As we enter the age of precision measurement in neutrino physics, improved flux sources are required. These must have a well defined flavor content with energies in ranges where backgrounds are low and cross-section knowledge is high. Very few sources of neutrinos can meet these requirements. However, pion/muon and isotope decay-at-rest sources qualify. The ideal drivers for decay-at-rest sources are cyclotron accelerators, which are compact and relatively inexpensive. This paper describes a scheme to produce decay-at-rest sources driven by such cyclotrons, developed within the DAE ALUS program. Examples of the value of the high precision beams for pursuing Beyond Standard Model interactions are reviewed. New results on a combined DAE ALUS—Hyper-K search for CP violation that achieve errors on the mixing matrix parameter of 4° to 12° are presented. 1. Introduction As we reach the 100th anniversary of the birth of Bruno Pontecorvo, neutrino physics is facing a transition. Neutrino oscillations are well established, albeit in a different form from what Pontecorvo expected [1, 2]. We have a data-driven “Neutrino Standard Model,” ( SM) which, despite questions about its underlying theoretical description, is remarkably predictive. Now, the neutrino community must pivot from “searches” to “precision measurements,” in which we can test the SM. The transition requires new and better tools for these measurements and further calls for original approaches to experiments. The SM is simply described in Figure 1. The three known neutrino flavors mix within three mass states. The separations between the states, or “mass splittings,” are defined as , for The historical name for the smaller splitting ( ) is and the larger mass splitting ( is referred to as , in honor of the solar and atmospheric experiments that established the existence of each. The early solar [3–6] and atmospheric [7–9] experiments have been joined by new results [10–15] to establish this phenomenology . Figure 1: Illustration of the “ SM” showing mass states and mixings. Note that this drawing depicts only one possible mass ordering. There remain many open questions that surround this data-driven picture of neutrinos and oscillations. The mixings are described with a matrix, commonly called the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) matrix, that connects the mass eigenstates ( , , and ) to the flavor eigenstates ( , , and ): where the ranges indicate our knowledge of each of the entries . Together with the mass splittings, the mixing matrix is pictorially represented in Figure 1, in which
Q. Ahmad, R. C. Allen, T. C. Anderson, et al., “Measurement of the rate of -interactions produced by 8B solar neutrinos at the sudbury neutrino observatory,” Physical Review Letters, vol. 87, no. 7, Article ID 071301, 6 pages, 2001.
D. Michael, P. Adamson, and T. Alexopoulos, “Observation of Muon neutrino disappearance with the MINOS detectors in the NuMI neutrino beam,” Physical Review Letters, vol. 97, no. 19, Article ID 191801, 6 pages, 2006.
A. Anderson, J. M. Conrad, E. Figueroa-Feliciano, et al., “Measuring active-to-sterile neutrino oscillations with neutral current coherent neutrino-nucleus scattering,” Physical Review D, vol. 86, no. 1, Article ID 013004, 11 pages, 2012.
A. Bungau, A. Adelmann, and J. R. Alonso, “Proposal for an electron antineutrino disappearance search using high-rate 8Li production and decay,” Physical Review Letters, vol. 109, no. 14, Article ID 141802, 5 pages, 2012.
J. Ahn, S. Chebotaryov, J. H. Choi, et al., “Observation of reactor electron antineutrinos disappearance in the RENO experiment,” Physical Review Letters, vol. 108, no. 19, Article ID 191802, 6 pages, 2012.
K. Abe, N. Abgrall, Y. Ajima, et al., “Indication of electron neutrino appearance from an accelerator-produced off-axis Muon neutrino beam,” Physical Review Letters, vol. 107, no. 4, Article ID 041801, 8 pages, 2011.
G. Fogli, E. Lisi, A. Marrone, D. Montanino, A. Palazzo, and A. Rotunno, “Global analysis of neutrino masses, mixings, and phases: entering the era of leptonic CP violation searches,” Physical Review D, vol. 86, no. 1, Article ID 013012, 10 pages, 2012.
J. Conrad, C. Ignarra, G. Karagiorgi, M. Shaevitz, and J. Spitz, “Sterile neutrino fits to short-baseline neutrino oscillation measurements,” Advances in High Energy Physics, vol. 2013, Article ID 163897, 26 pages, 2013.
R. L. Burman, M. E. Potter, and E. S. Smith, “Monte Carlo simulation of neutrino production by medium-energy protons in a beam stop,” Nuclear Instruments and Methods in Physics A, vol. 291, no. 3, pp. 621–633, 1990.
C. Athanassopoulos, L. B. Auerbach, R. L. Burman et al., “Evidence for oscillations from the LSND experiment at the los alamos meson physics facility,” Physical Review Letters, vol. 77, no. 15, pp. 3082–3085, 1996.
A. Adelmann, A. Gsell, C. Kraus, et al., “The OPAL framework (object oriented parallel accelerator library) version 1.2.01,” User’s Reference Manual PSI-PR-08-02, Paul Scherrer Institut, Villigen, Switzerland, 2008–2013, http://amas.web.psi.ch/docs/opal/opal_user_guide.pdf.
J. J. Yang, A. Adelmann, M. Humbel, M. Seidel, and T. J. Zhang, “Beam dynamics in high intensity cyclotrons including neighboring bunch effects: model, implementation, and application,” Physical Review Special Topics, vol. 13, no. 6, Article ID 064201, 2010.
I. E. Stockdale, A. Bodek, F. Borcherding et al., “Search for muon neutrino and antineutrino oscillations in the mass range 15<Δm2<1,000 eV2/c4,” Zeitschrift für Physik C Particles and Fields, vol. 27, no. 1, pp. 53–56, 1985.
M. Sorel, J. M. Conrad, and M. H. Shaevitz, “Combined analysis of short-baseline neutrino experiments in the (3 + 1) and (3 + 2) sterile neutrino oscillation hypotheses,” Physical Review D, vol. 70, no. 7, pp. 1–73004, 2004.
A. Gando, Y. Gando, K. Ichimura, et al., “Constraints on θ13 from a three-flavor oscillation analysis of reactor antineutrinos at KamLAND,” Physical Review D, vol. 83, no. 5, Article ID 052002, 11 pages, 2011.
A. Gomonaǐ and I. Zapesochnyǐ, “Resonance excitation of bound and autoionization states of the ytterbium atom in the course of three-photon ionization,” JETP Letters, vol. 57, no. 12, pp. 765–768, 1993.