Arbuscular mycorrhizal fungi associated to Zea Mays L. plants in an agroecosystem of Atlántico, Colombia.

El maíz es considerado uno de los más importantes cultivos a nivel mundial. Como en muchos otros países, Colombia ha utilizado este cereal no solo como alimento para humanos y animales sino también para fabricar diferentes productos industriales. Las plantas de maíz están bien adaptadas a las diferentes condiciones climáticas y agroecológicas de Colombia, lo cual le permite estar ampliamente distribuido en todo el país. Algunas de sus adaptaciones naturales son atribuidas a la existencia de relaciones simbióticas con hongos micorrizógenos arbusculares (HMA), los cuales promueven la captación de nutrientes en especial de aquellos que tienen escasa movilidad tales como el fósforo (P) y el nitrógeno (N). Se identificaron HMA asociados a cultivos de maíz localizados en el municipio de Sabanalarga, Atlántico, Colombia. El número de esporas en 100 g de suelo se determinó mediante tamizado, siguiendo protocolos de centrifugación en sacarosa. El número de esporas por 100 g de suelo mostró diferencias estadísticas significativas durante los meses de muestreo (p<0,05). Se identificaron un total de 19 morfotipos correspondientes a doce especies del género Glomus, cinco del género Gigaspora y una especie para los géneros Acaulospora y Scutellospora. Se encontró correlación negativa entre temperatura y número de esporas; sin embargo no existió correlación entre el pH y las variables densidad de esporas, porcentaje de colonización y temperatura del suelo. Asimismo, se reportó bajo contenido de materia orgánica (0,99 %) y baja capacidad de intercambio catiónico (7,50 cmol.kgr-1suelo). Estos resultados, sumados al hecho de que este tipo de cultivos son grandemente dependientes de la actividad de hongos micorrizógenos, explican la densidad de esporas (400-1350 esp/100 g) y el elevado porcentaje de colonización (40-98 %) que fue encontrado durante el muestreo. Es claro que este cereal depende de la presencia de hongos micorrizógenos durante la toma de nutrientes.Corn is considered one of the most important cereal crops worldwide. As many other countries, Colombia has used this cereal not only to feed humans and animals but also to manufacture many different industrial products. Corn plants are well adapted in different climatic and ecological conditions in Colombia which allows it to be widely distributed throughout the country. Some of its natural adaptations are attributed to the existence of symbiotic relationships with Arbuscular Mycorrhizal fungi (AMF) which promote the nutrient uptake, especially those with known low mobility such as phosphorus (P) and nitrogen (N). AMFs associated to corn crops were identified in samples collected in the fields of the municipality of Sabanalarga (Atlántico, Colombia). The number of spores per 100 g of soil was determined by sieving following sucrose centrifugation standard protocols. The number of spores per 100 g of soil showed statistically significant differences during the months of sampling (p < 0.05). A total of 19 morphotypes, corresponding to twelve species of the genus Glomus, five of the genus Gigaspora, and one species of both genus Acaulospora and Scutellospora were identified. A negative correlation between temperature and number of spores was found but no correlation between pH and the spore density, percentage of colonization and soil temperature variables was found. Additionally, low organic matter content (0.99%) and low cation exchange capacity (7.50 cmol*soil-Kg-1) were reported. These results, in addition to the fact that this kind of crops are highly dependent of mycorrhizal fungi activity, explain the spore density (400-1350 spore/ 100 g) and the high percentage of colonization (40-98%) that were obtained during sampling. It is clear that this cereal crop depends on the presence of mycorrhizal fungi during nutrient uptake

Combined searches for the production of supersymmetric top quark partners in proton-proton collisions at root s=13 TeV

A combination of searches for top squark pair production using proton-proton collision data at a center-of-mass energy of 13 TeV at the CERN LHC, corresponding to an integrated luminosity of 137 fb(-1) collected by the CMS experiment, is presented. Signatures with at least 2 jets and large missing transverse momentum are categorized into events with 0, 1, or 2 leptons. New results for regions of parameter space where the kinematical properties of top squark pair production and top quark pair production are very similar are presented. Depending on themodel, the combined result excludes a top squarkmass up to 1325 GeV for amassless neutralino, and a neutralinomass up to 700 GeV for a top squarkmass of 1150 GeV. Top squarks with masses from 145 to 295 GeV, for neutralino masses from 0 to 100 GeV, with a mass difference between the top squark and the neutralino in a window of 30 GeV around the mass of the top quark, are excluded for the first time with CMS data. The results of theses searches are also interpreted in an alternative signal model of dark matter production via a spin-0 mediator in association with a top quark pair. Upper limits are set on the cross section for mediator particle masses of up to 420 GeV

Search for new particles in events with energetic jets and large missing transverse momentum in proton-proton collisions at root s=13 TeV

A search is presented for new particles produced at the LHC in proton-proton collisions at root s = 13 TeV, using events with energetic jets and large missing transverse momentum. The analysis is based on a data sample corresponding to an integrated luminosity of 101 fb(-1), collected in 2017-2018 with the CMS detector. Machine learning techniques are used to define separate categories for events with narrow jets from initial-state radiation and events with large-radius jets consistent with a hadronic decay of a W or Z boson. A statistical combination is made with an earlier search based on a data sample of 36 fb(-1), collected in 2016. No significant excess of events is observed with respect to the standard model background expectation determined from control samples in data. The results are interpreted in terms of limits on the branching fraction of an invisible decay of the Higgs boson, as well as constraints on simplified models of dark matter, on first-generation scalar leptoquarks decaying to quarks and neutrinos, and on models with large extra dimensions. Several of the new limits, specifically for spin-1 dark matter mediators, pseudoscalar mediators, colored mediators, and leptoquarks, are the most restrictive to date.Peer reviewe

Probing effective field theory operators in the associated production of top quarks with a Z boson in multilepton final states at root s=13 TeV

Peer reviewe

Measurement of B-c(2S)(+) and B-c*(2S)(+) cross section ratios in proton-proton collisions at root s=13 TeV

Peer reviewe

Measurements of the Electroweak Diboson Production Cross Sections in Proton-Proton Collisions at root s=5.02 TeV Using Leptonic Decays

The first measurements of diboson production cross sections in proton-proton interactions at a center-of-mass energy of 5.02 TeV are reported. They are based on data collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 302 pb(-1). Events with two, three, or four charged light leptons (electrons or muons) in the final state are analyzed. The WW, WZ, and ZZ total cross sections are measured as sigma(WW) = 37:0(-5.2)(+5.5) (stat)(-2.6)(+2.7) (syst) pb, sigma(WZ) = 6.4(-2.1)(+2.5) (stat)(-0.3)(+0.5)(syst) pb, and sigma(ZZ) = 5.3(-2.1)(+2.5)(stat)(-0.4)(+0.5) (syst) pb. All measurements are in good agreement with theoretical calculations at combined next-to-next-to-leading order quantum chromodynamics and next-to-leading order electroweak accuracy

Performance of the CMS muon trigger system in proton-proton collisions at √s = 13 TeV

The muon trigger system of the CMS experiment uses a combination of hardware and software to identify events containing a muon. During Run 2 (covering 2015-2018) the LHC achieved instantaneous luminosities as high as 2 × 10 cm s while delivering proton-proton collisions at √s = 13 TeV. The challenge for the trigger system of the CMS experiment is to reduce the registered event rate from about 40 MHz to about 1 kHz. Significant improvements important for the success of the CMS physics program have been made to the muon trigger system via improved muon reconstruction and identification algorithms since the end of Run 1 and throughout the Run 2 data-taking period. The new algorithms maintain the acceptance of the muon triggers at the same or even lower rate throughout the data-taking period despite the increasing number of additional proton-proton interactions in each LHC bunch crossing. In this paper, the algorithms used in 2015 and 2016 and their improvements throughout 2017 and 2018 are described. Measurements of the CMS muon trigger performance for this data-taking period are presented, including efficiencies, transverse momentum resolution, trigger rates, and the purity of the selected muon sample. This paper focuses on the single- and double-muon triggers with the lowest sustainable transverse momentum thresholds used by CMS. The efficiency is measured in a transverse momentum range from 8 to several hundred GeV

Measurement of the top quark mass using events with a single reconstructed top quark in pp collisions at root s=13 TeV

Abstract:A measurement of the top quark mass is performed using a data sample en-riched with single top quark events produced in thetchannel. The study is based on proton-proton collision data, corresponding to an integrated luminosity of 35.9 fb−1, recorded at√s= 13TeV by the CMS experiment at the LHC in 2016. Candidate events are selectedby requiring an isolated high-momentum lepton (muon or electron) and exactly two jets,of which one is identified as originating from a bottom quark. Multivariate discriminantsare designed to separate the signal from the background. Optimized thresholds are placedon the discriminant outputs to obtain an event sample with high signal purity. The topquark mass is found to be172.13+0.76−0.77GeV, where the uncertainty includes both the sta-tistical and systematic components, reaching sub-GeV precision for the first time in thisevent topology. The masses of the top quark and antiquark are also determined separatelyusing the lepton charge in the final state, from which the mass ratio and difference aredetermined to be0.9952+0.0079−0.0104and0.83+1.79−1.35GeV, respectively. The results are consistentwithCPTinvariance

Measurements of Higgs boson production cross sections and couplings in the diphoton decay channel at root s=13 TeV

Measurements of Higgs boson production cross sections and couplings in events where the Higgs boson decays into a pair of photons are reported. Events are selected from a sample of proton-proton collisions at root s = 13TeV collected by the CMS detector at the LHC from 2016 to 2018, corresponding to an integrated luminosity of 137 fb(-1). Analysis categories enriched in Higgs boson events produced via gluon fusion, vector boson fusion, vector boson associated production, and production associated with top quarks are constructed. The total Higgs boson signal strength, relative to the standard model (SM) prediction, is measured to be 1.12 +/- 0.09. Other properties of the Higgs boson are measured, including SM signal strength modifiers, production cross sections, and its couplings to other particles. These include the most precise measurements of gluon fusion and vector boson fusion Higgs boson production in several different kinematic regions, the first measurement of Higgs boson production in association with a top quark pair in five regions of the Higgs boson transverse momentum, and an upper limit on the rate of Higgs boson production in association with a single top quark. All results are found to be in agreement with the SM expectations.Peer reviewe

Search for dark photons in Higgs boson production via vector boson fusion in proton-proton collisions at √s = 13 TeV

A search is presented for a Higgs boson that is produced via vector boson fusion and that decays to an undetected particle and an isolated photon. The search is performed by the CMS collaboration at the LHC, using a data set corresponding to an integrated luminosity of 130 fb−1, recorded at a center-of-mass energy of 13 TeV in 2016–2018. No significant excess of events above the expectation from the standard model background is found. The results are interpreted in the context of a theoretical model in which the undetected particle is a massless dark photon. An upper limit is set on the product of the cross section for production via vector boson fusion and the branching fraction for such a Higgs boson decay, as a function of the Higgs boson mass. For a Higgs boson mass of 125 GeV, assuming the standard model production rates, the observed (expected) 95% confidence level upper limit on the branching fraction is 3.5 (2.8)%. This is the first search for such decays in the vector boson fusion channel. Combination with a previous search for Higgs bosons produced in association with a Z boson results in an observed (expected) upper limit on the branching fraction of 2.9 (2.1)% at 95% confidence level