B_(s)→ V M_X decays as probes of dark-matter scenarios of Belle II enhancement in B→ KM_X decays

Abstract

Recently, we have shown that the hypothesis of the dark-matter (DM) origin of the Belle II excess events in B→ K M_X decays allows for a successful description of the data. The DM parameters (masses and couplings) in two DM scenarios with either scalar (S-scenario) or vector (V-scenario) mediator have been extracted with rather small uncertainty from fits to the B→ K M_X data. The same mechanism leads to a similar enhancement of the B_s→ (η,η',ϕ) M_X decay rates. We present a detailed analysis of B→ K^* M_X and B_s→ ϕM_X decays and show that these decays provide a clear probe of the S- and V-scenarios: Compared to the Standard Model, in the S-scenario an enhancement by a factor ∼ 1.6 is expected, whereas the V-scenario leads to a much larger enhancement by a factor ∼ 3.5. For the B→ K^* M_X decays, we provide the expected number of events at Belle II for the sample for which a rather large enhancement of B→ K M_X decays compared to the Standard Model expectations has been reported.

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BibTeX RIS

BibTeX

@misc{berezhnoy2026decays,
  title = {{$B_(s)\to V M_X$ decays as probes of dark-matter scenarios of Belle II enhancement in $B\to KM_X$ decays}},
  author = {Alexander Berezhnoy and Wolfgang Lucha and Dmitri Melikhov},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.13069},
  eprint = {2609.13069},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.13069},
  note = {CC BY 4.0},
}

RIS

TY  - UNPB
TI  - B_(s)→ V M_X decays as probes of dark-matter scenarios of Belle II enhancement in B→ KM_X decays
AU  - Alexander Berezhnoy
AU  - Wolfgang Lucha
AU  - Dmitri Melikhov
PY  - 2026
DA  - 2026/09/11
PB  - arXiv
DO  - 10.48550/arxiv.2609.13069
UR  - https://arxiv.org/abs/2609.13069
AB  - Recently, we have shown that the hypothesis of the dark-matter (DM) origin of the Belle II excess events in B→ K M_X decays allows for a successful description of the data. The DM parameters (masses and couplings) in two DM scenarios with either scalar (S-scenario) or vector (V-scenario) mediator have been extracted with rather small uncertainty from fits to the B→ K M_X data. The same mechanism leads to a similar enhancement of the B_s→ (η,η',ϕ) M_X decay rates. We present a detailed analysis of B→ K^* M_X and B_s→ ϕM_X decays and show that these decays provide a clear probe of the S- and V-scenarios: Compared to the Standard Model, in the S-scenario an enhancement by a factor ∼ 1.6 is expected, whereas the V-scenario leads to a much larger enhancement by a factor ∼ 3.5. For the B→ K^* M_X decays, we provide the expected number of events at Belle II for the sample for which a rather large enhancement of B→ K M_X decays compared to the Standard Model expectations has been reported.
ER  -

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