Abstract
A measurement of four branching-fraction ratios for three-body decays of B mesons involving two open-charm hadrons in the final state is presented. Run 1 and Run 2 pp collision data are used, recorded by the LHCb experiment at centre-of-mass energies 7, 8, and 13 TeV and corresponding to an integrated luminosity of 9 fb−1. The measured branching-fraction ratios areBB+→D∗+D−K+BB+→D¯0D0K+=0.517±0.015±0.013±0.011,BB+→D∗−D+K+BB+→D¯0D0K+=0.577±0.016±0.013±0.013,BB0→D∗−D0K+BB0→D−D0K+=1.754±0.028±0.016±0.035,BB+→D∗+D−K+BB+→D∗−D+K+=0.907±0.033±0.014,\\documentclass[12pt]{minimal}\t\t\t\t\\usepackage{amsmath}\t\t\t\t\\usepackage{wasysym}\t\t\t\t\\usepackage{amsfonts}\t\t\t\t\\usepackage{amssymb}\t\t\t\t\\usepackage{amsbsy}\t\t\t\t\\usepackage{mathrsfs}\t\t\t\t\\usepackage{upgreek}\t\t\t\t\\setlength{\\oddsidemargin}{-69pt}\t\t\t\t\\begin{document}$$ {\\displaystyle \\begin{array}{c}\\frac{\\mathcal{B}\\left({B}^{+}\\to {D}^{\\ast +}{D}^{-}{K}^{+}\\right)}{\\mathcal{B}\\left({B}^{+}\\to {\\overline{D}}^0{D}^0{K}^{+}\\right)}=0.517\\pm 0.015\\pm 0.013\\pm 0.011,\\\\ {}\\frac{\\mathcal{B}\\left({B}^{+}\\to {D}^{\\ast -}{D}^{+}{K}^{+}\\right)}{\\mathcal{B}\\left({B}^{+}\\to {\\overline{D}}^0{D}^0{K}^{+}\\right)}=0.577\\pm 0.016\\pm 0.013\\pm 0.013,\\\\ {}\\begin{array}{c}\\frac{\\mathcal{B}\\left({B}^0\\to {D}^{\\ast -}{D}^0{K}^{+}\\right)}{\\mathcal{B}\\left({B}^0\\to {D}^{-}{D}^0{K}^{+}\\right)}=1.754\\pm 0.028\\pm 0.016\\pm 0.035,\\\\ {}\\frac{\\mathcal{B}\\left({B}^{+}\\to {D}^{\\ast +}{D}^{-}{K}^{+}\\right)}{\\mathcal{B}\\left({B}^{+}\\to {D}^{\\ast -}{D}^{+}{K}^{+}\\right)}=0.907\\pm 0.033\\pm 0.014,\\end{array}\\end{array}} $$\\end{document}where the first of the uncertainties is statistical, the second systematic, and the third is due to the uncertainties on the D-meson branching fractions. These are the most accurate measurements of these ratios to date.
Highlights
U u D0 c s K+ u and topology, providing the best cancellation of systematic uncertainties on the ratio
The minimum distance of a track to a primary pp collision vertex (PV), the impact parameter (IP), is measured with a resolution of (15 + 29/pT) μm, where pT is the component of the momentum transverse to the beam, in GeV/c
After selecting the signal candidates an unbinned extended maximum-likelihood fit is performed to the distribution of reconstructed B-candidate mass, m(D(∗)DK), where the reconstruction is performed with D-candidate masses constrained to their known values [20] and the B-candidate direction of flight to be originating at the PV
Summary
The LHCb detector [8, 9] is a single-arm forward spectrometer covering the pseudorapidity range 2 < η < 5, designed for the study of particles containing b or c quarks. The minimum distance of a track to a primary pp collision vertex (PV), the impact parameter (IP), is measured with a resolution of (15 + 29/pT) μm, where pT is the component of the momentum transverse to the beam, in GeV/c. The online event selection is performed by a trigger, which consists of a hardware stage, based on information from the calorimeter and muon systems, followed by a software stage at which the full event is reconstructed. Simulated samples are produced to model the effect of the detector acceptance and selection requirements, and to guide subsequent fits to the data. To produce these samples, pp collisions are generated using Pythia [12, 13] with a specific LHCb configuration [14]. The interaction of the generated particles with the detector, and its response, are implemented using the Geant toolkit [17, 18] as described in ref. [19]
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