4,759 research outputs found
Relationship of runoff, erosion and sediment yield to weather types in the Iberian Peninsula
Precipitation has been recognized as one of the main factors driving soil erosion and sediment yield (SY), and its spatial and temporal variability is recognized as one of themain reasons for spatial and temporal analyses of soil erosion variability. The weather types (WTs) approach classifies the continuumof atmospheric circulation into a small number of categories or types and has been proven a good indicator of the spatial and temporal variability of precipitation. Thus, themain objective of this study is to analyze the relationship betweenWTs, runoff, soil erosion (measured in plots), and sediment yield (measured in catchments) in different areas of the Iberian Peninsula (IP) with the aimof detecting spatial variations in these relationships. To this end, hydrological and sediment information covering the IP from several Spanish research teams has been combined, and related with daily WTs estimated by using the NMC/NCAR 40-Year Reanalysis Project. The results showthat, in general, a fewWTs (particularly westerly, southwesterly and cyclonic) provide the largest amounts of precipitation; and southwesterly, northwesterly and westerly WTs play an important role in runoff generation, erosion and sediment yield as they coincide with the wettest WTs. However, this study highlights the spatial variability of erosion and sediment yield in the IP according to WT, differentiating (1) areas under the influence of north and/or north-westerly flows (the north coast of Cantabria and inland central areas), (2) areas under the influence of westerly, southwesterly and cyclonic WTs (western and southwestern IP), (3) areas in which erosion and sediment yield are controlled by easterly flows (Mediterranean coastland), and (4) lastly, a transitional zone in the inland northeast Ebro catchment,wherewe detected a high variability in the effects ofWTs on erosion. Overall results suggest that the use of WTs derived fromobserved atmospheric pressure patterns could be a useful tool for inclusion in future projections of the spatial variability of erosion and sediment yield, as models capture pressure fields reliably
Differential branching fraction and angular analysis of the decay B0âKâ0ÎŒ+ÎŒâ
The angular distribution and differential branching fraction of the decay B 0â K â0 ÎŒ + ÎŒ â are studied using a data sample, collected by the LHCb experiment in pp collisions at sâ=7 TeV, corresponding to an integrated luminosity of 1.0 fbâ1. Several angular observables are measured in bins of the dimuon invariant mass squared, q 2. A first measurement of the zero-crossing point of the forward-backward asymmetry of the dimuon system is also presented. The zero-crossing point is measured to be q20=4.9±0.9GeV2/c4 , where the uncertainty is the sum of statistical and systematic uncertainties. The results are consistent with the Standard Model predictions
Measurement of the relative rate of prompt Ïc0, Ïc1 and Ïc2 production at âs=7TeV
Prompt production of charmonium Ïc0, Ïc1 and Ïc2 mesons is studied using proton-proton collisions at the LHC at a centre-of-mass energy of âs=7TeV. The Ïc mesons are identified through their decay to J/ÏÎł, with J/ÏâÎŒ+muâ using photons that converted in the detector. A data sample, corresponding to an integrated luminosity of 1.0fbâ1 collected by the LHCb detector, is used to measure the relative prompt production rate of Ïc1 and Ïc2 in the rapidity range 2.0<y<4.5 as a function of the J/Ï transverse momentum from 3 to 20 GeV/c. First evidence for Ïc0 meson production at a hadron collider is also presented
Searching for converging research using field to field citations
We define converging research as the emergence of an interdisciplinary research area from fields that did not show interdisciplinary connections before. This paper presents a process to search for converging research using journal subject categories as a proxy for fields and citations to measure interdisciplinary connections, as well as an application of this search. The search consists of two phases: a quantitative phase in which pairs of citing and cited fields are located that show a significant change in number of citations, followed by a qualitative phase in which thematic focus is sought in publications associated with located pairs. Applying this search on publications from the Web of Science published between 1995 and 2005, 38 candidate converging pairs were located, 27 of which showed thematic focus, and 20 also showed a similar focus in the other, reciprocal pair
Search for the decay Bs0âD*âϱ
A search for the decay Bs0âD*âϱ is presented using a data sample corresponding to an integrated luminosity of 1.0ââfb-1 of pp collisions collected by LHCb. This decay is expected to be mediated by a W-exchange diagram, with little contribution from rescattering processes, and therefore a measurement of the branching fraction will help us to understand the mechanism behind related decays such as Bs0âÏ+Ï- and Bs0âDD- . Systematic uncertainties are minimized by using B0âD*âϱ as a normalization channel. We find no evidence for a signal, and set an upper limit on the branching fraction of B(Bs0âD*âϱ)<6.1(7.8)Ă10-6 at 90% (95%) confidence level
Study of DJ meson decays to D+Ïâ, D0Ï+ and Dâ+Ïâ final states in pp collisions
A study of D+Ïâ, D0Ï+ and Dâ+Ïâ final states is performed using pp collision data, corresponding to an integrated luminosity of 1.0 fbâ1, collected at a centre-of-mass energy of 7 TeV with the LHCb detector. The D1(2420)0 resonance is observed in the Dâ+Ïâ final state and the Dâ2(2460) resonance is observed in the D+Ïâ, D0Ï+ and Dâ+Ïâ final states. For both resonances, their properties and spin-parity assignments are obtained. In addition, two natural parity and two unnatural parity resonances are observed in the mass region between 2500 and 2800 MeV. Further structures in the region around 3000 MeV are observed in all the Dâ+Ïâ, D+Ïâ and D0Ï+ final states
Observation of the decay
The decay is observed for the first
time, using proton-proton collisions collected with the LHCb detector
corresponding to an integrated luminosity of 3fb. A signal yield of
decays is reported with a significance of 6.2 standard deviations.
The ratio of the branching fraction of \B_c \rightarrow J/\psi K^+ K^- \pi^+
decays to that of decays is measured to be
, where the first uncertainty is statistical and the
second is systematic.Comment: 18 pages, 2 figure
Searches for B0(s)âJ/ÏppË and B+âJ/ÏppËÏ+ decays
The results of searches for B0(s)âJ/Ï ppÂŻ and B + â J/Ï p pÂŻ Ï+ decays are reported. The analysis is based on a data sample, corresponding to an integrated luminosity of 1.0 fbâ1 of pp collisions, collected with the LHCb detector. An excess with 2.8 Ï significance is seen for the decay B0sâJ/Ï ppÂŻ and an upper limit on the branching fraction is set at the 90 % confidence level: B(B0sâJ/Ï ppÂŻ) < 4.8 Ă 10â6, which is the first such limit. No significant signals are seen for B0 â J/Ï ppÂŻ and B+ â J/Ï ppÂŻ Ï + decays, for which the corresponding limits are set: B(B0âJ/Ï ppÂŻ) < 5.2 Ă 10â7, which significantly improves the existing limit; and B(B+âJ/Ï ppÂŻÏ+) < 5.0 Ă 10â7, which is the first limit on this branching fraction
Measurement of B meson production cross-sections in proton-proton collisions at âs= 7 TeV
The production cross-sections of B mesons are measured in pp collisions at a centre-of-mass energy of 7 TeV using data collected with the LHCb detector corresponding to a integrated luminosity of 0.36fbâ1. The B+, B0 and B0s mesons are reconstructed in the exclusive decays B+âJ/ÏK+, B0âJ/ÏKâ0 and B0sâJ/ÏÏ, with J/ÏâÎŒ+ÎŒâ, Kâ0âK+Ïâ and ÏâK+Kâ. The differential cross-sections are measured as functions of B meson transverse momentum pT and rapidity y, in the range 0 < pT<40GeV/c2 and 2.0<y<4.5. The integrated cross-sections in the same pT and y ranges, including charge-conjugate states, are measured to be
Ï(ppâB++X)=38.9±0.3(stat.)±2.5(syst.)±1.3(norm.)ÎŒb,
Ï(ppâB0+X)=38.1±0.6(stat.)±3.7(syst.)±4.7(norm.)ÎŒb,
Ï(ppâB0s+X)=10.5±0.2(stat.)±0.8(syst.)±1.0(norm.)ÎŒb,
where the third uncertainty arises from the pre-existing branching fraction measurements
Measurements of the branching fractions of B+âppK+ decays
The branching fractions of the decay B+ â ppÌK+ for different intermediate states are measured using data, corresponding to an integrated luminosity of 1.0 fb-1, collected by the LHCb experiment. The total branching fraction, its charmless component MppÌ < 2.85 GeV/c2 and the branching fractions via the resonant ccÌ states η c(1S) and Ï(2S) relative to the decay via a J/Ï intermediate state are [Equation not available: see fulltext.] Upper limits on the B + branching fractions into the η c(2S) meson and into the charmonium-like states X(3872) and X(3915) are also obtained
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