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Study of $B \to K_0^*(1430)\,\ell^+ \ell^-$ Decay in the Standard Model and Scalar Leptoquark Scenario

M. Dadashzadeh, K. Azizi

TL;DR

This work investigates the rare decay $B \to K_0^*(1430)\ell^+\ell^-$ as a probe of new physics in $b \to s\ell^+\ell^-$ transitions, comparing the Standard Model with a scalar leptoquark scenario. Using QCD sum-rule form factors for $B\to K_0^*(1430)$ and the full effective Hamiltonian including chirality-flipped operators, the authors compute differential decay rates, partially integrated branching fractions in short-distance $q^2$ windows, LFU ratios, forward-backward asymmetry, and lepton polarization observables for $\ell = e,\mu,\tau$. They stress regions away from $J/\psi$ and $\psi'$ where long-distance charm effects are minimized. The analysis finds that scalar leptoquarks can induce non-negligible shifts in several observables, notably in $P_L(\hat{s})$ for light leptons and in high-$q^2$ regions for $\tau$, while $R_{K_0^*}$ remains near unity, indicating limited LFU violation in the chosen benchmarks. These results establish $B \to K_0^*(1430)\ell^+\ell^-$ as a promising channel for future precision tests at Belle II and LHCb, capable of constraining or revealing scalar NP through clean angular and polarization observables in short-distance windows.

Abstract

This study examines the rare decay $B \to K_0^*(1430)\,\ell^+ \ell^-$ as a possible probe for new physics beyond the standard model (SM). We first analyze this channel within the SM and then include scalar leptoquark (LQ) contributions. We provide predictions for key observables, like differential decay rate, branching ratio, ratio of branching fractions at different channels, forward-backward asymmetry and different lepton polarizations, and assess their sensitivity to leptoquark scenarios, highlighting $q^2$ regions less affected by the long-distance charmonium effects. The results can be useful for future Belle II and LHCb measurements.

Study of $B \to K_0^*(1430)\,\ell^+ \ell^-$ Decay in the Standard Model and Scalar Leptoquark Scenario

TL;DR

This work investigates the rare decay as a probe of new physics in transitions, comparing the Standard Model with a scalar leptoquark scenario. Using QCD sum-rule form factors for and the full effective Hamiltonian including chirality-flipped operators, the authors compute differential decay rates, partially integrated branching fractions in short-distance windows, LFU ratios, forward-backward asymmetry, and lepton polarization observables for . They stress regions away from and where long-distance charm effects are minimized. The analysis finds that scalar leptoquarks can induce non-negligible shifts in several observables, notably in for light leptons and in high- regions for , while remains near unity, indicating limited LFU violation in the chosen benchmarks. These results establish as a promising channel for future precision tests at Belle II and LHCb, capable of constraining or revealing scalar NP through clean angular and polarization observables in short-distance windows.

Abstract

This study examines the rare decay as a possible probe for new physics beyond the standard model (SM). We first analyze this channel within the SM and then include scalar leptoquark (LQ) contributions. We provide predictions for key observables, like differential decay rate, branching ratio, ratio of branching fractions at different channels, forward-backward asymmetry and different lepton polarizations, and assess their sensitivity to leptoquark scenarios, highlighting regions less affected by the long-distance charmonium effects. The results can be useful for future Belle II and LHCb measurements.
Paper Structure (9 sections, 38 equations, 2 figures, 3 tables)

This paper contains 9 sections, 38 equations, 2 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Effective Hamiltonian
  3. Form factors and decay amplitude
  4. Differential decay rate
  5. Numerical results
  6. Differential decay-rate spectra
  7. Other observables results
  8. Forward-backward asymmetry and lepton polarization
  9. Conclusions

Figures (2)

  • Figure 1: Differential decay rate for $B \to K_0^*(1430)\,\ell^+\ell^-$ in the SM and in the scalar LQ scenario ($\ell=e,\mu,\tau$). For $\tau^+\tau^-$ the spectrum starts at $q^2\ge 4m_\tau^2$, so the low-$q^2$ region is not accessible.
  • Figure 2: Longitudinal lepton polarization asymmetry $P_L(\hat{s})$ in $B\to K_0^*(1430)\,\ell^+\ell^-$ for $\ell=e,\mu,\tau$, comparing the SM prediction with the scalar leptoquark scenario.