Suprabh Prakash

Potential of optimized NOνA for large θ13 & combined performance with a LArTPC & T2K

A bstractNOνA experiment has reoptimized its event selection criteria in light of the recently measured moderately large value of θ13. We study the improvement in the sensitivity to the neutrino mass hierarchy and to leptonic CP violation due to these new features. For favourable values of δCP, NOνA sensitivity to mass hierarchy and leptonic CP violation is increased by 20%. Addition of 5 years of neutrino data from T2K to NOνA more than doubles the range of δCP for which the leptonic CP violation can be discovered, compared to stand alone NOνA. But for unfavourable values of δCP, the combination of NOνA and T2K are not enough to provide even a 90% C.L. hint of hierarchy discovery. Therefore, we further explore the improvement in the hierarchy and CP violation sensitivities due to the addition of a 10 kt liquid argon detector placed close to NOνA site. The capabilities of such a detector are equivalent to those of NOνA in all respects. We find that combined data from 10 kt liquid argon detector (3 years of ν + 3 years of

Neutrino Mass Hierarchy and Octant Determination with Atmospheric Neutrinos

\overline{\nu}

Getting the Best Out of T2K and NOvA

run), NOνA (6 years of ν + 6 years of

Resolving the octant of theta23 with T2K and NOvA

\overline{\nu}

Exploring the three flavor effects with future superbeams using liquid argon detectors

run) and T2K (5 years of ν run) can give a close to 2σ hint of hierarchy discovery for all values of δCP. With this combined data, we can achieve CP violation discovery at 95% C.L. for roughly 60% values of δCP.

The need for an early anti-neutrino run of NOνA

The recent discovery by the Daya-Bay and RENO experiments, that θ(13) is nonzero and relatively large, significantly impacts existing experiments and the planning of future facilities. In many scenarios, the nonzero value of θ(13) implies that θ(23) is likely to be different from π/4. Additionally, large detectors will be sensitive to matter effects on the oscillations of atmospheric neutrinos, making it possible to determine the neutrino mass hierarchy and the octant of θ(23). We show that a 50 kT magnetized liquid argon neutrino detector can ascertain the mass hierarchy with a significance larger than 4σ with moderate exposure times, and the octant at the level of 2-3σ with greater exposure.

Resolving the octant of θ23 with T2K and NOνA

We explore the combined physics potential of T2K and NOvA in light of the moderately large measured value of theta13. For sin^2 2*theta13 = 0.1, which is close to the best fit value, a 90% C.L. evidence for the hierarchy can be obtained only for the combinations (Normal hierarchy, -170 <= deltaCP <= 0) and (Inverted hierarchy, 0 <= deltaCP <= 170), with the currently planned runs of NOvA and T2K. However, the hierarchy can essentially be determined for any value of deltaCP, if the statistics of NOvA are increased by 50% and those of T2K are doubled. Such an increase will also give an allowed region of deltaCP around its true value, except for the CP conserving cases deltaCP = 0 or 180. We demonstrate that any measurement of deltaCP is not possible without first determining hierarchy. We find that comparable data from a shorter baseline (L ~ 130 km) experiment will not lead to any significant improvement.

PHYSICS POTENTIAL OF A 2540 km BASELINE SUPERBEAM EXPERIMENT

A bstractPreliminary results of MINOS experiment indicate that θ23 is not maximal. Global fits to world neutrino data suggest two nearly degenerate solutions for θ23: one in the lower octant (LO: θ23 < 45◦) and the other in the higher octant (HO: θ23 > 45◦). νμ→ νe oscillations in superbeam experiments are sensitive to the octant and are capable of resolving this degeneracy. We study the prospects of this resolution by the current T2K and upcoming NOνA experiments. Because of the hierarchy-δCP degeneracy and the octant-δCP degeneracy, the impact of hierarchy on octant resolution has to be taken into account. As in the case of hierarchy determination, there exist favorable (unfavorable) values of δCP for which octant resolution is easy (challenging). However, for octant resolution the unfavorable δCP values of the neutrino data are favorable for the anti-neutrino data and vice-verse. This is in contrast to the case of hierarchy determination. In this paper, we compute the combined sensitivity of T2K and NOνA to resolve the octant ambiguity. If sin2θ23 = 0.41, then NOνA can rule out all the values of θ23 in HO at 2σ C.L., irrespective of the hierarchy and δCP. Addition of T2K data improves the octant sensitivity. If T2K were to have equal neutrino and anti-neutrino runs of 2.5 years each, a 2σ resolution of the octant becomes possible provided sin2θ23 ≤ 0.43 or ≥ 0.58 for any value of δCP.

Mass hierarchy determination using current and upcoming neutrino experiments

A bstractRecent measurement of a moderately large value of θ13 signifies an important breakthrough in establishing the standard three flavor oscillation picture of neutrinos. It has provided an opportunity to explore the sub-dominant three flavor effects in present and future long-baseline experiments. In this paper, we perform a comparative study of the physics reach of two future superbeam facilities, LBNE and LBNO in their first phases of run, to resolve the issues of neutrino mass hierarchy, octant of θ23, and leptonic CP violation. We also find that the sensitivity of these future facilities can be improved significantly by adding the projected data from T2K and NOνA. Stand-alone LBNO setup with a 10 kt detector has a mass hierarchy discovery reach of more than 7σ, for the lowest allowed value of sin2θ23(true) = 0.34. This result is valid for any choice of true δCP and hierarchy. LBNE10, in combination with T2K and NOνA, can achieve 3σ hierarchy discrimination for any choice of δCP, sin2θ23, and hierarchy. The same combination can provide a 3σ octant resolution for sin2θ23(true) ≤ 0.44 or for sin2θ23(true) ≥ 0.58 for all values of δCP(true). LBNO can give similar results with 10 kt detector mass. In their first phases, both LBNE10 and LBNO with 20 kt detector can establish leptonic CP violation for around 50% values of true δCP at 2σ confidence level. In case of LBNE10, CP coverage at 3σ can be enhanced from 3% to 43% by combining T2K and NOνA data, assuming sin2θ23(true) = 0.5. For LBNO setup, CP violation discovery at 3σ is possible for 46% values of true δCP if we add the data from T2K and NOνA.

Hierarchy and Octant Determination Potential of LBNE and LBNO

A bstractThe moderately large value of θ13, measured recently by reactor experiments, is very welcome news for the future neutrino experiments. In particular, the NOνA experiment, with 3 years each of ν and v¯