A search for cosmic point sources of neutrinos has been performed using data taken in 1999 with the AMANDA-B10 neutrino telescope. This work describes methods for signal and background separation and the statistical analysis of the final data sample. In particular, the multivariate method Support Vector Machines has been applied to achieve good background rejection while at the same time retaining high signal efficiency. A grid search covering the complete northern hemisphere revealed no statistical significant excess of events over the expected background from mis-reconstructed cosmic ray induced muons and muons induced by atmospheric neutrinos. Thus, no cosmic point sources of neutrinos have been detected. Upper limits on the neutrino flux for each cell of the grid are presented. Twenty potential sources of neutrinos chosen among three classes of astronomical objects (Blazars, Super Nova Remnants and Microquasars) have been preselected. Upper Limits on the flux of cosmic neutrinos from those are presented. The presence of systematic uncertainties makes the calculation of confidence limits an intricate problem. A method is presented which makes it possible to include these uncertainties into the frequentist construction of confidence intervals. Statistical properties of the presented method have been studied.

Apresentamos um estudo do setor da quebra espontânea de simetria da teoria eletrofraca através do formalismo de lagrangianas quirais, analisando os operadores que geram vértices anômalos genuinamente quárticos entre os bósons de gauge, os quais podem ser sondados pela próxima geração de aceleradores: LHC e NLC. Com o objetivo de obter vínculos aos acoplamentos anômalos relativos a esses operadores, estudamos as reações e POT. +e POT. - W POT. + W POT. Z e e POT. +e POT. - ZZZ no NLC operando com energias no centro de massa de s = 0.5 TeV e 1 TeV, estendendo as nossas análises para a colisão com o feixe de elétrons polarizado. Avaliamos também o impacto desses mesmos acoplamentos ao processo pp VV + 2 jatos (V = W±, Z) no LHC. No intuito de desenvolver cálculos realísticos, todas as amplitudes de espalhamento das reações estudadas foram determinadas sem qualquer tipo de aproximação. / We present a study of electroweak symmetry breaking sector in the framework or chiral Lagrangians, analyzing the operators that lead to genuine quartic gauge boson couplings, which could be probed by the next generation accelerators; LHC and NLC. In order to get bounds on the anomalous couplings related to these operators, we studied the reactions e+e- W+W-Z and e+e- ZZZ at the NLC operating with center-or-mass energy of s = 0.5 TeV and 1 TeV, extending our analysis to polarized electron beam collisions. We also estimate the impact of these couplings to the process pp VV + 2 jets (V = W±, Z) at the LHC. In order to develop realistic calculations, all the scattering amplitudes considered have been determined without any kind of approximation.

No description available.

A measurement of the W+ and W− cross section in the electron channel is presented. The measurement is performed using data collected with the ATLAS experiment in 2011, amounting to an integrated luminosity of 4.58 fb⁻¹. The centre of mass energy is √s = 7 TeV. The measurement is performed differentially in the electron pseudorapidity. The W charge asymmetry is also presented. The results are compared to theoretical predictions calculated at next-to-next-to-leading order in perturbative QCD using various Parton Distribution Functions.

In the Standard Model of particle physics, the non-zero masses of the W and Z bosons and the fermions are generated through interactions with the Higgs field, excitations of which correspond to Higgs bosons. Thus, the experimental discovery of the Higgs boson is of prime importance to physics, and would confirm our understanding of fundamental mass generation. This thesis describes a search for the gg → H → WW → lνlν process of Higgs boson production and decay. It uses the LHC Run I dataset of pp collisions recorded by the ATLAS detector, which corresponds to an integrated luminosity of 4.5 fb⁻¹ at √s = 7 TeV and 20.3 fb⁻¹ at √s = 8 TeV. An excess of events is observed with a significance of 4.8 standard deviations, which is consistent with Higgs boson production. The significance is extended to 6.1 standard deviations when the vector boson fusion production process is included. The measured signal strength is 1.11^+0.23<sub style='position: relative; left: -2.1em;'>-0.21</sub> at m_H = 125 GeV. A cross section measurement of WW production, a major background to this search, is also presented using the √s = 7 TeV dataset only.

No description available.

<p>The annihilation of weakly interacting massive particles (WIMPs), accumulated in gravitational potentials (e.g., the core of the Earth, the Sun or the Galactic halo) would lead to neutrino production. This thesis investigates the possibility of searching for WIMPs in the form of the lightest supersymmetric particle (neutralino) trapped in the Sun using the AMANDA-II neutrino telescope. AMANDA-II is a large Cherenkov detector located deep in the ice at the geographical South Pole. The presented work is based on data taken during the year 2001. An analysis optimized to search for the neutralino-induced flux from the Sun has been developed. The observation of no excess with respect to the expected atmospheric neutrino background has been interpreted as an upper limit on the neutralino annihilation rate in the Sun and on the neutralino-induced muon flux in the vicinity of the detector.</p>

<p>The nature of the dark matter in the Universe is one of the greatest mysteries in modern astronomy. The neutralino is a nonbaryonic dark matter candidate in minimal supersymmetric extensions to the standard model of particle physics. If the dark matter halo of our galaxy is made up of neutralinos some would become gravitationally trapped inside massive bodies like the Earth. Their pair-wise annihilation produces neutrinos that can be detected by neutrino experiments looking in the direction of the centre of the Earth.</p><p>The AMANDA neutrino telescope, currently the largest in the world, consists of an array of light detectors buried deep in the Antarctic glacier at the geographical South Pole. The extremely transparent ice acts as a Cherenkov medium for muons passing the array and using the timing information of detected photons it is possible to reconstruct the muon direction.</p><p>A search has been performed for nearly vertically upgoing neutrino induced muons with AMANDA-B10 data taken over the three year period 1997-99. No excess above the atmospheric neutrino background expectation was found. Upper limits at the 90 % confidence level has been set on the annihilation rate of neutralinos at the centre of the Earth and on the muon flux induced by neutrinos created by the annihilation products.</p>

No description available.

We study light hadron phenomenology using Lattice QCD. We focus on the calculations of the light pseudoscalar quantities: masses, decay constants and B-parameters; in particular the calculation of the Kaon B-parameter, BK, which when combined with experimental results yields a constraint of the unitarity triangle apex. We describe a calculation with 2+1 dynamical flavours of Domain Wall Fermions on two lattice volumes, with a lattice spacing a = 0:1 fm. The Iwasaki gauge action was used with coupling beta = 2:13 and the extent of the fifth dimension was Ls = 16. Following a brief review of continuum QCD and Lattice QCD we describe the Domain Wall formalism and the lattice methods used to calculate physical quantities. We present results from the two simulations and make comparisons with next-to-leading order chiral perturbation theory. We study the region of validity of chiral perturbation theory and calculate the associated low energy constants. We find these to agree with phenomenological estimates and other lattice calculations. We calculate the physical decay constants and find them to be in relatively good agreement with experimental values. We present a renormalised value for BK which includes systematic error estimates.