[pt] O experimento LHCb (CERN) tem como um de seus objetivos principais o estudo do fenômeno de Violalção da Simetria Carga-Paridade (CP), que seria uma das condições necessárias para assimetria de matéeria-antimatéria observada no Universo. O LHCb foi especialmente desenhado para coletar eventos com produção de mésons B (que contém o quark b), cujos decaimentos são a melhor fonte para o estudo da Violação de CP. A observação de efeitos de Violação de CP no decaimento B+- -> pi +- pi- pi+ depende fundamentalmente dos canais ressonantes intermediários que são produzidos. Ainda que experimentos recentes não tenham observado Violação de CP neste canal, a alta estatística a ser atingida pelo LHCb pode vir a permitir a observação de assimetrias no chamado Dalitz Plot, que fornece informações diretas sobre a dinâmica do decaimento. Nesta dissertação, apresentamos um estudo do decaimento B+- -> pi+- pi- pi+ com dados simulados do experimento LHCb. O objetivo é estabelecer o número de eventos deste canal que podem ser observados com a luminosidade integrada de 2 fb(-1), o que corresponderia a um ano nominal de tomada de dados. Foram feitos estudos com amostras simuladas de sinal e de fundo, de forma a estabelecer um critério de seleção de eventos que oferecesse uma alta eficiência para eventos de sinal, com grande rejeição para eventos de fundo. De acordo a este critério, o rendimento esperado para 2 fb(-1) é de cerca de 87 mil eventos B+- -> pi+- pi- pi+ , com um relação fundo/sinal da ordem de 2. / [en] The LHCb experiment (CERN) has the main objective of studying the phenomenon of Charge-Parity (CP) Violation, which is one of the requisites for observed matter-antimatter asymmetry in the universe. The LHCb has been specially designed to collect events with production of B mesons (containing the b quark), since their decays are the best source for the study of CP violation. The observation of effects of CP violation in the decay B+- -> pi+- pi- pi+ depends on its resonant intermediate states. Although CP violation has been observed in this channel so far, the high statistics to achieve by the LHCb may allow the observation of asymmetries in the so–called Dalitz plot distribution, which provides direct information about the dynamics of decay. In this dissertation we present a study of the decay B+- -> pi+- pi- pi+ with simulated data of the experiment LHCb. The goal is to establish the number of events in this channel that can be reached with the integrated luminosity of 2 fb(-1), corresponding to one nominal year of data taking. Studies were performed using signal and background samples, in order to establish selection criteria to achieve a high efficiency for signal events with high background rejection. We obtain an expected yield for 2 fb(-1) of about 87 thousand events of B+- -> pi+- pi- pi+ , with a background to signal ratio of about 2.

This thesis studies the rare decay η' → π+π-e+e- using Monte Carlo simulations and data from the BES-III detector in Beijing, China. The branching ratio of the reaction was measured at BES-III in 2013 using a data set of 225×106 J/Ψ events. This work lays the groundwork for an updated branching ratio measurement using the full data set of 1.3×109 J/Ψ and determines a potential CP-violating asymmetry in the angle between the decay planes of the π+π-- and e+e--pairs. A total of 2558 signal events are observed after cuts, and the asymmetry parameter is determined to be  Aφ = (1.96 ± 1.97stat.± 0.4syst. ) × 10-2. The result is consistent with zero within the uncertainty.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第23403号 / 理博第4738号 / 新制||理||1679(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 中家 剛, 准教授 田島 治, 准教授 成木 恵 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

We present a first measurement of time-dependent CP-violation in B0 → D∗∓ ρ± , where D∗∓ → D0 π. The analysis was performed using the final Belle dataset containing 772 × 106 B ¯B pairs collected at the KEKB e+ e− collider. Three D0 decay modes are analyzed, K∓ π± , K∓ π± π0 , and K∓ π± π∓ π± . Since the studied decay is a scalar → vector vector decay, three helicity configurations are present. Exploiting the helicity configura- tions via angular analysis, the time-dependent CP-violation parameters encoding 2ϕ1 +ϕ3 are obtained from the fit. 1

This thesis is devoted to studies of the proper decay-time resolution function and particle decay vertex reconstruction tools, their applicability and role in the studies of time-dependent CP violation at the Belle II experiment. A positive effect of beam spot constraints and new beam spot calibration on the vertex reconstruction precision is seen via MC/data comparison. The core part of the work focuses on studying universality of the time resolution function across nine different neutral and charged B-meson decay channels. The possibility to use a single form of this function for all studied channels is demon- strated and supported by the consistency between the lifetime values used for simulation and obtained as results of the decay time difference fit. 1

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18076号 / 理博第3954号 / 新制||理||1570(附属図書館) / 30934 / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)准教授 野村 正, 教授 中家 剛, 教授 鶴 剛 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

This thesis studies CP violation in the decay of the Ξ− hyperon, also known as the cascade baryon, which decays in the sequence Ξ− → Λπ− → pπ−π−. A difference between the angular distribution of this decay sequence and the angular distribution of the charge conjugate decay sequence ͞Ξ+ →͞Λπ+ → ͞pπ+π+, after taking into account the inversion of the momenta due to the parity operation, is indicative of CP violation. The decay sequence is described by three asymmetry parameters: αΞ, αΛ and φΞ, while the charge conjugate decay's sequence is described by: ͞αΞ, ͞αΛ and ͞φΞ. A measure of CP violation is given by the CP violating observables: AΞ, AΛ and ΦΞ. The aim of this thesis is to study how the normalised statistical uncertainties in the asymmetry parameters and in the CP violating observables depend on the magnitude of the polarisation vector (polarisation) of the cascade and the anticascade. This was done by simulating 1.0×107 Ξ− → Λπ− → pπ−π− and  ͞Ξ+ →͞Λπ+ → ͞pπ+π+ decays for different values of polarisation of the cascades using Monte Carlo, and then utilising maximum likelihood estimation and error propagation to estimate the uncertainties in the parameters and in the observables. It was shown using the methods of this thesis that the normalised statistical uncertainties in the asymmetry parameters and the CP violating observables decreased whenever the polarisation was increased, although with diminishing returns. In the region of 10% − 50% polarisation, the decrease in the uncertainties was substantial. An increase from 10% to 50% polarisation lowered all of the uncertainties by 76% − 80%. In the region of 50% − 100% polarisation, the decrease in the uncertainties was slightly less. An increase from 50% to 100% polarisation lowered the uncertainties in αΞ,  ͞αΞ and AΞ by roughly 33%, in αΛ,  ͞αΛ and AΛ by roughly 40%, and in φΞ,  ͞φΞ and ΦΞ it went down by 53%. It was also shown that, if one were to produce 60% polarised cascades and use the method of this thesis, it would require a sample of 1.1×1011 − 1.3×1011 Ξ− → Λπ− → pπ−π− and  ͞Ξ+ →͞Λπ+ → ͞pπ+π+ decays to reach the precision in the observables of the order given by the Standard Model. However, if one wished to match the uncertainty given by the most recent and best measurement of the observables, using 60% polarised cascades, one would only need a sample of 5.7×104 − 8.6×104 for each decay sequence.

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京都大学 / 新制・課程博士 / 博士(理学) / 甲第24962号 / 理博第4987号 / 新制||理||1712(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 中家 剛, 教授 永江 知文, 教授 田島 治 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM