Current Direct Neutrino Mass Experiments

Abstract

In this contribution we review the status and perspectives of direct neutrino mass experiments. These experiments investigate the kinematics of β-decays of specific isotopes ( 3 H, 187 Re, 163 Ho) to derive model-independent information on the averaged electron (anti-) neutrino mass, which is formed by the incoherent sum of the neutrino mass eigenstates contributing to the electron neutrino. We first review the kinematics of β-decay and the determination of the neutrino mass, before giving a brief overview of past neutrino mass measurements (SN1987a-ToF studies, Mainz and Troitsk experiments for 3 H, cryo-bolometers for 187 Re). We then describe the Karlsruhe Tritium Neutrino (KATRIN) experiment which is currently under construction at Karlsruhe Institute of Technology. The large-scale setup will use the MAC-E-Filter principle pioneered earlier to push the sensitivity down to a value of 200 meV (90% C.L.). KATRIN faces many technological challenges that have to be resolved with regard to source intensity and stability, as well as precision energy analysis and low background rate close to the kinematic endpoint of tritium β-decay at 18.6 keV. We then review new experimental approaches such as the MARE, ECHO and Project8 experiments, which offer the promise to perform an independent measurement of the neutrino mass in the sub-eV region. This variety of methods and the novel technologies developed in all present and future experiments demonstrate the great potential of direct neutrino mass experiments in providing vital information on the absolute mass scale of neutrinos.

Tritium calibration of the LUX dark matter experiment

“…For the December 2013 tritium dataset presented here, g 1 ,g 2 , and the extraction efficiency are measured to be 0.115 ± 0.005 phd/photon, 12.1 ± 0.9 phd/electron, and 50.9% ± 3.8%. The constraint was set by allowing g 1 and g 2 to float and fitting the data to a true tritium spectrum [10]. In the LUX Run 3 WIMP search, g 1 , g 2 , and the extraction efficiency are measured with mono-energetic source data and single electron events to be 0.117±0.003 phd/photon, 12.1 ± 0.8 phd/electron, and 49.1% ± 3.2% [3,16], consistent with the values adopted here.…”

“…It has a broad peak at 2.5 keV and a mean energy of 5.6 keV [8][9][10]. 64.2% of the decays occur between 1 and 8 keV, the energy range of interest for WIMP searches in LUX.…”

Beta Decay and the Cosmic Neutrino Background

“…Here we discuss the relic neutrino induced beta capture (1) and the beta decay of tritium 3 H → 3 He + e − +ν e ; Q = 18.562 keV (19) with the focus on the KATRIN experiment [15] which we believe has the detection potential to set an upper limit for the relic electron neutrino density in our neighborhood. The electron spectrum of the reactions (1) and (19) for tritium has for infinite good energy resolution the form:…”

“…[15]). The energy resolution of a KATRIN type spectrometer is determined by the perpendicular energy of the decay electrons in the spectrometer in the cyclotron motion E f ⊥ .…”

“…4 we present a formalism for analysis of both the relic neutrino capture reaction (1) and tritium beta decay. Then we discuss prospects of searches for the reaction (1) with the KATRIN experiment [15].…”