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- Aad, G., et al.
(author)
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- 2014
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Journal article (peer-reviewed)
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| 5. |
- Bhandari, Rajendra, 1986-
(author)
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Provenance, transport, and the fate of organic matter and sediments drained through Himalayan Rivers in Nepal
- 2022
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Doctoral thesis (other academic/artistic)abstract
- Despite its small area (ca. 595,000 km2), the Himalayan region transfers disproportionally high amounts of sediments and organic matter (OM) through a network of rivers into the oceanic sink. Such a high contribution is due to the synergistic effects of active tectonics, variable precipitation, and steep slopes aided by human perturbations on exhumed and young mountain terrains. Seasonality in the mobilization and transport of fresh biogenic OM and petrogenic carbon, including paleosols, is dominant in this unique landscape with implications for climate change and the global carbon budget. However, a comprehensive assessment of sources and the fate of organic carbon (OC) in Himalayan rivers remains elusive, driving considerable uncertainty in estimates of the fluvial transport of carbon, its budget, and its impacts on the global carbon cycle. Four rivers from diverse physiographic zones with specific rock types were selected from the Nepal Himalayas to characterize the OM sources and their fate using C:N ratios, lipid biomarkers, and lignin phenols. The seasonal OC fluxes were estimated, and strontium (Sr) and neodymium (Nd) isotope data were utilized to elucidate the provenance. Finally, monitoring of runoff plots and RUSLE modeling was conducted to estimate soil erosion from different land-use practices. The suspended sediment load in these rivers was proportional to the erosional intensity. Unlike suspended sediments, OM in bedload samples was derived from multiple sources with weak terrigenous dominance. The influence of seasonality on OM and elemental concentrations was evident in the new data. The abundance of sedimentary lipids in these small rivers represents high OM sequestration and corroborates the inference derived from diagnostic lignin ratios. These rivers transport > 90% POC and ca. 75% DOC during the short monsoon season, highlighting rapid transport/mobilization of OC from the Nepal Himalayas. The high strontium isotope (87Sr/86Sr) ratio in silicates drives the high radiogenic Sr input, which exceeds the global average. The clusters in Sr and Nd isotope data represent specific physiographic zones and rock types that can help infer OM provenance and trace the fate of carbon from source to sink. Data from the runoff plots suggest that irrigated croplands drive topsoil erosion. The soil erosion rate in the watersheds is high (> 24 tons ha-1 yr-1). This is attributed to anthropogenic disturbance associated with cropping patterns, soil disturbance, and waterlogging. The contrasting features in the Himalayan region and new data on the role of mountain rivers invite global attention to infer ongoing and future changes in OM flux.
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| 6. |
- Aaltonen, T., et al.
(author)
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Combination of measurements of the top-quark pair production cross section from the Tevatron Collider
- 2014
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In: Physical Review D. - 1550-7998 .- 1550-2368. ; 89:7
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Journal article (peer-reviewed)abstract
- We combine six measurements of the inclusive top-quark pair (t(sic)) production cross section (sigma(t)(sic)) from data collected with the CDF and D0 detectors at the Fermilab Tevatron with proton-antiproton collisions at root s = 1.96 TeV. The data correspond to integrated luminosities of up to 8.8 fb(-1). We obtain a value of sigma tt = 7.60 +/- 0.41 pb for a top-quark mass of m(t) = 172.5 GeV. The contributions to the uncertainty are 0.20 pb from statistical sources, 0.29 pb from systematic sources, and 0.21 pb from the uncertainty on the integrated luminosity. The result is in good agreement with the standard model expectation of 7.35(-0.33)(+0.28) pb at next-to-next-to-leading order and next-to-next-to leading logarithms in perturbative QCD.
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| 7. |
- Aaltonen, T., et al.
(author)
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Observation of s-Channel Production of Single Top Quarks at the Tevatron
- 2014
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 112:23
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Journal article (peer-reviewed)abstract
- We report the first observation of single-top-quark production in the s channel through the combination of the CDF and D0 measurements of the cross section in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV. The data correspond to total integrated luminosities of up to 9.7 fb(-1) per experiment. The measured cross section is sigma(s) = 1.29(-0.24)(+0.26) pb. The probability of observing a statistical fluctuation of the background to a cross section of the observed size or larger is 1.8 x 10(-10), corresponding to a significance of 6.3 standard deviations for the presence of an s-channel contribution to the production of single-top quarks.
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| 8. |
- Aaltonen, T., et al.
(author)
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Search for neutral Higgs bosons in events with multiple bottom quarks at the Tevatron
- 2012
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In: Physical Review D. - 1550-7998 .- 1550-2368. ; 86:9, s. 091101-
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Journal article (peer-reviewed)abstract
- The combination of searches performed by the CDF and D0 collaborations at the Fermilab Tevatron Collider for neutral Higgs bosons produced in association with b quarks is reported. The data, corresponding to 2.6 fb(-1) of integrated luminosity at CDF and 5.2 fb(-1) at D0, have been collected in final states containing three or more b jets. Upper limits are set on the cross section multiplied by the branching ratio varying between 44 pb and 0.7 pb in the Higgs boson mass range 90 to 300 GeV, assuming production of a narrow scalar boson. Significant enhancements to the production of Higgs bosons can be found in theories beyond the standard model, for example, in supersymmetry. The results are interpreted as upper limits in the parameter space of the minimal supersymmetric standard model in a benchmark scenario favoring this decay mode.
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- Aaltonen, T., et al.
(author)
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Combination of Tevatron Searches for the Standard Model Higgs Boson in the W+W- Decay Mode
- 2010
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 104:6, s. 061802-
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Journal article (peer-reviewed)abstract
- We combine searches by the CDF and D0 Collaborations for a Higgs boson decaying to W+W-. The data correspond to an integrated total luminosity of 4.8 (CDF) and 5.4 (D0) fb(-1) of p (p) over bar collisions at root s = 1.96 TeV at the Fermilab Tevatron collider. No excess is observed above background expectation, and resulting limits on Higgs boson production exclude a standard model Higgs boson in the mass range 162-166 GeV at the 95% C.L.
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| 10. |
- Aaltonen, T., et al.
(author)
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Combination of the top-quark mass measurements from the Tevatron collider
- 2012
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In: Physical Review D. - 1550-7998 .- 1550-2368. ; 86:9, s. 092003-
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Journal article (peer-reviewed)abstract
- The top quark is the heaviest known elementary particle, with a mass about 40 times larger than the mass of its isospin partner, the bottom quark. It decays almost 100% of the time to a W boson and a bottom quark. Using top-antitop pairs at the Tevatron proton-antiproton collider, the CDF and D0 Collaborations have measured the top quark's mass in different final states for integrated luminosities of up to 5.8fb -1. This paper reports on a combination of these measurements that results in a more precise value of the mass than any individual decay channel can provide. It describes the treatment of the systematic uncertainties and their correlations. The mass value determined is 173.18±0.56(stat)±0.75(syst)GeV or 173.18±0.94GeV, which has a precision of ±0.54%, making this the most precise determination of the top-quark mass.
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