Neste trabalho estudamos a influência dos efeitos da saturação de pártons nas seções de choque totais próton-próton e próton--antipróton ($pp(\\bar{p})$), a seção de choque inelástica próton-Ar ($p-Ar$) e fazemos uma previsão para as seções de choque total e inelástica próton-chumbo ($p-Pb$). Para todos estes cálculos e previsões utilizamos duas abordagens completamente distintas onde os efeitos da saturação ou são incluidos nas distribuições de pártons da componente perturbativa de um modelo de minijatos eiconalizado ou são introduzidos através de modelos fenomenológicos com inspiração não-perturbativa, em uma região de momento transversal abaixo da chamada escala de saturação. Embora em cada uma das abordagens utilizadas os resultados não sejam muito distintos, podemos verificar que os efeitos da saturação de pártons conduzem a um crescimento dessas seções de choque mais moderado com a energia da reação e que a inclusão desses efeitos permite uma descrição bastante satisfatória e simultânea dos dados experimentais existentes em colisões próton-próton e próton-Ar. Essas são as principais conclusões deste trabalho. / In this work we study the influence of the parton saturation effects on the proton-proton and proton-antiproton ($pp(\\bar{p})$) total cross sections, the inelastic proton-Air ($p-Air$) cross section and we make a prediction for the proton-Plumbum ($p-Pb$) total and inelastic cross sections. For all these calculus and predictions we use two completely distinct approaches, where the parton saturation effects or are included in the parton distribution functions on the perturbative component of a eikonalized minijet model or are included through of phenomenologic models with non-perturbative inspiration in a region of transversal momentum below of the called saturation scale. Although in each of the approaches used the results aren\'t very distincts, we can verify which the parton saturation effects leads to a more moderated rise of these cross sections with the reaction\'s energy and which the inclusion of these effects permit a very satisfactory and simultaneous description of the experimental data of the proton-proton and proton-Air collisions. These are the main conclusions of this work.

This thesis contains the work of two recent developments in the Herwig general purpose event genrator. Firstly, the results from an new implementation of the KrkNLO method in the Herwig event generator are presented. This method allows enables the generation of matched next-to-leading order plus parton shower events through the application of simple positive weights to showered leading order events. This simplicity is achieved by the construction Monte Carlo scheme parton distribution functions. This implementation contains the necessary components to simulation Drell-Yan production as well as Higgs production via gluon fusion. This is used to generate the first differential Higgs results using this method. The results from this implementation are shown to be comparable with predictions from the well established approaches of POWHEG and MC@NLO. The predictions from KrkNLO are found to closely resemble the original configuration for POWHEG. Secondly, a benchmark study focussing on the source of perturbative uncertainties in parton showers is presented. The study employs leading order plus parton shower simulations as a starting point in order to establish a baseline set of controllable uncertainties. The aim of which is to build an understanding of the uncertainties associated with a full simulation which includes higher-order corrections and interplay with non- perturbative models. The uncertainty estimates for a number of benchmark processes are presented. The requirement that these estimates be consistent across the two distinct parton show implementations in Herwig provided an important measure to assess the quality of these uncertainty estimates. The profile scale choice is seen to be an important consideration with the power and hfact displaying inconsistencies between the showers. The resummation profile scale is shown to deliver consistent predictions for the central value and uncertainty bands.

This dissertation dicusses two topics; the cross section measurement of ϓ(1S) meson pair production [1] and simulation studies of High Granularity Calorimetry (HGCal). The first part of the dissertation is dedicated for the analysis of ϓ(1S) meson pair production and measurement of its cross section. The data for this analysis were collected by the CMS experiment at Large Hadron Collider (LHC) at a center-of-mass energy of 8 TeV and correspond to an integrated luminosity of 20.7 fb −1 . Simultaneous production of two ϓ(1S) mesons is observed for the first time with 38 events, corresponding to a local significance exceeding five standard deviations from the expected combinatorial background b-quark decays. Both ϓ(1S) candidates are fully reconstructed via their decays to μ + μ − . The fiducial acceptance of the detector is measured from the simulation and is defined by an absolute Υ(1S) rapidity smaller than 2.0. To minimize the model-dependence, the acceptance and efficiency corrections are calculated on an event-by-event basis using measured ϓ meson and muon momenta. The fiducial cross section of ϓ(1S) meson production, assuming both ϓ(1S) mesons decay isotropically, is measured to be 68.8 ± 12.7 (stat) ± 7.4 (syst) ± 2.8 (B) pb, where the third uncertainty comes from the uncertainty in the branching fraction of ϓ(1S) decays to μ + μ − . Different assumptions about ϓ productions imply modifications to the cross section ranging from −38% to +36%. Cross section measurement of ϓ pair production will provide better understanding of the parton vstructure of proton and enhance precision of existing particle production models. LHC is planning to increase luminosity and energy of colliding protons. Due to accumulated radiation damage and to improve detector performance CMS experiment is expected to undergo upgrade plans. Hadron calorimeter is among them, and it is planned to be replaced with better performance high granularity calorimetry (HGCal). HGCal needs to be integrated with existing components of CMS and its smooth functioning is essential. The second part of the dissertation describes simulation studies performed to validate readiness of HGCal for the Phase II upgrade.

LHC proton-proton collisions at a centre of mass energy of $\sqrt{s} = 7 TeV were observed in 2011. From a 1.68 fb$^{-1}$ sample of the data collected using the ATLAS detector, electron-positron pairs originating from the Drell-Yan process were selected using a cut based analysis. After the selection process, an estimate of the background was determined followed by the selection efficiency, detector resolution, reconstruction efficiency, and kinematic acceptance. Using these, the Drell-Yan differential cross section was calculated as a function of invariant mass between 26 and 66 GeV/c$^2$. This measurement has a precision between 12.4\% and 8.01\% from the lower invariant mass bins to the higher ones. The Drell-Yan cross section in proton-proton collisions depends on empirical quantities known as parton distribution functions which parametrize the structure of the proton. The measurement outlined in this thesis observes a region in parton distribution function phase space previously untouched by experiments. / Graduate

Neste trabalho estudamos a influência dos efeitos da saturação de pártons nas seções de choque totais próton-próton e próton--antipróton ($pp(\\bar{p})$), a seção de choque inelástica próton-Ar ($p-Ar$) e fazemos uma previsão para as seções de choque total e inelástica próton-chumbo ($p-Pb$). Para todos estes cálculos e previsões utilizamos duas abordagens completamente distintas onde os efeitos da saturação ou são incluidos nas distribuições de pártons da componente perturbativa de um modelo de minijatos eiconalizado ou são introduzidos através de modelos fenomenológicos com inspiração não-perturbativa, em uma região de momento transversal abaixo da chamada escala de saturação. Embora em cada uma das abordagens utilizadas os resultados não sejam muito distintos, podemos verificar que os efeitos da saturação de pártons conduzem a um crescimento dessas seções de choque mais moderado com a energia da reação e que a inclusão desses efeitos permite uma descrição bastante satisfatória e simultânea dos dados experimentais existentes em colisões próton-próton e próton-Ar. Essas são as principais conclusões deste trabalho. / In this work we study the influence of the parton saturation effects on the proton-proton and proton-antiproton ($pp(\\bar{p})$) total cross sections, the inelastic proton-Air ($p-Air$) cross section and we make a prediction for the proton-Plumbum ($p-Pb$) total and inelastic cross sections. For all these calculus and predictions we use two completely distinct approaches, where the parton saturation effects or are included in the parton distribution functions on the perturbative component of a eikonalized minijet model or are included through of phenomenologic models with non-perturbative inspiration in a region of transversal momentum below of the called saturation scale. Although in each of the approaches used the results aren\'t very distincts, we can verify which the parton saturation effects leads to a more moderated rise of these cross sections with the reaction\'s energy and which the inclusion of these effects permit a very satisfactory and simultaneous description of the experimental data of the proton-proton and proton-Air collisions. These are the main conclusions of this work.

Double hard parton-parton interactions are expected to occur frequently in proton-proton (p-p) collisions at the LHC. They can give rise to significant backgrounds to certain rare single scattering (SPS) signals, and are an interesting signal process in their own right. In this thesis, we discuss the theoretical description of the double parton scattering (DPS) cross section in the context of Quantum ChromoDynamics (QCD). After an overview of QCD and an introduction to DPS in Chapter 1, we describe in Chapter 2 a framework for calculating the p-p DPS cross section introduced by Snigirev et al., in which this cross section is expressed in terms of double PDFs D_p {ij}(x_1,x_2,Q_A 2,Q_B 2) (dPDFs). We show that the equal-scale dPDFs are subject to momentum and number sum rule constraints, and use these in the construction of an explicit set of leading order (LO) equal-scale dPDFs (the 'GS09' dPDFs). The leptonic same-sign WW DPS signal obtained using GS09 dPDFs is compared with that obtained using simple factorised forms, and the prospects of observing this signal taking into account SPS backgrounds are analysed. We discuss two ways in which the dPDF framework for describing p-p DPS is deficient in Chapter 3. We discuss interference and correlated parton effects in flavour, spin, colour, and parton type, which are ignored by the dPDF framework. We then study DPS-type graphs in which the parton pairs from both protons have arisen from a perturbative 1->2 branching, derive an expression for the part of such graphs associated with the particles arising from the 1->2 branchings being almost on-shell, and use this to demonstrate that the treatment of these graphs by the the dPDF framework is unsatisfactory. In Chapter 4, we study DPS-type graphs in which the parton pair from only one proton has arisen from a perturbative 1->2 branching. We discover that such graphs contribute to the LO p-p DPS cross section, and that crosstalk between partons in the 'nonperturbatively generated' pair is allowed provided that it occurs at a lower scale than that of the perturbative 1->2 branching in the other proton. The result of this analysis is combined with that of the previous chapter to propose a formula for the LO total DPS cross section, and our proposal is compared with those from other authors. We finish in Chapter 5 with some conclusions and suggestions for further work.

Since the discovery in the 1960's that the proton is not a fundamental particle but instead composed of even smaller particles known as quarks and gluons, there has been a concerted effort to understand the proton's internal structure. There still remain many mysteries about the proton and the theory that describes the interactions within: Quantum Chromodynamics (QCD). The distributions of quarks and gluons are encoded in objects known as parton correlation functions. Physicists use high-energy scattering experiments to access these functions by means of QCD factorization. This process of extracting information is known as a global QCD analysis. Further insight can be gained through first-principles calculations in lattice QCD as well as models for the strong interaction. In this thesis, we will use global QCD analyses to provide information on the one-dimensional (1D) structure of the proton using the latest experimental data available. Among the mysteries that remain within the proton, we provide insight on the non-perturbative nature of the proton's sea quarks, for both cases where the proton is unpolarized and longitudinally polarized. We also bring new information on the "proton spin puzzle," which concerns the delegation of the proton's spin into its constituent quarks and gluons. We shed light on the proton's transversely polarized structure, where current results from global QCD analyses and lattice QCD fail to paint a consistent picture. Our analyses also reveal a new feature of nuclear effects within light, highly asymmetric nuclei such as helium and tritium. Finally, we perform derivations in a spectator diquark model to glean information on the proton's 3D structure, and calculate moments that can be used in future lattice QCD studies. / Physics

Measurements of inclusive electron scattering cross-section ratios from light nuclei over a wide range of the Björken �� (0.3 < �� < 1) up to �� 2 = 8.3 GeV2 were made as part of experiment E10-10-008, which was conducted in Hall C at the Thomas Jefferson National Accelerator Facility. The measurements were performed using a beam energy of 10.602 GeV and an average beam current of 45 ��A. This dissertation provides a thorough description of the experiment as well as the extracted ratios of inclusive nuclear cross-sections with respect to the deuterium cross-sections (the EMC effect) for the targets 9 Be, 12 C, 10 B, and 11 B. The nuclear dependence of the inclusive inelastic electron scattering cross-section has been measured for the first time in 10 B and 11 B.

<p>The Standard Model describes all elementary particles known today, but at larger energies it will have to be complemented with new particles and interactions. To be able to distinguish new physics at proton colliders such as LHC at CERN, it is essential to have an appropriate description of the colliding protons and their interactions. The study of the proton is important also in itself, to get a better understanding of the non-perturbative aspects of the strong interaction.</p><p>In paper I-IV of this thesis, a model for the non-perturbative dynamics of quarks and gluons is developed, based on quantum fluctuations in hadrons. The parton distributions of the proton are given by momentum fluctuations, with sea quark distributions generated by fluctuations into baryon-meson pairs. This model can reproduce proton structure function data, as well as measured asymmetries between up and down valence quark distributions and between the anti-up and anti-down sea. It provides an intrinsic charm quark component as indicated by data. It also predicts an asymmetry in the strange sea of the proton, which can explain the NuTeV anomaly first attributed to new physics beyond the Standard Model.</p><p>Charged Higgs bosons are predicted by several theories for new physics, including Supersymmetry. At proton colliders, the predicted dominant production mechanism is in association with top and bottom quarks. In paper V-VII, different contributions to this production are studied, and an algorithm is developed for combining the two dominant processes gb -> tH^+/- and gg -> tbH^+/-. The algorithm gives a smooth transition from small to large transverse momenta of the b-quark, which is important when the b-quark is observed. It also gives arguments for the choice of factorisation scale in the process.</p>

The Standard Model describes all elementary particles known today, but at larger energies it will have to be complemented with new particles and interactions. To be able to distinguish new physics at proton colliders such as LHC at CERN, it is essential to have an appropriate description of the colliding protons and their interactions. The study of the proton is important also in itself, to get a better understanding of the non-perturbative aspects of the strong interaction. In paper I-IV of this thesis, a model for the non-perturbative dynamics of quarks and gluons is developed, based on quantum fluctuations in hadrons. The parton distributions of the proton are given by momentum fluctuations, with sea quark distributions generated by fluctuations into baryon-meson pairs. This model can reproduce proton structure function data, as well as measured asymmetries between up and down valence quark distributions and between the anti-up and anti-down sea. It provides an intrinsic charm quark component as indicated by data. It also predicts an asymmetry in the strange sea of the proton, which can explain the NuTeV anomaly first attributed to new physics beyond the Standard Model. Charged Higgs bosons are predicted by several theories for new physics, including Supersymmetry. At proton colliders, the predicted dominant production mechanism is in association with top and bottom quarks. In paper V-VII, different contributions to this production are studied, and an algorithm is developed for combining the two dominant processes gb -&gt; tH+/- and gg -&gt; tbH+/-. The algorithm gives a smooth transition from small to large transverse momenta of the b-quark, which is important when the b-quark is observed. It also gives arguments for the choice of factorisation scale in the process.