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The scalar component of B0 → K+ π- μ+ μ- decays

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Title: The scalar component of B0 → K+ π- μ+ μ- decays
Authors: Cunliffe, Samuel Thomas
Item Type: Thesis or dissertation
Abstract: The differential branching fraction of B0 → K*(892)0 μ+ μ- decays is measured as a function of the squared invariant mass of the dimuon system. The data corresponds to 3/fb of integrated luminosity collected in 2011 and 2012 by the LHCb detector at the Large Hadron Collider at CERN. Integrated across squared dimuon invariant mass, and interpolated through excluded regions, the total branching fraction is found to be B[B0 → K*(892)0 μ+ μ-] = (1.058 +0.017-0.016 ± 0.013 ± 0.070) × 10**-6 In the theoretically favoured region of squared dimuon invariant mass, (1.1 < q² < 6) GeV²/c**4 , the differential branching fraction is found to be dB[B0 → K*(892)0 μ+ μ-]/dq² = (0.402 +0.020-0.019 ± 0.008 ± 0.027) × 10**-7 In the two results above, the first uncertainty is statistical, the second systematic, and the third due to the uncertainty of the branching fraction of the normalisation channel. The differential branching fraction is in agreement with, although lower than, the Standard Model prediction of (0.49 ± 0.08) × 10**-7. As with the measurement of several decay modes including a quark-level b → sl+l- transition, the Standard Model predictions are consistently higher than the measured values. In this analysis, for the first time, the fraction of S-wave in the Kπ system is measured and explicitly accounted for. Previous analyses had measured the branching fraction of both P- and S-wave components and compared to predictions for pure P-wave. In the same theoretically favoured region of (1.1 < q² < 6) GeV²/c**4 , and for the Kπ invariant mass range (796 < m[Kπ] < 996) MeV/c², the fraction of S-wave is found to be F_S = 0.097 ± 0.016 ± 0.008, where the first uncertainty is statistical, and the second is systematic. This value is somewhat larger than expected, although no concrete theoretical predictions exist.
Content Version: Open Access
Issue Date: Aug-2015
Date Awarded: Mar-2016
URI: http://hdl.handle.net/10044/1/39779
DOI: https://doi.org/10.25560/39779
Supervisor: Patel, Mitesh
Egede, Ulrik
Sponsor/Funder: Science and Technology Facilities Council (Great Britain)
Funder's Grant Number: ST/J500616/1
Department: Physics
Publisher: Imperial College London
Qualification Level: Doctoral
Qualification Name: Doctor of Philosophy (PhD)
Appears in Collections:Physics PhD theses



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