The Standard Model has been very successful in describing existing experimental data in nuclear and particle physics, but it still depends on numerous experiments for the determination of several important properties. For example, the assumption that only Vector(V) and Axial-Vector(A) interactions are present out of five possible types of weak interactions: V, A, Scalar(S), Pseudoscalar(P) and Tensor(T) is based on experimental results. The ion trap is an promising way for precise measurement of the beta-neutrinoangular correlation parameter "a" in beta decay. The unperturbed observation of the recoiled nucleus and electron allows reconstruction of the full decay kinematics. The goal of the BPT (Beta-decay Paul Trap) project is to measure "a" in the decay of 8Li. A deviation from the predicted value a =―1/3 would be an indication of a tensor contribution. 8Li was produced at the Argonne National Laboratory and about 20,000 events were recorded. By measuring the energy shift of the alpha particles in the 8Li decay, "a" is determined to be a =―0.329±0.009. This measurement is consistent with the Standard Model prediction. Upgrade of the system for a higher precision measurement is discussed. / Le Modèle Standard a connu un très grand succès pour décrire les mesures expérimentales autant en physique nucléaire qu'en physique des particules. Cependant, plusieurs expériences tentent toujours de vérifier certaines de ses hypothèses de base. Par exemple, c'est grace à des résultats expérimentaux, que l'on sait que seules les interactions de type Vecteur (V) et Axial-Vecteur (A) sont présentes dans le Modèle Standard, bien qu'il y a théoriquement trois autres types d'interactions faibles possibles : Scalaire (S), Pseudoscalaire (P) et Tenseur (T). Les pièges d'ions sont une avenue prometteuse pour mesurer précisément le paramètre de correlation angulaire bêta-neutrino, "a", des désintégrations bêta. L'observation du noyau de recul et de l'électron en l'absence de perturbations externes permet la reconstruction de la cinématique complète des désintégrations. Le but du projet BPT (Beta-decay Paul Trap) est de mesurer "a" à partir de désintégrations d'ions 8Li. Toute déviation des mesures par rapport à la valeur théorique a = ―1/3 serait une indication d'une contribution d'interactions de type Tenseur. Des ions 8Li ont été produits au Argonne National Laboratory, où prês de 20 000 événements ont été enregistrés. En mesurant le décalage énergétique des particules alpha originant de désintégrations 8Li, une valeur de a =―0.329±0.009 a été déterminée pour le paramètre de corrélation angulaire. Cette valeur est en accord avec la prédiction du Modèle Standard. Une amélioration du dispositif pour permettre des mesures de plus grande précision est discutée.

An electrostatic deceleration system was developed for the injection of the 60-keV mass-separated ion beam at the ISOLDE facility at CERN (Geneva, Switzerland) into a new segmented radio-frequency quadrupole (RFQ) ion guide at the ISOLTRAP experiment. A detailed computer simulation of the ion motion through the electrostatic decelerating and focusing electrodes into the RFQ ion guide was carried out. A complete decelerating structure was designed and built using the parameters extracted from the simulation, as was the first half of a segmented RFQ ion guide for capturing and cooling the decelerated beam. With experiments conducted partly with the ISOLTRAP apparatus at CERN and partly with our apparatus at McGill University, we were able to show that the decelerating structure can in fact inject a beam into the RFQ ion guide. The measured transmission rate of 15 to 30 percent is in agreement with the value that was predicted by the simulations.

We investigate both directed and elliptic flow and linear momentum transfer in intermediate energy heavy ion collisions. The model that we have adapted for this work is the BUU transport equation solved with a momentum-dependent lattice Hamiltonian algorithm. We introduce an extension of this transport model that consistently takes into account the momentum-dependent in-medium modification of the nucleon-nucleon collision cross section. Comparison with linear momentum transfer data favours a soft momentum-dependent nuclear mean field of compressibility K = 215 MeV. Analysis of higher energy elliptic flow data favours a momentum-dependent over that of a momentum-independent nuclear mean field. Furthermore, we find that both the linear momentum transfer and elliptic flow data favour an in-medium nucleon-nucleon cross section over the free space cross section.

Photoproduction events which have two or more jets have been studied in the $W sb{ gamma p}$ range 135 GeV $< W sb{ gamma p} <$280 GeV with the ZEUS detector at HERA. A class of events is observed with little hadronic activity between the jets. The jets are separated by pseudorapidity intervals (${ Delta eta}$) of up to four units and have transverse energies greater than 6 GeV. A gap is define as the absence between the jets of particles with transverse energy greater than 300 MeV. The fraction of events containing a gap is measured as a function of ${ Delta eta}$. It decreases exponentially as expected for processes in which colour is exchanged between the jets, up to a value of ${ Delta eta} sim3$, then reaches a constant value of about 0.1. The excess above the exponential fall-off can be interpreted as evidence for hard scattering via a strongly interacting colour singlet object.

We compute the thermal photon production of a quark gluon plasma in thermal equilibrium at finite baryon chemical potential. We show that the photon production is equivalent to the integral of a Wightman current-current correlator. Subsequently, we present an introduction to quantum field theory at finite temperature, with emphasis on the real time formalism. Expressions for real time QCD propagators in the Keldysh basis at finite baryon chemical potential are derived in detail. In the second part, a power counting analysis is performed to determine exactly which Feynman diagrams contribute to the evaluation of the Wightman correlator at leading order. It is found that, just like in the case without chemical potential, one has to resum an infinity of so-called "ladder diagrams" and obtain an integral equation whose solution yields the photon production. / L'objet de cette thèse est de calculer la production de photons thermiques d'un plasma de quarks et de gluons en état d'équilibre thermodynamique à potentiel chimique non nul. Nous montrons que la production de photons est déterminée par l'intégrale d'un corrélateur de Wightman pour deux insertions de l'opérateur de courant électromagnétique. Par la suite, nous décrivons les rudiments de la théorie des champs à température non nulle. Nous mettons l'emphase sur le formalisme à temps réel et calculons en détails les propagateurs de la QCD à potentiel chimique non nul dans la base de Keldysh. Dans la deuxième partie de cette thèse, nous analysons l'ordre de magnitude des diagrammes de Feynman contribuant au corrélateur de Wightman pour déterminer lesquels fournissent une contribution dominante. Tout comme dans le cas à potentiel chimique nul, nous trouvons qu'il faut additionner une infinité de diagrammes en forme d'échelle. Cette addition mène à une équation intégrale dont la solution détermine la production de photons.

The Canadian Penning trap Mass Spectrometer (CPTMS) was reassembled and commissioned at Argonne National Laboratory. It consists of three systems: a laser desorption ion source, used for stable isotope production; a radio-frequency quadrupole ion trap (Paul trap); and a Penning trap, which sits inside a homogeneous 6 Tesla magnetic field. The CPTMS was tested using gold ions: these were accelerated toward the Paul trap, where they were accumulated and cooled down. They were then sent to the Penning trap, in which ions undergo circular motion. These motions were resonantly excited using an RF dipole electric field, and the resonant frequency was measured as a minimum in time-of-flight of the ejected ions as they were led to a region of low magnetic field, converting their cyclotron energy to axial kinetic energy. The apparatus was found to be operational: multiple-bunch accumulation was observed for the first time in a Paul trap, and the Fourier limited frequency resolution of 2 x 10--6 was attained for a one second excitation time in the Penning trap.

In this thesis, the classical field model developed by Krasnitz et al. is used to compute quark and photon production in heavy ion collisions. The first part of the thesis serves as an independent verification of previous results for quark production. To do so, an iterative method is developed to solve the non-linear system of equations that gives the initial condition for the gluonic field. In the second part, the expression giving the photon production rate is simplified using the symmetries and properties of the Color Glass Condensate and McLerran-Venugopalan models. From the two Feynman diagrams that give the leading order contribution, one is much larger than the other. The dominant diagram is given by a continuum spectrum with a very prominent peak superimposed on it. / Dans cette thèse, le modèle développé par Krasnitz et al. basé sur les champs classiques est utilisé pour calculer la production de quarks et de photons dans les collisions d'ions lourds. La première partie de la thèse consiste en une vérification indépendante de certains résultats sur la production de quarks. Pour se faire, une méthode itérative est développée afin de solutionner le système d'équations non-linéaires qui donnent les conditions initiales du champ de gluon. Dans la seconde partie, l'expression donnant le taux de production de photons est simplifié en utilisant les symétries et les propriétés du Color Glass Condensate et du modèle de McLerran-Venugopalan. Deux diagrammes de Feynman donnent la contribution à l'ordre dominant mais l'un d'eux est plus important que l'autre. Le diagramme dominant donne un spectre continu superposé d'un pic proéminant.

Comparative features of the Cascade Model and the BUU model are presented and followed by a Quantum Theory Derivation of the Vlasov equation. Several modifications are made to the BUU model: the inclusion of a momentum-dependent potential instead of the usual Skyrme potential, the replacement of the "old" detailed balance cross section for delta reabsorption by the Danielewicz cross section, and a proper generation of the $ Delta$ mass, using a Monte-Carlo simulation. The effects of these ingredients on pion yields at beam kinetic energies in the range (0.4 AGeV-1.8 AGeV), and pion energy spectra at 90$ sp circ$ are analyzed. It is found that our numerical simulations agree quite well with experiments, except for pion energy spectra at low pion kinetic energies.

A high electric field RFQ device was developed and tested to investigate the design requirements needed for such a device to effectively cool and confine ions in gaseous environments. Segmented cylindrical quadrants placed 1mm apart were used to create axially confining fields similar to present trapping systems. High Q air-cored resonating coils were designed to drive the RFQ device at 4.76 MHz and place up to 5.4 kV between adjacent electrodes in vacuum. By removing the transformer cores from the resonating circuit and using a 1 kW RF amplifier it was found that up to 15 kV of RF potential could be achieved across adjacent quadrants at helium pressures of up to 80 Pa. / The main limiting factor associated to the device's function was found to be the power losses in the transformer coupling the resonant circuit to the RF amplifier. These results show that with a proper RF power supply RFQ confinement of ions severaI hundred times stronger than in present devices is indeed possible.

Lambda production in central Au+Au collisions at 11.5 A&middot;GeV/c has been studied at forward rapidities (y > 2.2) using the upgraded E877 experimental setup at the AGS. Lambdas are measured via the charged decay channel: &Lambda; &rarr; ppi- and identified from the ppi - invariant mass spectra with the aids of a set of pair cuts. A comprehensive Monte Carlo simulation is made to extensively study the lambda reconstruction. The details of the data analysis for lambda identification are presented. The consistence of data analysis is examined by detailed comparison of the constructed proton and pion spectra with the previous results from the E877 1993 data set. The double differential multiplicities for lambda as a function of collision centrality are presented. Lambda rapidity distribution dN/dy is also studied. A pure thermal model is used to characterize the lambda spectra. The experimental results are compared to the predictions of the RQMD model (v2.3) in its cascade version and in the mode that takes into account the effect of mean-field. We also present the first measurement of the lambda directed flow at the AGS. In spite of limited statistics, a strong positive directed flow for lambda, which is comparable to the amplitude of the proton flow, is observed at forward rapidities (2.8 < y < 3.4) in the semi-central Au+Au collisions. The measured flow amplitude as a function of pt, v 1(pt), is in agreement with the predictions of the RQMD model.