We review the Regge theory and the minijet model for pp and pp collisions. We show that, in the conventional minijet approach, the asymptotic behavior of the total cross section calculated using currently accepted gluon distribution function and perturbative QCD rises too rapidly when compared with the data and fails to satisfy Froissart bound. To tame the rise, we have developed a new formalism for the interaction between QCD gluon and the classical color field of the colliding nucleons, and show how the gluon propagator is modified. The corresponding gauge invariance condition of the propagator is derived and shown to be satisfied. The modified gluon propagator leads to a suppression of the minijet cross section due to the gg [rightwards arrow] gg sub-process in the small-x region. We show that the pp and pp total cross section from [square root]s = 5 GeV to 30 TeV can be described as a sum of a hard component contributed by the classical field modified minijet model and a soft component due to the exchange of the Pomeron and the I=0 exchange-degenerate [omega] and f Regge trajectories. The soft-component model is motivated by the notion of duality. The predicted total cross section has a ln s asymptotic behavior. / text

The position reconstruction performance of the Electromagnetic Endcap Calorimeter (EMEC) is assessed in terms of its response to electrons. The electromagnetic and hadronic endcap calorimeter modules of the ATLAS detector are exposed to beams of electrons, pions, and muons in the energy range 6 GeV ≤ E ≤ 200 GeV at several impact positions in the pseudo-rapidity 1.6 ≤ |η| ≤ 1.8 in a beam test at CERN. The EMEC is a lead-liquid argon sampling calorimeter with a unique accordion structure designed to provide complete hermiticity and excellent energy and position resolution, the attribute on which several physics measurements envisioned at the LHC will depend. Unlike the real ATLAS situation, the beam test setup used a non-pointing geometry in η due to the experimental constraints. Hence, the position resolution of the EMEC is evaluated in the φ direction only and found to be at least as good as σφ = (4.36 ± 0.10)/ √E (12.64 ± 0.82) / E (0.00 ± 0.10) in milliradians.

The position reconstruction performance of the Electromagnetic Endcap Calorimeter (EMEC) is assessed in terms of its response to electrons. The electromagnetic and hadronic endcap calorimeter modules of the ATLAS detector are exposed to beams of electrons, pions, and muons in the energy range 6 GeV ≤ E ≤ 200 GeV at several impact positions in the pseudo-rapidity 1.6 ≤ |η| ≤ 1.8 in a beam test at CERN. The EMEC is a lead-liquid argon sampling calorimeter with a unique accordion structure designed to provide complete hermiticity and excellent energy and position resolution, the attribute on which several physics measurements envisioned at the LHC will depend. Unlike the real ATLAS situation, the beam test setup used a non-pointing geometry in η due to the experimental constraints. Hence, the position resolution of the EMEC is evaluated in the φ direction only and found to be at least as good as σφ = (4.36 ± 0.10)/ √E (12.64 ± 0.82) / E (0.00 ± 0.10) in milliradians.

The mechanism of the isospin violating η→π+π−π0 decay is studied in a high precision experiment using a Dalitz plot analysis. The process is sensitive to the difference between up and down quark masses. The measurement provides an important input for the determination of the light quark masses and for the theoretical description of the low energy strong interactions. The measurement was carried out between 2004 and 2005 using the KLOE detector at the DAΦNE e+e− collider located in Frascati, Italy. The data was collected at a center of mass energy corresponding to the φ-meson peak (1019.5 MeV) with an integrated luminosity of 1.6 fb−1. The source of the η-mesons is the radiative decay of the φ-meson: e+e−→φ→ηγ, resulting in the world’s largest data sample of about 4.7·106 η→π+π−π0 decay events. In this thesis, the KLOE Monte Carlo simulation and reconstruction programs are used to optimize the background rejection cuts and to evaluate the signal efficiency. The background contamination in the final data sample is below 1%. The data sample is used to construct the Dalitz plot distribution in the normalized dimensionless variables X and Y. The distribution is parametrized by determining the coefficients of the third order polynomial in the X and Y variables (so called Dalitz plot parameters). The statistical accuracy of the extracted parameters is two times better than any of the previous measurements. In particular the contribution of the X2Y term is found to be different from zero with a significance of approximately 3σ. The systematic effects are studied and found to be of the same size as the statistical uncertainty. The contribution of the terms related to charge conjugation violation (odd powers of the X variable) and the measured charge asymmetries are consistent with zero. The background subtracted and acceptance corrected bin contents of the Dalitz plot distribution are provided to facilitate direct comparison with other experiments and with theoretical calculations.

abstract: The nucleon resonance spectrum consists of many overlapping excitations. Polarization observables are an important tool for understanding and clarifying these spectra. While there is a large data base of differential cross sections for the process, very few data exist for polarization observables. A program of double polarization experiments has been conducted at Jefferson Lab using a tagged polarized photon beam and a frozen spin polarized target (FROST). The results presented here were taken during the first running period of FROST using the CLAS detector at Jefferson Lab with photon energies ranging from 329 MeV to 2.35 GeV. Data are presented for the E polarization observable for eta meson photoproduction on the proton from threshold (W=1500 MeV) to W=1900 MeV. Comparisons to the partial wave analyses of SAID and Bonn-Gatchina along with the isobar analysis of eta-MAID are made. These results will help distinguish between current theoretical predictions and refine future theories. / Dissertation/Thesis / Ph.D. Physics 2011

xii, 118 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / This dissertation describes a search for the decays B 0 [arrow right] invisible and B 0 [arrow right] invisible+γ, where invisible refers to a final state consisting of long lived particles with a low cross-section for interaction with matter, leading to a low probability of detection in typical particle detectors. While the branching fractions for these decays predicted by the Standard Model are far below what could be feasably measured by current experiments, new physics such as right-handed neutrinos propagating in large extra space-time dimensions or light R-parity violating neutralinos in supersymmetry could greatly enhance the branching fractions. The decays are searched for in data corresponding to 423.5 fb -1 integrated luminosity produced at the Υ(4 S ) resonance collected with the BABAR detector at the PEP-II B factory, corresponding to 2.30 × 10 8 B 0 B¯ 0 pairs. Using those events that contain a hadronically reconstructed neutral B meson, evidence for the signal decays is sought in the remainder of the event. In (5.00 ± 0.02) × 10 5 events with a fully reconstructed neutral B meson, a total of 39 events consistent with the B 0 [arrow right] invisible decay mode are seen in data with an expected background of 28.5 ± 7.8(stat.)±9.2(syst.) events, and 8 events consistent with the B 0 [arrow right] invisible+γ decay mode are seen in data mode with an expected background of 14.1 ± 5.5(stat.)±8.1(syst.) events, from which upper limits of [Special characters omitted.] ( B 0 [arrow right] invisible) < 11.7 × 10 -5 and of [Special characters omitted.] ( B 0 [arrow right] invisible+γ) < 4.3 × 10 -5 at the 90% confidence level are obtained. / Adviser: David Strom

abstract: A series of experiments using a polarized beam incident on a polarized frozen spin target (FROST) was conducted at Jefferson Lab in 2010. Results presented here were taken during the second running period with the FROST target using the CEBAF Large Acceptance Spectrometer (CLAS) detector at Jefferson Lab, which used transversely-polarized protons in a butanol target and a circularly-polarized incident tagged photon beam with energies between 0.62 and 2.93 GeV. Data are presented for the F and T polarization observables for h meson photoproduction on the proton from W = 1.55 GeV to 1.80 GeV. The data presented here will improve the world database and refine theoretical approaches of nucleon structure. / Dissertation/Thesis / Doctoral Dissertation Physics 2016

Nesta tese investigamos uma possível componente de partículas previstas por modelos além do modelo padrão da física de partículas, como por exemplo o massive gluino LSP, nos raios cósmicos de altíssimas energias (UHECR). Nosso objetivo é determinar os sinais experimentais em telescópios de fluorescência devidos a hádrons exóticos massivos e neutros, genericamente denominados de UHECRons. Para simular chuveiros iniciados por essa classe de partículas, alteramos o pacote Aires de simulação de chuveiros atmosféricos e o modelo hadrônico Sibyll. Estes chuveiros foram utilizados como entrada em simulações de telescópios de fluorescência por nós desenvolvidas, obtendo-se assim as distribuições dos observáveis desses chuveiros exóticos. A partir da comparação entre as características de chuveiros iniciados uhecrons e prótons, desenvolvemos métodos para a separação de sinais entre esses dois tipos de partículas. Esses métodos podem ser utilizados em uma análise inicial, com o intuito de procurar por sinais de partículas exóticas nos dados reais de observatórios de UHECR. / In this thesis we investigate a possible component of particles predicted by models beyond the standard model of particle physics, like the massive gluino LSP, in the ultra high energy cosmic rays (UHECR). Our objective is to determine the experimental signals on fluorescence telescopes due to exotic massive and neutral hadrons, generically called UHECRons. To simulate showers initiated by this class of particle, we altered the shower simulation package Aires and the hadronic model Sibyll. These showers were used as input in our simulations of fluorescence telescopes, thus obtaining the distribuitons of the observables for these exotic showers. By comparing the characteristics of showers initiated by uhecrons and protons, we developed methods to distinguish the signals between these two particles. These methods can be used in an initial analysis in order to look for signals of exotic particles in the real data of UHECR observatories.

Orientador: Marcio José Menon / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-23T19:57:59Z (GMT). No. of bitstreams: 1 Silva_PauloVictorRecchiaGomesda_M.pdf: 2869539 bytes, checksum: f4a19979ffd76131dcd50a629c0afdfd (MD5) Previous issue date: 2013 / Resumo: Ao longo dos últimos anos a Cromodinâmica Quântica (QCD) tem se estabelecido como a teoria quântica de campos das interações fortes. Entretanto, os estados de espalhamento elástico de hádrons em altas energias não possuem uma descrição formal a partir dos primeiros princípios da teoria. Como consequência, esses processos são ainda estudados num contexto eminentemente fenomenológico, constituindo um problema em aberto para a QCD. Os novos dados experimentais de espalhamentos elástico e detrativo próton-próton, obtidos recentemente pela Colaboração TOTEM no LHC/CERN a 7 e 8 TeV, têm permitido importantes testes de previsões de modelos fenomenológicos e originado também novos desafios para a QCD. Em especial, o crescimento com a energia da seção de choque total, stot(s) (grandeza correlacionada ao espalhamento elástico através do teorema óptico), não possui uma descrição baseada exclusivamente na QCD e previsões de modelos fenomenológicos representativos para a seção de choque diferencial, nas regiões de médio e grande momento transferido na colisão, apresentam desacordo com os dados experimentais recentemente obtidos a 7 TeV. Esses dois aspectos, associados ás seções de choque total e diferencial, constituem o tema central desta dissertação e são abordados através de dois estudos independentes. No primeiro estudo, apresentamos uma análise sobre o crescimento da stot(s) próton-próton (pp) e antipróton-próton (pp), através de ajustes de diferentes parametrizações analíticas aos dados experimentais acima de 5 GeV (incluindo os dados mais recentes obtidos a 7 e 8 TeV). Os resultados indicam soluções consistentes com um crescimento dessa grandeza mais rápido que a dependência com o quadrado do logaritmo da energia, estabelecida pelo limite de Froissart-Martin. Esse comportamento não implica, necessariamente, em violação da unitaridade, segundo estudo formal recente de Ya. Azimov, referido no texto. Extensões das parametrizações para ajustes de dados experimentais da seção de choque elástica integrada (sel) indicam valores assintóticos para a razão sel=stot inferiores ao limite 1/2 do disco negro. No segundo estudo, apresentamos uma análise empírica sobre a aplicabilidade da distribuição de Tsallis na descrição de dados experimentais de seção de choque diferencial pp, na região de médio e grande momento transferido e intervalo de energia de 19.4 GeV a 7 TeV. Os resultados apresentam consistência com todos os dados experimentais analisados. Para o conjunto a 7 TeV, extrapolação do resultado para a região de grande momento transferido prevê um decréscimo monotonico (sem oscilação) da seção de choque diferencial, o que também indica desacordo com o cenário de disco negro como limite assintótico (oscilações) / Abstract: The Quantum Chromodynamics (QCD) has been recognized as the quantum field theory of the strong interactions. However, QCD is not yet able to provide a formal description of the high-energy elastic hadron scattering from its _rst principles. As a consequence, the theoretical investigation of these processes still has a strictly phenomenological character, constituting, therefore, an open problem for QCD. New experimental data on proton-proton elastic and di_ractive scattering, recently obtained by the TOTEM Collaboration at 7 and 8 TeV (LHC/CERN), have allowed important tests on different phenomenological predictions and have also provided new challenges for the QCD. Of interest here, we mention that the rise of the total cross section with the energy, stot(s), a quantity related to the elastic scattering through the optical theorem, can not be accessed by QCD without model assumptions; moreover, predictions from representative phenomenological models for the differential cross section at intermediate and large values of the momentum transfer present no agreement with the experimental data recently obtained at 7 TeV. These two aspects, related to the total and differential cross sections, constitute the central subject of this thesis and are treated here through two independent studies. In the first study, an analysis on the rise of stot(s) from proton-proton (pp) e antiproton-proton (pp) scattering is presented. We consider different analytic parametrizations and fits to the experimental data above 5 GeV (including the recent measurements at 7 and 8 TeV). The results indicate consistent solutions with a rise of stot(s) faster than the log-squared bound predicted by Froissart and Martin. This behavior, according to recent formal results by Ya. Azimov, does not necessarily mean violation of unitarity. Extensions of the parametrizations to _t the elastic (integrated) cross section data, sel, lead to asymptotic values for the ratio sel=stot below the limit 1/2 of the black-disc. In the second study, an empirical analysis on the applicability of the Tsallis distribution in the description of the pp di_erential cross section data at intermediate and large values of the momentum transfer and energy interval 19.4 GeV - 7 TeV is presented. The results show consistence with all the experimental data investigated. At 7 TeV, extrapolation of the _t result to large values of the momentum transfer indicates a monotonic decrease of the di_erential cross section (without oscillation), a result also in contrast with the black-disc as an asymptotic scenario / Mestrado / Física / Mestre em Física

Le Collisionneur Linéaire International ILC est un projet de collisionneur électron-positon développé pour prendre le relais du Grand Collisionneur de Hadrons LHC. Ce projet permettra d'étudier précisément les caractéristiques du nouveau boson de 125 GeV , découvert en 2012 par les expérience CMS et ATLAS, compatible avec le boson de Higgs du modèle standard. Cette expérience pourrait aussi permettre aux physiciens de mettre à jour des phénomènes physiques inconnus. Pour exploiter au maximum ce nouvel accélérateur, deux collaborations travaillent sur le développement de deux détecteurs : le Grand Détecteur International ILD et le Détecteur au Silicium SiD. Ces détecteurs sont dits généralistes et sont optimisés pour la mise en oeuvre de technique de suivi des particules. Ils sont constitués d'un trajectographe dans leur partie centrale et de systèmes de calorimétrie. L'ensemble est inséré dans un aimant supraconducteur, lui même entouré d'une culasse instrumentée avec des chambres à muon. Le groupe lyonnais dans lequel j'ai effectué mes travaux de recherche pendant mon doctorat, a grandement participé au développement du calorimètre hadronique à lecture semi-digitale. Ce calorimètre ultra-granulaire fait partie des options pour le calorimètre hadronique du Grand Détecteur International. Un prototype a été construit en 2011. D'environ 1 m3, il est constitué de 48 chambres à plaque résistive de verre, comporte plus de 440000 canaux de lecture de 1 cm2 et pèse environ 10 tonnes. Ce calorimètre répond aux contraintes imposées pour le Collisionneur Linaire International (une haute granularité, une consommation électrique faible, une alimentation pulsée etc) et est régulièrement testé sur des lignes de faisceau au CERN. Les données ainsi collectées m'ont permis d'étudier en détail le phénomène de gerbe hadronique. De nombreux efforts ont été réalisé pour développer des méthodes efficace de reconstruction de l'énergie des gerbes hadroniques et pour améliorer la résolution en énergie du prototype SDHCAL. La simulation des gerbes hadroniques dans le SDHCAL constitue une part importante de mes travaux de recherche. Une simulation réaliste des chambres à plaque résistive de verre a été développée en étudiant la réponse du prototype au passage de muons et de gerbes électromagnétiques. J'ai alors confronté les modèles de simulation des gerbes hadroniques avec des données expérimentales. La granularité du SDHCAL rend aussi possible des études fines sur la topologie des gerbes hadroniques, notamment sur leur extension latéraleet longitudinale. J'ai finalement pu étudier, en m'appuyant sur mes travaux de simulations, la reconstruction de la masse des bosons W et Z dans une simulation complète du Grand Détecteur International. Cette étude permet d'estimer les performances de l'ILD avec le SDHCAL et les techniques de suivi des particules / The International Linear Collider ILC is an electron-positron collider project proposed to become the next particle collider after the Large Hadron Collider LHC. This collider will allow to study, in details, the new 125 GeV boson, discovered in 2012 by CMS and ATLAS experiments. This new particle seems compatible with the standard model Higgs boson. The International Collider may also allow physicists to discover new physics. In order to operate this new collider, two collaborations are developing two detectors : the International Large Detector ILD and the Silicon Detector SiD. These general-purpose detectors are optimised for particle flow algorithms. The team from Lyon in which I worked during my Ph.D., has widely participated in the development of the semi-digital hadronic calorimeter SDHCAL. This high granular calorimeter is one option for the International Large Detector hadronic calorimeter. A prototype has been built in 2011. This 1 m3 prototype is made of 48 glass resistive plate chambers and contains more than 440000 electronic readout channels. This technological calorimeter is often tested with beam of particles at CERN. The collected allowed me to study the hadronic showers with many details. Methods to reconstruct precisely the hadronic showers energy has been developed in order to improve the SDHCAL energy resolution. My main contribution was the development of the hadronic shower simulation within the SDHCAL. A realistic simulation of the SDHCAL was performed by studying the SDHCAL response to the passage of muons and electromagnetic showers. I was then able to compared different simulation models with experimental data. The SDHCAL granularity allows precise studies on the hadronic showers topology, such as longitudinal and lateral shower extent. I finally worked on the W and Z boson mass reconstruction in a full simulation of the International Large Detector in order to study the performance of this calorimeter option with particle flow techniques