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Register a new userThe Nested_fit data analysis program
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Added by
Martino Trassinelli
Publication date
2019
fields
Physics
and research's language is
English
Authors
Martino Trassinelli
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We present here Nested_fit, a Bayesian data analysis code developed for investigations of atomic spectra and other physical data. It is based on the nested sampling algorithm with the implementation of an upgraded lawn mower robot method for finding new live points. For a given data set and a chosen model, the program provides the Bayesian evidence, for the comparison of different hypotheses/models, and the different parameter probability distributions. A large database of spectral profiles is already available (Gaussian, Lorentz, Voigt, Log-normal, etc.) and additional ones can easily added. It is written in Fortran, for an optimized parallel computation, and it is accompanied by a Python library for the results visualization.
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Measuring the size of permanent electric dipole moments (EDM) of a particle or system provides a powerful tool to test Beyond-the-Standard-Model physics. The diamagnetic $^{129}$Xe atom is one of the promising candidates for EDM experiments due to its obtainable high nuclear polarization and its long spin-coherence time in a homogeneous magnetic field. By measuring the spin precession frequencies of polarized $^{129}$Xe and $^{3}$He, a new upper limit on the $^{129}$Xe atomic EDM $d_mathrm{A}(^{129}mathrm{Xe})$ was reported in Phys. Rev. Lett. 123, 143003 (2019). This writeup proposes a new evaluation method based on global phase fitting (GPF) for analyzing the continuous phase development of the $^{3}$He-$^{129}$Xe comagnetometer signal. The Cramer-Rao Lower Bound on the $^{129}$Xe EDM for the GPF method is theoretically derived and shows the benefit of achieving high statistical sensitivity without bringing new systematic uncertainties. The robustness of the GPF method is verified with Monte-Carlo studies. By optimizing the analysis parameters and adding few more data that could not be analyzed with the former method, a result of [ { d_mathrm{A} (^{129}mathrm{Xe})=(1.1 pm 3.6_mathrm{(stat)} pm 2.0_mathrm{(syst)})times 10 ^{-28} e~mathrm{cm}}, ] is obtained and is used to derive the upper limit of $^{129}$Xe permanent EDM at 95% C.L. [ {|d_text{A}(^{129}text{Xe})| < 8.3 times 10^{-28}~e~mathrm{cm}}. ] This limit is a factor of 1.7 smaller as compared to the previous result.
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