Observation of the charmless two-body decay B → ′K∗ using data collected by the BABAR experiment.
Robertson, Alan Iain
A search for B decays to quasi two-body charmless final states involving a pseudoscalar η′ meson recoiling against a K∗ vector meson is described. This thesis primarily describes the analysis of two of the six possible decay channels, with the other four channels necessarily included as the subdecay modes are combined to give an overall branching fraction measurement. The method of analysis is a multivariate maximum likelihood fit for each subdecay channel. The likelihood curves for both modes are then combined, firstly with two other charged modes to yield an overall charged result, and finally the four charged modes are combined with two neutral modes to give an overall branching fraction and significance for the decay channel B → η′K∗. All results use the full Run 1 to Run 4 datasets, comprising 210.5 fb−1 of data, equivalent to 232 million BB pairs, gathered by the BABAR detector at Stanford Linear Accelerator Center in Menlo Park, California. The measured branching fractions and upper limits at 90% confidence limit (CL) are: B(B+ → η′ηππK∗+ K+π0) < 9.5 × 10−6B(B+ → η′ργK∗+ K+π0) < 22 × 10−6.The four-mode combined fit determined the branching fraction for the decay B+ → η′K∗+: B(B+ → η′K∗+) < 7.9 × 10−6. The six-mode combined fit determined the branching fraction for the decay B → η′K∗: B(B → η′K∗) = (4.1 ± 1.0 ± 0.5) × 10−6 at a significance of 5.6 standard deviations.