Periodic Reporting for period 4 - SENSE (Sterile neutrino search in tritium beta decay)
Période du rapport: 2023-11-01 au 2025-02-28
Despite the remarkable success of the Standard Model of Particle physics, we know today that it cannot be complete. One of the most fundamental open questions is the nature of dark matter, which makes up 25% of the content of our universe. One minimal extension of the Standar Model of Particle physics is the introduction of a new type of neutrino, the so-called sterile neutrino. With a mass in the kilo-electron-volt (keV) range, such neutrino would be a viable dark matter candidate. With a mass in the electron-volt (eV) regime, such neutrino could resolve long-standing anomalies in neutrino oscillation experiments.
A promising way to search for eV to keV sterile neutrinos is via the kinematics of beta decay, where this new particle would manifest itself as characteristic spectral deformation. The Karlsruhe Tritium Neutrino (KATRIN) experiment operates one of the strongest tritium sources for scientific research. Its primary goal is a direct measurement of the absolute neutrino mass scale. It has recently published a world-leading direct limit on the neutrino mass of m < 0.45 eV in Science.
The aim of the SENSE project is to extend the KATRIN experiment to search for eV and keV-scale sterile neutrinos. The former can be searched for with the data that is currently being recorded for the neutrino mass measurement. However, a keV-scale sterile neutrino search requires an upgrade of the focal plane detector system in the 70-m long KATRIN beamline. In the framework of SENSE we develop a beyond-the-state-of-the art multi-pixel Silicon Drift Detector focal plane array to be installed in the beamline after the completion of the neutrino mass program of KATRIN.
A promising way to search for eV to keV sterile neutrinos is via the kinematics of beta decay, where this new particle would manifest itself as characteristic spectral deformation. The Karlsruhe Tritium Neutrino (KATRIN) experiment operates one of the strongest tritium sources for scientific research. Its primary goal is a direct measurement of the absolute neutrino mass scale. It has recently published a world-leading direct limit on the neutrino mass of m < 0.45 eV in Science.
The aim of the SENSE project is to extend the KATRIN experiment to search for eV and keV-scale sterile neutrinos. The former can be searched for with the data that is currently being recorded for the neutrino mass measurement. However, a keV-scale sterile neutrino search requires an upgrade of the focal plane detector system in the 70-m long KATRIN beamline. In the framework of SENSE we develop a beyond-the-state-of-the art multi-pixel Silicon Drift Detector focal plane array to be installed in the beamline after the completion of the neutrino mass program of KATRIN.
The first major achievements of SENSE are world-leading searches for eV-scale sterile neutrinos based on the first five data taking campaigns of KATRIN. These outcomes are highly complementary to other searches, which are typically based on short-baseline neutrino oscillation experiments. No eV-sterile neutrino signal was observed, setting stringent limits on the preferred parameter space of eV-scale sterile neutrinos.
A second major achievement of SENSE is the search for keV-scale sterile neutrinos based on an initial low-statistics commissioning dataset. The low rates during this measurement allowed to use the current focal plane detector of KATRIN. Based on this data set a leading limit on sterile neutrinos with a mass of around 1 keV could be set.
The third major achievement is the development, commissioning, and characterization of a novel multi-pixel Silicon Drift Detector system (named TRISTAN). This development included 1) the design and production of 166-pixel SDD chips with an integrated amplification at the Semiconductor Laboratory of the Max Planck Society, 2) the development of high-density front-end electronics, including dedicated ASIC chips, 3) the development of a high-performance Data Acquisition system, and 4) the construction of the mechanical holding and cooling infrastructure. Moreover, a number of dedicated calibration systems and test stands were developed to characterize the system. Our tests show an excellent performance of the system with respect to energy resolution and stability. An installation in a full replica system of the KATRIN detector section shows excellent performance in a realistic environment. The final installation of the 9 TRISTAN modules (each 166-pixels) is scheduled for 2026.
A second major achievement of SENSE is the search for keV-scale sterile neutrinos based on an initial low-statistics commissioning dataset. The low rates during this measurement allowed to use the current focal plane detector of KATRIN. Based on this data set a leading limit on sterile neutrinos with a mass of around 1 keV could be set.
The third major achievement is the development, commissioning, and characterization of a novel multi-pixel Silicon Drift Detector system (named TRISTAN). This development included 1) the design and production of 166-pixel SDD chips with an integrated amplification at the Semiconductor Laboratory of the Max Planck Society, 2) the development of high-density front-end electronics, including dedicated ASIC chips, 3) the development of a high-performance Data Acquisition system, and 4) the construction of the mechanical holding and cooling infrastructure. Moreover, a number of dedicated calibration systems and test stands were developed to characterize the system. Our tests show an excellent performance of the system with respect to energy resolution and stability. An installation in a full replica system of the KATRIN detector section shows excellent performance in a realistic environment. The final installation of the 9 TRISTAN modules (each 166-pixels) is scheduled for 2026.
Unchartered parameter space for light eV-scale sterile neutrinos could be explored, which helps to shed light on long-standing anomalies in neutrino physics. A novel detector system was developed which will allow to perform beta-spectroscopy with unprecedented precision and will enable a search for keV-scale sterile neutrinos in beta decays.