Branching ratio measurements and isospin violation in B-meson decays

Abstract

The approximate symmetry of the strong interactions under isospin transformations is among the most precise tools available to control hadronic matrix elements. It is crucial in extracting fundamental parameters, but also provides avenues for the search of phenomena beyond the Standard Model. The precision of the resulting predictions requires special care when determining the quantities they are to be tested with. Specifically, in the extraction of branching ratios often isospin symmetry is assumed at one point or another implicitly, implying a significant bias for precision analyses. We extract a bias-free value for the production asymmetry between charged and neutral $B$ meson pairs at $B$ factories and discuss its consequences for the determination of branching fractions generally, and isospin-violating observables like the rate asymmetries in B -> J/psi K or B -> K* gamma decays specifically.

5 pages. v2: proposal for new measurement of production fractions added, accepted for publication in PLB

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• Measurement of the phase difference between short- and long-distance amplitudes in the $B^{+}\to K^{+}{\mu }^{+}{\mu }^{-}$ decay
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• A puzzle in ${\bar{B}}_{(s)}^0\to D_{(s)}^{(\ast )+}\{{\pi }^{-},K^{-}\}$ decays and extraction of the $f_s/f_d$ fragmentation fraction
• Measurements of isospin asymmetry and difference of direct $CP$ asymmetries in inclusive $B\to X_s\gamma$ decays
• Reexamining the photon polarization in $B\to K\pi \pi \gamma$
• Status of rare exclusive $B$ meson decays in 2018
• Measurement of the dependence of the hadron production fraction ratio $f_{\mathrm{s}}/f_{\mathrm{u}}$ and $f_{\mathrm{d}}/f_{\mathrm{u}}$ on B meson kinematic variables in proton-proton collisions at $\sqrt{s}$ = 13 TeV
• Towards a Global Analysis of the $b\to c\bar{u}q$ Puzzle
• Measurement of the branching fraction of the ${\Lambda }_b^0\to J/\psi \Lambda$ decay and isospin asymmetry of $B\to J/\psi K$ decays
• Rescaling the isospin triangle argument for constraining ${\varphi }_2$ ($\alpha$): consolidating Belle II and a potential path forward for LHCb
• Summary of CKM 2016 Working Group 4 : mixing and mixing-related $CP$ violation in the $B$ system