Strahlungskorrekturen zur Hadronproduktion bei niedrigen Energien, wie man sie an den e+e- -Beschleunigern DAFNE und VEPP-2M misst, werden untersucht. Ziel dieser Arbeit ist es, die von QED--Korrekturen befreiten hadronischen Wirkungsquerschnitte aus den hadronischen Daten mit einer Praezision auf Promille-Niveau zu extrahieren. Hadronische Praezisionsdaten werden benoetigt, um den theoretischen Fehler zur laufenden Feinstrukturkonstanten alpha(s) und zum anomalen magnetischen Moment des Myons a(mu) zu senken und sie stellen daher einen Schluessel zur moeglichen Entdeckung ``neuer Physik'' dar. Insbesondere die Paarproduktion geladener Pionen e+e- -> pi+ pi- unterhalb einer Energie von 1 GeV ist von grosser Wichtigkeit. Zu diesem Prozess werden die vollstaendigen O(alpha)-QED-Korrekturen zum Anfangszustand, Endzustand sowie die Interferenzkorrekturen berechnet. Analytische Formeln zu den virtuellen und reellen photonischen Korrekturen werden angegeben. Der totale Wirkungsquerschnitt sigma, die Pion-Winkelverteilung dsigma/dcos(theta) und die Invariantemasseverteilung des Pionpaars dsigma/ds' werden fuer den Fall realistischer kinematischer Schnitte untersucht. Es wird gezeigt, dass zusaetzlich zu den vollstaendigen O(alpha)-Korrekturen zusaetzlich die photonischen Anfangszustandskorrekturen der Ordnung O(alpha^2) und fuehrende Photonbeitraege der Ordnung O(alpha^3) sowie Beitraege zur e+ e- -Paarabstrahlung vom Anfangszustand beruecksichtigt werden muessen wenn mindestens eine Genauigkeit auf Prozent-Niveau verlangt wird. Fuer die Datenanalyse wird der Schwerpunkt auf eine inklusive Behandlung aller Photonen gelegt. Die Messung sowohl des totalen Wirkungsquerschnitts als auch der pi+ pi- Invariantemasseverteilung betreffend wird der theoretische Fehler dieser Behandlung der Strahlungskorrekturen mit 2 Promille abgeschaetzt. Ausserdem wird die Modellunsicherheit als Folge der Pion-Substruktur diskutiert. Um den Formfaktor mit der gewuenschten Praezision aus den experimentellen Daten extrahieren zu koennen, wurde ein auf diese Fragestellung zugeschnittenes Fortran-Programm geschrieben, welches die Beruecksichtigung realistischer kinematischer Schnitte erlaubt. Insgesamt erfuellt die Genauigkeit der theoretischen Vorhersagen die Erfordernisse der Niedrigenergie- e+ e- -Experimente wie diejenigen bei DAFNE oder VEPP-2M. / Radiative corrections to low energy hadron production as measured at the e+ e- colliders DAFNE and VEPP-2M are investigated. The goal of this work is to provide the theoretical condition for extracting hadronic cross sections undressed from QED corrections from the measured data with a precision of per mill level. High precision hadronic data are required to reduce the theoretical error of the running fine structure constant alpha(s) and the muon anomalous magnetic moment a(mu) and therefore represent a key to a possible discovery of ``new physics''. Especially the channel of charged pion pair production e+e- -> pi+ pi- below 1 GeV appears to be of great importance. To this process the complete O(alpha) QED initial state, final state and initial-final state interference corrections are calculated. Analytic formulae are given for the virtual and for the real photon corrections. The total cross section sigma, the pion angular distribution dsigma/dcos(theta) and the pi+ pi- invariant mass distribution dsigma/ds' are investigated in the regime of experimentally realistic kinematical cuts. It is shown that in addition to the full O(alpha) corrections also the O(alpha^2) and leading log O(alpha^3) photonic corrections as well as the contributions from IS e+ e- pair production have to be taken into account if at least per cent accuracy is required. For the data analysis I focus on an inclusive treatment of all photons. The theoretical error concerning this treatment of radiative corrections is then estimated to be 2 per mill for both the measurement of the total cross section and the pi+ pi- invariant mass distribution. In addition the model uncertainty due to the pion substructure is discussed. To be able to extract the pion form factor from the experimental data with the desired accuracy a dedicated Fortran program was written which allows to take into account experimentally realistic kinematical cuts. Altogether the precision of the theoretical prediction matches the requirements of low energy e+ e- experiments like the ones at DAFNE and VEPP-2M.

In dieser Arbeit wurde die Produktion der Charmonium-Zust\"ande $\chi_{c1}$ und $\chi_{c2}$ in Proton-Kern-Wechselwirkungen bei einer Proton-Nukleon-Schwerpunktenergie von $\sqrt{s}=41.6~{\rm GeV}$ untersucht. Die f\"ur die Analyse verwendeten Daten wurden mit dem HERA-B-Experiment genommen, das die Streuung von Protonen des HERA-Rings an feststehenden Draht-Targets verschiedener Materialien untersucht. Die Analyse basiert auf etwa $10\,000$ radiativen $\chi_{c}$-Zerf\"allen, $\chi_{c}\rightarrow J/\psi\gamma$, die aus mehr als $122\cdot10^{3}$ myonischen $J/\psi$-Zerf\"allen, $J/\psi\rightarrow\mu^{+}\mu^{-}$, rekonstruiert wurden. Das Verh\"altnis der Rate der $J/\psi$, die aus $\chi_{c}$-Zerf\"allen stammen, zu der Gesamtrate der $J/\psi$, $R_{\chi_{c}}=\sum_{i=1,2}{\sigma(\chi_{ci})Br(\chi_{ci}\rightarrow J/\psi\gamma)/\sigma(J/\psi)}$, wurde in dem kinematischen Bereich $-0.35 / In this thesis the production of the charmonium states $\chi_{c1}$ and $\chi_{c2}$ in proton-nucleus collisions at a proton-nucleon center-of-mass energy $\sqrt{s}=41.6~{\rm GeV}$ was studied. The data used for the analysis have been taken by the fixed-target experiment HERA-B that uses the HERA proton beam to scatter protons off the nuclei of different wire targets. About $122\cdot10^{3}$ recorded muonic $J/\psi$ decays, $J/\psi\rightarrow\mu^{+}\mu^{-}$, resulted in almost $10\,000$ reconstructed $\chi_{c}\rightarrow J/\psi\gamma$. The ratio $R_{\chi_{c}} = \sum_{i=1,2}{\sigma(\chi_{ci}) Br(\chi_{ci}\rightarrow J/\psi\gamma) /\sigma(J/\psi)}$, which is the ratio of $J/\psi$ from $\chi_c$ decays to all produced $J/\psi$, was measured in the kinematical range $-0.35

Orientador: Marcio José Menon / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-09-03T06:43:58Z (GMT). No. of bitstreams: 1 Silva_PauloVictorRecchiaGomesDa_D.pdf: 2099457 bytes, checksum: 1ee131514df28d70491b1009310811be (MD5) Previous issue date: 2017 / Resumo: A Cromodinâmica Quântica (QCD) constitui a teoria quântica de campos da interação forte. Apesar do seu sucesso na descrição de diversos processos envolvendo hádrons, o espalhamento elástico ainda é um desafio para a teoria. Este processo é caracterizado por pequeno momento transferido e, nessa escala, não é possível utilizar a abordagem perturbativa. Embora resultados não-perturbativos tenham sido obtidos recentemente, ainda não possuímos uma descrição completa (para qualquer energia e momento transferido) no âmbito da QCD para grandezas físicas associadas ao espalhamento elástico, por exemplo, a seção de choque total ($\sigmatot$), o parâmetro $\rho$, a seção de choque elástica ($\sigmael$) e a seção de choque diferencial. As descrições dos dados experimentais associados baseiam-se em abordagens empíricas e fenomenológicas tais como o Formalismo de Regge-Gribov e modelos inspirados em QCD. Desde o início das operações do LHC, nós tivemos a oportunidade de estudar essas grandezas nas energias mais altas disponíveis em experimentos de aceleradores, especificamente 7 e 8 TeV para o espalhamento próton-próton ($pp$). Nesta tese, o interesse principal é a dependência com a energia de três grandezas, especificamente a razão $X=\sigmael/\sigmatot$, $\sigmatot$ e o parâmetro $\rho$, ou seja, o comportamento destas grandezas em energias altas e assintóticas, bem como a influência de contribuições sub-dominantes para $\sigmatot$. Estes tópicos estão divididos em três estudos independentes, mas complementares, envolvendo aspectos empíricos, fenomenológicos e teóricos. No primeiro tópico, desenvolvemos uma análise empírica da razão $\sigmael/\sigmatot$, a qual está relacionada com a função perfil com parâmetro de impacto nulo (opacidade hadrônica central). Através de parametrizações apropriadas, com um número pequeno de parâmetros livres, obtivemos boas descrições dos dados experimentais dos espalhamentos $pp$ e antipróton-próton ($\ppbar$). A partir dos ajustes aos dados utilizando quatro variantes, concluímos que o cenário assintótico de disco negro não é a única solução e, além disso, os resultados favorecem um cenário de disco cinza. No segundo tópico, estudamos o crescimento de $\sigmatot$ em função da energia através de parametrizações baseadas no formalismo de Regge-Gribov e testamos dois termos dominantes, um logaritmo ao quadrado e um logaritmo elevado a um número real $\gamma$, onde $\gamma$ é um parâmetro livre de ajuste. Adicionalmente, discutimos dois métodos analíticos para conectar as partes real e imaginária da amplitude de espalhamento elástico, especificamente Relações de Dispersão Derivativas (RDD) e Unicidade Assintótica (UA), os quais resultam em diferentes parametrizações para $\sigmatot$ e parâmetro $\rho$. Por sua vez, essas diferenças são também discutidas. Os resultados favorecem a método RDD tanto no contexto formal, quanto no contexto prático. A recente tensão entre os dados das Colaborações TOTEM e ATLAS em 7 e 8 TeV também é discutida e considerada nas reduções de dados. No terceiro e último tópico, dois termos subdominantes de $\sigmatot$ obtidos em uma abordagem não-perturbativa da QCD para o espalhamento elástico são considerados em ajustes aos dados de $pp$ e $\ppbar$, bem como em ajustes aos dados de outras reações bárion-bárion e méson-bárion. Nesta análise, com um parâmetro extra e com informações teóricas adicionais, também obtemos um cenário assintótico de disco cinza / Abstract: Quantum Chromodynamics (QCD) constitutes the quantum field theory of the strong interaction. Despite the success of this theory in the description of several processes involving hadrons, the elastic scattering is still a theoretical challenge. This process is characterized by a small transferred momentum and, in this range, the perturbative techniques are not applicable. Although nonperturbative results have been obtained in recent years, we still do not have a full description within QCD of the quantities related to the elastic scattering, valid for all the energies and transferred momentum, for example, the total cross section ($\sigmatot$), the $\rho$ parameter, the elastic cross section ($\sigmael$) and the differential cross section. The attempts to describe experimental data rely on empirical and phenomenological approaches such as Regge-Gribov Formalism and QCD inspired models. Since the start of Run 1 at the LHC, we have the opportunity to study the quantities above in the largest energies available in accelerator experiments, namely 7 and 8 TeV for proton-proton ($pp$) scattering. In this thesis, the main interest is in the energy dependence of three quantities, the ratio $X=\sigmael/\sigmatot$, the $\sigmatot$ and the $\rho$ parameter, namely the behaviour at high and asymptotic energies, as well as the influence of sub-leading contributions to $\sigmatot$. These topics are divided into three different, but complementary studies, involving empirical, phenomenological and theoretical aspects. In the first topic, we develop an empirical analysis on the ratio $\sigmael/\sigmatot$, a quantity related to the profile function at impact parameter zero (the hadronic central opacity). By means of suitable parameterizations, with a small number of free parameters, we have obtained good descriptions of the experimental data on $pp$ and antiproton-proton ($\ppbar$) data. From the fits with four variants, we conclude that the asymptotic black-disk scenario is not a unique solution and, moreover, the results favour a grey-disk scenario. In the second topic, we study the rise of $\sigmatot$ with the energy through parameterizations based on the Regge-Gribov formalism and we consider two options for the leading terms: a log-square and a log-raised-to-$\gamma$, with $\gamma$ a free fit parameter. In addition, we discuss two analytic methods to connect the real and imaginary parts of the elastic scattering amplitude, namely Derivative Dispersion Relations (DDR) and Asymptotic Uniqueness (AU), which lead to different parameterizations for $\sigmatot$ and the $\rho$ parameter; these differences are critically discussed. The results favour the DDR method in both formal and practical contexts. The recent tension between the TOTEM and ATLAS data at 7 and 8 TeV is discussed and considered in the data reductions. In the third topic, two sub-leading terms for $\sigmatot$, obtained in a nonperturbative QCD approach to the elastic scattering, are considered in fits to $pp$ and $\ppbar$ data and also in fits to data from meson-baryon and other baryon-baryon scattering. In this analysis, with an extra parameter, and with theoretical inputs, we also obtain an asymptotic grey-disk scenario for the colliding particles / Doutorado / Física / Doutor em Ciências / 152985/2013-1 / 2013/27060-3, 2015/21855-0 / CNPQ / FAPESP

La première partie rapporte la caractérisation de prototypes de chambre MICROMEGAS en tests sous faisceaux et en laboratoire. L'étude détaille notamment l'efficacité de détection, la multiplicité de la réponse et dépendance du gain du détecteur vis à vis des conditions environnementales. Dans la seconde partie, La détection d'un boson de jauge Z', prédit par différends modèles de types Randal-Sundrum est étudiées dans le cadre de l'expérience CLIC. Le canal considéré implique l'émission du Z' par une paire de quarks top. Le Z' se désintègre ensuite en particules de matière noire. / The first part of the thesis reports on the characterisation of MICROMEGAS prototypes in beam and laboratory tests. Detection efficiency, response multiplicity and detector gain dependency against environmental conditions are detailed. In the second part, the detection of a Z' gauge boson predicted by a Randal & Sundrum inspired model together with a dark matter candidate (nu') is investigated in the framework of the CLIC experiment. The considered channel involves a top quark pair emmiting the Z' which, in turn, decays into nu', anti-nu'.

This dissertation investigates CsI(Tl) pulse shape discrimination (PSD) as a novel experimental technique to improve challenging areas of particle identification at high energy $e^+ e^-$ colliders using CsI(Tl) calorimeters. In this work CsI(Tl) PSD is implemented and studied at the Belle II experiment operating at the SuperKEKB $e^+ e^-$ collider, representing the first application of CsI(Tl) PSD at a $B$ factory experiment. Results are presented from Belle II as well as a testbeam completed at the TRIUMF proton and neutron irradiation facility. From the analysis of the testbeam data, energy deposits from highly ionizing particles are shown to produce a CsI(Tl) scintillation component with decay time of $630\pm10$ ns, referred to as the hadron scintillation component, and not present in energy deposits from electromagnetic showers or minimum ionizing particles. By measuring the fraction of hadron scintillation emission relative to the total scintillation emission, a new method for CsI(Tl) pulse shape characterization is developed and implemented at the Belle II experiment's electromagnetic calorimeter, constructed from 8736 CsI(Tl) crystals. A theoretical model is formulated to allow for simulations of the particle dependent CsI(Tl) scintillation response. This model is incorporated into GEANT4 simulations of the testbeam apparatus and the Belle II detector, allowing for accurate simulations of the observed particle dependent scintillation response of CsI(Tl). With $e^\pm$, $\mu^\pm$, $\pi^\pm$, $K^\pm$ and $p/\bar{p}$ control samples selected from Belle II collision data the performance of this new simulation technique is evaluated. In addition the performance of hadronic interaction modelling by GEANT4 particle interactions in matter simulation libraries is studied and using PSD potential sources of data vs. simulation disagreement are identified. A PSD-based multivariate classifier trained for $K_L^0$ vs. photon identification is also presented. With $K_L^0$ and photon control samples selected from Belle II collision data, pulse shape discrimination is shown to allow for high efficiency $K_L^0$ identification with low photon backgrounds as well as improved $\pi^0$ identification compared to shower-shape based methods. / Graduate

The first 900 four-anode Photomultiplier Tubes (PMTs) have been evaluated for use in the 2013 Hadronic Forward (HF) calorimeter upgrade. HF is a part of the Compact Muon Solenoid (CMS), which is one of the two large general-purpose particle detectors of the Large Hadron Collider (LHC) at CERN in Geneva, Switzerland. HF requires 1728 PMTs. These small tubes are the sensitive light detectors that provide the output signals of HF. Before installing PMTs in HF, their quality control demands need to be satisfied. These tests, done at the University of Iowa, are designed in three categories to test seventeen different parameters for each PMT. The three most basic and most important groups of parameters are: dark current, gain (anode and cathode), and timing. There are secondary tests which are performed on a smaller percentage of the PMTs such as surface uniformity, double pulse and single photo-electron resolution. The PMTs that meet the specifications of HF will be sent to CERN where they are expected to be in use for at least a decade.

This thesis deals with a broad range of aspects that concern the simulation of QCD jet physics by Monte Carlo event generators. Phenomenological work is presented in validating the CKKW approach for merging tree-level matrix elements and parton showers. In the second part the main project is documented comprising the definition, realization and verification of a new QCD colour-dipole cascade. Finally, a new cluster-hadronization model is introduced.

The Q-weak experiment at Thomas Jefferson National Accelerator Facility (USA) will make a precision determination of the proton weak charge with approximately 4% combined statistical and systematic uncertainties via a measurement of the parity violating asymmetry in elastic electron-proton scattering at very low momentum transfer and forward angle. This will allow an extraction of the weak mixing angle at Q^2=0.026 (GeV/c)^2 to approximately 0.3%. The weak mixing angle is a fundamental parameter in the Standard Model of electroweak interactions. At the proposed accuracy, a measured deviation of this parameter from the predicted value would indicate new physics beyond what is currently described in the Standard Model. Without deviation from the predicted value, this measurement would place stringent limits on possible extensions to the Standard Model and constitute the most precise measurement of the proton's weak charge to date. The key experimental apparatus include a liquid hydrogen target, a toroidal magnetic spectrometer and a set of eight Cerenkov detectors. The Cerenkov detectors form the main detector system for the Q-weak experiment and are used to measure the parity violating asymmetry during the primary Q-weak production runs. The Cerenkov detectors form the main subject of this thesis. Following a brief introduction to the experiment, the design, development, construction, installation, and testing of this detector system will be discussed in detail. This is followed by a detailed discussion of detector diagnostic data analysis and the corresponding detector performance. The experiment has been successfully constructed and commissioned, and is currently taking data. The thesis will conclude with a discussion of the preliminary analysis of a small portion of the liquid hydrogen data.

The Q-weak experiment at Thomas Jefferson National Accelerator Facility (USA) will make a precision determination of the proton weak charge with approximately 4% combined statistical and systematic uncertainties via a measurement of the parity violating asymmetry in elastic electron-proton scattering at very low momentum transfer and forward angle. This will allow an extraction of the weak mixing angle at Q^2=0.026 (GeV/c)^2 to approximately 0.3%. The weak mixing angle is a fundamental parameter in the Standard Model of electroweak interactions. At the proposed accuracy, a measured deviation of this parameter from the predicted value would indicate new physics beyond what is currently described in the Standard Model. Without deviation from the predicted value, this measurement would place stringent limits on possible extensions to the Standard Model and constitute the most precise measurement of the proton's weak charge to date. The key experimental apparatus include a liquid hydrogen target, a toroidal magnetic spectrometer and a set of eight Cerenkov detectors. The Cerenkov detectors form the main detector system for the Q-weak experiment and are used to measure the parity violating asymmetry during the primary Q-weak production runs. The Cerenkov detectors form the main subject of this thesis. Following a brief introduction to the experiment, the design, development, construction, installation, and testing of this detector system will be discussed in detail. This is followed by a detailed discussion of detector diagnostic data analysis and the corresponding detector performance. The experiment has been successfully constructed and commissioned, and is currently taking data. The thesis will conclude with a discussion of the preliminary analysis of a small portion of the liquid hydrogen data.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A física de partículas vem atualmente estudando tópicos como o plasma de quarks e glúons (QGP), o bóson de Higgs e a matéria escura, que requerem experimentos de colisões entre partículas cada vez mais energéticas. Para isso, são necessários aceleradores capazes de gerar partículas projéteis a cada vez mais altas energias, o que pode levar a uma nova física. Quando novos dados surgem nos laboratórios, novos processos são necessários para explicar estes dados e algumas vezes a estrutura interna das partículas envolvidas é desconhecida. Nos modelos teóricos, usados para descrever estes processos de espalhamento, é comum introduzir o fator de forma. O fator de forma é simplesmente uma maneira de simular a sub-estrutura das partículas envolvidas nestes processos com função da energia ou momento. A obtenção dos atores de forma pode ser feita usando o método conhecido como Regras de Soma da QCD (RSQCD). Neste trabalho, será estudado o vértice D*Dp usando as RSQCD, de modo que seja possível obter os seus fatores de forma e sua constante de acoplamento. Para isso, foram estudados os casos em que o méson ρ e o méson D estão fora de suas camadas de massa. O vértice D*Dp é muito importante para entender melhor o ρπ Puzzle, onde o méson Ј/ψ decai ρπ em com um branching ratio maior do que o esperado (este é um processo suprimido pela regra de OZI). Estudando este processo com graus de liberdade mesnicos, é possível escapar da regra de OZI, uma vez que o processo Ј/ψ→ DD → ρπ não é suprimido por OZI. Ao se fazer isso, aparecerá, entre outros, o vértice D*Dp . Este é um vértice que também aparece em outros decaimentos, como por exemplo X(3872) →Ј/ψp e B→Ј/ψD. Ao final do desenvolvimento, os resultados obtidos neste trabalho para o vértice D*Dp foram comparados com outros encontrados na literatura, se mostrando compatíveis com estes outros trabalhos. / The particle physics have been studying topics like the Quark-Gluon Plasma (QGP), Higgs boson and dark matter, which require experiments in heavy-ion collisions. Therefore, accelerators capable of generate high energy particle beams are necessary and may generate new physics. When new data arise in the laboratories, new processes are necessary to explain this data and sometimes, the internal structure of the involved particles is unknow or are virtual. In the theoretical models, used to describe this scattering processes, is common to introduce the form factors. The form factor is a way to simulate the sub-structure of the involved particles as function of energy or momentum. The form factor can be obtained using a method called QCD Sum Rules (QCDSR). In this work, the vertex D*Dp will be studied using the QCDSR, in order to obtain its form factors and coupling constant.The D*Dp vertex is very important to understand the ρπ Puzzle, where the Ј/ψ meson decays in ρπ with a branching ratio bigger than expected (this is a suppressed process by the OZI Rule). Studying this process with hadronic degrees of freedom, its possible to escape of the OZI rule, once the Ј/ψ→ DD → ρπ is not suppressed by the OZI rule. In this process, the D*Dp vertex is necessary. There are other processes where this vertex is necessary: X(3872)→Ј/ψp and B→Ј/ψD for example. In this work, was only possible to obtain results from the ρ off-shell diagram. This results were compared with others obtained in the literature.