https://repositorioinstitucional.uaslp.mx/xmlui/handle/i/5031 2026-09-02T04:16:25Z https://repositorioinstitucional.uaslp.mx/xmlui/handle/i/10071 Studies of π + → e + + invisible topologies in the NA62 experiment Briano Olvera, Alejandro A search for Heavy Neutral Leptons (HNL) in the decay π+ → e+N is presented using the data set collected by the NA62 experiment in the period 2017-2024. The analysis scans 63 distinct HNL mass hypotheses in the range 95–126 MeV/c2, assuming a lifetime exceeding 50 ns. The observed data are consistent with the background-only hypothesis across the entire mass range, resulting in upper limits on the mixing matrix element |Ue4|2 at the 90% confidence level of the order of 10−8. The same analysis framework was applied to perform studies of the Rπ ratio (Γ(πe2)/Γ(πμ2)) using the common event sample, where both decay modes are identified via their characteristic decay signatures. This work provides a statistical benchmark of the measurement precision; the computed ratio, considering only statistical uncertainties, establishes the intrinsic statistical resolution of the dataset pending future systematic evaluation. 2026-08-26T00:00:00Z https://repositorioinstitucional.uaslp.mx/xmlui/handle/i/9914 Magnetic T3-Atomic and Light-Based Gravimetry Zuñiga Perez, Edgar Alberto Esta tesis desarrolla y analiza enfoques alternativos para la gravimetría de alta precisión basados en interferencia cuántica y óptica. Se estudian dos estrategias principales. En primer lugar, se analiza un gravímetro atómico magnético tipo T³, en el que fuerzas dependientes del estado en un gradiente de campo magnético generan una aceleración diferencial entre paquetes de onda atómicos, produciendo una fase que escala cúbicamente con el tiempo de interrogación. Se presenta un marco teórico que incluye descripciones semiclasicas y cuánticas, así como un análisis de limitaciones como la expansión de la nube atómica y la decoherencia. En segundo lugar, se propone un gravímetro basado en luz, donde la gravedad se mide mediante el corrimiento al rojo gravitacional de fotones en un interferómetro óptico. El modelo considera efectos realistas como potenciales gravitacionales, contribuciones atmosféricas y sistemáticos ópticos, y se compara su sensibilidad con la de gravímetros atómicos. Ambos enfoques se describen dentro de un marco unificado en el que la fase interferométrica está determinada por la acción a lo largo de cada trayectoria, contribuyendo al desarrollo de sensores cuánticos para la medición de la gravedad.; This thesis develops and analyzes alternative approaches to high-precision gravimetry based on quantum and optical interference. Two main strategies are explored. First, a magnetic T³-atomic gravimeter is studied, where state-dependent forces in a magnetic field gradient generate differential acceleration between atomic wave packets, leading to a phase that scales cubically with interrogation time. A theoretical framework is presented, including semiclassical and quantum descriptions, as well as an analysis of limitations such as atomic cloud expansion and decoherence. Second, a light-based gravimeter is proposed, where gravity is measured through the gravitational redshift of photons in an optical interferometer. The model incorporates realistic effects such as gravitational potentials, atmospheric contributions, and optical systematics, and its sensitivity is compared with atomic gravimeters. Both approaches are discussed within a unified framework, where the interferometric phase is determined by the action along each path, contributing to the development of quantum-enhanced gravimetric sensors. 2025-11-01T00:00:00Z https://repositorioinstitucional.uaslp.mx/xmlui/handle/i/9631 Uncontrollabe Errors in the Measurements of an Atomic Gravimeter & A Novel Hybrid Microwave Interferometer for Detection of Molecular Interactions Cervantes Martínez, Juan Mario Abstract 1: There is a persistent interest in minimizing the dimensions of portable atomic gravimeters. This reduction inevitably results in the truncation of the Gaussian wings of the excitation laser beams, the implications of which have not yet been fully assessed. The diffraction pattern generated by this aperture creates ripples in the wavefront, influencing both the phase and the intensity. We examine the alteration in the measured value of an atomic gravimeter due to phase fluctuations in the wavefront. Fortunately, this alteration demonstrates a Gaussian decay in relation to the size of the aperture. For larger clouds, we notice a reduced effect due to averaging across transverse positions that show different shift values. Interestingly, we found that variations in intensity also provide a notable correction to the photon recoil, contributing roughly equally to the previously mentioned shift in the measurement of gravitational acceleration. Our results should aid in establishing the minimum size of an apparatus necessary to achieve a certain level of accuracy. Abstract 2: We expand on a new approach for determining whether two molecules interact to create a compound molecule. This method involves exciting the sample using two distinct laser frequencies and assessing the relative phase shift of the transmitted light. The proposed design stimulates the sample within the optical range where a significant response occurs and utilizes a hybrid microwave interferometer to measure the phase. The method has advantageous scaling with the experimental parameters. This approach is highly resilient to external phase variations, including those caused by temperature changes, which typically pose the greatest challenge in interferometric measurements. 2025-11-27T00:00:00Z https://repositorioinstitucional.uaslp.mx/xmlui/handle/i/8788 Construction of SU(N) Projection Operators: Applications to Particle and Nuclear Physics Hernández Ybarra, Johann Edir Projection operators for irreducible representation of SU(N) have been constructed, and a method to decompose any tensor operator which transforms under this group is described. Two applications for the method have been developed, the first one in the context of the 1/Nc expansion of QCD, and a second one for the interacting boson model (IBM). 2024-09-03T00:00:00Z