Paper

{
  "raw_xml": "<entry>\n    <id>http://arxiv.org/abs/2603.17900v1</id>\n    <title>$K π$ scattering as a step towards $B \\to K^* \\ell^+ \\ell^-$ from Lattice QCD</title>\n    <updated>2026-03-18T16:33:43Z</updated>\n    <link href='https://arxiv.org/abs/2603.17900v1' rel='alternate' type='text/html'/>\n    <link href='https://arxiv.org/pdf/2603.17900v1' rel='related' title='pdf' type='application/pdf'/>\n    <summary>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.</summary>\n    <category scheme='http://arxiv.org/schemas/atom' term='hep-lat'/>\n    <published>2026-03-18T16:33:43Z</published>\n    <arxiv:primary_category term='hep-lat'/>\n    <author>\n      <name>Felix Erben</name>\n    </author>\n    <author>\n      <name>Matthew Black</name>\n    </author>\n    <author>\n      <name>Peter Boyle</name>\n    </author>\n    <author>\n      <name>Matteo Di Carlo</name>\n    </author>\n    <author>\n      <name>Vera Gülpers</name>\n    </author>\n    <author>\n      <name>Maxwell T. Hansen</name>\n    </author>\n    <author>\n      <name>Nelson Pitanga Lachini</name>\n    </author>\n    <author>\n      <name>Rajnandini Mukherjee</name>\n    </author>\n    <author>\n      <name>Antonin Portelli</name>\n    </author>\n    <author>\n      <name>J. Tobias Tsang</name>\n    </author>\n  </entry>"
}