Reactor Neutrino Experiments Compared to Superbeams

We present a detailed quantitative discussion of the measurement of the leptonic mixing angle $\sin^2 2 \theta_{13}$ with a future reactor neutrino oscillation experiment consisting of a near and far detector. We perform a thorough analysis of the impact of various systematical errors and compare the resulting physics potential to the one of planned first-generation superbeam experiments. Furthermore, we investigate the complementarity of both types of experiments. We find that, under realistic assumptions, a determination of $\sin^2 2 \theta_{13}$ down to $10^{-2}$ is possible with reactor experiments. They are thus highly competitive to first-generation superbeams and may be able to test $\sin^2 2 \theta_{13}$ on shorter timescales. In addition, we find that the combination of a KamLAND-size reactor experiment with one or two superbeams could substantially improve the ability to access the neutrino mass hierarchy or the leptonic CP phase.Comment: Typo in Eq. (9) corrected. 36 pages, 12 figure

Understanding CP phase-dependent measurements at neutrino superbeams in terms of bi-rate graphs

We discuss the impact of the true value of the CP phase on the mass hierarchy, CP violation, and CP precision measurements at neutrino superbeams and related experiments. We we use a complete statistical experiment simulation including spectral information, systematics, correlations, and degeneracies to produce the results. However, since it is very complicated to understand the results in terms of a complete experiment simulation, we show the corresponding bi-rate graphs as useful tools to investigate the CP phase-dependencies qualitatively. Unlike bi-probability graphs, which are based upon oscillation probabilities, bi-rate graphs use the total event rates of two measurements simultaneously as a function of the CP phase. Since they allow error bars for direct quantitative estimates, they can be used for a direct comparison with a complete statistical experiment simulation. We find that one can describe the CP phase dependencies of the mentioned measurements at neutrino superbeam setups, as well as one can understand the role of the $\mathrm{sgn} (\Delta m_{31}^2)$-degeneracy. As one of the most interesting results, we discuss the dependence of the CP precision measurement as a function of the CP phase itself, which leads to ``CP patterns''. It turns out that this dependence is rather strong, which means that one has to be careful when one is comparing the CP precisions of different experiments.Comment: Major revisions: Scope reduced and discussions simplified. Summary and conclusions unchanged. 14 pages, 4 figures. Final version to appear in PR

Neutrino Physics, Superbeams, and the Neutrino Factory

We summarize what has been learned about the neutrino mass spectrum and neutrino mixing, identify interesting open questions that can be answered by accelerator neutrino facilities of the future, and discuss the importance and physics of answering them.Comment: To appear in the Proceedings of the 4th International Workshop on Neutrino Factories (Nu Fact 02). LaTeX, 10 pages, 1 eps figur

Comparison of LMA and LOW Solar Solution Predictions in an SO(10) GUT Model

Within the framework of an SO(10) GUT model that can accommodate both the LMA and LOW solar neutrino mixing solutions by appropriate choice of the right-handed Majorana matrix elements, we present explicit predictions for the neutrino oscillation parameters \Delta m^2_{21}, \sin^2 2\theta_{12}, \sin^2 2\theta_{23}, \sin^2 2\theta_{13}, and \delta_{CP}. Given the observed near maximality of the atmospheric mixing, the model favors the LMA solution and predicts that \delta_{CP} is small. The suitability of Neutrino Superbeams and Neutrino Factories for precision tests of the two model versions is discussed.Comment: Title, abstract and emphasis changed, references adde

Lepton Flavor Violating Era of Neutrino Physics

The physics agenda for future long-baseline neutrino oscillation experiments is outlined and the prospects for accomplishing those goals at future neutrino facilities are considered. Neutrino factories can deliver better reach in the mixing and mass-squared parameters but conventional super-beams with large water or liquid argon detectors can probe regions of the parameter space that could prove to be interesting.Comment: 12 pages, Latex, uses sprocl.sty and epsf.sty. 5 postscript figures. Talk presented at Joint U.S./Japan Workshop On New Initiatives In Lepton Flavor Violation and Neutrino Oscillation With High Intense Muon and Neutrino Sources, Honolulu, Hawaii, October 200

Prospects of accelerator and reactor neutrino oscillation experiments for the coming ten years

We analyze the physics potential of long baseline neutrino oscillation experiments planned for the coming ten years, where the main focus is the sensitivity limit to the small mixing angle $\theta_{13}$. The discussed experiments include the conventional beam experiments MINOS, ICARUS, and OPERA, which are under construction, the planned superbeam experiments J-PARC to Super-Kamiokande and NuMI off-axis, as well as new reactor experiments with near and far detectors, represented by the Double-Chooz project. We perform a complete numerical simulation including systematics, correlations, and degeneracies on an equal footing for all experiments using the GLoBES software. After discussing the improvement of our knowledge on the atmospheric parameters $\theta_{23}$ and $\Delta m^2_{31}$ by these experiments, we investigate the potential to determine $\theta_{13}$ within the next ten years in detail. Furthermore, we show that under optimistic assumptions and for $\theta_{13}$ close to the current bound, even the next generation of experiments might provide some information on the Dirac CP phase and the type of the neutrino mass hierarchy.Comment: 38 pages, 13 figures, Eqs. (1) and (5) corrected, small corrections in Figs. 8, 9, and Tab. 4, discussion improved, ref. added, version to appear in PRD, high resolution figures are available at http://www.sns.ias.edu/~winter/figs0403068.htm

How astrophysical neutrino sources could be used for early measurements of neutrino mass hierarchy and leptonic CP phase

We discuss the possible impact of astrophysical neutrino flux measurements at neutrino telescopes on the neutrino oscillation program of reactor experiments and neutrino beams. We consider neutrino fluxes from neutron sources, muon damped sources, and pion sources, where we parameterize the input from these sources in terms of the flux ratio $R=\phi_\mu/(\phi_e+\phi_\tau)$ which can be extracted from the muon track to shower ratio in a neutrino telescope. While it is difficult to obtain any information from this ratio alone, we demonstrate that the dependence on the oscillation parameters is very complementary to the one of reactor experiments and neutrino beams. We find that for large values of $\sin^2 2 \theta_{13}$, a measurement of R with a precision of about 20% or better may not only improve the measurement of the leptonic CP phase, but also help the determination of the mass hierarchy. In some cases, early information on $\delta_{CP}$ may even be obtained from Double Chooz and an astrophysical flux alone without the help of superbeams. For small values of $\sin^2 2 \theta_{13}$, we find that using the information from an astrophysical neutrino flux could eliminate the octant degeneracy better than reactor experiments and beams alone. Finally, we demonstrate that implementing an additional observable based on the electromagnetic to hadronic shower ratio at a neutrino telescope (such as at higher energies) could be especially beneficial for pion beam sources.Comment: Minor changes and additions, final version to appear in PRD. 32 pages, 15 figure

Summary of Working Group 1: Theory Part

I will summarize theoretical issues in Working Group 1 at Nufact'01. Although there may not be complete agreement yet on the exact optimum baseline $L$ and the muon energy $E_\mu$ for measurements of the CP phase at a neutrino factory, all the works done so far indicate that the optimum set ($L$, $E_\mu$) tends to be smaller than (3000km, 50GeV) if the uncertainty of the matter effect is assumed to be larger than $\pm$5% or the background fraction is much larger than $10^{-5}$.Comment: 9 pages, uses elsart.cls. Summary talk of theoretical part of WG1 at 3rd International Workshop on Neutrino Factory based on Muon Storage Rings (NuFACT'01), Tsukuba, Japan, 24-30 May 2001 . 1 references added slight modification adde