B-flavor tagging at Belle II

Abstract

We report on new flavor tagging algorithms developed to determine the quark-flavor content of bottom () mesons at Belle II. The algorithms provide essential inputs for measurements of quark-flavor mixing and charge-parity violation. We validate and evaluate the performance of the algorithms using hadronic decays with flavor-specific final states reconstructed in a data set corresponding to an integrated luminosity of 62.8 fb^{-1}, collected at the resonance with the Belle II detector at the SuperKEKB collider. We measure the total effective tagging efficiency to be εeff=(30.0±1.2(stat)±0.4(syst))%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\begin{aligned} \\varepsilon _\\mathrm{eff} = \\big (30.0 \\pm 1.2(\ ext {stat}) \\pm 0.4(\ ext {syst})\\big )\\% \\end{aligned}$$\\end{document}for a category-based algorithm and εeff=(28.8±1.2(stat)±0.4(syst))%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\begin{aligned} \\varepsilon _\\mathrm{eff} = \\big (28.8 \\pm 1.2(\ ext {stat}) \\pm 0.4(\ ext {syst})\\big )\\% \\end{aligned}$$\\end{document}for a deep-learning-based algorithm.