Search results for "Dark matter"
showing 10 items of 627 documents
Simulations of the effect of the contact energy levels on a simple model of a hot carrier cell
2016
In the present work, the performance of a simplified model of a hot carrier cell is examined at different energy levels of carrier collection. Incident photons, Monte Carlo generated by employing the ASTM G173-03 data set, are accounted for individually as they interact with the cell. It is assumed that the carriers can be collected ultra-fast, thus avoiding considering hot carrier thermalisation effects. Although the model is preliminary and lacking some mechanisms of hot carrier cells, it has been demonstrated that the present approach to modelling hot carrier solar cells can be developed into fully working models. Some effects of the absorption energy levels in the valence band have been…
Dark matter search in the top-quark sector with the ATLAS detector at the LHC
2020
Astronomical and cosmological observations support the existence of invisible matter that can only be detected through its gravitational effects, thus making it very difficult to study. This component, called dark matter, makes up about 26.8\% of the known universe. Experiments at the LHC, located at CERN, search for new particles to be dark matter candidates. A dark matter production can consist of an excess of events with a single final-state object X recoiling against large amount of missing momentum of energy called mono-X signal. The studies presented in this thesis are focused on the mono-X signature, with X being a top quark, named mono-top. The topology is studied, where the $W$ bos…
Topics in Physics Beyond the Standard Model
2020
El Modelo Estándar (SM) de partículas es una teoría hermosa y extensamente contrastada. De hecho, sus éxitos son innumerables y algunas de sus predicciones, como el momento magnético anómalo de los electrones, se han confirmado con una precisión de una parte en 1010 (!). Sin embargo, y por suerte para mi doctorado, todavía hay preguntas abiertas que no se explican dentro del SM y requieren probablemente una dinámica subyacente o nueva física más allá del SM (BSM). Esta tesis explora, desde un punto de vista fenomenológico, algunas de las posibles extensiones del SM que permiten las preguntas abiertas en física fundamental: • El origen de las masas de los neutrinos • El origen de la asimetrí…
Dark Matter Phenomenology: Sterile Neutrino Portal and Gravitational Portal in Extra-Dimensions
2021
El Modelo Estándar de las Interacciones Fundamentales (SM) representa una de las teorías más precisas de la física. Entre las predicciones del SM encontramos, por ejemplo, el momento magnético anómalo del electrón a_e = 0,001159652181643 (764). Esta predicción coincide con los resultados experimentales en más de diez dígitos significativos, la predicción más precisa en la historia de la física. Sin embargo, hoy en día tenemos varias evidencias de que el SM solo explica el 5% del contenido de materia del Universo. El otro 95% está compuesto por las denominadas Energía Oscura y Materia Oscura. Como sugieren sus nombres, la naturaleza de estos dos componentes del contenido de energía / materia…
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…
Search for a Stable Six-Quark State at BABAR
2019
Recent investigations have suggested that the six-quark combination uuddss could be a deeply bound state (S) that has eluded detection so far, and a potential dark matter candidate. We report the first search for a stable, doubly strange six-quark state in Upsilon -> S anti-Lambda anti-Lambda decays based on a sample of 90 million Upsilon(2S) and 110 million Upsilon(3S) decays collected by the BABAR experiment. No signal is observed, and 90% confidence level limits on the combined Upsilon(2S,3S) -> S anti-Lambda anti-Lambda branching fraction in the range (1.2-1.4)x10^-7 are derived for m_S < 2.05 GeV. These bounds set stringent limits on the existence of such exotic particles.
Using machine learning to disentangle LHC signatures of Dark Matter candidates
2019
We study the prospects of characterising Dark Matter at colliders using Machine Learning (ML) techniques. We focus on the monojet and missing transverse energy (MET) channel and propose a set of benchmark models for the study: a typical WIMP Dark Matter candidate in the form of a SUSY neutralino, a pseudo-Goldstone impostor in the shape of an Axion-Like Particle, and a light Dark Matter impostor whose interactions are mediated by a heavy particle. All these benchmarks are tensioned against each other, and against the main SM background ($Z$+jets). Our analysis uses both the leading-order kinematic features as well as the information of an additional hard jet. We explore different representa…
Robust Neutrino Constraints by Combining Low Redshift Observations with the CMB
2009
We illustrate how recently improved low-redshift cosmological measurements can tighten constraints on neutrino properties. In particular we examine the impact of the assumed cosmological model on the constraints. We first consider the new HST H-0 = 74.2 +/- 3.6 measurement by Riess et al. (2009) and the sigma(8)(Omega(m)/0.25)(0.41) = 0.832 +/- 0.033 constraint from Rozo et al. (2009) derived from the SDSS maxBCG Cluster Catalog. In a ACDM model and when combined with WMAP5 constraints, these low-redshift measurements constrain Sigma m(v) < 0.4 eV at the 95% confidence level. This bound does not relax when allowing for the running of the spectral index or for primordial tensor perturbations…
Future CMB cosmological constraints in a dark coupled universe
2010
Cosmic microwave background satellite missions as the ongoing Planck experiment are expected to provide the strongest constraints on a wide set of cosmological parameters. Those constraints, however, could be weakened when the assumption of a cosmological constant as the dark energy component is removed. Here we show that it will indeed be the case when there exists a coupling among the dark energy and the dark matter fluids. In particular, the expected errors on key parameters as the cold dark matter density and the angular diameter distance at decoupling are significantly larger when a dark coupling is introduced. We show that it will be the case also for future satellite missions as EPIC…
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: Baryon Acoustic Oscillations in the Data Release 10 and 11 galaxy…
2014
We present a one per cent measurement of the cosmic distance scale from the detections of the baryon acoustic oscillations in the clustering of galaxies from the Baryon Oscillation Spectroscopic Survey (BOSS), which is part of the Sloan Digital Sky Survey III (SDSS-III). Our results come from the Data Release 11 (DR11) sample, containing nearly one million galaxies and covering approximately $8\,500$ square degrees and the redshift range $0.2<z<0.7$. We also compare these results with those from the publicly released DR9 and DR10 samples. Assuming a concordance $\Lambda$CDM cosmological model, the DR11 sample covers a volume of 13\,Gpc${}^3$ and is the largest region of the Universe ever su…