2006-2011
Ph.D. ThesisFree neutron decay, n→peν, is the simplest nuclear beta decay, well described as a purely left-handed, vector minus axial-vector interaction within the framework of the Standard Model (SM) of elementary particles and fields. Due to its highly precise theoretical description, neutron beta decay data can be used to test certain extensions to the SM [Kon11a]. Possible extensions require, e.g., new symmetry concepts like left-right symmetry, new particles, leptoquarks, supersymmetry, or the like. Precision measurements of observables in neutron beta decay address important open questions of particle physics and cosmology, and are generally complementary to direct searches for new physics beyond the SM in high-energy physics.
In my doctoral thesis [Kon11b], a measurement of the proton recoil spectrum with the neutron decay spectrometer aSPECT [Zim00, Glu05] is described. From the proton spectrum the antineutrino-electron angular correlation coefficient a can be derived. In our first beam time at the Forschungs-Neutronenquelle Heinz Maier-Leibnitz in Munich, Germany (2005-2006), background instabilities due to particle trapping and the electronic noise level of the proton detector prevented us from presenting a new value for a [Bae08] In the following beam time at the Institut Laue-Langevin (ILL) in Grenoble, France (2007-2008), the trapped particle background has been reduced sufficiently and the electronic noise problem has essentially been solved [Kon09, Sim09, Bor10]. For the first time, a silicon drift detector was used [Sim07]. As a result of the data analysis, we identified and fixed a problem in the detector electronics which caused a significant systematic error [Sim10]. The target figure of this beam time was a new value for a with a total relative error well below the present literature value of 4%. A statistical accuracy of about 1.4% was reached, but we could only set upper limits on the correction of the problem in the detector electronics, which are too high to determine a meaningful result. My doctoral thesis focused on the investigation of several different systematic effects. With the knowledge of the systematic effects gained in this thesis, we have been able to improve the aSPECT spectrometer to perform a 1% measurement of a in a further beam time at the ILL [Wun14, Mai15, Bec20]. References
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Ph.D. Degree
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© Copyright Gertrud Konrad. July 6, 2021