Probing dark-matter scenarios of Belle II excess in B⁺→ K⁺M_X with K⁺→ π⁺ M_X decays

@misc{berezhnoy2026probing,
  title = {{Probing dark-matter scenarios of Belle II excess in $B^+\to K^+M_X$ with $K^+\to π^+ M_X$ decays}},
  author = {Alexander Berezhnoy and Wolfgang Lucha and Dmitri Melikhov},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.24701},
  eprint = {2610.24701},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.24701},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - Probing dark-matter scenarios of Belle II excess in B^+→ K^+M_X with K^+→ π^+ M_X decays
AU  - Alexander Berezhnoy
AU  - Wolfgang Lucha
AU  - Dmitri Melikhov
PY  - 2026
DA  - 2026/10/17
PB  - arXiv
DO  - 10.48550/arxiv.2610.24701
UR  - https://arxiv.org/abs/2610.24701
AB  - The hypothesis of top-philic dark matter as the origin of the Belle II excess events in B→ K M_X decays has direct impact on K→ πM_X decays: Both of these decays proceed via loop diagrams~with a top quark emitting some mediator field R and the subsequent decay of R into a pair of dark-matter fermions χ̅χ. The Belle II results on B→ K M_X allowed us to extract the parameters of the mediator R with reasonable accuracy, whereas the sensitivity to the fermion mass m_χ proved to be rather low. In contrast to B→ K M_X decays, the K→ πM_X decays exhibit a strong sensitivity to m_χ; therefore, if - upon reducing theoretical and experimental uncertainties - the tension between standard-model predictions for the K→πM_X decays and the most recent NA62 measurements becomes pronounced the latter decays may either enable the extraction of the value of m_χ or provide a lower limit on~m_χ.
ER  -