Implications of new physics in B → K₁μ⁺μ⁻ decay processes

Recently, several discrepancies at the level of (2–3)σ have been observed in the decay processes mediated by flavour changing neutral current (FCNC) transitions b → sℓ ⁺ ℓ ⁻, which may be considered as the smoking-gun signal of new physics (NP). These intriguing hints of NP have attracted a lot of attention and many attempts are being made to find the possible NP signature in other related processes, which are mediated through the same quark-level transitions. In this work, we perform a comprehensive analysis of the FCNC decays of the B meson to axial vector mesons K ₁(1270) and K ₁(1400), which are an admixture of the 1³ P ₁ and 1¹ P ₁ states K _1A and K _1B, in a model independent framework. Using the B → K ₁ form factors evaluated in the light cone sum rule approach, we investigate the rare exclusive semileptonic decays B → K ₁(1270)μ ⁺ μ ⁻ and B → K ₁(1400)μ ⁺ μ ⁻. Considering all the possible relevant operators for b → sℓ ⁺ ℓ ⁻ transitions, we study their effects on various observables such as branching fractions, the lepton flavor universality violating ratio $\left(R_{K_1}\right)$, forward–backward asymmetries, and lepton polarization asymmetries of these processes. These results will not only enhance the theoretical understanding of the mixing angle but also serve as a good tool for probing NP. (paper)