Muon decay is a unique process involving only the four leptons of the first two generations. This makes it an ideal framework to study the weak interaction. The momentum-angle spectrum of the decay positron can be studied using a general 4-fermion interaction model. Only four parameters are needed in this model to entirely describe the spectrum. The measurement of these four muon decay parameters, rho, eta, delta and Pmu xi, provide a direct test of the Standard Model and its extensions. This thesis presents the final results from the blind analysis of the decay parameter delta using the TWIST (TRIUMF Weak Interaction Symmetry Test) spectrometer. The new precision on the parameter delta is a factor of 11.5 better than the last experimental result prior to TWIST achieving the goal of the TWIST collaboration of an order of magnitude improvement. The challenging parameter eta is also measured from the momentum-angle spectrum for the first time since 1969 with a precision improved by a factor of 7.4. The results are included in a global analysis to obtain stringent limits on some of the coupling constants of the 4-fermion interaction. The result of the measurement of delta are used to evaluate the possibility for a non-local tensor interaction.

Thesis (Ph.D.)--Michigan State University. Dept. of Physics, 2008. / Title from PDF t.p. (viewed on Mar. 27, 2009) Includes bibliographical references (p. 216-218). Also issued in print.

The search for lepton flavour violation is significant to our understanding of the standard model of particle physics. This measurement uses the muon decay data collected by the TWIST experiment at TRIUMF to search for lepton flavour violation between charged lepton species. Specifically, I searched for the decay µ+→e+X0, where X° is an unknown, undetected, neutral boson, against a background of stan¬dard muon decays, µ+→e+vevµ I set branching ratios for these decays such that B(µ+→e+X0)< 2 x 10-5 - 5 x 10-5, for X0 of various masses accessable by the momenta of the muon decay spectrum, to a confidence level of 95%. This improves upon the previous best limits by a. factor of three. A correction to the spectrum was required to set a limit on a massless X0 of B(µ+→e+X0)< 6.3 x 10-5.

The ATLAS experiment pushes the leading edge of experimental particle physics. Increasingly complex hardware, however, brings increasingly complex problems which manifest themselves not only in the detector, but also within the software which drives the detector. The magnitude of the expected interaction rate, too, adds enormous stress to the detector system and the software trigger. In order to prepare the software for these challenges, various detector quantities are considered which may provide debugging handles and robustness against detector problems arising in the ATLAS calorimeter trigger. The effect of electronics noise suppression on these quantities is studied and a brief study of the software trigger performance is followed by recommendations for the implementation of robustness checks.

The study of the muon decay process μ+ → e+νeν ̄μ is a powerful constraint on the behaviour of the weak interaction, without contamination of the other, stronger, fundamental interactions. The spectrum measured from the momentum and angles of the decay positrons is parametrized using a set of four decay parameters. The purpose of the TWIST experiment is to measure these decay parameters to an unprecedented precision; an order of magnitude improvement in the uncertainties over measurements completed before the TWIST experiment. Measurements of the muon decay parameters constrain the values of a series of 19 weak coupling constants. In the standard model, V-A weak interaction, 18 of these constants are 0, while the remaining constant describes interactions between left handed particles, gV_LL= 1.The decay parameter ρ quantifies the behaviour of the spectrum with respect to momentum. According to the standard model the value of this parameter is 3/4. TWIST measured a value of ρ = 0.74991±0.00009(stat)±0.00028(sys). The measurement is limited by its systematic uncertainty, so a large focus of the experiment was on the determination and control of these uncertainties. The systematic uncertainties are derived from uncertainties in the detector construction and uncertainties in the biases generated by differences between the data and a matching Monte Carlo. Muon decay also limits the possibility of family symmetry breaking interactions. TWIST can be used to search for the possibility of muons decaying into a positron and a single unidentified neutral particle μ+ → e+X0 that does not otherwise interact with normal matter. The large momentum and angle acceptance of the TWIST spectrometer allows for searches of two body decays for masses of the X0 boson mX0 ∈ [0,80] MeV/c, with a variety of behaviours with respect to the angle of the positron track. Upper limits on massive and mass-less X0 decays are set with a 90% confidence level separately at parts per million for massive decays and parts in 10000 for mass-less decays.

An intra-pulse Interaction Point fast feedback system (IPFB) has been designed for the Next Linear Collider (NLC), to correct relative beam-beam misalignments at the Interaction Point (IP). This system will utilise the large beam-beam kick that results from the beam-beam interaction and apply a rapid correction to the beam misalignment at the IP within a single bunch train. A detailed examination of the IPFB system is given, including a discussion of the necessary electronics, and the results of extensive simulations based on the IPFB concept for fast beam correction are presented. A recovery of the nominal luminosity of the NLC is predicted well within the NLC bunch train of 266 ns. The FONT experiment - Feedback On Nanosecond Timescales - was proposed as a direct test of the IPFB concept and was realised at the NLC Test Accelerator at SLAC. As part of FONT, a novel X-band BPM was designed and tested at the NLCTA. The results of these tests with the NLCTA short and long-pulse beam are presented, demonstrating a linear response to the position of the 180 ns long-pulse beam: measurements show a time constant of ~1.5 ns and a precision of better than 20 microns. A novel BPM processor for use at X-band, making use of the difference-over-sum processing technique, is also presented in detail, with results given for both short and long-pulse beams. The FONT design concepts and modification of the IPFB system for use at the NLCTA are described. The design of a fast charge normalisation circuit, to process the difference and sum signals produced by the BPM processor, forming part of the FONT feedback circuit, is detailed extensively. Bench tests of the feedback electronics demonstrate the effectiveness of the normalisation and feedback stages, for which a signal latency of 11 ns was measured. These bench tests also show the correct operation of the normalisation and feedback principles. Finally, the results of a full beam test of the FONT system are presented, during which a system latency of 70 ns was measured. These rigorous tests establish the soundness of the IPFB scheme and show correction of a mis-steered bunch train within the full NLCTA pulse length of 180 ns.

Un des objectifs principaux de l'expérience PHENIX est l'étude de la matière nucléaire soumise à des conditions extrêmes de température et de densité d'énergie. Dans les collisions ultra-relativistes Au+Au à 200~GeV par paires de nucléon, il serait possible de former un état de la matière pour lequel les quarks et les gluons ne seraient plus liés au sein des nucléons mais pourraient évoluer de façon quasi-libre sur des distances plus grandes que la taille caractéristique de ces derniers. Cet état est dénommé le Plasma de Quarks et de Gluons (QGP).<br /><br />L'étude de la production du $\jpsi$, particule lourde formée d'une paire de quarks charme ($c \bar c$), est une des sondes initialement proposée pour étudier le QGP. Une suppression de la production du $\jpsi$ était en effet attendue en présence d'un QGP, en raison de l'écrantage du potentiel de liaison entre les quarks charme le constituant par la présence du milieu dense coloré environnant. De nombreuses mesures du $\jpsi$ ont eu lieu depuis au SPS (CERN) et à RHIC (BNL). Elles ont permis de mettre en évidence non seulement l'existence d'une telle suppression, mais également la présence de mécanismes supplémentaires, rendant plus difficile l'interprétation des résultats correspondants.<br /><br />L'expérience PHENIX est la seule des quatre expériences de RHIC capable de mesurer le $\jpsi$ à rapidité positive via sa désintégration en deux muons. En 2007 des collisions Au+Au à une énergie par paire de nucléons dans le centre de masse $\sqrt{s_{NN}}=200$~GeV ont été réalisées à BNL, ce qui a permis d'augmenter d'un facteur quatre la statistique disponible pour l'étude du $\jpsi$ par rapport aux résultats publiés précédemment. Cette augmentation, ajoutée à la mise en oeuvre de nouveaux détecteurs dans PHENIX, a permis de préciser les mesures précédentes, et de mesurer des observables jusqu'alors inaccessibles telles que l'asymétrie azimutale de la production du $\jpsi$.<br /><br />Ce manuscrit présente la compréhension actuelle de la production de quarkonia et l'utilisation de cette sonde dans l'étude du QGP. L'analyse conduisant à la première mesure de l'anisotropie azimutale du $\jpsi$ à rapidité positive dans les collisions Au+Au à 200~GeV par paire de nucléons est détaillée. Cette mesure devrait permettre de préciser le mécanisme de production du méson, en particulier en ce qui concerne la part de recombinaison des quarks $c$ en $\jpsi$.

There are hints coming from some scenarios of modern String and Quantum Gravity theories that Lorentz invariance may not be an exact symmetry of Nature. The study of Lorentz violating theories therefore provides an insight into ultraviolet physics. We employ the Effective Field Theory technique to study the most general extension of the Standard Model and its Supersymmetric modifications with Lorentz-violating interactions of mass dimension five. We provide a complete classification of the interactions in these theories and determine a typical experimental sensitivity to the size of Lorentz violation. A detailed study of the operators that induce CPT-odd Electric Dipole Moments is performed and it is shown that they yield an independent constraint on Lorentz violating physics. We provide an application of Lorentz violating physics to the problem of generation of baryon asymmetry of the universe. A scenario of Leptogenesis driven by CPT-odd interactions is considered and confronted with experimental constraints on Lorentz-violating physics.

We study the impact of long lived strongly interacting particles on primordial nuclear abundances. Particularly we look at the case of anti-squark quark bound states called mesinos. These mesinos are similar to massive nucleons in that they have the same spin and isospin. Like nucleons, the mesinos take part in nucleosynthesis and are bound into nuclei. We incorporate the mesinos into the various stages of BBN, from the QCD phase transition, to their capture of nucleons, to their eventual decay. We identify the mechanisms by which the mesinos could impact primordial abundances and show which actually do so. We nd that for the predicted mesino abundance, only one mechanism exists that has the potential of generating an observable signature.

Thesis (Ph.D.); Submitted to Univ. of California, Berkeley, CA (US); 1 Jun 2003. / Published through the Information Bridge: DOE Scientific and Technical Information. "LBNL--54350" Scielzo, Nicholas David. USDOE Director. Office of Science. Nuclear Physics (US) 06/01/2003. Report is also available in paper and microfiche from NTIS.