Automation of NLO QCD and EW corrections with Sherpa and Recola

This publication presents the combination of the one-loop matrix-element generator Recola with the multipurpose Monte Carlo program Sherpa. Since both programs are highly automated, the resulting Sherpa+Recola framework allows for the computation of -in principle- any Standard Model process at both NLO QCD and EW accuracy. To illustrate this, three representative LHC processes have been computed at NLO QCD and EW: vector-boson production in association with jets, off-shell Z-boson pair production, and the production of a top-quark pair in association with a Higgs boson. In addition to fixed-order computations, when considering QCD corrections, all functionalities of Sherpa, i.e. particle decays, QCD parton showers, hadronisation, underlying events, etc. can be used in combination with Recola. This is demonstrated by the merging and matching of one-loop QCD matrix elements for Drell-Yan production in association with jets to the parton shower. The implementation is fully automatised, thus making it a perfect tool for both experimentalists and theorists who want to use state-of-the-art predictions at NLO accuracy.Comment: 38 pages, 29 figures. Matches the published version (few typos corrected

QCD and electroweak corrections to WZ scattering at the LHC

We present the first computation of the full next-to-leading-order QCD and electroweak corrections to the WZ scattering process at the LHC. All off-shell, gauge-boson-decay, and interference effects are taken into account for the process $\mathrm{p} \mathrm{p} \to \mu^+\mu^-\mathrm{e}^+\nu_\mathrm{e} \mathrm{j} \mathrm{j} + X$ at the orders $\mathcal{O}{\left( \alpha_\mathrm{s} \alpha^6 \right)}$ and $\mathcal{O}{\left( \alpha^7 \right)}$. The electroweak corrections feature the typical Sudakov behaviour towards high energy and amount to $-16\%$ relative to the electroweak contribution to the integrated cross section. Moreover, the corrections induce significant shape distortions in differential distributions. The next-to-leading-order analysis of the quark- and gluon-induced channels is supplemented by a leading-order study of all possible contributions to the full 4\ell+2\mbox{jets} production cross section in a realistic fiducial phase-space volume

Dissociative dynamics of spin-triplet and spin-singlet O2 on Ag(100)

10 páginas, 8 figuras.We study the dissociative dynamics of O2 molecules on the Ag(100) surface. Initially, the impinging molecules are either in the spin-triplet ground state or in the spin-singlet excited state. The molecule-surface interaction is obtained in each case by constructing the six-dimensional potential energy surface (PES) from the interpolation of the energies calculated with spin-polarized and non-spin-polarized density functional theories, respectively. Classical trajectory calculations performed in both PESs show that O2 molecules initially in the spin-triplet ground state only dissociate for incidence energies above 1.05 eV. This result is consistent with molecular beam experiments performed in this system. Interestingly, our results also suggest that for the spin-singlet O2 dissociation occurs even for incidence energies as low as 50 meV. We propose the use of spin-singlet excited O2 molecules to improve the otherwise low dissociative reactivity of O2 at clean Ag(100).We acknowledge partial support by the Spanish MEC (Grant No. FIS2007-66711-C02-02), the Basque Government (Grant No. CTP07-P02), and the Basque Departamento de Educación, Universidades e Investigación, the University of the Basque Country UPV/EHU (Grant No. IT-366-07). Computational resources were provided by the SGI/IZO-SGIker at the UPV/EHU (supported by the Spanish Ministry of Education and Science and the European Social Fund) and the DIPC computer center.Peer reviewe

EVALUATION OF THE CYTOTOXICITY OF PULP FLOOR PERFORATION FILLING MATERIALS BY USING IN PARALLEL 2D AND 3D CULTURE MODELS

Oral Communication presented at the ";Forum des Jeunes Chercheurs";, Brest (France) 2011

NNLO QCD predictions for W+c-jet production at the LHC

We study the production of a W boson in association with a c-jet at the LHC. We calculate, for the first time, the complete set of NNLO QCD corrections to the dominant CKM-diagonal contribution to this process. Both signatures, ${\rm p}{\rm p}\to \mu^+\nu_\mu{\rm j}_{\rm c}$ and ${\rm p}{\rm p}\to \mu^-\bar\nu_\mu{\rm j}_{\rm c}$ are considered. We present predictions for fiducial cross sections and differential distributions for each one of the two signatures as well as for their ratio. The theoretical predictions are compared with ATLAS measurements at $7 \; {\rm TeV}$. The results of this work are essential for the precision description of associated heavy flavor production at hadron colliders and for the determination of the strange-quark content of the proton from LHC data in NNLO QCD

NLO QCD and EW corrections to vector-boson scattering into ZZ at the LHC

We present the first calculation of the full next-to-leading-order electroweak and QCD corrections for vector-boson scattering (VBS) into a pair of Z bosons at the LHC. We consider specifically the process ${\rm pp\to e^{+}e^{-}\mu^{+}\mu^{-}jj}+X$ at orders $\mathcal{O}(\alpha^7)$ and $\mathcal{O}(\alpha_s\alpha^6)$ and take all off-shell and interference contributions into account. Owing to the presence of enhanced Sudakov logarithms, the electroweak corrections amount to $-16\%$ of the leading-order electroweak fiducial cross section and induce significant shape distortions of differential distributions. The QCD corrections on the other hand are larger ($+24\%$) than typical QCD corrections in VBS. This originates from considering the full computation including tri-boson contributions in a rather inclusive phase space. We also provide a leading-order analysis of all contributions to the cross section for ${\rm pp \to e^{+}e^{-}\mu^{+}\mu^{-}jj}+X$ in a realistic setup

Utilidad de un sistema de seguimiento óptico de instrumental en cirugía laparoscópica para evaluación de destrezas motoras

En este trabajo se estudia la utilidad de un sistema de evaluación de destrezas quirúrgicas basado en el análisis de los movimientos del instrumental laparoscópico. Método: El sistema consta de un simulador físico laparoscópico y un sistema de seguimiento y evaluación de habilidades técnicas quirúrgicas. En el estudio han participado 6 cirujanos con experiencia intermedia (entre 1 y 50 intervenciones laparoscópicas) y 5 cirujanos expertos (más de 50 intervenciones laparoscópicas), todos ellos con la mano derecha como dominante. Cada sujeto realizó 3 repeticiones de una tarea de corte con la mano derecha en tejido sintético, una disección de la serosa gástrica y una sutura en la disección realizada. Para cada ejercicio se analizaron los parámetros de tiempo, distancia recorrida, velocidad, aceleración y suavidad de movimientos para los instrumentos de ambas manos. Resultados: En la tarea de corte, los cirujanos expertos muestran menor aceleración (p = 0,014) y mayor suavidad en los movimientos (p = 0,023) en el uso de la tijera. Respecto a la actividad de disección, los cirujanos expertos requieren menos tiempo (p = 0,006) y recorren menos distancia con ambos instrumentos (p = 0,006 para disector y p = 0,01 para tijera). En la tarea de sutura, los cirujanos expertos presentan menor tiempo de ejecución que los cirujanos de nivel intermedio (p = 0,037) y recorren menos distancia con el disector (p = 0,041). Conclusiones: El sistema de evaluación se mostró útil en las tareas de corte, disección y sutura, y constituye un progreso en el desarrollo de sistemas avanzados de entrenamiento y evaluación de destrezas quirúrgicas laparoscópicas

A Stokes-based spectro-polarimetric analysis of the amplified spontaneous emission in a semiconductor optical amplifier

Semiconductor Optical Amplifiers (SOAs), key devices for future all-optical communication systems, are inherently polarisation-dependent, which is a major drawback for most networks applications. In spite of numerous studies carried out in order to design polarisation-insensitive structures, no complete spectro-polarimetric characterization of a SOA has been published so far. In particular, the spectral and polarimetric behaviour of the Amplified Spontaneous Emission (ASE), acting as a partly polarized broadband source, is of interest, since ASE draws from the same carrier reservoir as the amplified signal. In this paper, we present a full spectro-polarimetric characterization of ASE emitted from a commercial, strained-bulk SOA within the frame of the Stokes formalism. This formalism not only allows a determination of the degree of polarisation (DOP) of ASE directly from its Stokes vector, but also gives access to a full, spectrally resolved characterization of its polarized fraction with respect to the bias current applied to the SOA. The way the state of polarisation of that fraction is governed by the dependence of the material gain upon polarisation is spectrally resolved, quantified, and discussed. The same study is performed when a polarized signal is injected into the SOA

Interaction of low-energy electrons with surface polarity near ferroelastic domain boundaries

We derive surface polarity at and near ferroelastic domain boundaries from molecular dynamics simulations based on an ionic spring model. Interatomic gradient forces lead to flexoelectricity which, in turn, generates polarity at the surface and in twin boundaries. We then derive generic properties of electron scattering spectra equivalent to those observed in low-energy electron microscopy (LEEM) and mirror electron microscopy (MEM) experiments. Negatively (positively) charged surfaces reflect (attract) incident electrons with low kinetic energy. The electron images reveal the valley and ridge surface structures near the intersection of the twin boundary and the surface. Polarity in surface layers is predicted to be visible in LEEM and MEM spectra at neutral surfaces, but much less when surfaces are charged. Inward polarity reflects electrons similar to negative surface charges, and outward polarity backscatters electrons like positive surface charges. Both the polarity in the twin boundary and the physical topography scatter electrons, consistent with experimental LEEM and MEM experiments on CaTi O 3 with (001) and (111) surface terminations.EPSR

Vector boson scattering processes: Status and prospects

Insight into the electroweak (EW) and Higgs sectors can be achieved through measurements of vector boson scattering (VBS) processes. The scattering of EW bosons are rare processes that are precisely predicted in the Standard Model (SM) and are closely related to the Higgs mechanism. Modifications to VBS processes are also predicted in models of physics beyond the SM (BSM), for example through changes to the Higgs boson couplings to gauge bosons and the resonant production of new particles. In this review, experimental results and theoretical developments of VBS at the Large Hadron Collider, its high luminosity upgrade, and future colliders are presented