QUBIC: an algorithm for detecting cosmic rays

Sofia Ferazzoli^1*Elia Stefano Battistelli^2,3Silvia Masi^1,3Alessandro Coppolecchia^1,3Belen Costanza⁴Paolo De Bernardis^1,3Giancarlo De Gasperis^1,3Massimo Gervasi^5,6Jean-Christophe Hamilton⁷Nauhel Miron Granese⁴Creidhe O'sullivan⁸Michel Piat⁹Stephen Torchinsky^10,7Mario Zannoni^5,6Claudia Scoccola^11,4

• ¹Sapienza University of Rome, Rome, Italy
• ²Universita degli Studi di Roma Unitelma Sapienza, Roma, Italy
• ³Istituto Nazionale di Fisica Nucleare Sezione di Roma, Rome, Italy
• ⁴Universidad Nacional de La Plata Facultad de Ciencias Astronomicas y Geofisicas, La Plata, Argentina
• ⁵Universita degli Studi di Milano-Bicocca, Milan, Italy
• ⁶Istituto Nazionale di Fisica Nucleare Sezione di Milano-Bicocca, Milan, Italy
• ⁷Astroparticule et Cosmologie, Paris, France
• ⁸Maynooth University, Maynooth, Ireland
• ⁹Universite Paris Cite, Paris, France
• ¹⁰Observatoire de Paris, Paris, France
• ¹¹Universidad de Chile Facultad de Ciencias Fisicas y Matematicas, Santiago, Chile

Introduction QUBIC (the Q & U Bolometric Interferometer for Cosmology) is an international 3 ground-based experiment designed to observe the polarization of the Cosmic Microwave 4 Background. It has been installed at a high-altitude site in Alto Chorillos, Argentina (4869 m 5 above sea level). At this altitude, the cosmic ray flux is high, thus requiring advanced algorithm for 6 their detection and removal from raw data. Cosmic rays can leave two types of traces in the data: 7 above and below the noise level. This paper describes an algorithm for detecting the above-noise 8 traces. 9 Methods An algorithm was developed for detecting cosmic ray events in Transition Edge Sensors 10 detectors (TES bolometers) time-ordered data (TOD). Raw signals were pre-processed to obtain 11 de-noised data. Events were searched by applying a threshold to isolate segments showing a 12 rapid rise and subsequent exponential decay. The final goal is to fit each segment to extract the 13 time scale of the candidate, and to verify fit quality statistically. 14 Results The cosmic ray detection algorithm was applied to datasets acquired in Salta (Argentina) 15 in 2022, during a testing campaign. So far, no candidates have been found after exploring different 16 thresholds for initiating the cosmic ray search, as well as various combinations of minimum points 17 required for the sudden rise and exponential decay expected in the signal. 18 Discussion We select only high signal-to-noise regions in order to find the most energetic cosmic 19 ray candidates matching the filters proposed in the method. The null result is not surprising, 20 since for the energy range of cosmic muons of interest here (about [1, 100] Gev), the expected 21 energy deposited in our very thin bolometer membranes is small, and produces a signal small 22 with respect to the measured noise. However, this methodology could be applied to future longer 23 campaigns, in order to estimate, from the largest (and rare) cosmic ray energy depositions the 24 TES time constants.