The sensitivity of liquid scintillator detectors to CP-violation with atmospheric neutrinos

Abstract

The detection of CP violation in neutrino oscillations is one of the most important goals of the next generation of neutrino experiments. Here we study the detectability of the CP-violating phase in the oscillation of atmospheric neutrinos. Liquid scintillator detectors of a few kilotons can probe the low-energy range of the atmospheric neutrino flux. We calculate the expected rate, spectrum, and zenith angle distribution for a typical liquid scintillator detector for different detector sites. We include a typical detector response with different capabilities for flavour identification and a background model. The sensitivity is estimated using a Poisson likelihood analysis.

Figures (11)

• Figure 1: Expected number of charged current atmospheric neutrino events versus neutrino energy and zenith angle, assuming an exposure of $250\,\mathrm{kt}\,\mathrm{years}$, for NO, upper octant $\theta_{23}$, and $\delta_{\mathrm{CP}}{}=0^{\circ}$ for the SNOLABDuncan:2010zz site. Left electron flavour, right muon flavour, top neutrinos, and bottom antineutrinos.
• Figure 2: Expected difference $\Delta_{\delta_{\mathrm{CP}}{}=0^{\circ}}$ in the number of charged current atmospheric neutrino events versus neutrino energy and zenith angle for $\delta_{\mathrm{CP}}{} = 90^{\circ}$ with respect to $0^{\circ}$ and upper octant $\theta_{23}$ for the SNOLABDuncan:2010zz. An exposure of $250\,\mathrm{kt}\,\mathrm{years}$ is assumed. Upper plot NO and lower plot IO. For both: Left side electron flavour, right side muon flavour, top neutrinos, and bottom antineutrinos.
• Figure 3: Zenith angle resolution versus neutrino energy. Given by extrapolating the resolution shown in Figure 4 of JUNOzenith using a cubic spline.
• Figure 4: Upper plot: Expected number of charged current atmospheric neutrino events versus neutrino energy and zenith angle with realistic detector resolution, NO, upper octant $\theta_{23}$, and $\delta_{\mathrm{CP}}{}=0^{\circ}$ for the SNOLABDuncan:2010zz site. Lower plot: Difference $\Delta_{\delta_{\mathrm{CP}}{}=0^{\circ}}$ in the number of events for $\delta_{\mathrm{CP}}{} = 90^{\circ}$ with respect to $0^{\circ}$. An exposure of $250\,\mathrm{kt}\,\mathrm{years}$ is assumed. Left electron flavour, right muon flavour, top neutrinos, and bottom antineutrinos.
• Figure 5: Expected number of neutral current atmospheric neutrino events versus neutrino energy and zenith angle, assuming an exposure of $250\,\mathrm{kt}\,\mathrm{years}$ for the SNOLABDuncan:2010zz site. Left side neutrino, and right side antineutrino. A fraction of these events can mimic charged current events.