Search results for "Partículas"
showing 10 items of 105 documents
Search for new physics in single-top-quark production with the ATLAS detector at the LHC
2018
Esta tesis presenta dos análisis dedicados a la búsqueda de nueva física en eventos de producción de quarks top únicos con datos recopilados por el detector ATLAS en el LHC. A pesar de su gran éxito, se cree que debe haber una teoría más general que subyace al Modelo Estándar de física de partículas que arroge luz a preguntas sin respuesta, como la asimetría de materia-antimateria del universo o la existencia de la Materia Oscura. Esta tesis cubre dos enfoques diferentes para abordar los dos temas anteriores. El objetivo del primer análisis es explorar la estructura del vértice Wtb a través de la medición de asimetrías angulares relacionadas con los observables de polarización del bosón W q…
Study of Bs->PhiGamma decays at LHCb
2021
This thesis describes two different analyses performed at LHCb using the B0s→φγ and B0→K∗0γ decay channels. First, the measurement of the ratio of branching fractions B(B0→K∗0γ)/B(B0s→φγ) is presented, giving the most precise value for B(B0s→φγ) to date. Secondly, the CP-violating observables S and C, as well as the mixing-induced A∆ parameter are measured through a time-dependent analysis of the B0s→φγ decay channel, this being the first time the S and C observables are probed in the Bs system. These studies are performed using data collected in 2011 and 2012 by the LHCb experiment at CERN, corresponding to an integrated luminosity of 3.0 fb−1 of pp collisions at a center-of-mass energy of…
Bottom-up approach within the electroweak effective theory: Constraining heavy resonances
2020
The LHC has confirmed the existence of a mass gap between the known particles and possible new states. Effective field theory is then the appropriate tool to search for low-energy signals of physics beyond the Standard Model. We adopt the general formalism of the electroweak effective theory, with a non-linear realization of the electroweak symmetry breaking, where the Higgs is a singlet with independent couplings. At higher energies we consider a generic resonance Lagrangian which follows the above-mentioned non-linear realization and couples the light particles to bosonic heavy resonances with $J^P=0^\pm$ and $J^P=1^\pm$. Integrating out the resonances and assuming a proper short-distance…
Coherent neutrino scattering
2009
We present a microscopic model for coherent pion production off nuclei induced by neutrinos. This model is built upon a model for single nucleon processes that goes beyond the usual Delta dominance by including non resonant background contributions. We include nuclear medium effects: medium corrections to Delta$ properties and outgoing pion absortion via an optical potential. This results in major modifications to cross sections for low energy experiments when compared with phenomenological models like Rein-Sehgal's.
Measurement of the flavour composition of dijet events in pp collisions at √s = 7 TeV with the ATLAS detector
2013
This paper describes a measurement of the flavour composition of dijet events produced in pp collisions at s√=7~TeVs=7~TeV using the ATLAS detector. The measurement uses the full 2010 data sample, corresponding to an integrated luminosity of 39 pb−1. Six possible combinations of light, charm and bottom jets are identified in the dijet events, where the jet flavour is defined by the presence of bottom, charm or solely light flavour hadrons in the jet. Kinematic variables, based on the properties of displaced decay vertices and optimised for jet flavour identification, are used in a multidimensional template fit to measure the fractions of these dijet flavour states as functions of the leadin…
Efectos vasculares de las nanopartículas de óxido de cerio en la vena safena humana
2022
Las nanopartículas de óxido de cerio (CeO2NPs) podrían tener un futuro prometedor como nanomaterial de uso médico debido a su poder antioxidante y su alta biocompatibilidad, entre otras características. Sin embargo, sus efectos en el sistema cardiovascular están poco estudiados y es por ello que, en la presente tesis nos centramos en el estudio de las CeO2NPs a nivel vascular, utilizando segmentos de vena safena interna humana. Nuestra hipótesis es que las CeO2NPs podrían tener propiedades antioxidantes a nivel vascular, especialmente por actuar como miméticas de la superóxido dismutasa (SOD) y disminuir los niveles del anión superóxido (.O2 ). Esto aumentaría la biodisponibilidad de óxido …
Composite scalars and dark matter from four-fermion interactions
2022
Parte I: Emergencia de masas en el Modelo Estándar El bosón de Higgs es un campo escalar del Modelo Estándar (SM, por sus siglas en inglés) de partı́culas elementales que cumple dos funciones muy importantes. Por un lado permite construir una teorı́a renormalizable. El potencial escalar contiene un término de masa y un término cuadrático en el campo de Higgs, los cuales son ajus- tados en base a mediciones experimentales y haciéndolos compatible con la aparición de una ruptura espontánea de la simetrı́a SU (2) L × U (1) Y del SM. Y por otra parte ayuda a explicar la masa de todos los fermiones en el esquema de la teorı́a cuántica de campos, al poseer interacciones de tipo Yukawa que son aju…
Estudio unificado del espectro y propiedades de mesones pesados para energı́as por debajo y por encima de umbrales mesón-mesón
2022
Asymptotic freedom and color confinement are undoubtedly the most remarkable aspects of quantum chromodynamics (QCD). Indeed, it is because of these features that QCD is universally accepted as the quantum field theory of strong interactions. On the one hand, asymptotic freedom, meaning that the theory approaches a noninteracting one in the high energy limit, allows for a perturbative treatment, so that the QCD Lagrangian can be used to derive analytical expressions describing high-energy processes. On the other hand, color confinement, implying that all observable states are color-neutral, is a purely nonperturbative phenomenon, which prevents an analytical calculation of the low-energy in…
Universal features of the nuclear matrix elements governing the mass sector of the 0νββ decay
2005
In this work we report on manifest universal features found in the nuclear matrix elements which govern the mass sector of the neutrinoless double beta decay. The results are based on the analysis of the calculated matrix elements corresponding to the decays of 76Ge, 82Se, 100Mo, and 116Cd. The results suggest a dominance of few low-lying nuclear states of few multipoles in these matrix elements. Dedicated charge-exchange reactions could be used to probe these key states to determine experimentally the value of the nuclear matrix element.
Microscopic calculations of the hipernucleus λ5He
1993
Ground state results for the hypernucleus λ5He are reported. They have been calculated with a variatonal Jastrow-like trial wave function and also within the Diffusion Monte Carlo method. Simple central potential have been used to describe NN and λN interactions. The validity of the rigid core approximation is discussed. Guardiola Barcena, Rafael, Rafael.Guardiola@ific.uv.es Navarro Salas, Jose, Jose.Navarro@ific.uv.es