since 2005
Precision Experiments with Cold Neutrons
The Standard Model of elementary particles and fields is a theory that describes all interactions of subatomic particles, except those due to gravity. Although the Standard Model explains a wide variety of experimental results, it falls short of being a complete theory of fundamental interactions. Extensions of the Standard Model are needed to explain its deficiencies, such as the origin of mass, neutrino oscillations, and the nature of dark matter and dark energy.
My research focuses on precision experiments with cold neutrons. Precision measurements of the parameters describing the beta decay of free neutrons address important questions in nuclear and particle physics, astrophysics, and cosmology [Abe08, Dub11, Sev11]. My main emphasis is on the search for evidence of possible extensions of the Standard Model and on searches for new symmetry concepts [Kon11a]. In high energy physics with colliders, one directly searches for new particles, complementary to low energy physics with neutrons, where we indirectly probe their existence. Together with scientists and engineers from the Universities of Heidelberg and Mainz, the TU München (all Germany), the Institut Laue-Langevin (ILL) in Grenoble (France), and the TU Wien (Austria), we propose to perform next generation high-precision measurements with the new instrument PERC (short for Proton and Electron Radiation Channel) [Dub08]. In the search for new symmetries, measurements of correlation coefficients, inter alia a, A, B, C, and the Fierz interference term b, are of uttermost importance: unitarity of the CKM matrix, left-right symmetry, leptoquarks, supersymmetry, etc. With the new facility PERC, several symmetry tests based on neutron beta decay data become competitive [Kon11a, Kon11b]. PERC is under development by an international collaboration [Kon12]. It will be set up at the new position of the beam facility MEPHISTO of the Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II) in Garching (Germany). The first milestone, the design of the superconducting magnet system [Wan12] together with its magnetic shielding [Hai13], has been achieved. At its exit, PERC delivers neutron decay products under well-defined and precisely variable conditions. Depending on the parameters studied, the analysis of the extracted decay particles is performed with different and specialized detectors. The Vienna group focuses on the development of novel detection systems for electron energy spectroscopy, electron and proton momentum spectroscopy, and proton spectroscopy. Our goal is spectroscopy in which the spectra and angular distributions of the emerging particles are distortion- and background-free on the level of 1E-4. For the measurement of the Fierz term b, e.g., we propose a novel detection system for electron and proton momentum spectroscopy based on the R×B drift effect. In the R×B spectrometer, the charged decay particles are dispersed in a uniformly curved magnetic field, and then measured with large phase space acceptance and high resolution [Wan13]. The Fierz term is measurable in decays of unpolarized neutrons, as a distortion of the beta spectrum. A non-zero value for b would be an indication of the existence of scalar or tensor interactions. Scalar or tensor couplings in turn would occur if yet unknown charged Higgs bosons or leptoquarks were exchanged instead of a W boson [Her01]. The R×B spectrometer will be built within the scope of the NoMoS (short for Neutron decay prOducts MOmentum Spectrometer) project [Kon15]. Recently, the Presiding Committee of the Austrian Academy of Sciences (ÖAW) selected my project 'NoMoS: Beyond the Standard Model Physics in Neutron Decay' for funding through the ‘New Frontiers Groups Programme’. My junior research group is hosted at the Stefan-Meyer-Institut in Vienna. Until PERC and NoMoS are built and installed at the new position of MEPHISTO at FRM II, we perform precision measurements of neutron decay observables with the existing aSPECT [Glu05] and PERKEO III [Mae09, Mes11] experiments at ILL. Such measurements require the almost complete suppression or the perfect knowledge of all systematic effects. We experienced that residual gas and particle trapping are a severe problem in the analysis of decay protons [Bae08], but developed solutions to overcome this problem [Kon09, Sim09]. From another proton measurements with aSPECT [Wun14,Mai15] and PERKEO III, we can gather further knowledge. For instruments that profit from specific properties of a long-pulse spallation source (such as PERC), we are looking forward to the fundamental physics programme of the European Spallation Source (ESS) in Lund (Sweden); see also [Kli15]. |
My main research
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References
[Abe08]
[Bae08] [Dub11] [Dub08] [Glu05] [Hai13] [Her01] [Kli15] [Kon15] [Kon12] [Kon11a] [Kon11b] [Kon09] [Mae09] [Mai15] [Mes11] [Sev11] [Sim09] [Wan13] [Wan12] [Wun14] |
H. Abele, Prog. Part. Nucl. Phys. 60 (2008), 1.
S. Baeßler et al., Eur. Phys. J. A 38 (2008), 17. D. Dubbers and M.G. Schmidt, Rev. Mod. Phys. 83 (2011), 11111171. D. Dubbers et al., Nucl. Instrum. Meth. 596 (2008), 238; see also: arXiv:0709.4440 (2007). F. Glück et al., Eur. Phys. J. A 23, 1 (2005), 135. P. Haiden, Master thesis, Atominstitut, TU Wien, 2013 P. Herczeg, Prog. Part. Nucl. Phys. 46 (2001), 413. E. Klinkby [N-Nbar Collaboration] and T. Soldner [ANNI Collaboration], in: Proc. of ECNS 2015, submitted. G. Konrad, PoS(EPS-HEP2015)592. G. Konrad et al. [PERC Collaboration], J. Phys.: Conf. Ser. 340 (2012), 012048. G. Konrad, W. Heil, S. Baeßler, D. Pocanic, F. Glück, World Sci. ISBN 9789814340854, 660, 2011; arXiv:1007.3027 (2010). G. E. Konrad, Ph.D. thesis, Johannes Gutenberg-Universität Mainz, Germany, 2011. G. Konrad et al., Nucl. Phys. A 827 (2009), 529c. B. Märkisch et al., Nucl. Instrum. Meth. A 611 (2009), 216. R. Maisonobe et al., PoS(EPS-HEP2015)595. H. Mest, Ph.D. thesis, Ruperto Carola Universität Heidelberg, Germany, 2011. N. Severijns and O. Naviliat-Cuncic, Annu. Rev. Nucl. Part. Sci. 61 (2011), 23. M. Simson et al., Nucl. Instrum. Meth. A 611 (2009), 203. X. Wang, G. Konrad, H. Abele, Nucl. Instrum. Meth. 701 (2013), 254; arXiv:1209.6595 (2012). X. Wang, Ph.D. thesis, Technische Universität München, Germany, 2012. A. Wunderle et al., DOI:10.3204/DESY-PROC-2014-04/72. |
© Copyright Gertrud Konrad. March 3, 2020