Universidad Iberoamericana Ciudad de México

About: Universidad Iberoamericana Ciudad de México is a education organization based out in Mexico City, Mexico. It is known for research contribution in the topics: Large Hadron Collider & Standard Model. The organization has 2259 authors who have published 3981 publications receiving 109298 citations.

Search for high mass dijet resonances with a new background prediction method in proton-proton collisions at √s = 13 TeV

Abstract: A search for narrow and broad resonances with masses greater than 1.8 TeV decaying to a pair of jets is presented. The search uses proton-proton collision data at $ \sqrt{s} $ = 13 TeV collected at the LHC, corresponding to an integrated luminosity of 137 fb$^{−1}$. The background arising from standard model processes is predicted with the fit method used in previous publications and with a new method. The dijet invariant mass spectrum is well described by both data-driven methods, and no significant evidence for the production of new particles is observed. Model independent upper limits are reported on the production cross sections of narrow resonances, and broad resonances with widths up to 55% of the resonance mass. Limits are presented on the masses of narrow resonances from various models: string resonances, scalar diquarks, axigluons, colorons, excited quarks, color-octet scalars, W′ and Z′ bosons, Randall-Sundrum gravitons, and dark matter mediators. The limits on narrow resonances are improved by 200 to 800 GeV relative to those reported in previous CMS dijet resonance searches. The limits on dark matter mediators are presented as a function of the resonance mass and width, and on the associated coupling strength as a function of the mediator mass. These limits exclude at 95% confidence level a dark matter mediator with a mass of 1.8 TeV and width 1% of its mass or higher, up to one with a mass of 4.8 TeV and a width 45% of its mass or higher.[graphic not available: see fulltext]

Optimization of the antioxidant and antimicrobial response of the combined effect of nisin and avocado byproducts

Abstract: This study is focused on optimizing, by surface response methodology, the mixture of natural additives: nisin (an antimicrobial peptide) in combination with avocado seed or avocado peel extracts (both with antioxidant capacities) in order to maximize the antioxidant activity and antimicrobial response against some food-borne bacteria such as Listeria . The peel or seed extracts used in the mixture showed radical scavenging capacity and antioxidant activity due to their polyphenol composition, including kaempferide, epicatechin, chlorogenic acid, epicatechin gallate, among others. During optimization, the results showed that the major antioxidant response in the mixture was mainly provided by the peel extract compared with nisin, seed and their combinations in different proportions. In the antimicrobial response, a synergic effect was observed in the mixtures of each avocado byproduct extract with nisin. Maximum antioxidant and antimicrobial response were obtained with the mixture of 61% of peel extract with 39% of nisin ( p

Search for electroweak production of charginos and neutralinos using leptonic final states in pp collisions at sqrt(s) = 7 TeV

Abstract: The 2011 dataset of the CMS experiment, consisting of an integrated luminosity of 4.98 inverse femtobarns of pp collisions at sqrt(s) = 7 TeV, enables expanded searches for direct electroweak pair production of charginos and neutralinos in supersymmetric models as well as their analogs in other models of new physics. Searches sensitive to such processes, with decays to final states that contain two or more leptons, are presented. Final states with three leptons, with a same-sign lepton pair, and with an opposite-sign lepton pair in conjunction with two jets, are examined. No excesses above the standard model expectations are observed. The results are used in conjunction with previous results on four-lepton final states to exclude a range of chargino and neutralino masses from approximately 200 to 500 GeV in the context of models that assume large branching fractions of charginos and neutralinos to leptons and vector bosons.

Charged particle transverse momentum spectra in pp collisions at s√=0.9 and 7 TeV

Abstract: The charged particle transverse momentum (pT) spectra are presented for pp collisions at sqrt(s)=0.9 and 7 TeV. The data samples were collected with the CMS detector at the LHC and correspond to integrated luminosities of 231 inverse microbarns and 2.96 inverse picobarns, respectively. Calorimeter-based high-transverse-energy triggers are employed to enhance the statistical reach of the high-pT measurements. The results are compared with both leading-order QCD and with an empirical scaling of measurements at different collision energies using the scaling variable xT = 2 pT/sqrt(s) over the pT range up to 200 GeV/c. Using a combination of xT scaling and direct interpolation at fixed pT, a reference transverse momentum spectrum at sqrt(s)=2.76 TeV is constructed, which can be used for studying high-pT particle suppression in the dense QCD medium produced in heavy-ion collisions at that centre-of-mass energy.

Search for neutral MSSM Higgs bosons decaying into a pair of bottom quarks

Abstract: A search for neutral Higgs bosons decaying into a b (b) over bar quark pair and produced in association with at least one additional b quark is presented. This signature is sensitive to the Higgs sector of the minimal supersymmetric standard model (MSSM) with large values of the parameter tan beta. The analysis is based on data from proton-proton collisions at a center-of-mass energy of 8 TeV collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 19.7 fb(-1). The results are combined with a previous analysis based on 7 TeV data. No signal is observed. Stringent upper limits on the cross section times branching fraction are derived for Higgs bosons with masses up to 900 GeV, and the results are interpreted within different MSSM benchmark scenarios, m(h)(max), m(h)(mod+), m(h)(mod-), light-stau and light-stop. Observed 95% confidence level upper limits on tan beta, ranging from 14 to 50, are obtained in the m(h)(mod+) benchmark scenario.