Browsing by Author "Universidad Tecnica Federico Santa Maria UTFSM FISICA"

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COLOR PROPAGATION IN COLD AND HOT MATTER
(2018) LOPEZ LOPEZ, JORGE ANDRES; BROOKS, WILLIAM; Universidad Tecnica Federico Santa Maria UTFSM FISICA
The propagation of color traversing the nuclear medium is studied in mediumenergy semi-inclusive deep inelastic scattering in nuclei and in high energylead-lead collisions, using existing published HERMES data and performinga measurement with the ATLAS detector at the LHC respectively. Differentaspects are analyzed. In the first part two related observables are combinedand modeled using a new geometric model that describes both simultaneously.The model provides information on the transport coefficient and the colorlifetime or production length in the cold medium produced in electron-nucleusscattering at medium energies. In the second part the measurement of theprompt and non-prompt J/u elliptic flow coefficient in lead-lead collisionswith the ATLAS detector at the LHC is performed. This coefficient is anexcellent observable linked to the color lifetime of charm and bottom quarks,probed by measuring the prompt and non-prompt J/u , in the hot densemedium created in high energy nucleus-nucleus collisions.
DARK MATTER AND HIGGS PHENOMENOLOGY BEYOND STANDARD MODEL
(2016) Rojas Abatte, Felipe Angel Custodio; Zerwekh Arroyo, Alfonso Raul; Universidad Tecnica Federico Santa Maria UTFSM FISICA
The Standard Model (SM) of Particles is a very successful theory, which with the input of a fewfree parameters is capable to explain a plethora of experimental data. However, the Dark Matter(DM) and Dark Energy (DE) problem, the non-inclusion of gravity, the strong CP problem, thenature of the electroweak symmetry breaking and others, make us to believe that this is not theultimate theory.In this Thesis we explored two different ways to go beyond the SM looking at different problems.In the first work we would like to urge the exploration of the inert Two-Higgs doublet model(i2HDM), a minimal consistent DM model which is very well motivated by different theoreticaland experimental arguments. We present preliminary studies on DM relic density and colliderphenomenology. At the same time this model can be potentially tested at the LHC via differentsignatures for potentially accessible production of Dark Matter. We examine limits from presentday 8 TeV and projected 13 TeV LHC data, concentrating on limits from monojet processes.In the second work, we consider a possible extension of the SM where an effective Lagrangianis built, motivated by dynamical electroweak symmetry breaking models. In this particular modelwe consider that the Higgs boson and two new vector resonances come from a strongly interactingsector which originates the Fermi scale. Using the ATLAS measurements of the dijet spectrumwe set limits on the masses of the resonances. Additionally, we compute the Higgs boson decayinto two photons and find a small excess which is compatible with ATLAS measurements. Finallywe make prediction for Higgs-strahlung processes for the LHC running at 14 TeV.
ESTUDIO DE RESPUESTA ÓPTICA DE NANOCINTAS DE GRAFENO BICAPA ROTADAS
(2017) Kroeger Nowogrodski, Daniel Albert Alexander; Universidad Tecnica Federico Santa Maria UTFSM FISICA
En este trabajo de tesis se estudiaron las propiedades de conductividad ópticay se revisaron las principales caractísticas de la estructura de banda eléctrónicade las Nano-Cintas de Grafeno Bicapa Rotado (Twisted Bilayer GrapheneNano-Ribbons (TBNR)). Nuestro trabajo utilizó como técnica principal paracalcular estas propiedades un modelo de Enlace Fuerte (TB - Tight Binding).En primer lugar, para la estructura de banda se utilizó un modelo para orbitalespz en su aproximación de vecinos más cercanos y la respuesta óptica fuécalculada mediante la fórmula de Kubo (aproximación de respuesta lineal[35]).En forma paralela, se realizaron simulaciones desde Primeros Principios (Ab-Initio) basados en La Teoría del Funcional Densidad (Density Functional Theory(DFT)) mediante el software de simulación SIESTA[55] utilizando un funcionalque considera interacciones del tipo Van der Waals. Para los cálculos DFT, lascoordenadas atómicas correspondientes a las superceldas de nuestras estructurasfueron totalmente relajadas para luego proceder a calcular la estructura debanda y la respuesta óptica las cuales fueron utilizadas para contrastar con losresultados obtenidos desde la aproximación de Enlace Fuerte. Proponemos quesi nuestra descripción tipo TB de estos sistemas, dentro del estrecho rango deconfiguraciones estudiadas, está en concordancia con los resultados de DFT,entonces la aproximación de Enlace Fuerte debiera ser aplicable a sistemas cristalinosdonde el número de constituyentes atómicos es excesivamente grandey en consecuencia abordar este tipo de cálculo vía DFT no sería posible. Laestructura de banda y el espectro de conducción óptico de las TBNR hacende huella digital de estas estructuras lo cual nos permitía reconocer una buenaparte del catálogo de Nano-Cintas de Grafeno Bicapa Rotadas.
EXPERIMENTAL STUDIES OF PARTON PROPAGATION IN STRONGLY INTERACTING MATTER
(2018) TAPIA ARAYA, SEBASTIAN; BROOKS, WILLIAM; Universidad Tecnica Federico Santa Maria UTFSM FISICA
One important area of forefront research in strong interaction physics involves understanding how thefundamental particles of Quantum ChromoDynamics (QCD), the quarks and gluons, interact in spatiallyextended systems. Well-known research topics in this area include the study of gluon saturationat high parton densities, and jet quenching in ultra-relativistic collisions of large atomic nuclei. Whileperturbative treatments of QCD (pQCD) in proton-proton collisions produce excellent descriptions ofthe experimental data, the QCD-based description of processes in-medium is at a much more primitivestage, and there are many outstanding questions. One example is in the area of quark energyloss in-medium. Quark energy loss has long been conceived as occurring from two processes: partonicelastic scattering, and radiation of gluons, in analogy with the well-known processes in QuantumElectrodynamics (QED). Elastic scattering is expected to play a minor role for light quarks, while it isexpected to play a larger role for heavy quarks; gluon radiation is expected to be the dominant effectfor light quarks, and to play a smaller role for heavy quarks. These intuitive expectations have beenvalidated by explicit pQCD calculations in numerous studies. However, a comparison of light quarkobservables to heavy quark observables does not currently appear to conform to these expectations atall. As an example, b-quark jets appear to demonstrate the same suppression in heavy ion collisionsas light-quark jets in studies at the Large Hadron Collider (LHC). We propose to study heavy quarksuppression using data from the ATLAS detector at the LHC. The experimental technique of choice isto measure J= mesons in heavy ion collisions, comparing their production characteristics with thoseseen in proton-proton collisions, where no medium is present. To isolate the b-quark component, wefocus on J= mesons with a measured detached vertex relative to the primary collision vertex. Theb quarks predominantly decay into J= mesons long after they are produced, and thus these mesonsserve as a proxy for the primordial heavy quarks passing through the medium. Since any suppressionseen in heavy ion collisions is the result of attenuation of b-quarks in the hot, dense medium formedin those collisions, it is also of interest to compare these results to the same process as observed in coldmatter, such as the system produced in p+Pb collisions at the LHC. Further comparisons to cold mattercan be performed in electron-nucleus interactions, where the interaction of virtual photons provides aprobe that is free of initial-state interactions. Studies of this kind can be carried out with light-quarksignals using data from the EMC, HERMES, and CLAS experiments. Inter-comparison of the resultsfound from these different types of systems will provide new insights into the emerging field of partonicinteractions within systems of strongly interacting particles.
FENOMENOLOGÍA DE RESONANCIAS VECTORIALES EN EXTENSIONES DEL MODELO ESTÁNDAR CON UN NUEVO SECTOR FUERTE
(2018) Urbina Avalos, Jose Pablo; Zerwekh Arroyo, Alfonso Raul; Universidad Tecnica Federico Santa Maria UTFSM FISICA
Existe importante evidencia experimental, de Física más allá del Modelo Estándar, que impulsa a estudiar nuevos modelos, que puedan resolver los problemas de jerarquía y de naturalidad, prediciendo nuevas partículas a la escala del TeV. Por otro lado, tratar de explicar la materia oscura, también es importante dentro de estos marcos teóricos.El objetivo principal de esta tesis se centra en estudiar la fenomenología de un modelo más allá del Modelo Estándar, basado en esquemas de \Technicolor Extendido"; que denominamos como modelo LBESS, con la finalidad de ratifi car la posibilidad de que el bosón de Higgs y las nuevas partículas, provenientes de este nuevo sector con ruptura dinámica de la simetría, sean partículas compuestas. Como objetivo secundario se presenta el estudio de la fenomenología de un modelo efectivo proveniente de un nuevo sector fuerte, que incorpora un candidato a materia oscura a partir de un nuevo doblete de Higgs inerte.El estudio fenomenológico del primer modelo, se lleva a cabo a través de la realización de simulaciones, con la ayuda del programa CalcHEP, para tres procesos fundamentales. Los procesos involucran colisiones de protón-protón como estados iniciales a energías de CM. de raíz de s = 8 y raíz de s = 13 TeV según sea el caso. El primer proceso de estudio será p; p -> V -> j; j, en donde V representa cualquiera de las resonancias vectoriales masivas predichas porel modelo, mientras que j corresponde a un \jet". El segundo proceso corresponde a p; p -> V -> l+; l- en donde l+; l- corresponden a estados fi nales de leptones cargados. Finalmente estudiamos el ancho de decaimiento del bosón de Higgs a dos fotones representado por H -> A;A, cuyo cálculo se realiza a nivel de 1-lazo en teoría de perturbaciones. Hay que destacar que todos los calculos de secciones e ficaces arrojados por la simulación, serán comparados con los limites superiores entregados por la colaboración ATLAS, con la finalidad de descartar algunos valores en las masas de dichas resonancias y colocar limites a otros parámetros del modelo.Para estudiar la fenomenología del segundo modelo, se recurre nuevamente a CalcHEP y se realizan simulaciones para el proceso p; p -> V -> j; j, en donde V , corresponde a una resonancia vectorial denominada \technirho". Los resultados nuevamente son comparados con los limites superiores entregados por ATLAS, para dos casos cinemáticos.
FENÓMENOS DE TRANSPORTE A TRAVÉS DE ESTADOS LIGADOS DE MAJORANA
(2016) Ramos Andrade, Juan Pablo; Orellana Dinamarca, Pedro Alejandro; Universidad Tecnica Federico Santa Maria UTFSM FISICA
Este trabajo de tesis se enmarca en el estudio de diferentes sistemas queconsideran acoplamiento entre estados fermiónicos usuales y estadosligados de Majorana (ELM), los cuales son vistos como fraccionalización de los primeros en el modelo de Kitaev. Los ELM poseen interesantespropiedades, las cuales los lleva a ser pensados en potencialesaplicaciones en computación cuántica. En este sentido, entendemos laimportancia de detectar y utilizar estos estados con ese fin. En nuestrostrabajos consideramos el cálculo de las propiedades de transporte,tanto electrónico como termoeléctrico, para evidenciar característicasde la presencia de ELM. Estas son utilizadas para detección y posiblemanipulación de estos estados. Las cantidades de transporte se obtienenmediante el uso del método de funciones de Green, considerandodos contactos metálicos entre los cuales se encuentran embebidas nanoestructurasque albergan ELM con y sin conexión con puntos cuánticos(PC). Nuestros resultados muestran que cantidades termoeléctricasproveen características únicas de estos sistemas, las que pueden serutilizadas para detección. En el ámbito electrónico, los fenómenos deinterferencia, como el efecto Fano, son usados para proporcionar caracterización de la presencia de ELM. Por otra parte, también hemosencontrado que la filtración de ELM en PC, también puede ser alcanzadaa través de la mediación de estructuras con estados fermiónicos, endonde se manifiesta afectando las cantidades físicas. Adicionalmente,nuestros resultados permiten establecer propuestas que se enmarquenen la proposición de herramientas para posibles aplicaciones, porejemplo permitiendo monitoreo de conexiones entre ELM. Creemos que todos nuestros resultados pueden ser de utilidad e interés para detectary emplear las señales de la presencia de los ELM encontradas eninteracción con otras nanoestructuras.
HADRONIZATION STUDIES INTO ETA PARTICLES IN NUCLEAR MEDIUM WITH CLAS SPECTOMETER
(2018) Soto Sandoval, Orlando Javier; Hakobyan, Hayk; Universidad Tecnica Federico Santa Maria UTFSM FISICA; BROOKS, WILLIAM; KULESHOV, SERGEY
The confinement experienced by quarks does not allows to measure their individualcharacteristic isolated, they are always in colorless state. In order to extract informationabout them, Semi-Inclusive Deep Inelastic Scattering (SIDIS) measurements areperformed. In the analysed experiment, the measurement consist of an incoming andoutgoing electron, together with one hadron. The experiment E02-104, carried out atThomas Jefferson National Accelerator Facility (Newport news, VA), uses a doubletarget system including a liquid Deuterium target and a solid target, which are exposedtogether to the beamline, hence allowing to test the process of hadronization in a femtoscale. The observable measured is called Multiplicity Ratio, which is the ratio of themultiplicity of hadrons produced on a particular medium to the multiplicity producedon Deuterium.This thesis is focused in the measurement of the Multiplicity ratio of the Eta mesonon different nuclear environment (C,Fe,Pb) using the CLAS spectrometer.
MODERN DETECTORS TO STUDY THE STANDARD MODEL AND BEYOND
(2018) VASQUEZ ARENAS, GERARDO ALEXIS; KULESHOV, SERGEY; Universidad Tecnica Federico Santa Maria UTFSM FISICA
The needs for experimental proof of physics beyond the Standard Model (SM) andthe Dark Matter theories leads us to develop new detectors for high energy and highluminosity experiments. In this context, ATLAS with the muon upgrade (New SmallWheel project in particular) is an example of new detector technology designed for theHigh Luminosity LHC (HL-LHC). A big challenge is imposed on the conventional gaseousdetectors used for muon tracking and triggering. The high rate environment conditionsprevailing in HL-LHC will push the detectors to ful ll stringent requirements in terms oftime and spatial resolution.A search for Dark Matter experiment, called NA64 and located in one of the exit linesfrom the Super Proton Synchrotron (SPS) facilities at CERN, provides another exampleof the need for a new generation of detectors. The NA64 is looking speci cally for DarkMatter on invisible or visible decays of dark photons. Such detection requires a delicateunderstanding of every single event and a highly pure electron beam.For these two experiments, a team from the Physics Department of the UniversidadSanta Maria (USM) has built two detectors; a small-Strip Thin Gap Chamber (sTGC)and a compact calorimeter with fast scintillator crystals LYSO.In this dissertation, we rst present the novel gaseous detector sTGC and the constructionmethod. A gain uniformity measurement is shown as well as its stability under ahigh rate environment condition. These two tests are presented as a quality control afterthe sTGC Module 0 is built. Two beam tests are carried out to study spatial resolutionof the 3:2mm strips and pad timing performance. Both are new features to provide fasttrigger for the Region of Interest.In the second part, we focus on spectroscopy studies on the new Gamma IrradiationFacility (GIF++) at CERN. A method of peak identi cation using Wavelets is shownas well as fast algorithm to reconstruct pile-up events. Spectra of dierent attenuation lters from GIF++ are shown with estimated attenuation factors.In the last chapter, we present a particle identi cation technique as a solution to thebeam contamination in the NA64 experiment. A brief explanation of the dark photonmeasurements is shown. Afterwards we show results of hadron suppression level fromdierent detectors using synchrotron radiation as particle identi cation technique. Lastlywe show the rst measurements of dark photon invisible decays where no dark photonstrahlunginteraction is found so far with 109 events on target.
PARTON ENERGY LOSS ESTIMATES USING POSITIVE PIONS IN DIS ON NUCLEAR TARGETS (CLAS EG2-EXPERIMENT)
(2017) Aravena Ortega, Oscar Andres; Universidad Tecnica Federico Santa Maria UTFSM FISICA
Several models, both theoretical and experimental, have attempted to explain the process of hadronization.Some with more success than others. Using experimental data from the EG2 experiment onthe CLAS detector (Thomas Jefferson Laboratory), it was possible to measure the energy distributionof positive pions produced with a beam of 5 GeV incident electrons in a double target systemwith the aim of contrasting the nuclear medium with that produced in deuterium, which in practicalterms is considered as vacuum. Additionally, through the EG2 experiment it is sought to understandthe process of hadronization in the nuclear medium.In the present work, a model is developed to describe the process of hadronization in the nuclearmedium. This model explains the energy spectrum change of positive pions produced ondifferent nuclei. The studied nuclear medium (C, Fe, Pb) is compared to the spectrum produced byhadronization in deuterium nuclei. The complete modelling is done with realistic data, and additionan analysis is realized with the objective of finding characteristic values for ^q and L, parametersthat characterize the nuclear medium.
TOPICS ON COMPOSITE HIGGS
(2018) NORERO CÁRDENAS, SEBASTIÁN ARIEL; ZERWEKH ARROYO, ALFONSO RAUL; Universidad Tecnica Federico Santa Maria UTFSM FISICA

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