Charm Jets in photoproduction have been studied in electron-proton collisions with the ZEUS detector at HERA, using an integrated luminosity of 120 pb-1. Jets were reconstructed using the longitudinally invariant kT-clustering algorithm. The dijet cross section for events containing at least one D*+/- charmed meson was measured as a function of various observables sensitive to hard scattering and the structure of the photon. The results are compared with predictions from leading-order parton-shower Monte Carlo simulations and with next-to-leading-order QCD calculations. / Differential cross sections of dijets as a function of the angle between the charm jet and the proton-beam directions in the dijet rest frame have been measured for samples enriched in direct or resolved photon events. The angular distribution shows a steep rise for resolved photon events in the photon direction, providing a clear first evidence for the existence of charm originating from the photon. The shallower rise for direct photon events as well as for the resolved photon events in the proton direction are consistent with the quark exchange diagrams. / The charm fragmentation function has also been measured for the first time at HERA. The fragmentation variable z is given by the ratio of E + p∥ for the D* meson and that for the associated jet, where E is the energy and p∥ the longitudinal momentum relative to the jet axis. The measured cross section was compared to different fragmentation models incorporated in both leading- and next-to-leading-order frameworks and to the results from e+ e- experiments.

The cross-section of large transverse momentum photons and neutral pions in proton-proton collisions is calculated using the standard perturbative QCD formula at leading twist, next-to-leading order, and is compared to data from the Relativistic Heavy Ion Collider (RHIC). The cross-section of hard photons and neutral pions is also calculated for deuteron-gold collisions using a model based on an extension of the proton-proton calculation to nucleus-nucleus collisions and on phenomenological nuclear parton distribution functions. The deuteron-gold calculations are compared to data measured at the same collider. The effect of parton energy loss on the deuteron-gold calculations is also investigated. / La section efficace des photons et des pions neutres ayant de grandes quantités de mouvement tranversales produits dans des collisions proton-proton est calculée en utilisant la formule standard basée sur la chromodynamique quantique (QCD) perturbative. Les calculs sont faits au premier "twist" et au second ordre, et sont comparés à des mesures provenant du "Relativistic Heavy Ion Collider" (RHIC). La section efficace est aussi calculée pour des collisions deutéron-or à l'aide d'un modèle basé sur des distributions de partons nucléaires et sur un prolongement de la formule des collisions proton-proton aux collisions noyau-noyau. Les calculs basés sur ce modèle sont comparés à des mesures provenant du même accélérateur. L'effet des pertes d'énergie des partons sur les calculs de sections efficaces dans les collisions deutéron-or est aussi étudié.

A first measurement of the radiative contribution to deep inelastic electron-proton scattering has been performed with the ZEUS detector at HERA. Results show consistency with predictions made by the HERACLES Monte Carlo program. New calibration and simulation of the far luminosity measurement system, including a photon calorimeter and two aerogel Cherenkov detectors, have been implemented. Both calibration and simulation were applied to tag photons produced in the initial state radiative process. These tagged events were used to perform measurements of the deep inelastic ep scattering reduced cross section down to momentum transfer squared, Q2 = 3.0 GeV2, a region normally inaccessible to ZEUS. A determination of the radiative contribution to deep inelastic scattering has aided in the measurement of the structure functions F2 and FL, which were simultaneously extracted in the kinematic region 8.0 GeV2 < Q2 < 130 GeV2 and 2.5 × 10−4 < x < 0.005, where x is associated with the fraction of momentum carried by the interacting quark, using collision data at three centre-of-mass energies, 318 GeV, 251 GeV and 225 GeV. / La contribution radiative à la diffusion in èlastique profonde èlectron-proton a ètè mesurèe pour la première fois avec le dètecteur ZEUS à HERA. Les rèsultats dèmontrent un accord avec les prèdictions faites par le programme Monte-Carlo HERACLES. De nouvelles calibration et simulation du système èloignè de mesure de la luminositè, incluant un calorimètre à photons et deux dètecteurs Cherenkov en aèrogel, ont ètè effectuèes. Ces calibration et simulation ont ètè toutes deux utilisèes pour identifier les photons produits dans le processus de radiation de l'ètat initial. Les èvènements ainsi choisis ont permis de mesurer la section efficace rèduite de diffusion inèlastique profonde ep à des valeurs du carrè du transfert de quantitè de mouvement aussi basses que Q2 = 3.0 GeV2, une règion cinèmatique normalement non-accessibleà ZEUS. Une dètermination de la contribution radiative à la diffusion inèlastique profonde a aidè les mesures des fonctions de structure F2 et FL, qui ont ètè ex- traites simultanèment dans la règion cinèmatique 8.0 GeV2 < Q2 < 130 GeV2 et 2.5 × 10−4 < x < 0.005, où x peut être associè à la fraction de la quantitè de mouve- ment du proton participant à la rèaction, et ce en exploitant les donnèes de collisions prises à trois ènergies du centre de masse, 318 GeV, 251 GeV et 225 GeV.

This thesis is a report on the design, construction and data analysis of the Digital Hadron Calorimeter (DHCAL). The DHCAL was constructed as part of the CALICE collaboration efforts in the SiD detector design for the proposed International Linear Collider (ILC). The SiD detector design is one of two detector designs for the ILC. The DHCAL is but one of the detector sub-systems that are to make up the entire detector. The CALICE collaboration is involved in the development of calorimeters for the ILC. The DHCAL utilizes Resistive Plate Chamber technology to detect the physics events and is the world's first digital imaging calorimeter. The prototype construction was performed at Argonne National Laboratory and the detector studied locally in a cosmic ray test stand. In addition, the DHCAL was also put into multiple test beam runs at Fermi National Accelerator Laboratory. This work will be completed with the analysis of the DHCAL data with muons. The calibration with muons will be discussed, as well as its purpose to the overall viability of this technology in a full scale detector. / Cette thèse est un rapport sur la conception, la construction et l'analyse des données du calorimètre hadronique digital (CALHD). Le CALHD a été construit dans le cadre des efforts menés par la collaboration CALICE pour la conception du détecteur SiD destiné au future Collisionneur Linéaire International (CLI). Le SiD est un des deux détecteurs proposés pour le CLI. Le CALHD lui-même n'est qu'un des sous-systèmes devant constituer le détecteur complet. La collaboration CALICE est impliquée dans le développement des calorimètres pour le CLI. Le CALHD utilise la technologie des chambers à plaques résistives pour détecter les événements physiques et est le premier calorimètre par images digitales au monde. La construction du prototype a été realisée au Laboratoire National Argonne et ses performances étudiées dans un montage de tests avec des rayons cosmiques. De plus, le CALHD a été placé à plusieurs reprises dans une ligne de fasiceau de particules au Laboratoire National d'Accélérateur Fermi. Ce travail sera complété par l'analyse des données du CALHD avec des muons. La calibration à l'aide de muons sera discutée, ainsi que la viabilité globale de cette technologie pour un détecteur à grande échelle.

The production of massive scalar particles at $e sp+e sp-$ machines is studied in detail. In particular, we show that models which rely on scalar fields which couple only to heavy fermions cannot be rejected based on branching fractions for the $Z sb0$ decays at LEP.

In the present analysis, the constant alphas of Quantum Chromodynamics (QCD) is determined from dijets production in the regime of neutral current deep inelastic scattering (NC DIS) with high momentum transfer Q2. This measurement uses the data collected between the years 1998 to 2000 by the ZEUS detector located on the HERA ring collider in Hamburg, Germany. Corresponding to an integrated luminosity of 82.7 pb-1, the data were produced by the interactions between 27.5 GeV electrons (or positrons) and 920 GeV protons. Defined in a phase space reducing the theoretical and systematic uncertainties, the dijet production is observed as well as the total inclusive DIS cross-section. The resulting observable, the ratio of dijets over the number of DIS events, is then compared to the NLO predictions provided by the program DISENT. From a QCD fit performed on four bins in Q2, we obtain a value consistent with the world average: alpha s(MZ) = 0.1157 +/- 0.0017( stat.) +0.0054-0.00 59 (syst.) +0.0075-0.00 65 (th.).

Thesis (Ph.D.)--Indiana University, Dept. of Physics, 2007. / Source: Dissertation Abstracts International, Volume: 68-05, Section: B, page: 3121. Adviser: Rick Van Kooten. "Title from dissertation home page (viewed Jan. 24, 2008)."

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 68-02, Section: B, page: 1041. Adviser: Mats Selen. Includes bibliographical references (leaves 153-155) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 68-02, Section: B, page: 1042. Adviser: Yoshitsugu Oono. Includes bibliographical references (leaves 105-108) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Washington, 2005. / (UnM)AAI3183441. Source: Dissertation Abstracts International, Volume: 66-07, Section: B, page: 3770. Chair: Stephen R. Sharpe.