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This thesis presents measurements of charged current deep inelastic scattering cross sections in e+p collisions with longitudinally polarised positron beams. The measurements are based on data taken by the ZEUS detector at the HERA collider during the 2006-2007 run- ning period. The data sample has an integrated luminosity of 132 pb-1 and was taken at a centre-of-mass energy of 318 GeY. The total cross section has been measured at positive and negative values of the longitu- dinal polarisation of the positron beam (Pe). In addition, the single differential cross sections dδ / dQ2, dδ / dx and dδ / dy have been measured for Q2 > 200 Ge y2, also using both positively and negatively polarised positron beams. The reduced cross section has been measured in nine bins of Q2 in the kinematic range 280 < Q2 < 30000 Gey2 and 0.0078 < x < 0.42. The results are compared against the descriptions provided by the CTEQ6.6, MSTW 2008, HEARPDF1.0 and ZEUS-JETS PDFs. In general, the measured cross sections are well described by these predictions. Based on the measurement of the total cross section as a function of the polarisation of the positron beam, a lower limit on the mass of a hypothetical right-handed W boson has been extracted from the upper limit of the cross-section at Pe = -1. This limit is complementary to the limits obtained from direct searches (for example at CDF and D0) because the limit presented herein is for a space-like vV, whereas for direct searches, the limit on the mass of a time-like W boson is obtained. The results of this analysis have been published and have been included ill the determination of the HERAPDF theoretical prediction and also in HI and ZEUS combined results.

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Ph.D. (Physics) / Please refer to full text to view abstract

Calculamos o alargamento de linhas de inversão da amônia (NH3) provocado por colisões com gases nobres (He, A), utilizando um novo tratamento teórico sugerido por M. Cattani (1). Os nossos resultados teóricos são comparados com os experimentais (2, 3, 4), com os teóricos obtidos segundo o formalismo de Anderson-Tsao e Curnutte (5,6), usualmente utilizado no cálculo de largura de linha, e com outras aproximações encontradas na literatura. / We calculate the pressure broadening for the Ammonia (NH3) microwave inversion spectrum by inert gases (He, A), using a new theoretical formulation suggested by M. Cattani (1). Our theoretical results are compared with experimental results (2, 3, 4) and with theoretical results obtained by the usual Anderson-Tsao Curnutte (5, 6) theory and by other approximations found in the literature.

ATLAS measurements of the production of muons from heavy flavor decays in √sNN = 2.76 TeV Pb+Pb collisions and √s = 2.76 TeV pp collisions at the LHC are presented. Integrated luminosities of 0.14 nb−1 and 570 nb−1 are used for the Pb+Pb and pp measurements, respectively. The measurements are performed over the transverse momentum range 4 < pT < 14 GeV and for five Pb+Pb centrality intervals. Backgrounds arising from in-flight pion and kaon decays, hadronic showers, and mis-reconstructed muons are statistically re- moved using a template fitting procedure. The heavy flavor muon differential cross-sections and per-event yields are measured in pp and Pb+Pb collisions, respectively. The nuclear modification factor, RAA, obtained from these is observed to be independent of pT, within uncertainties, and to be less than unity, which indicates suppressed production of heavy flavor muons in Pb+Pb collisions. For the 0–10% most central Pb+Pb events, the measured RAA is ∼ 0.35. The azimuthal modulation of the heavy flavor muon yields is also measured and the associated Fourier coefficients vn for n=2, 3 and 4 are given as a function of pT and centrality. They vary slowly with pT and show a systematic variation with centrality that is characteristic of other anisotropy measurements. The measured RAA and vn values are also compared with theoretical calculations. We also present the ATLAS di-muon azimuthal correlation from heavy flavor decay in √√sNN = 5.02 TeV Pb+Pb collisions and s = 5.02 TeV pp collisions. Heavy flavor muons with 4 < pT < 8 GeV are selected. The azimuthal correlations are measured for both same sign muon pairs and opposite sign muon pairs. Comparing with the azimuthal correlations in pp data, Pb+Pb results are observed to have more broadening. Central collisions are also more broadened than peripheral collisions. The integrated luminosities used in the dimuon measurement are 26 pb−1 for the pp data and 0.49 nb−1 for the Pb+Pb data. In ultra-relativistic heavy-ion collisions, dilepton pairs may be produced through the interaction of the large electromagnetic fields of the nuclei. A measurement of γγ → μ+μ− in inclusive Pb+Pb collisions at √sNN = 5.02 TeV using 0.49 nb−1 is presented in this thesis. The contribution from background sources of dimuons is removed using a template fit method. The angular and transverse momentum correlations between the muons are measured as a function of collision centrality. In peripheral collisions, the muons exhibit a strong back-to-back correlation consistent with previous measurements of dimuon production in ultra-peripheral collisions. The correlations are observed to broaden significantly in central collisions. The modifications are qualitatively consistent with attenuation of the muons while passing through the hot matter produced in the collision.

The spacetime dimensions of the particle source in proton-lead collisions at √sNN = 5.02 TeV are measured with the ATLAS detector at the Large Hadron Collider. Femtoscopic measurements are made from correlation functions built with charged pions identified by their ionization energy loss. The measured HBT radii that represent the source dimensions are presented differentially as a function of centrality, transverse momentum, and rapidity. The effect of jet fragmentation on the two-particle correlation function is studied, and a method using opposite-charge pair data to constrain its contributions to the measured correlations is described. The measured source sizes are substantially larger in more central collisions and are observed to decrease with increasing pair transverse momentum. A correlation of the radii with the local charged-particle density dN/dy is demonstrated. The scaling of the extracted radii with the mean number of participating nucleons is also used to compare a parameterization of an initial-geometry model that allows for fluctuations in the proton cross-section. The cross-term R_ol is measured as a function of rapidity, and a nonzero value is observed that agrees with hydrodynamic predictions. The HBT radii are also shown for central events in intervals of azimuthal angle relative to the 2nd-order event plane, pair transverse momentum, and flow vector magnitude, where the correlation functions are corrected for the event plane resolution. Significant modulations of the transverse HBT radii R_out, R_side, and R_os are observed. The orientation of this modulation is the same as that in heavy-ion collisions, in which they are attributed to hydrodynamic evolution from an elliptic initial geometry. The sign and transverse momentum dependence of these modulations are consistent with a hydrodynamic evolution of a short-lived medium.

Yiu Yun Yip. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references (leaves 86-87). / Yiu Yun Yip. / Contents --- p.i / List of Figures --- p.iii / List of Tables --- p.vi / Abstract --- p.vii / Acknowledgements --- p.viii / Chapter Chapter 1. --- Introduction --- p.1 / Chapter Chapter 2. --- The Fragmentation Model --- p.4 / Chapter 2.1 --- Interaction Potential --- p.5 / Chapter 2.2 --- Initial Configuration --- p.6 / Chapter 2.2.1 --- Enforcement of momentum conservation at time zero --- p.8 / Chapter 2.3 --- Time Evolution --- p.9 / Chapter 2.4 --- Summary --- p.10 / Chapter Chapter 3. --- Results for object with an initial circular shape --- p.11 / Chapter 3.1 --- Measurement of F(m) --- p.11 / Chapter 3.2 --- Results and Analysis --- p.14 / Chapter 3.3 --- Discussion --- p.24 / Chapter Chapter 4. --- Results for object with an initial square shape --- p.35 / Chapter 4.1 --- Results and Analysis --- p.35 / Chapter 4.2 --- Discussion --- p.43 / Chapter Chapter 5. --- Comparsion with experimental observations --- p.49 / Chapter 5.1 --- The Experiment --- p.49 / Chapter 5.2 --- Comparison --- p.50 / Chapter 5.2.1 --- Relation between the power-law exponent and the falling height --- p.50 / Chapter 5.2.2 --- Relation between the falling height and the total number of fragments --- p.50 / Chapter 5.2.3 --- Relation between the power-law exponent and the total num- ber of fragments --- p.53 / Chapter 5.3 --- Summary --- p.53 / Chapter Chapter 6. --- Maximum entropy formalism for fragment distributions --- p.55 / Chapter 6.1 --- The formalism --- p.55 / Chapter 6.2 --- Average potential and kinetic energies for fragments with mass m --- p.57 / Chapter 6.3 --- Comparison with simulation results --- p.67 / Chapter 6.3.1 --- Analysis for small R --- p.67 / Chapter 6.3.2 --- Analysis for large R --- p.69 / Chapter 6.4 --- Conclusion --- p.69 / Chapter Chapter 7. --- Conclusion --- p.75 / Appendix A. Main program --- p.76 / Appendix B. Derivation of P*(nm，m) and n*(m) --- p.84 / Bibliography --- p.86

Thesis. 1976. Ph.D.--Massachusetts Institute of Technology. Dept of Physics. / Microfiche copy available in Archives and Science. / Vita. / Includes bibliographies. / Ph.D.

Calculamos o alargamento de linhas de inversão da amônia (NH3) provocado por colisões com gases nobres (He, A), utilizando um novo tratamento teórico sugerido por M. Cattani (1). Os nossos resultados teóricos são comparados com os experimentais (2, 3, 4), com os teóricos obtidos segundo o formalismo de Anderson-Tsao e Curnutte (5,6), usualmente utilizado no cálculo de largura de linha, e com outras aproximações encontradas na literatura. / We calculate the pressure broadening for the Ammonia (NH3) microwave inversion spectrum by inert gases (He, A), using a new theoretical formulation suggested by M. Cattani (1). Our theoretical results are compared with experimental results (2, 3, 4) and with theoretical results obtained by the usual Anderson-Tsao Curnutte (5, 6) theory and by other approximations found in the literature.