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| Main Authors: | , , , |
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| Format: | Preprint |
| Published: |
2025
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2505.10302 |
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| _version_ | 1866912796048883712 |
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| author | Ge, Shao-Feng Liang, Jinhan Liu, Zuowei Min, Ui |
| author_facet | Ge, Shao-Feng Liang, Jinhan Liu, Zuowei Min, Ui |
| contents | In this work, we investigate the contribution of the annihilation process with initial-state radiation ($e^+ e^- \to γA'$) to the invisible dark photon ($A'$) searches at the electron fixed-target configurations. For illustration, we consider both the disappearing positron track signature at Belle II and the large missing energy search at NA64. When the dark photon has a narrow decay width, the effect of the initial-state radiation to the annihilation process can dominate over its $s$-channel and bremsstrahlung counterparts around $m_{A'} \simeq 60\,\rm{MeV}$ ($m_{A'} \simeq 200\,\rm{MeV}$) for Belle II (NA64), to enhance the corresponding sensitivity on the kinetic mixing parameter $ε$ by a factor of up to approximately 2.7 (1.3). For Belle II, we further perform a multi-bin analysis with the spectrum information to better separate the background and signal channels for significant improvement of the sensitivity. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2505_10302 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Dark Photon Searches with Initial-State Radiation at Fixed-Target Configurations Ge, Shao-Feng Liang, Jinhan Liu, Zuowei Min, Ui High Energy Physics - Phenomenology In this work, we investigate the contribution of the annihilation process with initial-state radiation ($e^+ e^- \to γA'$) to the invisible dark photon ($A'$) searches at the electron fixed-target configurations. For illustration, we consider both the disappearing positron track signature at Belle II and the large missing energy search at NA64. When the dark photon has a narrow decay width, the effect of the initial-state radiation to the annihilation process can dominate over its $s$-channel and bremsstrahlung counterparts around $m_{A'} \simeq 60\,\rm{MeV}$ ($m_{A'} \simeq 200\,\rm{MeV}$) for Belle II (NA64), to enhance the corresponding sensitivity on the kinetic mixing parameter $ε$ by a factor of up to approximately 2.7 (1.3). For Belle II, we further perform a multi-bin analysis with the spectrum information to better separate the background and signal channels for significant improvement of the sensitivity. |
| title | Dark Photon Searches with Initial-State Radiation at Fixed-Target Configurations |
| topic | High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2505.10302 |