185 research outputs found

    Construcci贸n de un sistema de detecci贸n de part铆culas para su aplicaci贸n en la ense帽anza de f铆sica de part铆culas

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    En este art铆culo se presenta una descripci贸n detallada de la construcci贸n de un sistema b谩sico de detecci贸n de part铆culas. Esta construcci贸n podr谩 ser replicada en diferentes instituciones de educaci贸n universitaria o media. Adem谩s, se presenta una comparaci贸n entre dos dise帽os de sistemas de detecci贸n de part铆culas usando como material de detecci贸n el centellador pl谩stico. El primer sistema de detecci贸n consiste de una barra pl谩stica centelladora con dos fotomultiplicadores de silicio, cada uno con 谩rea de 6x6 mm2. El segundo sistema de detecci贸n consiste de una barra pl谩stica centelladora, un fotomultiplicador de silicio con 谩rea de 3x3 mm2, y una fibra 贸ptica de corrimiento de longitud de onda ubicada dentro de la barra centelladora. La comparaci贸n entre los dos sistemas de detecci贸n favorece la segunda opci贸n de dise帽o, que muestra m谩s eficiencia en la detecci贸n de las part铆culas. La metodolog铆a descrita en este art铆culo puede ser aplicada en la ense帽anza de la f铆sica de detectores de part铆culas elementales

    Search for CP violation in D+KK++D^{+} \to K^{-}K^{+}\pi^{+} decays

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    A model-independent search for direct CP violation in the Cabibbo suppressed decay D+KK++D^+ \to K^- K^+\pi^+ in a sample of approximately 370,000 decays is carried out. The data were collected by the LHCb experiment in 2010 and correspond to an integrated luminosity of 35 pb1^{-1}. The normalized Dalitz plot distributions for D+D^+ and DD^- are compared using four different binning schemes that are sensitive to different manifestations of CP violation. No evidence for CP asymmetry is found.Comment: 13 pages, 8 figures, submitted to Phys. Rev.

    First observation of the decay Bs0D0K0\bar{B}^0_s \to D^0 K^{*0} and a measurement of the ratio of branching fractions B(Bs0D0K0)B(B0D00)\frac{{\cal B}(\bar{B}^0_s \to D^0 K^{*0})}{{\cal B}(\bar{B}^0 \to D^0 \rho^0)}

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    The first observation of the decay Bs0D0K0\bar{B}^0_s \to D^0 K^{*0} using pppp data collected by the LHCb detector at a centre-of-mass energy of 7 TeV, corresponding to an integrated luminosity of 36 pb1^{-1}, is reported. A signal of 34.46.834.4 \pm 6.8 events is obtained and the absence of signal is rejected with a statistical significance of more than nine standard deviations. The Bs0D0K0\bar{B}^0_s \to D^0 K^{*0} branching fraction is measured relative to that of B0D00\bar{B}^0 \to D^0 \rho^0: B(Bs0D0K0)B(B0D00)=1.480.340.150.12\frac{{\cal B}(\bar{B}^0_s \to D^0 K^{*0})}{{\cal B}(\bar{B}^0 \to D^0 \rho^0)} = 1.48 \pm 0.34 \pm 0.15 \pm 0.12, where the first uncertainty is statistical, the second systematic and the third is due to the uncertainty on the ratio of the B0B^0 and Bs0B^0_s hadronisation fractions.Comment: 10 pages, 3 figures, submitted to Phys. Lett. B; ISSN 0370-269

    First observation of Bs -> D_{s2}^{*+} X mu nu decays

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    Using data collected with the LHCb detector in proton-proton collisions at a centre-of-mass energy of 7 TeV, the semileptonic decays Bs -> Ds+ X mu nu and Bs -> D0 K+ X mu nu are detected. Two structures are observed in the D0 K+ mass spectrum at masses consistent with the known D^+_{s1}(2536) and $D^{*+}_{s2}(2573) mesons. The measured branching fractions relative to the total Bs semileptonic rate are B(Bs -> D_{s2}^{*+} X mu nu)/B(Bs -> X mu nu)= (3.3\pm 1.0\pm 0.4)%, and B(Bs -> D_{s1}^+ X munu)/B(Bs -> X mu nu)= (5.4\pm 1.2\pm 0.5)%, where the first uncertainty is statistical and the second is systematic. This is the first observation of the D_{s2}^{*+} state in Bs decays; we also measure its mass and width.Comment: 8 pages 2 figures. Published in Physics Letters

    Low emission development strategies in agriculture. An agriculture, forestry, and other land uses (AFOLU) perspective

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    As countries experience economic growth and choose among available development pathways, they are in a favorable position to adopt natural resource use technologies and production practices that favor efficient use of inputs, healthy soils, and ecosystems. Current emphasis on increasing resilience to climate change and reducing agricultural greenhouse gasses (GHG) emissions strengthens the support for sustainable agricultural production. In fact, reducing losses in soil fertility, reclaiming degraded lands, and promoting synergistic interaction between crop production and forests are generally seen as good climate change policies. In order for decision-makers to develop long-term policies that address these issues, they must have tools at their disposal that evaluate trade-offs, opportunities, and repercussions of the options considered. In this paper, the authors combine and reconcile the output of three models widely accessible to the public to analyze the impacts of policies that target emission reduction in the agricultural sector. We present an application to Colombia which reveals the importance of considering the full scope of interactions among the various land uses. Results indicate that investments in increasing the efficiency and productivity of the livestock sector and reducing land allocated to pasture are preferable to policies that target deforestation alone or target a reduction of emissions in crop production. Investments in livestock productivity and land-carrying capacity would reduce deforestation and provide sufficient gains in carbon stock to offset greater emissions from increased crop production while generating higher revenues

    Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

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    Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection

    Long-baseline neutrino oscillation physics potential of the DUNE experiment