Search for pair-produced resonances decaying to quark pairs in proton-proton collisions at root s=13 TeV

A general search for the pair production of resonances, each decaying to two quarks, is reported. The search is conducted separately for heavier resonances (masses above 400 GeV), where each of the four final-state quarks generates a hadronic jet resulting in a four-jet signature, and for lighter resonances (masses between 80 and 400 GeV), where the pair of quarks from each resonance is collimated and reconstructed as a single jet resulting in a two-jet signature. In addition, a b-tagged selection is applied to target resonances with a bottom quark in the final state. The analysis uses data collected with the CMS detector at the CERN LHC, corresponding to an integrated luminosity of 35.9 fb(-1), from proton-proton collisions at a center-of-mass energy of 13 TeV. The mass spectra are analyzed for the presence of new resonances, and are found to be consistent with standard model expectations. The results are interpreted in the framework of R-parity-violating supersymmetry assuming the pair production of scalar top quarks decaying via the hadronic coupling lambda ''(312) or lambda ''(323) and upper limits on the cross section as a function of the top squark mass are set. These results probe a wider range of masses than previously explored at the LHC, and extend the top squark mass limits in the (t) over tilde -> qq' scenario.Peer reviewe

Operation and performance of the ATLAS Tile Calorimeter in Run 1

The Tile Calorimeter is the hadron calorimeter covering the central region of the ATLAS experiment at the Large Hadron Collider. Approximately 10,000 photomultipliers collect light from scintillating tiles acting as the active material sandwiched between slabs of steel absorber. This paper gives an overview of the calorimeter’s performance during the years 2008–2012 using cosmic-ray muon events and proton–proton collision data at centre-of-mass energies of 7 and 8TeV with a total integrated luminosity of nearly 30 fb−1. The signal reconstruction methods, calibration systems as well as the detector operation status are presented. The energy and time calibration methods performed excellently, resulting in good stability of the calorimeter response under varying conditions during the LHC Run 1. Finally, the Tile Calorimeter response to isolated muons and hadrons as well as to jets from proton–proton collisions is presented. The results demonstrate excellent performance in accord with specifications mentioned in the Technical Design Report

Obtención de celulosa blanqueada de Ricinus communis L. mezclada con fibra industrial para fabricar papel bond

En este estudio se describe el procedimiento para obtener celulosa de Ricinus communis blanqueada y mezclada con fibra industrial para su evaluación e incorporación en la fabricación de papel bond. Se extrajo una muestra del tallo, se le descortezó y astilló; posteriormente, se aplicó el proceso alcalino para celulosa (sosa y Kraft). Mediante un modelo factorial, se determinó el número de Kappa y de viscosidad, y se llevó acabo la evaluación fisicomecánica de las pulpas al sulfato y a la sosa, así como de la industrial, denominadas fibra corta (FC) y fibra larga (FL). En la segunda etapa, se caracterizó la pulpa de la especie señalada y se le blanqueó con la secuencia OD (OP) D; enseguida, se aplicaron las variables de mezcla fibrosa (100, 80, 60, 40 y 20 %) y se calificó, de nuevo, para determinar la mejor. Los resultados indican que la celulosa de R. communis blanqueada por el proceso señalado y obtenida por medio de la cocción de alcalinos (sosa-Kraft), sí puede proponerse como componente fibroso del papel bond, acompañado de fibra larga en un intervalo de 40 a 80 % Esto representaría una disminución en los costos de la fibra corta industrial (FC), y favorecería el aprovechamiento de una fuente fibrosa no convencional, clasificada como maleza vegetal

Group 10 Metal Benzene-1,2-dithiolate Derivatives in the Synthesis of Coordination Polymers Containing Potassium Countercations

The use of theoretical calculations has allowed us to predict the coordination behavior of dithiolene [M­(SC₆H₄S)₂]^2– (M = Ni, Pd, Pt) entities, giving rise to the first organometallic polymers {[K₂(μ-H₂O)₂]­[Ni­(SC₆H₄S)₂]}_<i>n</i> and {[K₂(μ-H₂O)₂(thf)]₂[K₂(μ-H₂O)₂(thf)₂]­[Pd₃(SC₆H₄S)₆]}_<i>n</i> by one-pot reactions of the corresponding d¹⁰ metal salts, 1,2-benzenedithiolene, and KOH. The polymers are based on σ,π interactions between potassium atoms and [M­(SC₆H₄S)₂]^2– (M = Ni, Pd) entities. In contrast, only σ interactions are observed when the analogous platinum derivative is used instead, yielding the coordination polymer {[K₂(μ-thf)₂]­[Pt­(SC₆H₄S)₂]}_<i>n</i>

Electrical Bistability around Room Temperature in an Unprecedented One-Dimensional Coordination Magnetic Polymer

The synthesis, crystal structure, and physical properties of an unprecedented one-dimensional (1D) coordination polymer containing [Fe₂(S₂C₆H₂Cl₂)₄]^2– entities bridged by dicationic [K₂(μ-H₂O)₂(THF)₄]²⁺ units are described. The magnetic properties show that the title compound presents pairwise Fe–Fe antiferromagnetic interactions that can be well reproduced with a <i>S</i> = 1/2 dimer model with an exchange coupling, <i>J</i> = −23 cm^–1. The electrical conductivity measurements show that the title compound is a semiconductor with an activation energy of about 290 meV and two different transitions, both with large hysteresis of about 60 and 30 K at 260–320 K and 350–380 K, respectively. These two transitions are assumed to be due to slight structural changes in the cation–anion interactions. Differential Scanning Calorimetry confirms the presence of both transitions. This compound represents the first sample of a coordination polymer showing electrical bistability