Observation of the May 2024 Forbush event with the EEE detectors operated with an eco-friendly gas mixture

Abbrescia, M.; Avanzini, C.; Baldini, L.; Baldini Ferroli, R.; Batignani, G.; Battaglieri, M.; Boi, S.; Bossini, E.; Carnesecchi, F.; Cavazza, D.; Cicalò, C.; Cifarelli, L.; Coccetti, F.; Coccia, E.; Corvaglia, A.; De Caro, A.; De Gruttola, D.; De Pasquale, S.; Galante, L.; Garbini, M.; Ghezzer, L. E.; Gnesi, I.; Gramegna, F.; Grazzi, S.; Hatzifotiadou, D.; La Rocca, P.; Liu, Z.; Mandaglio, G.; Margotti, A.; Maron, G.; Mazziotta, M. N.; Mulliri, A.; Nania, R.; Noferini, F.; Nozzoli, F.; Palmonari, F.; Panareo, M.; Panetta, M. P.; Paoletti, R.; Pellegrino, C.; Perasso, L.; Pinazza, O.; Pinto, C.; Pisano, S.; Quaglia, L.; Rasà, M.; Riggi, F.; Righini, G.; Ripoli, C.; Rizzi, M.; Sabiu, B.; Sartorelli, G.; Scapparone, E.; Schioppa, M.; Scioli, G.; Scribano, A.; Selvi, M.; Shtimmerman, A.; Taiuti, M.; Terreni, G.; Trifirò, A.; Trimarchi, M.; Vistoli, C.; Votano, L.; Williams, M. C. S.; Zichichi, A.; Zuyeuski, R.

doi:10.1140/epjp/s13360-026-07922-z

The Extreme Energy Events Project (EEE) is devoted to studying cosmic-ray fluxes using a large network of measuring stations equipped with Multigap Resistive Plate Chambers (MRPCs) and positioned across Italy, mainly inside high-school institutes. This paper presents the first measurements obtained operating the MRPCs with an eco-friendly gas mixture, namely the observation of the charged cosmic-ray rate variation (Forbush decrease) associated with the intense geomagnetic storm that occurred in May 2024. It is the first time a large-scale experiment has been successfully operated with a new eco-friendly gas mixture, keeping its physics performance substantially unchanged.