C2GT: intercepting CERN neutrinos to Gran Sasso in the Gulf of Taranto to measure θ₁₃

Today's greatest challenge in accelerator-based neutrino physics is to measure the mixing angle theta(13) which is known to be much smaller than the solar mixing angle theta(12) and the atmospheric mixing angle theta(23). A non-zero value of the angle theta(13) is a prerequisite for observing CP violation in neutrino mixing. In this paper, we discuss a deep-sea neutrino experiment with 1.5 Mt fiducial target mass in the Gulf of Taranto with the prime objective of measuring theta(13). The detector is exposed to the CERN neutrino beam to Gran Sasso in off-axis geometry. Monochromatic muon neutrinos of approximate to 800 MeV energy are the dominant beam component. Neutrinos are detected through quasi-elastic, charged-current reactions in sea water; electrons and muons are detected in a large-surface, ring-imaging Cherenkov detector. The profile of the seabed in the Gulf of Taranto allows for a moveable experiment at variable distances from CERN, starting at 1100 km. From the oscillatory pattern of the disappearance of muon neutrinos, the experiment will measure sin(2) theta(23) and especially Delta m(23)(2) with high precision. The appearance of electron neutrinos will be observed with a sensitivity to P(nu(mu) -> v(e)) as small as 0.0035 (90% CL) and sin(2) theta(13) as small as 0.0019 (90% CL; for a CP phase angle delta=0 degrees and for normal neutrino mass hierarchy).