ZZ production at high transverse momenta beyond NLO QCD

We study the production of the four-lepton final state $l^+ l^- l^+ l^-$, predominantly produced by a pair of electroweak Z bosons, ZZ. Using the LoopSim method, we merge NLO QCD results for ZZ and ZZ+jet and obtain approximate NNLO predictions for ZZ production. The exact gluon-fusion loop-squared contribution to the ZZ process is also included. On top of that, we add to our merged sample the gluon-fusion ZZ+jet contributions from the gluon-gluon channel, which is formally of N^3LO and provides approximate results at NLO for the gluon-fusion mechanism. The predictions are obtained with the VBFNLO package and include the leptonic decays of the Z bosons with all off-shell and spin-correlation effects, as well as virtual photon contributions. We compare our predictions with existing results for the total inclusive cross section at NNLO and find a very good agreement. Then, we present results for differential distributions for two experimental setups, one used in searches for anomalous triple gauge boson couplings, the other in Higgs analyses in the four charged-lepton final state channel. We find that the approximate NNLO corrections are large, reaching up to 20% at high transverse momentum of the Z boson or the leading lepton, and are not covered by the NLO scale uncertainties. Distributions of the four-lepton invariant mass are, however, stable with respect to QCD corrections at this order.Comment: 21 pages, 2 tables, 9 figure

Análisis de la intención de realizar comercio social en webs con herramientas sociales

El comercio social, o comercio a través de los medios sociales (también conocido como social commerce) es una de las modalidades de comercio electrónico con mayor potencial de crecimiento. Sin embargo, su estudio aún es limitado, por lo que las dinámicas y elementos que afectan a la intención de realizar comercio social requieren de una mayor investigación. La bibliografía existente principalmente analiza la intención de los usuarios de practicar comercio social en una red social, pero no en una web de comercio electrónico que tenga sus propias herramientas sociales (p. ej. foros, valoraciones de productos, etc.). Por lo tanto, la presente investigación tiene como objetivo identificar los antecedentes de la intención de comercio social en webs de comercio electrónico en las que se emplean herramientas sociales. A partir de la revisión de la literatura, se desarrolla un modelo para analizar la influencia de cinco posibles antecedentes de la intención de comercio social: calidad de la web, apoyo social emocional, apoyo social informativo, presencia social e inmersión o flow. Para ello, se realizó un estudio empírico entre los usuarios de una web de comercio electrónico que cuenta con un sistema de valoración, comentarios de productos y foros. Los datos se obtuvieron a partir de una encuesta realizada a 200 compradores, y fueron analizados mediante la técnica PLS. Los resultados indican que los elementos más racionales y emocionales de la experiencia del usuario, como son la calidad del sitio web, flow y el apoyo social emocional, son los que motivan la compra; mientras que la presencia social y el apoyo social informativo, no son significativos. Este estudio contribuye a la teoría del comportamiento del consumidor al aplicar variables predictivas de la intención de comercio social a webs con herramientas sociales. Además, los resultados ayudan a los profesionales del comercio electrónico a mejorar el uso que hacen de las herramientas sociales.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Destination Image on the DMO's Platforms: Official Website and Social Media

Tourists usually configure and develop ideas about possible destinations based on information previously gathered from both social media and the official web of the destination management organization (DMO). In spite of the relevance of said information sources, there have not been many studies evaluating how these different sources influence the destination image. This research proposes a model intended to explain the image creation process of a destination taking into account both the DMO’s online platforms and the perceived psychological distance. The proposed model is tested with an empirical study including a questionnaire which collects data from 264 participants. The validity of the model is reviewed through PLS analysis. Results show that the psychological distance does not influence the overall destination image. In addition, the overall destination image can be estimated to a larger extent when tourists approach social media as their main source of information. Implications and conclusions are discussed.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

El valor percibido en webs de social commerce: Efectos sobre la lealtad del consumidor.

El estudio del comportamiento del consumidor en webs de social commerce está en auge, debido al gran crecimiento del sector en los últimos años. A pesar de ello, su comprensión se encuentra en su infancia, debido a la multitud de factores influyentes. Esta investigación, a través de la metodología del estímulo-organismo-respuesta, estudia qué papel tiene el valor percibido (O) por el consumidor, mediante el análisis de dos de sus principales antecedentes (calidad del sistema y del servicio) (S), así como de sus efectos sobre la lealtad (R). Los resultados obtenidos a partir de la aplicación de la técnica PLS a una muestra de 272 consumidores habituales de estas webs ponen de manifiesto la gran importancia que la calidad de la web tiene en la generación de valor en el consumidor, así como el rol clave de éste sobre las intenciones del consumidor tanto para volver a comprar como para recomendar.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Generalized f(R,ϕ,X)f(R,\phi,X) gravity and the late-time cosmic acceleration

High-precision observational data have confirmed with startling evidence that the Universe is currently undergoing a phase of accelerated expansion. This phase, one of the most important and challenging current problems in cosmology, represents a new imbalance in the governing gravitational equations. Historically, physics has addressed such imbalances by either identifying sources that were previously unaccounted for, or by altering the gravitational theory. Several candidates, responsible for this expansion, have been proposed in the literature, in particular, dark energy models and modified gravity models, amongst others. Outstanding questions are related to the nature of this so-called "dark energy" that is driving this acceleration, and whether it is due to the vacuum energy or a dynamical field. On the other hand, the late-time cosmic acceleration may be due to modifications of General Relativity. In this work we explore a generalised modified gravity theory, namely $f(R,\phi,X)$ gravity, where $R$ is the Ricci scalar, $\phi$ is a scalar field, and $X$ is a kinetic term. This theory contains a wide range of dark energy and modified gravity models. We considered specific models and applications to the late-time cosmic acceleration.Comment: 13 pages, 1 figure; slightly revised version, displayed name corrected. arXiv admin note: text overlap with arXiv:1412.086

Stokes polarimetry and magnetometry using a thermal Rb vapour in the Voigt geometry with large magnetic field

We present investigations of magneto-optical phenomena using a $^{87}$Rb thermal vapour in large magnetic fields. At this point, in the hyperfine Paschen-Back regime, optical transitions can be separated by more than their Doppler-broadened linewidth, providing a high level of control over the atomic system and a simpler theoretical model for studying atom-light-magnetic field interactions. In this context, we study the spectra of $^{87}$Rb at magnetic fields of $0.4~$T and $1.5~$T in the Voigt geometry. In both cases we find excellent agreement between experimental and theoretical absorption spectra. With the $1.5~$T field we also study polarisation changes induced in the light by the atoms subject to a large magnetic field. Using this approach, we consider the practical applications of our system as a vector magnetometer. We present a scheme that eliminates most sources of systematic errors in the measurement of the field strength by using pairs of transitions that cancel excited-state terms in the energy shifts. Finally, we extend the concepts and ideas investigated to an application in precision thermometry. We discuss how good understanding of the spectra and the magnetic field strength potentially allow detection of small differences in different spectral features, which could then be traced to the effect of the Boltzmann factor, $k_{\rm{B}}T$, on the atomic populations