absence of native competitors and eutrophication, including guanotrophication by waterfowl, explain the establishment success and invasiveness of C. helmsii. Given the fact that eradication of C. helmsii is very challenging, our results imply that management should focus on a combination of increasing local species densities and abating eutrophication. This will strongly limit the window of opportunity for invasion of C. helmsii and enhance resistance by native plant communities

    Reducing nutrient availability and enhancing biotic resistance limits settlement and growth of the invasive Australian swamp stonecrop (Crassula helmsii)

    No full text
    The Australian swamp stonecrop is invasive due to its efficient colonization of empty niches. The establishment of dense C. helmsii growth is threatening native biodiversity and functioning of freshwater ecosystems. In this study we’ve tested the competitive strength of C. helmsii in a greenhouse experiment with two native competitor species of the same habitat type, Pilularia globulifera and Littorella uniflora. After the collection of native vernation and bare soil sods we manually infested these with 60 propagules of C. helmsii. The settlement and growth of C. helmsii was assessed (by counting) after five weeks. In addition, the effect of nutrient enrichment by water bird feces on competition was studied by adding waterfowl droppings. Additionally we’ve measured nutrients in soil and water samples (by AA- and ICP analysis) collected from the sods. This gives insights in the establishment success and invasiveness of C. helmsii in absence of native competitors and eutrophication. *The data appropriate to this article may contain Dutch notes. For an English explanation, please contact the author of the data Abstract of the paper: The invasive Australian swamp stonecrop, Crassula helmsii, is a perennial amphibious herb originating from Australia and New Zealand. In freshwater wetlands of North-western Europe, this alien plant species is invasive due to its efficient colonization of empty niches. The establishment of dense C. helmsii growth is threatening native biodiversity and functioning of freshwater ecosystems, especially oligotrophic wetlands with high disturbance and nutrient enrichments. As the effects of these potential drivers of ecosystem degradation are generally difficult to determine in the field, we tested the competitive strength of C. helmsii in a greenhouse experiment with two native competitor species of the same habitat type, Pilularia globulifera and Littorella uniflora. Sods dominated by either of the native species, as well as bare soils, were collected from the field and manually infested with propagules of C. helmsii. Settlement and growth of C. helmsii was assessed after five weeks. In addition, the effect of nutrient enrichment by water bird feces on competition was studied by adding waterfowl droppings. C. helmsii was able to settle successfully in all treatments, but P. globulifera and L. uniflora dominance reduced settlement success and growth of C. helmsii. On vegetated sods, the addition of waterfowl droppings had a low effect on the performance of C. helmsii, however, this treatment significantly increased biomass production on bare soils with low nutrient availability. We conclude that both absence of native competitors and eutrophication, including guanotrophication by waterfowl, explain the establishment success and invasiveness of C. helmsii. Given the fact that eradication of C. helmsii is very challenging, our results imply that management should focus on a combination of increasing local species densities and abating eutrophication. This will strongly limit the window of opportunity for invasion of C. helmsii and enhance resistance by native plant communities

    Measurement of CP-Averaged Observables in the B-0 -> K-star 0 mu(+)mu(-) Decay

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    An angular analysis of the B-0 -&gt; K-0 (-&gt; K+pi(-))mu(+)mu(-) decay is presented using a dataset corresponding to an integrated luminosity of 4.7 fb(-1) of pp collision data collected with the LHCb experiment. The full set of CP-averaged observables are determined in bins of the invariant mass squared of the dimuon system. Contamination from decays with the K+ pi(-) system in an S-wave configuration is taken into account. The tension seen between the previous LHCb results and the standard model predictions persists with the new data. The precise value of the significance of this tension depends on the choice of theory nuisance parameters

    Search for the rare decay D-0 -> mu(+) mu(-)

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    A search for the rare decay D-0 -> mu(+) mu(-) is performed using a data sample, corresponding to an integrated luminosity of 0.9 fb(-1), of pp collisions collected at a centre-of-mass energy of 7 TeV by the LHCb experiment. The observed number of events is consistent with the background expectations and corresponds to an upper limit of B(D-0 -> mu(+) mu(-)) < 6.2 (7.6) x 10(-9) at 90% (95%) confidence level. This result represents an improvement of more than a factor twenty with respect to previous measurements. (C) 2013 CERN. Published by Elsevier B.V. All rights reserved

    First Observation of the Radiative Decay Lambda(0 )(b)-> Lambda gamma

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    The radiative decay Λ0b→Λγ is observed for the first time using a data sample of proton-proton collisions corresponding to an integrated luminosity of 1.7  fb−1 collected by the LHCb experiment at a center-of-mass energy of 13 TeV. Its branching fraction is measured exploiting the B0→K*0γ decay as a normalization mode and is found to be B(Λ0b→Λγ)=(7.1±1.5±0.6±0.7)×10−6, where the quoted uncertainties are statistical, systematic, and systematic from external inputs, respectively. This is the first observation of a radiative decay of a beauty baryon

    Search for the lepton-flavour-violating decays Bs0→τ±μ∓B^{0}_{s}\to\tau^{\pm}\mu^{\mp} and B0→τ±μ∓B^{0}\to\tau^{\pm}\mu^{\mp}

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