Searching for internal pair creation anomalies and the X17 boson at LNL

Gongora Servin, B.; Marchi, T.; Tagnani, D.; Caletano, A.; Goasduff, A.; Valiente-Dobon, J. J.; Aguilera, P.; Angelini, F.; Azaiez, F.; Baldesi, L.; Balogh, M.; Barlini, S.; Benito-Garcia, J.; Bolzonella, R.; Bottoni, S.; Brugnara, D.; Camaiani, A.; Carollo, S.; Casini, G.; Cobari, G.; Dell'Aquila, D.; Ercolano, F.; Ertroprak, A.; Fabris, D.; Galtarossa, F.; Gottardo, A.; Gozzelino, A.; Gramegna, F.; Lazzaretto, D.; Lombardo, I.; Mengoni, D.; Nannini, A.; Palombini, L.; Pellumaj, J.; Perez-Vidal, R. M.; Piantelli, S.; Pigliapoco, S.; Pilotto, E.; Polettini, M.; Sigmund, M.; Spina, G.; Stramaccioni, D.; Recchia, F.; Redigolo, L.; Rezynkina, K.; Rigon, L.; Rocchini, M.; Rossi, M.; Sedlak, M.; Simpsi, F.; Valdre, S.; Vigilante, M.; Zago, L.; Zanon, I.; Zappacosta, L.

doi:10.1393/ncc/i2025-25023-4

2016, a breakthrough anomaly was reported in the isoscalar magnetic dipole transition in8Be via the Internal Pair Creation process. An unexpected angular distribution of the relative angle of the e+e− was measured at the Atomki Laboratory. This phenomenon was explained considering the assumption of an emission of a neutral boson, named X17, with a mass of 16.70±0.35(stat)±0.5(syst) MeV/c2 and Jπ =1+. This finding triggered a global campaign to search for the new boson claimed. In Italy, at the Legnaro National Laboratories, a novel scintillator detector array has been designed and built. The present work reports the status of the first in-beam experiments performed in 2023 and 2024.

Searching for internal pair creation anomalies and the X17 boson at LNL / Gongora Servin B., Marchi T., Tagnani D., Caletano A., Goasduff A., Valiente-Dobon J.J., Aguilera P., Angelini F., Azaiez F., Baldesi L., Balogh M., Barlini S., Benito-Garcia J., Bolzonella R., Bottoni S., Brugnara D., Camaiani A., Carollo S., Casini G., Cobari G., et al.. - In: NUOVO CIMENTO DELLA SOCIETÀ ITALIANA DI FISICA. C, GEOPHYSICS AND SPACE PHYSICS. - ISSN 1826-9885. - ELETTRONICO. - 48:(2025), pp. 0-0. (16th Workshop on Particle Correlations and Femtoscopy, WPCF 2023 and 4th Resonance Workshop ita 2023) [10.1393/ncc/i2025-25023-4].