$K π$ scattering as a step towards $B \to K^* \ell^+ \ell^-$ from Lattice QCD
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| Format: | Preprint |
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2026
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| _version_ | 1866908898152153088 |
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| author | Erben, Felix Black, Matthew Boyle, Peter Di Carlo, Matteo Gülpers, Vera Hansen, Maxwell T. Lachini, Nelson Pitanga Mukherjee, Rajnandini Portelli, Antonin Tsang, J. Tobias |
| author_facet | Erben, Felix Black, Matthew Boyle, Peter Di Carlo, Matteo Gülpers, Vera Hansen, Maxwell T. Lachini, Nelson Pitanga Mukherjee, Rajnandini Portelli, Antonin Tsang, J. Tobias |
| contents | Rare $b\to s\ell^+\ell^-$ decays provide some of the most sensitive tests of the Standard Model and require precise and systematically improvable hadronic input from lattice QCD. For the phenomenologically important channel $B\to K^*\ell^+\ell^-$ this entails a first-principles treatment of a resonant $Kπ$ final state together with controlled heavy-quark dynamics. We present the status of a new exploratory lattice calculation that combines a variational determination of finite-volume $Kπ$ states with the $1+J\to2$ finite-volume formalism to access the relevant matrix elements. The computation is carried out on an RBC/UKQCD domain-wall fermion ensemble with $a^{-1} \approx 2.7\,\mathrm{GeV}$ and employs a dual heavy-quark strategy, using both a relativistic heavy-quark action tuned to the physical $b$ mass and domain-wall heavy masses extrapolating from charm. All correlation functions are computed using (stochastic) distillation, providing a versatile setup that supports a broad range of heavy-to-light transitions into resonant final states. We show first two-point results for the $K^*\leftrightarrow Kπ$ system and discuss the accessible kinematic region, which allows for a controlled study at high $q^2$. The outlook for extending the calculation to lower $q^2$ and for incorporating effects from charmonium resonances is outlined. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2603_17900 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | $K π$ scattering as a step towards $B \to K^* \ell^+ \ell^-$ from Lattice QCD Erben, Felix Black, Matthew Boyle, Peter Di Carlo, Matteo Gülpers, Vera Hansen, Maxwell T. Lachini, Nelson Pitanga Mukherjee, Rajnandini Portelli, Antonin Tsang, J. Tobias High Energy Physics - Lattice Rare $b\to s\ell^+\ell^-$ decays provide some of the most sensitive tests of the Standard Model and require precise and systematically improvable hadronic input from lattice QCD. For the phenomenologically important channel $B\to K^*\ell^+\ell^-$ this entails a first-principles treatment of a resonant $Kπ$ final state together with controlled heavy-quark dynamics. We present the status of a new exploratory lattice calculation that combines a variational determination of finite-volume $Kπ$ states with the $1+J\to2$ finite-volume formalism to access the relevant matrix elements. The computation is carried out on an RBC/UKQCD domain-wall fermion ensemble with $a^{-1} \approx 2.7\,\mathrm{GeV}$ and employs a dual heavy-quark strategy, using both a relativistic heavy-quark action tuned to the physical $b$ mass and domain-wall heavy masses extrapolating from charm. All correlation functions are computed using (stochastic) distillation, providing a versatile setup that supports a broad range of heavy-to-light transitions into resonant final states. We show first two-point results for the $K^*\leftrightarrow Kπ$ system and discuss the accessible kinematic region, which allows for a controlled study at high $q^2$. The outlook for extending the calculation to lower $q^2$ and for incorporating effects from charmonium resonances is outlined. |
| title | $K π$ scattering as a step towards $B \to K^* \ell^+ \ell^-$ from Lattice QCD |
| topic | High Energy Physics - Lattice |
| url | https://arxiv.org/abs/2603.17900 |