- Email: [email protected]
β+ decaying ion beams
Available online at www.sciencedirect.com
Nuclear Physics B (Proc. Suppl.) 229–232 (2012) 509 www.elsevier.com/locate/npbps
CP-Violation in Neutrino Oscillations from EC/β+ decaying ion beams Catalina Espinoza Centre for Theoretical Particle Physics, IST, Technical University of Lisbon, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal
Abstract We discuss the separation of unknown neutrino properties by means of the energy dependence of the oscillation probability and we consider an hybrid setup which combines the electron capture and the β+ decay from the same radioactive proton-rich ion with the same boost. We conclude that the combination of the two decay channels, with different neutrino energies, achieves remarkable results. Keywords: Neutrino oscillation, CP violation, Monochromatic beams
[1] J. Bernabeu, C. Espinoza, C. Orme, S. Palomares-Ruiz, S. Pascoli, JHEP 06 (2009) 040. arXiv:0902.4903.
0920-5632/$ – see front matter © 2012 Published by Elsevier B.V. doi:10.1016/j.nuclphysbps.2012.09.146
150 100
δCP [degrees]
50 0 -50 -100 -150 -5
10
-4
10
-3
10
-2
10
10
-1
2
Sin (2θ13)
Figure 1: CP-violation discovery potential at 99% CL (BB only: blue dotted lines, EC+BB: red solid lines), both without (thin lines) and with (thick lines) taking the hierarchy degeneracy into account.
1
0.8
fraction of delta
We have considered the use of a neutrino beam sourced from boosted 156 Yb ions directed to a single baseline. Ytterbium shares its weak decay between the two channels of electron capture and β+ . Taking into account the energy gap between the neutrino energies in these two channels, for the same boost of the parent ion, we have at our disposal the presence of well separated neutrino energies in a single experiment with a unique boost [1]. In the analysis we compare the results for the maximum boosts available from the current SPS, γ = 166, and an upgraded SPS, γ = 369, for two different baselines, 130 km versus 650 km in the low γ case, 650 km versus 1050 km in the high γ case. The detector choice is a 0.5 Mton WC. The conclusion from these comparative studies is that the setup of higher γ, a baseline L = 650 km and a WC detector is particularly attractive for the CPviolation discovery potential. The determination of the neutrino mass hierarchy is better obtained, however, for the longer baseline, as expected. The general conclusion is that the principle of energy dependence works for CP-violation studies, and there is no need of performing separate experiments, with different systematics and counting rates, for neutrinos and antineutrinos.
0.6
0.4
0.2
0 -5 10
-4
10
-3
10 Sin2(2θ13)
-2
10
10
-1
Figure 2: Fraction of δ for which the neutrino mass hierarchy can be determined at 99% CL (BB: blue dotted lines, EC+BB: red solid lines).
Nuclear Physics B (Proc. Suppl.) 229–232 (2012) 509 www.elsevier.com/locate/npbps
CP-Violation in Neutrino Oscillations from EC/β+ decaying ion beams Catalina Espinoza Centre for Theoretical Particle Physics, IST, Technical University of Lisbon, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal
Abstract We discuss the separation of unknown neutrino properties by means of the energy dependence of the oscillation probability and we consider an hybrid setup which combines the electron capture and the β+ decay from the same radioactive proton-rich ion with the same boost. We conclude that the combination of the two decay channels, with different neutrino energies, achieves remarkable results. Keywords: Neutrino oscillation, CP violation, Monochromatic beams
[1] J. Bernabeu, C. Espinoza, C. Orme, S. Palomares-Ruiz, S. Pascoli, JHEP 06 (2009) 040. arXiv:0902.4903.
0920-5632/$ – see front matter © 2012 Published by Elsevier B.V. doi:10.1016/j.nuclphysbps.2012.09.146
150 100
δCP [degrees]
50 0 -50 -100 -150 -5
10
-4
10
-3
10
-2
10
10
-1
2
Sin (2θ13)
Figure 1: CP-violation discovery potential at 99% CL (BB only: blue dotted lines, EC+BB: red solid lines), both without (thin lines) and with (thick lines) taking the hierarchy degeneracy into account.
1
0.8
fraction of delta
We have considered the use of a neutrino beam sourced from boosted 156 Yb ions directed to a single baseline. Ytterbium shares its weak decay between the two channels of electron capture and β+ . Taking into account the energy gap between the neutrino energies in these two channels, for the same boost of the parent ion, we have at our disposal the presence of well separated neutrino energies in a single experiment with a unique boost [1]. In the analysis we compare the results for the maximum boosts available from the current SPS, γ = 166, and an upgraded SPS, γ = 369, for two different baselines, 130 km versus 650 km in the low γ case, 650 km versus 1050 km in the high γ case. The detector choice is a 0.5 Mton WC. The conclusion from these comparative studies is that the setup of higher γ, a baseline L = 650 km and a WC detector is particularly attractive for the CPviolation discovery potential. The determination of the neutrino mass hierarchy is better obtained, however, for the longer baseline, as expected. The general conclusion is that the principle of energy dependence works for CP-violation studies, and there is no need of performing separate experiments, with different systematics and counting rates, for neutrinos and antineutrinos.
0.6
0.4
0.2
0 -5 10
-4
10
-3
10 Sin2(2θ13)
-2
10
10
-1
Figure 2: Fraction of δ for which the neutrino mass hierarchy can be determined at 99% CL (BB: blue dotted lines, EC+BB: red solid lines).