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Differential branching fractions and isospin asymmetries of $B \to K^{(*)}\mu^+\mu^+$ decays

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Abstract

The isospin asymmetries of $B \to K\mu^+\mu^-$ and $B \to K^{*}\mu^+\mu^-$ decays and the partial branching fractions of the $B^0 \to K^0\mu^+\mu^-$, $B^+ \to K^+\mu^+\mu^-$ and $B^+ \to K^{*+}\mu^+\mu^-$ decays are measured as functions of the dimuon mass squared, $q^2$. The data used correspond to an integrated luminosity of 3$ $fb$^{-1}$ from proton-proton collisions collected with the LHCb detector at centre-of-mass energies of 7$\,$TeV and 8$\,$TeV in 2011 and 2012, respectively. The isospin asymmetries are both consistent with the Standard Model expectations. The three measured branching fractions, while individually consistent, all favour lower values than their respective Standard Model predictions.

Figures and captions

Reconstructed $ B $ candidate mass for the four signal modes. The data are overlaid with the result of the fit described in the text. The long and downstream $ K ^0_{\rm\scriptscriptstyle S}$ categories are combined. The results of the fits, performed in separate $ q^{2}$ bins, are merged for presentation purposes. The blue (shaded) region is the combinatorial background.

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Differential branching fraction results for the $ B ^+ \!\rightarrow K ^+ \mu ^+ \mu ^- $ , $ B ^0 \!\rightarrow K ^0 \mu ^+ \mu ^- $ and $ B ^+ \!\rightarrow K^{*+} \mu ^+ \mu ^- $ decays. The uncertainties shown on the data points are the quadratic sum of the statistical and systematic uncertainties. The shaded regions illustrate the theoretical predictions and their uncertainties from light cone sum rule and lattice QCD calculations.

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Isospin asymmetries for (left) $ B \!\rightarrow K \mu ^+ \mu ^- $ and (right) $ B \!\rightarrow K^{*} \mu ^+ \mu ^- $ decays.

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Isospin asymmetry of $ B \!\rightarrow K \mu ^+ \mu ^- $ obtained separately from the 2011 and 2012 data sets.

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Tables and captions

Observed yields of the four signal channels summed over the $ q^{2}$ bins, excluding the charmonium resonance regions. Only the statistical uncertainties are shown.

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Summary of systematic uncertainties associated with the branching fraction and isospin asymmetry measurements.

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Integrated branching fractions $(10^{-8})$ in the high $ q^{2}$ region. For the $ B \!\rightarrow K \mu ^+ \mu ^- $ modes the region is defined as $15-22 {\mathrm{\,GeV^2\!/}c^4} $, while for $ B ^+ \!\rightarrow K^{*+} \mu ^+ \mu ^- $ it is $15-19 {\mathrm{\,GeV^2\!/}c^4} $. Predictions are obtained using the form factors calculated in lattice QCD over the same $ q^{2}$ regions. For the measurements, the first uncertainty is statistical and the second systematic.

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Differential branching fraction results ($10^{-9} \times c^4/ GeV^2$) for the $ B ^+ \!\rightarrow K ^+ \mu ^+ \mu ^- $ decay, including statistical and systematic uncertainties.

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Differential branching fraction results ($10^{-9} \times c^4/ GeV^2$) for the $ B ^0 \!\rightarrow K ^0 \mu ^+ \mu ^- $ decay, including statistical and systematic uncertainties.

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Differential branching fraction results ($10^{-9} \times c^4/ GeV^2$) for the $ B ^+ \!\rightarrow K^{*+} \mu ^+ \mu ^- $ decay, including statistical and systematic uncertainties.

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Isospin asymmetry results for the $ B \!\rightarrow K \mu ^+ \mu ^- $ decay, including statistical and systematic uncertainties.

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Isospin asymmetry results for the $ B \!\rightarrow K^{*} \mu ^+ \mu ^- $ decay, including statistical and systematic uncertainties.

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Supplementary Material [file]

Supplementary material full pdf

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Created on 09 December 2018.Citation count from INSPIRE on 18 December 2018.