Noves aplicacions de l'àlgebra geomètrica a la física matemàtica

En la presente tesis se han tratado los siguientes aspectos: 1,- Se ha reformulado la presentación de la teoría de espinores consiguiendo una única definición de espinor que da énfasis al observador y matiza el papel del espacio de representación. El formalismo utilizado ha permitido distinguir de manera efectiva entre espinores conceptualmente diferentes. Surge el concepto de espacio interno sin que se requiera ampliar las dimensiones del espacio-tiempo. 2,- En el marco de una teoría clásica de campos, el análisis algebraico de una generalización de la ecuación de Dirac-Hestenes ha permitido encontrar para la partícula y la antipartícula (con A=0) soluciones de energía positiva diferentes. Se demuestra que esta diferencia viene codificada por el ángulo de Yvon-Takabayasi. 3,- Se ha acotado la generalización anterior mediante un estudio de las posibles versiones multivectoriales de la ecuación de Dirac. La preocupación básica ha sido poder plantear la ecuación sobre espinores operadores. 4,- Hemos extendido los trabajos de Lounesto referentes al cambio de signatura. Ha sido realizado desde dos puntos de vista: Z-graduaciones y Z2-graduaciones, consiguiendo en ambos casos expresiones que permiten, dada una signatura, construir todas las estructuras algebraicas y diferenciales asociadas a todas las otras signaturas de la misma dimensión

Noves aplicacions de l'àlgebra geomètrica a la física matemàtica

[spa] En la presente tesis se han tratado los siguientes aspectos: 1,- Se ha reformulado la presentación de la teoría de espinores consiguiendo una única definición de espinor que da énfasis al observador y matiza el papel del espacio de representación. El formalismo utilizado ha permitido distinguir de manera efectiva entre espinores conceptualmente diferentes. Surge el concepto de espacio interno sin que se requiera ampliar las dimensiones del espacio-tiempo. 2,- En el marco de una teoría clásica de campos, el análisis algebraico de una generalización de la ecuación de Dirac-Hestenes ha permitido encontrar para la partícula y la antipartícula (con A=0) soluciones de energía positiva diferentes. Se demuestra que esta diferencia viene codificada por el ángulo de Yvon-Takabayasi. 3,- Se ha acotado la generalización anterior mediante un estudio de las posibles versiones multivectoriales de la ecuación de Dirac. La preocupación básica ha sido poder plantear la ecuación sobre espinores operadores. 4,- Hemos extendido los trabajos de Lounesto referentes al cambio de signatura. Ha sido realizado desde dos puntos de vista: Z-graduaciones y Z2-graduaciones, consiguiendo en ambos casos expresiones que permiten, dada una signatura, construir todas las estructuras algebraicas y diferenciales asociadas a todas las otras signaturas de la misma dimensión

Correlations between flow and transverse momentum in Xe + Xe and Pb + Pb collisions at the LHC with the ATLAS detector: A probe of the heavy-ion initial state and nuclear deformation

The correlations between flow harmonics v for n = 2, 3, and 4 and mean transverse momentum [p] in Xe + Xe and Pb + Pb collisions at s = 5.44 and 5.02 TeV, respectively, are measured using charged particles with the ATLAS detector. The correlations are potentially sensitive to the shape and size of the initial geometry, nuclear deformation, and initial momentum anisotropy. The effects from nonflow and centrality fluctuations are minimized, respectively, via a subevent cumulant method and an event-activity selection based on particle production at very forward rapidity. The v-[p] correlations show strong dependencies on centrality, harmonic number n, p, and pseudorapidity range. Current models qualitatively describe the overall centrality- and system-dependent trends but fail to quantitatively reproduce all features of the data. In central collisions, where models generally show good agreement, the v-[p] correlations are sensitive to the triaxiality of the quadruple deformation. Comparison of the model with the Pb + Pb and Xe + Xe data confirms that the Xe nucleus is a highly deformed triaxial ellipsoid that has neither a prolate nor oblate shape. This provides strong evidence for a triaxial deformation of the Xe nucleus from high-energy heavy-ion collisions

Search for dark matter produced in association with a single top quark and an energetic W boson in √s= 13 TeV pp collisions with the ATLAS detector

This paper presents a search for dark matter, χ , using events with a single top quark and an energetic W boson. The analysis is based on proton–proton collision data collected with the ATLAS experiment at s= 13 TeV during LHC Run 2 (2015–2018), corresponding to an integrated luminosity of 139 fb . The search considers final states with zero or one charged lepton (electron or muon), at least one b-jet and large missing transverse momentum. In addition, a result from a previous search considering two-charged-lepton final states is included in the interpretation of the results. The data are found to be in good agreement with the Standard Model predictions and the results are interpreted in terms of 95% confidence-level exclusion limits in the context of a class of dark matter models involving an extended two-Higgs-doublet sector together with a pseudoscalar mediator particle. The search is particularly sensitive to on-shell production of the charged Higgs boson state, H , arising from the two-Higgs-doublet mixing, and its semi-invisible decays via the mediator particle, a: H→ Wa(→ χχ) . Signal models with H masses up to 1.5 TeV and a masses up to 350 GeV are excluded assuming a tan β value of 1. For masses of a of 150 (250) GeV, tan β values up to 2 are excluded for H masses between 200 (400) GeV and 1.5 TeV. Signals with tan β values between 20 and 30 are excluded for H masses between 500 and 800 GeV

Measurements of the suppression and correlations of dijets in Xe+Xe collisions at Formula Presented TeV

Measurements of the suppression and correlations of dijets is performed using 3 µ b − 1 of Xe+Xe data at s N N = 5.44 TeV collected with the ATLAS detector at the CERN Large Hadron Collider. Dijets with jets reconstructed using the R = 0.4 anti- k t algorithm are measured differentially in jet p T over the range of 32 to 398 GeV and the centrality of the collisions. Significant dijet momentum imbalance is found in the most central Xe+Xe collisions, which decreases in more peripheral collisions. Results from the measurement of per-pair normalized and absolutely normalized dijet p T balance are compared with previous Pb + Pb measurements at s N N = 5.02 TeV. The differences between the dijet suppression in Xe+Xe and Pb + Pb are further quantified by the ratio of pair nuclear-modification factors. The results are found to be consistent with those measured in Pb + Pb data when compared in classes of the same event activity and when taking into account the difference between the center-of-mass energies of the initial parton scattering process in Xe+Xe and Pb + Pb collisions. These results should provide input for a better understanding of the role of energy density, system size, path length, and fluctuations in the parton energy loss

Search for Higgs boson pair production in association with a vector boson in pp collisions at √s=13TeV with the ATLAS detector

This paper reports a search for Higgs boson pair (hh) production in association with a vector boson (WorZ) using 139 fb of proton–proton collision data at s=13TeV recorded with the ATLAS detector at the Large Hadron Collider. The search is performed in final states in which the vector boson decays leptonically (W→ℓν,Z→ℓℓ,νν with ℓ= e, μ) and the Higgs bosons each decay into a pair of b-quarks. It targets Vhh signals from both non-resonant hh production, present in the Standard Model (SM), and resonant hh production, as predicted in some SM extensions. A 95% confidence-level upper limit of 183 (87) times the SM cross-section is observed (expected) for non-resonant Vhh production when assuming the kinematics are as expected in the SM. Constraints are also placed on Higgs boson coupling modifiers. For the resonant search, upper limits on the production cross-sections are derived for two specific models: one is the production of a vector boson along with a neutral heavy scalar resonance H, in the mass range 260–1000 GeV, that decays into hh, and the other is the production of a heavier neutral pseudoscalar resonance A that decays into a Z boson and H boson, where the A boson mass is 360–800 GeV and the H boson mass is 260–400 GeV. Constraints are also derived in the parameter space of two-Higgs-doublet models

Exclusive dielectron production in ultraperipheral Pb+Pb collisions at √sNN = 5.02 TeV with ATLAS

Exclusive production of dielectron pairs, γγ → e e , is studied using L = 1.72 nb of data from ultraperipheral collisions of lead nuclei at sNN = 5.02 TeV recorded by the ATLAS detector at the LHC. The process of interest proceeds via photon–photon interactions in the strong electromagnetic fields of relativistic lead nuclei. Dielectron production is measured in the fiducial region defined by following requirements: electron transverse momentum pTe > 2.5 GeV, absolute electron pseudorapidity |η | 5 GeV, and dielectron transverse momentum pTee < 2 GeV. Differential cross-sections are measured as a function of m, average pTe , absolute dielectron rapidity |y|, and scattering angle in the dielectron rest frame, |cos θ |, in the inclusive sample, and also with a requirement of no activity in the forward direction. The total integrated fiducial cross-section is measured to be 215±1(stat.)−20+23(syst.)±4(lumi.) μb. Within experimental uncertainties the measured integrated cross-section is in good agreement with the QED predictions from the Monte Carlo programs Starlight and SuperChic, confirming the broad features of the initial photon fluxes. The differential cross-sections show systematic differences from these predictions which are more pronounced at high |y | and |cos θ | values. [Figure not available: see fulltext.]

Measurement of the tt¯ production cross-section in pp collisions at √s = 5.02 TeV with the ATLAS detector

The inclusive top-quark pair (tt¯) production cross-section σ is measured in proton–proton collisions at a centre-of-mass energy s = 5.02 TeV, using 257 pb of data collected in 2017 by the ATLAS experiment at the LHC. The tt¯ cross-section is measured in both the dilepton and single-lepton final states of the tt¯ system and then combined. The combination of the two measurements yields σtt¯=67.5±0.9(stat.)±2.3(syst.)±1.1(lumi.)±0.2(beam)pb, where the four uncertainties reflect the limited size of the data sample, experimental and theoretical systematic effects, and imperfect knowledge of both the integrated luminosity and the LHC beam energy, giving a total uncertainty of 3.9%. The result is in agreement with theoretical quantum chromodynamic calculations at next-to-next-to-leading order in the strong coupling constant, including the resummation of next-to-next-to-leading logarithmic soft-gluon terms, and constrains the parton distribution functions of the proton at large Bjorken-x. [Figure not available: see fulltext.

Production of ϒ(nS) mesons in Pb + Pb and pp collisions at 5.02 TeV

A measurement of the production of vector bottomonium states, ϒ(1S), ϒ(2S), and ϒ(3S), in Pb + Pb and pp collisions at a center-of-mass energy per nucleon pair of 5.02 TeV is presented. The data correspond to integrated luminosities of 1.38 nb of Pb + Pb data collected in 2018, 0.44 nb of Pb + Pb data collected in 2015, and 0.26 fb of pp data collected in 2017 by the ATLAS detector at the Large Hadron Collider. The measurements are performed in the dimuon decay channel for transverse momentum p < 30 GeV, absolute rapidity |y| < 1.5, and Pb + Pb event centrality 0-80%. The production rates of the three bottomonium state

Search for resonant WZ production in the fully leptonic final state in proton–proton collisions at √s=13 TeV with the ATLAS detector

A search for a WZ resonance, in the fully leptonic final state (electrons or muons), is performed using 139 fb of data collected at a centre-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider. The results are interpreted in terms of a singly charged Higgs boson of the Georgi–Machacek model, produced by WZ fusion, and of a Heavy Vector Triplet, with the resonance produced by WZ fusion or the Drell–Yan process. No significant excess over the Standard Model prediction is observed and limits are set on the production cross-section times branching ratio as a function of the resonance mass for these processes