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Title: An amplitude analysis of the four body decay D^0 to K^+K^-pi^+pi^- and a study on the pi^+pi^- S wave for the decay D^0 to KS0pi^+pi^-
Author: Martin, Lauren
ISNI:       0000 0004 2744 0305
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2011
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The angle γ, with an uncertainty of approximately 10° is the least well constrained angle of the unitary triangle. Better experimental constraints on this parameter are required in order to provide a consistency check on the standard model description of CP violation. A promising strategy for measuring γ involves exploiting interference effects present in B± → DK± decays where the D subsequently decays to a three or four body final state. The three body decay D → KS 0p+p- and the four body decay D0 → K+K-p+p- are suitable candidates for making such a measurement. However independent knowledge of the decay structure of these decays is required. The impact of the model, used to describe the p+p- S wave, in the D0 → K+K-p+p- decay, on the uncertainty in the measurement of γ is estimated via a simulation study. It is determined that the uncertainty on a gamma measurement would be compromised by this model uncertainty within one year of LHCb data running. The four body decay D0 → K+K-p+p- also provides a candidate for making a γ measurement. This decay is expected to display a rich resonant structure. An understanding of this decay may also provide an insight into low energy QCD in addition to allowing a search for CP violation. Only one previous amplitude analysis has been performed on this decay. Using data collected at the CLEO-II.V, CLEO-III and CLEO-c experiments an amplitude model is developed for the D0 → K+K-p+p- decay. This model is qualitatively similar to that produced in the previous analysis although the model presented in this thesis considers higher orbital angular momentum states and distinguishes between conjugate states that the previous model did not. A search for CP violation is also carried out using the D0 → K+K-p+p- decay data. A positive confirmation of CP violation at the level of sensitivity provided by this decay data would provide evidence for a level of CP violation which could not be accounted for within the standard model. No significant evidence for CP violation is observed in this decay. A toy MC study was carried out in order to determine the sensitivity to γ which may be achieved using this decay. In this study, sets of 1000 B+ and B- events are generated and the decay model developed for the D → K+K-p+p- decay is used to describe the D decay. The sensitivity to γ determined in this study is 11°.
Supervisor: Charles, Matthew Sponsor: Science and Technology Facilities Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Particle physics ; Dalitz ; amplitude analysis ; CP violation ; four-body decays ; flavour physics