Abstract
For a number of years, there has been a certain inconsistency among the measurements of the branching ratios and CP asymmetries of the four B → πK decays (B+ → π+K0, B+ → π0K+, B 0 d → π−K+, B 0 d → π0K0). In this paper, we re-examine this B → πK puzzle. We find that the key unknown parameter is |C′/T ′|, the ratio of color-suppressed and color-allowed tree amplitudes. If this ratio is large, |C′/T ′| = 0.5, the SM can explain the data. But if it is small, |C′/T ′| = 0.2, the SM cannot explain the B → πK puzzle —new physics (NP) is needed. The two types of NP that can contribute to B → πK at tree level are Z′ bosons and diquarks. Z′ models can explain the puzzle if the Z′ couples to right-handed uū and/or \( d\overline{d} \), with g dd R ≠ g uu R . Interestingly, half of the many Z′ models proposed to explain the present anomalies in b → sμ+μ− decays have the required Z′ couplings to uū and/or \( d\overline{d} \). Such models could potentially explain both the b → sμ+μ− anomalies and the B → πK puzzle. The addition of a color sextet diquark that couples to ud can also explain the puzzle.
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Beaudry, N.B., Datta, A., London, D. et al. The B → πK puzzle revisited. J. High Energ. Phys. 2018, 74 (2018). https://doi.org/10.1007/JHEP01(2018)074
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DOI: https://doi.org/10.1007/JHEP01(2018)074