Mainz 2012 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 56: Astroteilchenphysik

HK 56.2: Talk

Friday, March 23, 2012, 11:30–11:45, RW 3

The KATRIN statistical sensitivity with various background conditions — •Ferenc Glück, Markus Hötzel, Wolfgang Käfer, and Susanne Mertens — Karlsruhe Institute of Technology, IEKP and IK

The aim of the KATRIN experiment is to determine the absolute neutrino mass scale in a model independent way, by measuring the electron energy spectrum shape near the endpoint of tritium beta decay. An ultra-low background level of 10 mHz is necessary to reach the design sensitivity of 200 meV. The 90 % CL statistical neutrino mass upper limit depends not only on the absolute background rate but also on the background characteristics. Large fluctuations of the background over time decrease the neutrino mass sensitivity.

Magnetically stored high energy electrons, arising from single radioactive decays of radon and tritium in the KATRIN main spectrometer, lead to enhanced background rates for several hours. A stored electron cooles down via ionization of residual gas, producing several hundreds of secondary electrons which can reach the detector. This mechanism causes a background with non-Poissonian fluctuations. With this background, the statistical sensitivity depends on the detailed measurement model (length and order of the measurement intervals), and also on detailed time dependent properties of the background events. For example, the statistical sensitivity is better with smaller measurement interval lengths, with randomized (instead of ordered) measurement intervals, and with smaller residual gas pressure.

We acknowledge support by the BMBF of Nr. 05A11VK3.