The Standard Model of particle physics describes all known elementary particles and their interactions. Despite its great experimental success, we know that the Standard Model is not a complete description of Nature and therefore new phenomena should be observed at higher energies. In the coming years the Large Hadron Collider will test the Standard Model by colliding protons with center of mass energies of up to 14 TeV providing some of the most stringent tests on the Standard Model. Experimental searches for Dark Matter provide a complementary program to test physics at the weak scale. In the near future new experimental data coming from direct detection experiments, and from satellites and telescopes will drastically improve our sensitivity to weak scale dark matter. This could lead to the first direct observation of dark matter, and thus of physics beyond the Standard Model. In this thesis I propose different extensions of the Standard Model and discuss their experimental consequences. I first discuss models for Axigluons, which are spin one particles in the adjoint representation of the SU(3) color gauge group. These models were motivated by the measurement of higher than predicted forward-backward asymmetry in top quark pair production at the Tevatron. I study different scenarios for Axigluon models that can explain the Tevatron result and explore their signatures at the Large Hadron Collider. Second I discuss the implications of ultraviolet scale invariance for the Standard Model, which has been advocated as a solution to the hierarchy problem. I show that in order to solve the hierarchy problem with scale invariance, new physics is required not far from the weak scale. In the last part of this thesis I propose a new model for dark matter, in which dark matter is charged under a hidden non-Abelian gauge group. This leads to modifications in the sensitivity of the usual experimental searches for dark matter in addition to distinct signatures in the Cosmic Microwave Background and in Large Scale Structure data.

Made available in DSpace on 2015-09-17T15:24:26Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-06-03. Added 1 bitstream(s) on 2015-09-17T15:47:50Z : No. of bitstreams: 1 000837676.pdf: 5906522 bytes, checksum: 4d7d813fa9837e6b5a068271f434ec38 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / No Modelo Padrão que descreve a física das partículas elementares e suas interações o campo de Higgs pode ser imaginado como um campo composto formado por uma força forte ainda desconhecida. Tal hípótese é bastante atrativa para completar o Modelo Padrão a altas energias. Problemas como hierarquia e naturalidade podem ser mais facilmente evitados. No contexto de uma força forte porém métodos de cálculo baseados em expansões perturbativas não tem mais validade. Uma alternativa para entender as propriedades básicas desse tipo de teoria é trabalhar em termos de teorias de gravitacão com dimensões extras. Nesta tese focamos no caso de uma dimensão espacial extra. Características genéricas desse tipo de cenário são a existência de partículas de gravidade massivas, associadas com a métrica penta-dimensional que acopla com o Modelo Padrão para matéria, levando a assinaturas diretas em colisores de partículas (como o LHC no CERN). Tais partículas de gravidade se acoplam com o setor de Higgs. A descoberta do bóson de higgs abriu um novo camp o de investigação para sua detecção direta, no estado final com dois bósons de higgs. Nós usamos técnicas de Monte Carlo para estudar as estratégias de análise que levariam a um melhor reconhecimento de novas ressonâncias que decaem em pares de bósons de higgs em colisores hadrônicos, que podem ser interpretadas como partículas de gravidade massivas. Finalmente apresentamos as buscas experimentais por tais ressonâncias realizadas no contexto do experimento CMS com dados retirados do primeiro run do LHC (com uma energia de centro de massa de 8 TeV) / The Higgs field of the Standard Model theory for elementary particles and interactions can be realized as a composite state from an underlying strong sector. Such hypothesis is very attractive as an ultraviolet completion of the Standard Model since it solves the hierarchy and avoids naturalness problems. The standard perturbative methods cannot be used in the context of strongly interacting theories, however thyose can be broadly describes in terms of extra dimensional models of gravity. We focus on the case of one additional Warped compact Extra Dimension (WED). The generic signatures of this scenario are the manifestation of heavy gravity particles, associated with the five dimensional metric, that couples with the Standard Model matter leading to direct collider signatures. The heavy gravity particles couples to the Higgs sector. The Higgs discovery had oponed a new investigation channel to LHC direct detection that is the di-higgs final state. We use Monte Carlo techniques to study the analysis strategies that would lead to a best recognition of new resonances decaying to a pair of higgses in hadron colliders, that can be interprets as the gravity particles. We finally present resonance searches performed with data taken by the CMS experiment on the 8 TeV LHC run. The results are interpreted as the gravity particles signatures in the WED context / CNPq: 141964/2009-0

Orientador: Rogério Rosenfeld / Co-orientador: Maxime Gouzevich / Banca: Eduardo Pontón Bayona / Banca: André Sznajder / Banca: Sérgio Ferraz Novaes / Banca: Oscar José Pinto Éboli / Resumo: No Modelo Padrão que descreve a física das partículas elementares e suas interações o campo de Higgs pode ser imaginado como um campo composto formado por uma força forte ainda desconhecida. Tal hípótese é bastante atrativa para completar o Modelo Padrão a altas energias. Problemas como hierarquia e naturalidade podem ser mais facilmente evitados. No contexto de uma força forte porém métodos de cálculo baseados em expansões perturbativas não tem mais validade. Uma alternativa para entender as propriedades básicas desse tipo de teoria é trabalhar em termos de teorias de gravitacão com dimensões extras. Nesta tese focamos no caso de uma dimensão espacial extra. Características genéricas desse tipo de cenário são a existência de partículas de gravidade massivas, associadas com a métrica penta-dimensional que acopla com o Modelo Padrão para matéria, levando a assinaturas diretas em colisores de partículas (como o LHC no CERN). Tais partículas de gravidade se acoplam com o setor de Higgs. A descoberta do bóson de higgs abriu um novo camp o de investigação para sua detecção direta, no estado final com dois bósons de higgs. Nós usamos técnicas de Monte Carlo para estudar as estratégias de análise que levariam a um melhor reconhecimento de novas ressonâncias que decaem em pares de bósons de higgs em colisores hadrônicos, que podem ser interpretadas como partículas de gravidade massivas. Finalmente apresentamos as buscas experimentais por tais ressonâncias realizadas no contexto do experimento CMS com dados retirados do primeiro run do LHC (com uma energia de centro de massa de 8 TeV) / Abstract: The Higgs field of the Standard Model theory for elementary particles and interactions can be realized as a composite state from an underlying strong sector. Such hypothesis is very attractive as an ultraviolet completion of the Standard Model since it solves the hierarchy and avoids naturalness problems. The standard perturbative methods cannot be used in the context of strongly interacting theories, however thyose can be broadly describes in terms of extra dimensional models of gravity. We focus on the case of one additional Warped compact Extra Dimension (WED). The generic signatures of this scenario are the manifestation of heavy gravity particles, associated with the five dimensional metric, that couples with the Standard Model matter leading to direct collider signatures. The heavy gravity particles couples to the Higgs sector. The Higgs discovery had oponed a new investigation channel to LHC direct detection that is the di-higgs final state. We use Monte Carlo techniques to study the analysis strategies that would lead to a best recognition of new resonances decaying to a pair of higgses in hadron colliders, that can be interprets as the gravity particles. We finally present resonance searches performed with data taken by the CMS experiment on the 8 TeV LHC run. The results are interpreted as the gravity particles signatures in the WED context / Doutor

Orientador: Marcelo Moraes Guzzo / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-16T08:14:40Z (GMT). No. of bitstreams: 1 VanegasForero_David_M.pdf: 1733110 bytes, checksum: 29e0f28a1fe9c2a5a633d3b0f7abcaf3 (MD5) Previous issue date: 2010 / Resumo: Estudamos as restrições fenomenologicas dos parâmetros das interações não-padrão de neutrinos (NSNI) com elétrons, usando os efeitos dessas interações tanto na detecção quanto na propagação, de maneira independente do modelo. As NSNI, a baixa energia, foram geradas da invariância pelo grupo de gauge do modelo padrão (SM), evitando os processos de léptons carregados a nível de árvore. Essas NSNI foram somadas às interações a baixa energia descritas pelo SM, razão pela qual consideramos que o efeito das novas interações é de segunda ordem. No caso dos efeitos na detecção , usamos as modificações das NSNI nas seções de choque: do espalhamento elástico de (anti)neutrinos por elétrons e do processo de aniquilação de pares em neutrinos. Para a restrição via seções de choque do espalhamento elástico, usamos experimentos de reatores e aceleradores, e para o caso da seção de choque do processo de aniquilação de pares produzindo neutrinos, usamos os quatro experimentos de LEP. No caso dos efeitos na propagação, calculamos as modificações as probabilidades de oscilação e revisamos as restrições dos parâmetros das NSNI diagonais (FDNI) com elétrons, calculadas na literatura usando experimentos solares mais KamLAND. Os parâmetros das FDNI com muons foram desconsiderados devido ao fato de serem muito restritos pelos processos dos léptons carregados que violam sabor. Dado o número de parâmetros, optamos por fazer a variação de dois deles ao mesmo tempo, fazendo os restantes igual a zero. Para os parâmetros do sabor a = e, incrementamos o número de experimentos em relação à literatura, e encontramos também quatro regiões possíveis restritas pelos experimentos de espalhamento elástico. A inclusão de LEP diminuiu o número de regiões a dois, com o que na análise global obtivemos os valores: -0.06 < e eR ee < 0.04 e - 0.02 < e eL ee < 0.10 (90% C.L.), ao redor do ponto descrito pelo SM, os quais são mais restritivos que os reportados na literatura. Recalculamos os parâmetros do sabor a = ? , e encontramos os valores - 0.47 < ? eRTT < 0.67 e -0.68 < ? eLTT < 0.46 (99% C.L.). Da comparação dos parâmetros restritos com experimentos solares mais KamLAND da literatura com os experimentos terrestres recalculados por nós vimos que são comparáveis. Os valores dos parâmetros, que são menores que a unidade, confirrmam que as NSNI ocupam um papel secundário, onde o SM continua descrevendo os dados / Abstract: We studied the phenomenological constrains of the Non-standard Neutrino Interactions (NSNI) parameters with electrons, using it's e ects in both detection and propagation, in a independent model way. Low energy NSNI were generated from the gauge invariant condition under the standard model (SM) gauge group, without the charged lepton flavor violation process at tree level. The NSNI were added to the effective low energy SM Lagrangian, and that is why we consider it's effect as sub-leading. In the detection case, we used the NSNI modifications to the cross sections: of the elastic scattering of (anti)neutrinos off electrons and the electron positron annihilation producing neutrinos. In the restriction from cross sections of elastic scattering process, we used reactor and accelerator data, and for the cross section of the annihilation process we used the four LEP experiments. For the propagation case, we calculated the modifications to the oscillation probability and we reviewed the restrictions to the diagonal parameters of the NSNI with electrons (FDNI), which were calculated in the literature from solar plus KamLAND data. We did not consider the NSNI for the muon flavor, because it's parameters are very constrained by the upper limits of the charged lepton flavor violating process. Due to the number of parameters, we have decided to make the variation of the two parameters at time, equaling the other two to zero. In order to calculate the parameter of flavor a = e, we added new experiments in relation with the literature and we also found four possible regions limited by the scattering data. By adding LEP data, we reduced the number of regions to two and obtained for the global analysis the parameters: -0.06 < e eR ee < 0.04 e - 0.02 < e eL ee < 0.10 (90% C.L.) calculated from the SM point those parameters are more restrictive than the literature ones. We recalculated the parameters of flavor a = ? and we obtained the values - 0.47 < ? eRTT < 0.67 and -0.68 < ? eLTT < 0.46 (99% C.L.). The parameter constrained with solar plus KamLAND data from the literature are comparable to the terrestrial calculated by us. The parameters values are less than the unity pointed the sub-leading NSNI effect, whereas the SM continue describing the data / Mestrado / Teoria Geral de Partículas e Campos / Mestre em Física

In a recent paper we studied the effect of new-physics operators with different Lorentz structures on the semileptonic Λb → Λcτν¯τ decay. This decay is of interest in light of the R(D(∗)) puzzle in the semileptonic B¯ → D(∗)τν¯τ decays. In this work we add tensor operators to extend our previous results and consider both model-independent new physics (NP) and specific classes of models proposed to address the R(D(∗)) puzzle. We show that a measurement of R(Λc) = B[Λb → Λcτν¯τ ]/B[Λb → Λcℓν¯ℓ] can strongly constrain the NP parameters of models discussed for the R(D(∗)) puzzle. We use form factors from lattice QCD to calculate all Λb → Λcτν¯τ observables. The Λb → Λc tensor form factors had not previously been determined in lattice QCD, and we present new lattice results for these form factors here.

The present neutrino oscillation data are compatible with tri-bimaximal mixing, to leading order. The addition of an A₄ family symmetry and extended Higgs sector to the Standard Model can generate this mixing pattern, assuming the correct vacuum expectation value alignment of Higgs scalars. The effect of deviating this alignment is studied, for different types of A₄ models, with a phenomenological emphasis: the effect of perturbations on the model predictions for the neutrino oscillation and neutrino mass observables. The standard theoretical description of neutrino oscillations is presented, along with a summary of the past, present and future experimental efforts aimed at measuring the neutrino mixing parameters. Additionally, the current constraints on the sum of absolute neutrino masses and the amplitude for neutrinoless double beta decay, which is yet to be observed, are discussed. These constraints provide a model-independent test of family symmetery models. The Standard Model is reviewed, and extensions to the Standard Model such as the seesaw mechanism(s) are discussed: these are designed to endow neutrinos with mass, and can be incorporated into A₄ symmetry models. Models with different A₄ particle assignments are analysed for deviations from tribimaximal mixing. There are nine models presented in Chapter 5, with lepton doublets transforming as 3 (underlined) and right-handed charged leptons transforming as 1, 1', 1" (all underlined) ; five of these include right-handed neutrinos transforming as 3 (underlined) and make use of the seesaw mechanism. Chapter 6 contains the analysis of six models that assign all leptons to the 3 (underlined) representation, with four of these utilising the seesaw mechanism. The models are tested for any degree of fine tuning of the parameters that define the mass matrices. The effect of perturbations on the mixing angle observables, in particular sin² ∅₁₃ and sin² ∅₂₃, is studied, as well as the effect on the Jarlskog invariant, Jcp. Investigations of the (Mee)- ∑Mv parameter space allow for comparison with current data, and can lead to the possible exclusion of a particular model by constraints from future data.

A search for heavy exotic diboson resonances decaying to llqq final states is presented using pp collision data collected with the ATLAS detector at the Large Hadron Collider. The analysis uses a data sample corresponding to an integrated luminosity of 20.3 fb^-1 at sqrt(s) = 8 TeV collected between April and December 2012. No significant excess of data events over the predicted Standard Model background is observed and 95% confidence level upper limits are set on the product of the production cross-section and the branching ratio for spin-2 Kaluza-Klein gravitons predicted by the bulk Randall-Sundrum model and for Extended Gauge Model W’ bosons. These results are subsequently combined with limits obtained from searches using the lvll, lvqq, and qqqq final states, and new mass limits are set on both signal models.

The Large Hadron Collider (LHC) marks a new era for particle physics. Thanks to the very high energy of the proton beams, and to the large amount of data collected in years 2010-12, the physicists at CERN can test the standard model (SM) consistency, can explore the scalar sector, and search for any hint of new physics. A measurement of the Z boson pair production cross section using proton-proton collisions at 7 and 8 TeV center-of-mass energy, recorded by the CMS (Compact Muon Solenoid) experiment is presented. Diboson production at the LHC is of particular interest: it validates rare SM processes never tested before with high accuracy, it probes the electroweak boson self-interactions, and it constitutes a background for many physics searches such as the searches for the Higgs boson or supersymmetry. The ZZ production cross section is measured via the decay channel ZZ to 2l2v. The data used for the analysis have been recorded in years 2011 and 2012 by CMS and correspond to an integrated luminosity of about 5.1 fb-1 at 7 TeV and 19.6 fb-1 at 8 TeV. The data are selected requiring the presence of two isolated leptons (electrons or muons) of the same flavor with high transverse momentum (pT). In addition, events containing jets or additional leptons are vetoed, and it is applied a selection based on the dilepton pT, on the dilepton invariant mass, and on the transverse momentum imbalance (Emiss). The main SM backgrounds for this analysis are the Z/gamma+jet (Drell-Yan) process, the fully leptonic tt and single-top decay, and the WW and WZ diboson processes. The Z/gamma + jet process has no neutrinos in the final state, thus it has no large Emiss, but its cross section at the Z-peak is four orders of magnitude larger than the ZZ production. For this reason, even if the fraction of Z/gamma + jet events reconstructed with significant instrumental Emiss is not large, a high Emiss cut must be applied in order to improve the signal purity. High Emiss in Z/gamma + jet events is due to misreconstruction of physical objects, and to the additional energy deposits arising from the other proton-proton interactions occurring in the same bunch crossing (pileup). These effects are not well described in simulation, for this reason a high statistic control sample has to be used in order to model these tails from data. The fully leptonic tt, the single-top decay, and the WW process have been estimated in a control sample obtained requiring exactly one electron and one muon in the final state. The WZ process instead, has been estimated directly from the simulation. All the background shapes and normalizations are then constrained to data from a fit to the shape of a discriminating variable (e.g. Emiss), allowing only the ZZ signal normalization to freely vary. The selected data were also analyzed to search for anomalous triple gauge couplings (aTGC) involving the ZZ final state, and subsequently combined with the ZZ to 2l2l' final state data, to increase the sensitivity. In the absence of signs of new physics we set limits on the relevant aTGC parameters. Between 2023 and 2025, to extend its discovery potential and/or characterize any new signal possibly discovered, the LHC will increase its instantaneous luminosity by a factor of 10 beyond its design value. The increasing in luminosity will produce an average of 140 pileup interactions, this will represent an issue for the trigger and the reconstruction, degrading the jet and photon energy resolution and all the physic objects isolation quantities. In order to maintain full sensitivity, from low to high energy scales under severe pileup and radiation conditions, the L1 trigger, the tracker, the ECAL endcap and the HCAL, and the forward muon system will be upgraded. Moreover it will be fundamental to tag and remove the extra activity from PU interactions in order to correct the relevant variables measurements. The last part of the thesis will test the utility of timing in pileup mitigation and object reconstruction. Timing could be exploited for the association of photons, electrons and jets to their collision vertices, for particle identification, or to reject energy deposits coming from secondary vertices. A time measurement, extract from simulation, will be used in several reconstruction algorithms, showing improvements in particle reconstruction. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

No description available.

In this thesis we consider a number of past, present, and future neutrino experiments designed to test physics beyond the Standard Model. First, we analyze potential new physics explanations of the NuTeV anomaly and check their compatibility with the most recent experimental data. The models we consider are: gauged Lmu-Ltau, gauged B-3Lmu, and S1, S3, V1, V3 leptoquarks. We find that only the triplet leptoquark models can explain NuTeV and be compatible with the data from other experiments at the same time, and only if the components of the triplet have different masses. Then, we analyze the prospects of discovery of heavy Majorana neutrinos (neutrissimos) suggested by the Okamura model at the LHC. We find that these particles, if produced, will live short enough to decay inside of the detector, while long enough to lead to a narrow peak in the invariant mass spectrum of the decay products. We estimate the typical masses of the neutrissimos to be in the TeV range. However, studies exist that have shown that if their masses are larger than about 150 GeV then the production cross-section is too small to lead to an observable event rate. Thus, we conclude that it will not be possible to detect the neutrissimo at the LHC unless its mass is smaller that about 150 GeV which corresponds to a very small region close to the edge of the parameter space of the Okamura model. Nevertheless, we argue that the signature of the neutrissimo may be detectable in other neutrino experiments which may be carried out in the future. As examples, we consider the NuSOnG experiment, which is a fixed target neutrino scattering experiment proposed at Fermilab, and a hypothetical long-baseline neutrino oscillation experiment in which the Fermilab NUMI beam is aimed at the Hyper-Kamiokande detector in Japan. In addition to the sensitivity to neutrissimos, we analyze the capabilities of these experiments to constraint the coupling constants and masses of new particles in various models of new physics suggested in the literature. The models we consider are: neutrissimo models, models with generation distinguishing Z's such as topcolor assisted technicolor, models containing various types of leptoquarks, R-parity violating SUSY, and extended Higgs sector models. In several cases, we find that the limits thus obtained could be competitive with those expected from direct searches at the LHC. In the event that any of the particles discussed here are discovered at the LHC, then the observation, or non-observation, of these particles in the NuSOnG and Fermilab-to-Hyper-Kamiokande experiments could help in identifying what type of particle had been observed. / Ph. D.