Vertexing displaced diphoton decays with recoil photons at Belle II
Abstract
We propose a recoil-assisted strategy for vertexing displaced diphoton decays in e+e-→γX, X→γγ, using only one converted daughter photon. The initial state and recoil-photon momentum define the LLP flight line, whose closest approach to the converted-photon trajectory locates the decay vertex. This removes the need for a second conversion, making the conversion-related efficiency scale linearly rather than quadratically with the photon-conversion probability. For photophilic axionlike particles at Belle II, the existing $408$ fb−1 data set could probe previously unconstrained parameter space near ma ≃ 100 MeV and gaγγ ≃ 2 × 10−4 GeV−1, improving leading bounds by almost an order of magnitude and testing the mass region below the π0 mass, which the existing Belle II three-photon searches cannot access. With $50$ ab−1, the reach extends to ma ≃ 310 MeV and gaγγ≃2×10−5 GeV−1.
Related
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BibTeX
@misc{wang2026vertexing,
title = {{Vertexing displaced diphoton decays with recoil photons at Belle II}},
author = {Zeren Simon Wang and Yu Zhang},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.15324},
eprint = {2609.15324},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.15324},
}
RIS
TY - UNPB
TI - Vertexing displaced diphoton decays with recoil photons at Belle II
AU - Zeren Simon Wang
AU - Yu Zhang
PY - 2026
DA - 2026/09/21
PB - arXiv
DO - 10.48550/arxiv.2609.15324
UR - https://arxiv.org/abs/2609.15324
AB - We propose a recoil-assisted strategy for vertexing displaced diphoton decays in e^+e^-→γX, X→γγ, using only one converted daughter photon. The initial state and recoil-photon momentum define the LLP flight line, whose closest approach to the converted-photon trajectory locates the decay vertex. This removes the need for a second conversion, making the conversion-related efficiency scale linearly rather than quadratically with the photon-conversion probability. For photophilic axionlike particles at Belle II, the existing $408$ fb^−1 data set could probe previously unconstrained parameter space near m_a ≃ 100 MeV and g_aγγ ≃ 2 × 10^−4 GeV^−1, improving leading bounds by almost an order of magnitude and testing the mass region below the π^0 mass, which the existing Belle II three-photon searches cannot access. With $50$ ab^−1, the reach extends to m_a ≃ 310 MeV and g_aγγ≃2×10^−5 GeV^−1.
ER -