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arXiv · 2605.23533

A search for the dark photon in the OKA experiment

The OKA Collaboration·A. S. Sadovsky·A. P. Filin·A. V. Artamonov·S. V. Donskov·A. M. Gorin·A. V. Inyakin·G. V. Khaustov·S. A. Kholodenko·V. N. Kolosov·A. K. Konoplyannikov·V. F. Kurshetsov·V. A. Lishin·M. V. Medynsky·A. G. Miagkov·V. F. Obraztsov·A. V. Okhotnikov·V. I. Romanovsky·V. I. Rykalin·V. D. Samoylenko·M. M. Shapkin·S. R. Slabospitsky·A. E. Sobol·I. S. Tiurin·V. A. Uvarov·O. P. Yushchenko·S. N. Filippov·E. N. Gushchin·A. A. Khudyakov·V. I. Kravtsov·Yu. G. Kudenko·A. V. Kulik·A. Yu. Polyarush·V. N. Bychkov·G. D. Kekelidze·V. M. Lysan·V. A. Polyakov·B. Zh. Zalikhanov
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Abstract

A search for the massless dark photon in the decay $K^{+}\to \pi^{+}\pi^{0}\overline{{} \gamma}$ is performed with the OKA detector exposed to 17.7 GeV/c RF separated secondary beam of the U70 Proton Synchrotron. A high-statistics data sample of the $K^{+}$ decays is used for a missing mass search of the stable massless invisible dark photon ($\overline{\gamma}$) in the final state. In the absence of a statistically valuable signal the upper limit on the branching ratio of the decay $Br<2.0\times10^{-6}$ is obtained with a 90% confidence level based on a realistic matrix element of the process. Currently, it is the best upper limit for this hypothetical decay channel.

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The OKA Collaboration, A. S. Sadovsky, A. P. Filin, A. V. Artamonov, S. V. Donskov, A. M. Gorin, A. V. Inyakin, G. V. Khaustov, S. A. Kholodenko, V. N. Kolosov, A. K. Konoplyannikov, V. F. Kurshetsov, V. A. Lishin, M. V. Medynsky, A. G. Miagkov, V. F. Obraztsov, A. V. Okhotnikov, V. I. Romanovsky, V. I. Rykalin, V. D. Samoylenko, M. M. Shapkin, S. R. Slabospitsky, A. E. Sobol, I. S. Tiurin, V. A. Uvarov, O. P. Yushchenko, S. N. Filippov, E. N. Gushchin, A. A. Khudyakov, V. I. Kravtsov, Yu. G. Kudenko, A. V. Kulik, A. Yu. Polyarush, V. N. Bychkov, G. D. Kekelidze, V. M. Lysan, V. A. Polyakov, B. Zh. Zalikhanov. 2026-05-22. A search for the dark photon in the OKA experiment. https://arxiv.org/abs/2605.23533

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