LABORATORI NAZIONALI DEL GRAN SASSO
Present global fits of world neutrino data hint towards non-maximal θ23 with two nearly degenerate solutions, one in the lower octant (θ23 < π/4), and the other in the higher octant (θ23 > π/4). This octant ambiguity of θ23 is one of the fundamental issues in the neutrino sector, and long-baseline (LBL) experiments can resolve this issue with the help of νμ → νe appearance channel. First, I will discuss how this measurement would be affected in the upcoming LBL experiments if there exist a light eV-scale sterile neutrino. I will show that in the so called 3+1 scheme involving three active and one sterile neutrinos, a new interference term in νμ → νe transition probability can spoil the chances of measuring θ23 octant completely. Next, I will describe in detail the degeneracy between the octant of θ23 and flavor-changing neutral-current non-standard interactions (NSIís) in neutrino propagation. I will show that for values of the NSI coupling as small as few%, the discovery potential of the octant of θ23 gets completely lost.
Sanjib Kumar Agarwalla
Institute of Physics (IOP)