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This thesis presents several studies of data collected at the LHCb detector during its first two years of operation. A detector upgrade study is first presented, using simulated events at an increased luminosity. A second study involves radiation damage to the silicon sensors of the LHCb Vertex Locator. During 2010 and 2011the silicon sensors were exposed to a range of fluences, with sensors in the mostactive regions exposed to fluences of up to approximately 45x10^12 1MeV neutron equivalent (1MeV neq). The first observation of n+-on-n sensor type inversion at the Large Hadron Collider is reported, occurring at a fluence of around (10-15)x10^12 of 1MeV neq. The effective depletion voltages of the only n+-on-p sensors in use at the Large Hadron Collider have also been studied, with decreases of around 25V observed after initial irradiation. Following this, the effective depletion voltage inn+-on-p type sensors is observed to increase at a comparable rate to type inverted n+-on-n type sensors. A reduction in the charge collection efficiency due to an unexpected effect involving the sensor readout lines is also observed. A third study relates to CP violation in neutral B-meson mixing, by the measurement of the flavour-specific asymmetry. In the Standard Model, CP violation from this source is expected to be of order 10^-4. Any measured enhancement of this would be a strong indication of new physics. The DØ collaboration has measured the flavour specific asymmetry from B0 and B0s mixing, and found it to be inconsistent with the Standard Model at a confidence level of 3.9 standard deviations, thus motivating an independent measurement from the LHCb experiment. Using the full 2011 LHCb dataset, corresponding to 1.0 fb^-1 of recorded luminosity, the B0s-meson component of the flavour-specific asymmetry is measured to be afs_s = (-0.12 +/- 0.48 +/- 0.34)%, where the first uncertainty is statistical and the second is systematic. This is the single most accurate measurement of afs_s, and is consistent with both the DØ measurement and the Standard Model prediction.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20913号 / 理博第4365号 / 新制||理||1626(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 永江 知文, 教授 鶴 剛, 教授 中家 剛 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

<p> A repulsive meson-meson interaction was suggested many years ago (1951 by Schiff) as a possible mechanism for nuclear saturation, but very little has been done since then. This is mainly because the meson field equation becomes nonlinear due to the meson-meson interaction. We realized that the nonlinear field equation is analytically solvable, within classical and adiabatic approximations, if the space is reduced to a one-dimensional one. Within the above context we investigate the effect of the meson-meson interaction on nuclear forces. The approximations which Schiff used are critically examined. A variational method for determining the meson field, which Schiff suggested but did not fully investigate, is found to be a very efficient approximation. Finally, quantum corrections are briefly examined.</p> / Thesis / Master of Science (MSc)

The decays, <img width=119 height=32 align=center src=https://vtechworks.lib.vt.edu/bitstream/handle/10919/28846/image006.gif> and <img width=119 height=29 align=center src=https://vtechworks.lib.vt.edu/bitstream/handle/10919/28846/image008.gif> are studied using data collected at the CLEO II detector at the Cornell Electron Storage Ring. Both decays are identified using a partial reconstruction method where the <I>D<SUP>*</SUP></I> is detected only through a pion daughter from the decay <img width=64 height=25 align=center src=https://vtechworks.lib.vt.edu/bitstream/handle/10919/28846/image010.gif>. Because of the similarities in the analyses of the two modes, the ratio of the rates is measured in a way that is independent of the decay model, limited mainly by the uncertainty in the relative efficiency for detecting neutral and charged pions. This ratio is equivalent to the ratio of the product of production fraction and lifetime for charged and neutral B mesons, <img width=31 height=29 align=center src=https://vtechworks.lib.vt.edu/bitstream/handle/10919/28846/image012.gif>. It is combined with measurements of the lifetime ratio to obtain the ratio of charged and neutral B meson production at the Y(4S) resonance, <img width=175 height=29 align=center src=https://vtechworks.lib.vt.edu/bitstream/handle/10919/28846/image014.gif>. / Ph. D.

Aiming at a systematic inclusion of pseudoscalar and vector mesons as active degrees of freedom in an effective Lagrangian, studies have been performed in this thesis concerning the foundations of such an effective Lagrangian as well as tree-level and beyond-tree-level calculations. Hereby, vector mesons are described by antisymmetric tensor fields. First, an existing power counting scheme for both pseudoscalar and vector mesons is extended to include the pseudoscalar-meson singlet in a systematic way. Based on this, tree-level calculations are carried out which are in good agreement with the available experimental data and several processes are predicted. In particular, the ω-π0 transition form factor is in better agreement with experimental data than the prediction done in the vector-meson-dominance model. Furthermore, a Lagrangian with vector mesons is used together with the leading contributions of chiral perturbation theory in order to calculate tree-level reactions in the sector of odd intrinsic parity. It turns out that both the Lagrangian with vector mesons and the Lagrangian of chiral perturbation theory are needed to describe experimental data. Additionally, a feasibility check for one-loop calculations with pseudoscalar and vector mesons in the loop is performed. Thereby, only a limited number of interaction terms in the Lagrangian with vector mesons is used. The results are used to both renormalise the low-energy constants of chiral perturbation theory up to chiral order Q4 and to determine the influence of loops with vector mesons on masses and decay constants of pseudoscalar mesons.

The recently discovered DsJ(2317) and DsJ(2460) mesons had stimulated many theoretical and experimental studies due to their unexpected properties. In this thesis, we make a review of the predictions on the properties of these mesons using the quark model and QCD Sum Rules. We studied different models about the structure of these mesons, which are suggested because of their unexpected properties. Moreover, using the quark model which implies that the structure of DsJ meson as cs and QCD Sum Rules method, we investigated the semileptonic decay DsJ(2317)--&gt / D0 l nu.

Techn. University, Diss., 2007--Darmstadt.

The mechanism of the isospin violating η→π+π−π0 decay is studied in a high precision experiment using a Dalitz plot analysis. The process is sensitive to the difference between up and down quark masses. The measurement provides an important input for the determination of the light quark masses and for the theoretical description of the low energy strong interactions. The measurement was carried out between 2004 and 2005 using the KLOE detector at the DAΦNE e+e− collider located in Frascati, Italy. The data was collected at a center of mass energy corresponding to the φ-meson peak (1019.5 MeV) with an integrated luminosity of 1.6 fb−1. The source of the η-mesons is the radiative decay of the φ-meson: e+e−→φ→ηγ, resulting in the world’s largest data sample of about 4.7·106 η→π+π−π0 decay events. In this thesis, the KLOE Monte Carlo simulation and reconstruction programs are used to optimize the background rejection cuts and to evaluate the signal efficiency. The background contamination in the final data sample is below 1%. The data sample is used to construct the Dalitz plot distribution in the normalized dimensionless variables X and Y. The distribution is parametrized by determining the coefficients of the third order polynomial in the X and Y variables (so called Dalitz plot parameters). The statistical accuracy of the extracted parameters is two times better than any of the previous measurements. In particular the contribution of the X2Y term is found to be different from zero with a significance of approximately 3σ. The systematic effects are studied and found to be of the same size as the statistical uncertainty. The contribution of the terms related to charge conjugation violation (odd powers of the X variable) and the measured charge asymmetries are consistent with zero. The background subtracted and acceptance corrected bin contents of the Dalitz plot distribution are provided to facilitate direct comparison with other experiments and with theoretical calculations.

Made available in DSpace on 2014-06-11T19:25:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2002-03Bitstream added on 2014-06-13T19:26:30Z : No. of bitstreams: 1 morales_ps_me_ift.pdf: 900348 bytes, checksum: 11b8ab9b4c422ec3a42face91d5074e6 (MD5) / O mecanismo de rearranjo de tubos de fluxo predito no limite de acoplamento forte da formulação Hamiltoniana da QCD na rede foi implementado num modelo de quarks constituintes e suas consequências investigadas para o espalhamento méson-méson. O rearranjo de tubos de fluxo leva a efeitos similares aos tradicionais efeitos de troca de quarks com troca de um glúon em interações hádron-hádron. Contudo, enquanto o primeiro está relacionado ao regime de confinamento da QCD, o último está relacionado ao regime de liberdade assintótica desta teoria. Mostra-se aqui que ambos mecanismos levam a resultados qualitativamente similares quando o potencial de rearranjo pode ser escrito como a soma de interações locais quark-quark, antiquark-antiquark e quark-antiquark. Para interações gerais, não locais e de longo alcance, o rearranjo de tubos de fluxo leva a resultados qualitativa e quantitativamente diferentes dos resultados de troca de quarks com troca de um glúon. As consequências disso para a fenomenologia das interações hádron-hádron são discutidas. / The mechanism of link rearrangement predicted in the strong coupling limit of Hamiltonian lattice QCD is implemented in a constituent quark model and its consequences for meson-meson scattering are investigated. Link rearrangement leads to effects similar to the traditional quark exchange with one gluon exchange in hadron-hadron interactions. However while the first is related to the confinement regime of QCD, the latter is related to the asymptotic freedom regime of this theory. It is shown here that both mechanisms lead to identical qualitative results when the rearrangement potential can be written as a sum of local quark-quark, antiqurk-antiquark e quark-antiquark. For general, long-range nonlocal interactions, link rearrangement leads to results qualitative and quantitatively different from those of quark exchange with one gluon exchange. The consequences of this for the phenomenology of hadron-hadron interactions are discussed.