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Posters at NeuTel – part A: 1 – KATRIN; 2 – Probing the leptonic Dirac CP-violating phase

March 14, 2013

The poster session of the conference received contributions from many participants. Here and in a few following posts are offered quick summaries on the information provided in the posters. I thank the submitters for the help!

1 – Sebastian Fischer: Status of the windowless gaseous tritium source of KATRIN

The aim of the Karlsruhe Tritium Neutrino experiment (KATRIN) is the model- independent measurement of the neutrino mass by the investigation of the endpoint region of the tritium beta spectrum. For that purpose a windowless gaseous tritium source (WGTS) generates ∼10^11 beta electrons per second. The beta electrons are adiabatically guided to an electrostatic spectrometer which subsequently measures the integrated beta spectrum by varying the spectrometer voltage. In order to reach the design sensitivity of 200 meV/c2 (90% C.L.) on the neutrino mass, the key parameters of the WGTS, e.g. column density, beta activity, and gas purity, have to be stabilized to the 0.1% level and accordingly monitored. This is essential because of the scanning nature of the KATRIN measurement principle and needed to control systematic effects. Dedicated instrumentation has been developed for this task. Many of the systems have passed the design and prototype stage and were extensively tested or are already in operation. The presented poster gives an overview of the WGTS and the status of the individual instrumentation systems.

2 – Tommy Ohlsson: Probing the leptonic Dirac CP-violating phase in neutrino oscillation experiments

The discovery of leptonic CP violation is one of the primary goals of next-generation neutrino oscillation experiments, which is feasible due to the recent measurement of a relatively large smallest leptonic mixing angle. We suggest two new working observables to describe the CP-violating effects in long-baseline and atmospheric neutrino oscillation experiments. One of them signifies the experimental sensitivity to the leptonic Dirac CP-violating phase and can be used to optimize the experimental setup, while the other one measures the intrinsic leptonic CP violation and can be used to extract the phase directly from the experimental observations. Both analytical and numerical analyses are carried out to illustrate their main features. It turns out that an intense neutrino beam with sub-GeV energies and a baseline of a few 100 km may serve as an optimal experimental setup for probing leptonic CP violation.

In the figure shown below, some of the optimal experimental setups to probe the CP phase are presented. The ongoing long-baseline experiments T2K and NOvA together with the proposed ones LBNE and LAGUNA-LBNO are considered for illustration. Except for T2K, all experiments are intended to equally operate both in the neutrino and antineutrino channels. Therefore, one can construct a CP asymmetry by measuring the neutrino and antineutrino probabilities. In the presented plot, we observe that these experimental setups are lying on the “first band” (i.e., CP asymmetry ~ 10%). To improve the experimental sensitivity, one can lower the neutrino beam energy and locate an experiment on the “second band” (i.e., CP asymmetry ~ 15%). Indeed, the ESS proposal is situated on the second band.


The neutrino oscillograms for other channels, neutrinos/antineutrinos, and different neutrino mass hierarchies can be found at:

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