Measurement of the double beta decay half-life of Nd-150 and search for neutrinoless decay modes with the NEMO-3 detector

Source: arXiv


The half-life for two-neutrino double beta decay of Nd-150 has been measured with data taken by the NEMO 3 experiment at the Modane Underground Laboratory. The limits are also set on the half-life of different neutrinoless double beta decay of this isotope. Comment: PhD thesis, the University of Manchester

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Available from: Nasim Fatemighomi, Apr 22, 2015
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    • "±10% external background precision ±0.3 [12] ±10% 150 Nd precision ±0.7 [11] "
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    • "At the moment, the most promising attempts to find lepton number violation are the experiments searching for neutrinoless double beta decay (0νββ). Several such experiments have been performed (IGEX [4], Heidelberg-Moscow [5], CUORICINO [6], NEMO [7], and others), so far without unambiguous detection. New second generation experiments like GERDA [8], which has been built and is being readied for data taking, will soon improve the sensitivity and may observe 0νββ. "
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    ABSTRACT: We evaluate the Schechter-Valle (Black Box) theorem quantitatively by considering the most general Lorentz invariant Lagrangian consisting of point-like operators for neutrinoless double beta decay. It is well known that the Black Box operators induce Majorana neutrino masses at four-loop level. This warrants the statement that an observation of neutrinoless double beta decay guarantees the Majorana nature of neutrinos. We calculate these radiatively generated masses and find that they are many orders of magnitude smaller than the observed neutrino masses and splittings. Thus, some lepton number violating New Physics (which may at tree-level not be related to neutrino masses) may induce Black Box operators which can explain an observed rate of neutrinoless double beta decay. Although these operators guarantee finite Majorana neutrino masses, the smallness of the Black Box contributions implies that other neutrino mass terms (Dirac or Majorana) must exist. If neutrino masses have a significant Majorana contribution then this will become the dominant part of the Black Box operator. However, neutrinos might also be predominantly Dirac particles, while other lepton number violating New Physics dominates neutrinoless double beta decay. Translating an observed rate of neutrinoless double beta decay into neutrino masses would then be completely misleading. Although the principal statement of the Schechter-Valle theorem remains valid, we conclude that the Black Box diagram itself generates radiatively only mass terms which are many orders of magnitude too small to explain neutrino masses. Therefore, other operators must give the leading contributions to neutrino masses, which could be of Dirac or Majorana nature.
    Journal of High Energy Physics 05/2011; 2011(6). DOI:10.1007/JHEP06(2011)091 · 6.11 Impact Factor
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    ABSTRACT: T2K, the long baseline neutrino experiment from J-PARC in Tokai to Kamioka (Japan), aims to precisely measure the last unknown neutrino mixing angle, θ13, by the observation of νμ → νe appearance. The goal is also to refine the measurements of {$\{\delta m^2_{23},\theta_{23}\}$ by studying νμ disappearance. Last year T2K published results claiming a strong indication of a nonzero value of $\theta_{13}$. Although not statistically significant enough to claim a discovery, they constitute the first evidence of $\theta_{13}\neq0$. It is also the first experiment to observe νe appearance. In T2K, the neutrino beam is generated by the J-PARC high intensity 30 GeV (kinetic energy) proton beam interacting in a 90 cm long graphite target to produce π and K mesons, which decay into neutrinos. The resulting neutrino beam is aimed towards a near detector complex, 280 m from the target, and to the Super-Kamiokande (SK) far detector located 295 km away at 2.5 degrees off-axis from the π and K beam. Neutrino oscillations are probed by comparing the neutrino event rates measured in SK to the predictions of a Monte-Carlo simulation based on flux calculations and near detector event rates. The flux calculations are generally based on hadron production models tuned to sparse available data, resulting in systematic uncertanties which are large and difficult to evaluate. In order to provide more precise and reliable estimates, direct measurements with the NA61/SHINE (SHINE ≡ SPS Heavy Ion and Neutrino Experiment) spectrometer at the CERN-SPS were conducted. We collected the first reference set of protoncarbon interactions, with the beam set at the T2K proton beam energy (30 GeV), in the fall of 2007. We published first results of charged pion cross-sections in early 2011 and positively charged kaon cross-sections in January 2012. As we shall see, the results have been of considerable benefit for T2K. The first chapter of this thesis provides a general introduction to neutrino oscillation and summarizes the status of the main ongoing experiments in the field. T2K is then described in more details, with emphasis on its needs for reference hadron production data. The NA61/SHINE detector is presented in Chapter 3 along with a summary of the tracking and detector simulation. The Chapter after that, covers the construction, calibration and achieved performances of the ToF-F detector. I then give a detailed description of the analysis that lead to the first charged pion and K+ cross-section measurements in proton-carbon interactions at 31 GeV/c. Charged pions generate most of the low energy neutrinos and positively charged kaons generate the high energy tail of the T2K neutrino beam. The latter also contribute substantially to the intrinsic νe background of the T2K beam. As will be demonstrated, the pion results have significantly contributed to reduce the systematic uncertainties of the first T2K νe appearance results. The K+ measurements are also widely expected to benefit the forthcoming results. Knowledge of proton production is also important since protons contribute to the neutrino flux through target re-interactions. The proton spectra obtained with the same tof-dE/dx method are given as an appendix.
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