Browsing by Author "Blennow, Mattias"
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- Quantifying the sensitivity of oscillation experiments to the neutrino mass orderingBlennow, Mattias; Coloma, Pilar; Huber, Patrick; Schwetz, Thomas (Springer, 2014-03-05)Determining the type of the neutrino mass ordering ( normal versus inverted) is one of the most important open questions in neutrino physics. In this paper we clarify the statistical interpretation of sensitivity calculations for this measurement. We employ standard frequentist methods of hypothesis testing in order to precisely define terms like the median sensitivity of an experiment. We consider a test statistic T which in a certain limit will be normal distributed. We show that the median sensitivity in this limit is very close to standard sensitivities based on Delta chi(2) values from a data set without statistical fluctuations, such as widely used in the literature. Furthermore, we perform an explicit Monte Carlo simulation of the INO, JUNO, LBNE, NO nu A, and PINGU experiments in order to verify the validity of the Gaussian limit, and provide a comparison of the expected sensitivities for those experiments.
- Reassessing the sensitivity to leptonic CP violationBlennow, Mattias; Coloma, Pilar; Fernandez-Martinez, Enrique (Springer, 2015-03-02)We address the validity of the usual procedure to determine the sensitivity of neutrino oscillation experiments to CP violation. An explicit calibration of the test statistic is performed through Monte Carlo simulations for several experimental setups. We find that significant deviations from a chi(2) distribution with one degree of freedom occur for experimental setups with low sensitivity to ffi. In particular, when the allowed region to which ffi is constrained at a given confidence level is comparable to the whole allowed range, the cyclic nature of the variable manifests and the premises of Wilk's theorem are violated. This leads to values of the test statistic significantly lower than a chi(2) distribution at that confidence level. On the other hand, for facilities which can place better constraints on ffi the cyclic nature of the variable is hidden and, as the potential of the facility improves, the values of the test statistics first become slightly higher than and then approach asymptotically a chi(2) distribution. The role of sign degeneracies is also discussed.
- Searching for sterile neutrinos at the ESSνSBBlennow, Mattias; Coloma, Pilar; Fernandez-Martinez, Enrique (Springer, 2014-12-17)The ESS nu SB project is a proposed neutrino oscillation experiment based on the European Spallation Source with the search for leptonic CP violation as its main aim. In this letter we show that a near detector at around 1 km distance from the beamline is not only very desirable for keeping the systematic errors affecting the CP search under control, but would also provide a significant sensitivity probe for sterile neutrino oscillations in the region of the parameter space favored by the long-standing LSND anomaly. We find that the effective mixing angle theta(mu e) can be probed down to sin(2)(2 theta(mu e)) similar or equal to 2(8) . 10(-3) at 5 sigma assuming 15% bin-to-bin (un) correlated systematics.