Session K15: Neutrino Physics

Neutrino Mass Measurement and Beyond with the KATRIN Experiment

The Karlsruhe Tritium Neutrino (KATRIN) experiment is designed to measure the effective electron anti-neutrino mass with a sensitivity of 0.2 eV (90% CL) via precision spectroscopy of the tritium β-decay spectrum. KATRIN’s current results improved the world’s direct limit of the upper bound to 0.8 eV (90% CL). Further data taking and analysis, and research into background reduction techniques are underway to push KATRIN towards our design goal sensitivity.

In this talk, the results of the neutrino mass measurement by KATRIN will be given, in addition to our path to a sensitivity of 0.2 eV (90% CL). The status of the TRISTAN detector upgrade, to enable KATRIN to search for keV sterile neutrinos, will also be presented.   

Quenching factor measurement of the undoped CsI at cryogenic temperature

We report on a measurement of the quenching factor of undated CsI at 77K, inspired by the COHERENT collaboration's experience measuring CEvNS using CsI[Na]. A serious background limiting its sensitivity was the Cherenkov radiation emitted from the PMT quartz window by charged particles. A switch from PMTs to SiPM arrays can be used to eliminate this background since SiPM arrays do not have a quartz window. In order to reduce the high dark count rate of SiPMs at room temperature, they need to be cooled to cryogenic temperatures. The cryogenic operation calls for the switch from doped CsI crystals to undoped ones, since the latter at 40 Kelvin have about twice as high light yield as the former at 300 Kelvin. Before we start using the combination of CsI and SiPM we need to study the properties of csi at low temperature. The first step we have done is the Quenching Factor measurement of undoped CsI at 77 K. The Am241 source is used to measure the electron recoil energy. The neutron source form Triangle Universities Nuclear Laboratory (TUNL) is used to do the nuclear recoil energy measurement. The nuclear recoil energy range is 3.9-59.7keV. We will present the experiment and analysis details in the presentation.   

Modular TES-based readout for ton-scale neutrino experiments based on cryogenic calorimeters

Neutrinos are elusive particles whose nature and properties are still mysterious. Precision measurements of coherent elastic neutrino-nucleus scattering and experiments searching for neutrinoless double beta decay are expected to reveal more information about neutrino interactions with nucleons, its magnetic moment, its nature (Majorana or Dirac), its mass ordering and scale. The next generation of experiments employing cryogenic calorimeters - like Ricochet phase-II and CUPID-1T - will require thousands of detectors to increase the sensitivity of the experiments to new physics. A TES-based read out, thanks to its adaptability to a multiplexed readout, is a very promising technology to scale up the mass while limiting the heat introduced in the cryogenic system by the cabling. A modular TES design has been developed in a collaboration of Northwestern University and Argonne National Laboratory. It can be easily mass produced and employed with different target materials. In this talk, we will present the first demonstration of a Li₂MoO₄ detector equipped with a TES-based readout.   

Project 8: Using Cyclotron Radiation Emission Spectroscopy to Measure the Neutrino Mass

Project 8 is an experiment that seeks to determine the electron-weighted neutrino mass via the precise measurement of the electron energy in beta decays, with a sensitivity goal of 40 meV/c². We have developed a technique called Cyclotron Radiation Emission Spectroscopy (CRES), which allows single electron detection and characterization through the measurement of cyclotron radiation emitted by magnetically-trapped electrons produced by a gaseous radioactive source. The technique has been successfully demonstrated on a small scale in waveguides to detect radiation from single electrons, and to measure the continuous spectrum from tritium. In order to achieve the projected sensitivity, the experiment will require novel technologies for performing CRES using tritium atoms in a magneto-gravitational trap in a multi-cubic-meter volume. In this talk, I will present a brief overview of the Project 8 experimental program, highlighting the latest results including our first tritium endpoint measurement and neutrino mass limit.   

Search for e+e− from monoenergetic dark scalars produced in ICARUS

This talk describes the status of a search for low energy "dark sector" particles produced in kaon decay which subsequently decay to e+e− in the ICARUS detector. If a new scalar boson mixes with the standard model Higgs with a small coupling, these particles could be produced in meson decays and decay to standard model particles. The ICARUS detector is exposed to abundant meson decays from the Neutrinos at the Main Injector (NuMI) Beam. The geometry of the detector and beam coupled with the kinematics of the two-body decay of a low mass scalar produce a unique signal with low background for scalars produced from kaon decay-at-rest (KDAR) in the NuMI absorber.   

GEANT4 Modeling of eV-scale Photon Backgrounds in STJ Sensors for the BeEST Experiment

The BeEST (Beryllium Electron Capture in Superconducting Tunnel Junctions) experiment searches for physics beyond the standard model (BSM) in the neutrino sector by utilizing the electron capture (EC) decay of ⁷Be. The rare isotopes are embedded in superconducting tunnel junction (STJ) quantum sensors such that the low-energy (< 0.1keV) radiation from EC decay is absorbed with unit efficiency – except for the neutrino and a 478 keV gamma ray that occurs in ~10% of decays. While the gamma ray does not interact in the thin STJ (~0.5um), it can interact and deposit energy in the silicon substrate that the STJ is deposited on. This is currently the dominant source of background in the BeEST experiment and is thus important to model and understand.  In this talk I will present preliminary work towards using specific low-energy physics packages within GEANT4 to model this background and compare the simulations with data collected from Lawrence Livermore National Laboratory.    

Signal Characterization for Phase-III of the BeEST Experiment using a Triggerless Digital DAQ

The BeEST experiment uses Superconducting Tunnel Junction (STJ) detectors to measure the daughter recoil energy following the EC decay of 7Be to search for heavy neutrino mass states. Past limit-setting results from the experiment used a list-mode ADC with a hardware trapezoidal filter to trigger the pulses from the STJ array. To improve our signal analysis capabilities, we have constructed a continuously sampling data acquisition system which allows for advanced offline characterization of events using pulse shape and timing information. This talk will demonstrate the advantages to the Phase-III BeEST experimental program enabled by continuous acquisition, and present performance metrics for the new system as well as the performance of the Phase-III BeEST detector array.   

Status of the BeEST Neutrino Experiment Phase-III

The Beryllium Electron-capture in Superconducting Tunnel junctions (BeEST) experiment searches for signatures of heavy neutrino mass eigenstates in the Be-7 electron capture (EC) decay by precisely measuring the nuclear recoil energy using superconducting quantum sensors. In the first release from the Phase-II data in 2021, BeEST has set a world-leading limit on the heavy neutrino mixing in the 100-850 keV mass range using a single detector pixel counting for a month. In 2022, its scaled-up version, the BeEST Phase-III, has initiated with a 36-pixel-array detector and an increased amount of the Be-7 implantation. In this talk, we present the status of the BeEST Phase-III experiment. We will describe the improved Be-7 implantation procedure which reduced the Li-7 contamination and minimized the systematics due to the Auger electron escape. Furthermore, we will describe reduction in systematics associated with the data fitting due to progress on understanding the spectral response. We will also illustrate the improved analysis scheme using the pulse shape discrimination method, enabled by the newly adapted continuous data acquisition system.

    

Aluminum STJ Development Towards Phase-IV of the BeEST Experiment

The Beryllium Electron capture in Superconducting Tunnel junction (BeEST) experiment is a search for sub-MeV neutrino mass states in the electron capture decay of ⁷Be.  Phase-IV of the experiment requires the use of new Al-based STJ arrays to improve our sensitivity by more than two orders of magnitude.  The Phase-IV STJ sensors are purpose designed and fabricated for the BeEST experiment and include several key features that allow for higher precision measurements of the decay spectrum.  In this talk, I will present the basic design changes and the motivation for using Al-based sensors, as well as show data collected from our prototype aluminum devices with a comparison to data from our previous tantalum-based arrays.

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