Measurements with a TRISTAN prototype detector system at the “Troitsk nu-mass” experiment in integral and differential mode

Abstract

A: Sterile neutrinos emerge in minimal extensions of the Standard Model which can solve a number of open questions in astroparticle physics. For example, sterile neutrinos in the keV-mass range are viable dark matter candidates. Their existence would lead to a kink-like distortion in the tritium β-decay spectrum. In this work we report about the instrumentation of the Troitsk nu-mass experiment with a 7-pixel TRISTAN prototype detector and measurements in both differential and integral mode. The combination of the two modes is a key requirement for a precise sterile neutrino search, as both methods are prone to largely different systematic uncertainties. Thanks to the excellent performance of the TRISTAN detector at high rates, a sterile neutrino search up to masses of about 6 keV could be performed, which enlarges the previous accessible mass range by a factor of 3. Upper limits on the neutrino mixing amplitude in the mass range < 5.6 keV (differential) and < 6.6 keV (integral) are presented. These results demonstrate the feasibility of a sterile neutrino search as planned in the upgrade of the KATRIN experiment with the final TRISTAN detector and read-out system.

Direct Measurements of Neutrino Mass

“…take advantage of the available tritium source strength, a new, highly segmented, high-resolution focal-plane detector for KATRIN is being developed [209][210][211] by the TRISTAN collaboration.…”

Calibration of Troitsk nu-mass detector readout electronics by signal digital filters

“…It is appropriate to mention that the detector energy resolution σ=0.11 keV is worse the best value for SDD detector of FWHM = 150 eV (or σ about 0.062 keV) as published in [7] . However, that value was obtained at SDD -20C temperature , and we also know from our experience [5] that this detector has a larger leakage current compared to a similar detectors we used before.…”

“…It is an 8-channel CUBE Bias Board, XGL-CBB-8CH. Similar detectors were already tested at the "Troitsk nu-mass" spectrometer in 2017-2019 [5] and demonstrated excellent energy resolution, less than 200 eV at full width at half maximum (FWHM). Continues signal digitization is provided by a 16-channel TQDC module in the VME case designed in the Joint Institute for Nuclear Research, JINR, Dubna, for the NICA project [6].…”

Prospects for finding sterile neutrino dark matter at KATRIN

“…After the option to modify KATRIN in order to probe keV-scale neutrinos was proposed in Ref. [80], first preliminary measurements have already been made [28]. We will use here the parameters from Ref.…”

“…Tritium beta decay experiments are currently in the "renaissance" era as the KATRIN experiment [23,24] is fully operative and has recently overriden the Mainz [25] and Troitsk [26] measurements, improving the upper limit on neutrino mass by roughly a factor of two [27]. In its next stage, KATRIN will be equipped with a novel detector system, TRISTAN [28], which will further improve the sensitivity on keV-scale sterile neutrinos by looking at the entire spectrum of the emitted electrons: in this condition, if a keV sterile neutrino with a mass m s < 18.6 keV is produced, the corresponding signal will be a kink in the spectrum at an energy equal to the value of m s . We wish to mention another tritium beta decay experiment, MATRIX [29], which is currently in a very early stage.…”