Münster 2017 – scientific programme

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T: Fachverband Teilchenphysik

T 81: Neutrinophysik 7 (Doppelbetazerfall, sterile Neutrinos)

T 81.8: Talk

Wednesday, March 29, 2017, 18:40–18:55, VSH 118

Impacts of magnetic traps in the source section of KATRIN on a sterile neutrino search — •Felix Knapp for the KATRIN collaboration — Karlsruhe Institute of Technology (KIT)

The main goal of the Karlsruhe Tritium Neutrino Experiment is the determination of the effective electron neutrino mass by measuring the endpoint of the energy spectrum of tritium beta decay electrons. With the search for a sterile neutrino in the keV-mass regime, the physical reach of the experiment can be extended. A sterile keV-scale sterile neutrino would imprint itself as a kink-like distortion of the tritium beta decay spectrum. However, this signature is of a very small value and therefore a very precise understanding of systematic effects is necessary. One effect is the appearance of magnetic traps in the KATRIN source. The electrons start in the windowless gaseous tritium source at a magnetic field of 450 Gs. This field is however not completely homogeneous. Local field minima create magnetic traps for electrons starting with a large pitch angle. All trapped electrons will eventually escape via two mechanisms: 1) Due to the high gradient of the magnetic field in a trap the guidance of an electron along the field lines is not fully adiabatic, resulting in chaotic angle changes, allowing the electron to escape. 2) The electrons can scatter with tritium molecules. Hereby also their angle can be changed and the electron is able to escape. Escaped electrons, that reach the detector would distort the spectral shape and hence impact the sensitivity of a sterile neutrino search. This Talk gives an insight on this systematic effect and its impact on the sensitivity of KATRIN to a sterile neutrino in the keV-mass range.