Periodic Reporting for period 1 - LightForNuLAND (Scintillation Light For New Physics with Liquid Argon Neutrino Detectors)
Berichtszeitraum: 2021-09-01 bis 2023-08-31
Neutrinos are the second most abundant known particle in the Universe but our understanding about them is still lacking many important neutrino properties. One of the most intriguing mysteries is their tiny mass, which is at least a million times lighter than an electron. A possible explanation for such a small value is the existence of new heavier particles known as heavy neutral leptons (HNLs for short), which are connected to the neutrinos like in a seesaw, making the neutrinos masses appear very light. The mass of the HNLs can take a large range of values, and therefore they must be sought in different experiments sensitive to different mass values.
The liquid argon (LAr) detector is a technology that has gained relevance because it has been selected for the future DUNE experiment that will investigate other mysteries such as if neutrinos and antineutrinos behave differently as they propagate, which could be connected to the dominance of matter over antimatter in our Universe. In this project we proposed to use SBND, a LAr detector located very close to the origin of the Booster Neutrino Beam at Fermilab, to search for HNLs and advance our expertise with this technology.
The overall objectives were 1) contribute to the data acquisition of the scintillating light produced in LAr when the particles excite it, 2) develop the simulation and analysis of this light which is used to reject fake signals that mimic the HNL signature, 3) develop the search for HNLs in SBND. Through this research program, the fellow was trained in LAr scintillation light in which the CIEMAT Neutrino Group is a reference, and the fellow was reintegrated in the European Union, becoming an independent researcher and bringing his previous expertise in LAr detectors and Beyond Standard Model physics to the host.
The liquid argon (LAr) detector is a technology that has gained relevance because it has been selected for the future DUNE experiment that will investigate other mysteries such as if neutrinos and antineutrinos behave differently as they propagate, which could be connected to the dominance of matter over antimatter in our Universe. In this project we proposed to use SBND, a LAr detector located very close to the origin of the Booster Neutrino Beam at Fermilab, to search for HNLs and advance our expertise with this technology.
The overall objectives were 1) contribute to the data acquisition of the scintillating light produced in LAr when the particles excite it, 2) develop the simulation and analysis of this light which is used to reject fake signals that mimic the HNL signature, 3) develop the search for HNLs in SBND. Through this research program, the fellow was trained in LAr scintillation light in which the CIEMAT Neutrino Group is a reference, and the fellow was reintegrated in the European Union, becoming an independent researcher and bringing his previous expertise in LAr detectors and Beyond Standard Model physics to the host.
We developed the simulation and analysis of scintillation light in LAr with the X-ARAPUCA photosensors. The X-ARAPUCAs are devices that trap the light into cells by shifting the light wavelength and using one-way filters until it is detected by silicon photomultipliers. These devices will also be used in the future DUNE experiment. The fellow began co-supervising his first PhD student thesis (expected in 2024) on the readout electronics simulation, signal processing, pulse reconstruction and clustering algorithms. The work was presented at conferences like Neutrino 2022, the XIV CPAN Days, and LIDINE 2023. An article summarising this work is currently under review by the SBND collaboration.
The fellow worked on the data acquisition system for the scintillation light, in which CIEMAT has taken the responsibility for the data acquisition of the X-ARAPUCA photosensors. In parallel, the photon detection efficiency of the X-ARAPUCAs was measured at the CIEMAT laboratory in a cryogenic setup. The fellow led the design, commissioning, data taking and analysis of the data from this setup. A publication is in preparation.
The fellow worked on implementing a simulation of the production of HNLs in the Booster Neutrino Beam and their decay inside the SBND detector, and began leading the HNL search in SBND as Co-Convener of the Beyond Standard Model Physics Group. His group produced the first sensitivity estimation to HNLs in SBND using a realistic beam simulation, and including the time of flight of HNLs to the detector. This time can be estimated from the timing of the scintillation light signals and used to discriminate the HNLs from other background contributions. The fellow presented this work at the XIV CPAN Days and TAUP 2023 conferences. A publication is in preparation.
The fellowship successfully reintegrated the researcher into the European Union research system and was instrumental for the fellow to obtain a permanent position, strengthening the CIEMAT contribution to SBND and the European contribution to the future DUNE experiment.
The fellow worked on the data acquisition system for the scintillation light, in which CIEMAT has taken the responsibility for the data acquisition of the X-ARAPUCA photosensors. In parallel, the photon detection efficiency of the X-ARAPUCAs was measured at the CIEMAT laboratory in a cryogenic setup. The fellow led the design, commissioning, data taking and analysis of the data from this setup. A publication is in preparation.
The fellow worked on implementing a simulation of the production of HNLs in the Booster Neutrino Beam and their decay inside the SBND detector, and began leading the HNL search in SBND as Co-Convener of the Beyond Standard Model Physics Group. His group produced the first sensitivity estimation to HNLs in SBND using a realistic beam simulation, and including the time of flight of HNLs to the detector. This time can be estimated from the timing of the scintillation light signals and used to discriminate the HNLs from other background contributions. The fellow presented this work at the XIV CPAN Days and TAUP 2023 conferences. A publication is in preparation.
The fellowship successfully reintegrated the researcher into the European Union research system and was instrumental for the fellow to obtain a permanent position, strengthening the CIEMAT contribution to SBND and the European contribution to the future DUNE experiment.
In this project we updated the simulation of the X-ARAPUCA signals with a more realistic modeling and developed a new signal reconstruction that has improved the precision of the scintillation light measurements. We have shared these tools with the DUNE experiment, and also applied them to our measurements at the CIEMAT laboratory. We have increased our expertise in the characterization of light sensors at cryogenic temperatures, measuring how effective the SBND X-ARAPUCAs are at detecting light, and contributed to the data acquisition of the scintillating light in the SBND detector.
The results obtained in this fellowship showed SBND has the potential to reach a world-leading sensitivity to HNLs produced through muon-flavor mixing in the mass region below 250 MeV/c^2. We paved the way for the search once the data arrives, advancing the Monte Carlo simulation that allows us to predict the expected number of HNLs, and when they will decay in the detector based on the scintillation light they will release.
The results obtained in this fellowship showed SBND has the potential to reach a world-leading sensitivity to HNLs produced through muon-flavor mixing in the mass region below 250 MeV/c^2. We paved the way for the search once the data arrives, advancing the Monte Carlo simulation that allows us to predict the expected number of HNLs, and when they will decay in the detector based on the scintillation light they will release.