Anushree Ghosh

Determining the neutrino mass hierarchy with INO, T2K, NOvA and reactor experiments

A bstractThe relatively large measured value of θ13 has opened up the possibility of determining the neutrino mass hierarchy through earth matter effects. Amongst the current accelerator-based experiments only NOvA has a long enough baseline to observe earth matter effects. However, NOvA is plagued with uncertainty on the knowledge of the true value of δCP, and this could drastically reduce its sensitivity to the neutrino mass hierarchy. The earth matter effect on atmospheric neutrinos on the other hand is almost independent of δCP. The 50 kton magnetized Iron CALorimeter at the India-based Neutrino Observatory (ICAL@INO) will be observing atmospheric neutrinos. The charge identification capability of this detector gives it an edge over others for mass hierarchy determination through observation of earth matter effects. We study in detail the neutrino mass hierarchy sensitivity of the data from this experiment simulated using the NUANCE based generator developed for ICAL@INO and folded with the detector resolutions and efficiencies obtained by the INO collaboration from a full Geant4-based detector simulation. The data from ICAL@INO is then combined with simulated data from T2K, NOvA, Double Chooz, RENO and Daya Bay experiments and a combined sensitivity study to the mass hierarchy is performed. With 10 years of ICAL@INO data combined with T2K, NOvA and reactor data, one could get about 2.3σ-5.7σ discovery of the neutrino mass hierarchy, depending on the true value of sin2θ23 [0.4-0.6], sin2 2θ13 [0.08-0.12] and δCP [0-2π].

The Reach of INO for Atmospheric Neutrino Oscillation Parameters

A bstractThe India-based Neutrino Observatory (INO) will host a 50 kt magnetized iron calorimeter (ICAL@INO) for the study of atmospheric neutrinos. Using the detector resolutions and efficiencies obtained by the INO collaboration from a full-detector GEANT4-based simulation, we determine the reach of this experiment for the measurement of the atmospheric neutrino mixing parameters

Neutrino physics with non-standard interactions at INO

\left( {\sin^2 {\theta_{23 }}\;\mathrm{and}\left| {\varDelta m_{32}^2} \right|} \right)

Measuring the mass hierarchy with muon and hadron events in atmospheric neutrino experiments

. We also explore the sensitivity of this experiment to the octant of θ23, and its deviation from maximal mixing.

Determining the Octant of

A bstractNon-standard neutrino interactions (NSI) involved in neutrino propagation inside Earth matter could potentially alter atmospheric neutrino fluxes. In this work, we look at the impact of these NSI on the signal at the ICAL detector to be built at the India-based Neutrino Observatory (INO). We show how the sensitivity to the neutrino mass hierarchy of ICAL changes in the presence of NSI. The mass hierarchy sensitivity is shown to be rather sensitive to the NSI parameters ϵeμ and ϵeτ , while the dependence on ϵμτ and ϵτ τ is seen to be very mild, once the χ2 is marginalised over oscillation and NSI parameters. If the NSI are large enough, the event spectrum at ICAL is expected to be altered and this can be used to discover new physics. We calculate the lower limit on NSI parameters above which ICAL could discover NSI at a given C.L. from 10 years of data. If NSI were too small, the null signal at ICAL can constrain the NSI parameters. We give upper limits on the NSI parameters at any given C.L. that one is expected to put from 10 years of running of ICAL. Finally, we give C.L. contours in the NSI parameter space that is expected to be still allowed from 10 years of running of the experiment.

\theta_{23}

A bstractNeutrino mass hierarchy can be measured in atmospheric neutrino experiments through the observation of earth matter effects. Magnetized iron calorimeters have been shown to be good in this regard due to their charge identification capabilities. The charged current interaction of νμ in this detector, produces a muon track and a hadron shower. The direction of the muon track can be measured very accurately. We show the improvement expected in the reach of this class of experiments to the neutrino mass hierarchy, as we improve the muon energy resolution and the muon reconstruction efficiency. We next propose to include the hadron events in the analysis, by tagging them with the zenith angle of the corresponding muon and binning the hadron data first in energy and then in zenith angle. To the best of our knowledge this way of performing the analysis of the atmospheric neutrino data has not be considered before. We show that the hadron events increase the mass hierarchy sensitivity of the experiment. Finally, we show the expected mass hierarchy sensitivity in terms of the reconstructed neutrino energy and zenith angle. We show how the detector resolutions spoil the earth matter effects in the neutrino channel and argue why the sensitivity obtained from the neutrino analysis cannot be significantly better than that obtained from the analysis using muon data alone. As a result, the best mass hierarchy sensitivity is obtained when we add the contribution of the muon and the hadron data. For sin2 2θ13 = 0.1, sin2θ23 = 0.5, a muon energy resolution of 2%, reconstruction efficiency of 80% and exposure of 50 × 10 kton-year, we could get up to 4.5σ signal for the mass hierarchy from combining the muon and hadron data. The signal will go up when the atmospheric data is combined with data from other existing experiments, particularly NOνA.

with PINGU, T2K, NOvA and Reactor Data

A bstractWe explore the prospects of determining the octant of θ23 with atmospheric neutrinos at PINGU. We study in detail the impact of energy and angle resolutions of the neutrino on the octant sensitivity. We show that the systematic uncertainties on the atmospheric neutrino flux predictions, especially the ones which affect the energy and zenith angle spectrum of the neutrinos, make a rather drastic reduction of the sensitivity of PINGU. We also study the prospects of measuring the octant of θ23 in the long baseline experiments T2K and NOνA in conjunction with the reactor experiments. We study this for two configurations of NOνA and T2K and make a comparative analysis of them. With just 3 years of statistics, PINGU would have an octant sensitivity of more than 3σ C.L. for sin2θ23 < 0.419 and sin2θ23 > 0.586 if we add the reactor data and if normal hierarchy is true. On addition of the data from T2K and NOνA, the sensitivity improves so that we have an octant sensitivity at the 4σ C.L. for sin2θ23 < 0.426 and sin2θ23 > 0.586 if normal hierarchy is true. Even a 5σ significance for the right octant can be expected if sin2θ23(true) < 0.413 for the true normal hierarchy. The sensitivity for the true inverted hierarchy is lower and we expect a 3σ sensitivity of the octant of θ23 for sin2θ23(true) < 0.43 and > 0.585 from the combined data set for this case.

Simulation studies of hadron energy resolution as a function of iron plate thickness at INO-ICAL

We report on a detailed simulation study of the hadron energy resolution as a function of the thickness of the absorber plates for the proposed Iron Calorimeter (ICAL) detector at the India-based Neutrino Observatory (INO). We compare the hadron resolutions obtained with absorber thicknesses in the range 1.5–8 cm for neutrino interactions in the energy range 2–15 GeV, which is relevant to hadron production in atmospheric neutrino interactions. We find that at lower energies, the thickness dependence of energy resolution is steeper than at higher energies, however there is a thickness-independent contribution that dominates at the lower thicknesses discussed in this work. As a result, the gain in hadron energy resolution with decreasing plate thickness is marginal. We present the results in the form of fits to a function with energy-dependent exponent.

Determining the octant of θ23 with PINGU, T2K, NOνA and reactor data

A bstractWe explore the prospects of determining the octant of θ23 with atmospheric neutrinos at PINGU. We study in detail the impact of energy and angle resolutions of the neutrino on the octant sensitivity. We show that the systematic uncertainties on the atmospheric neutrino flux predictions, especially the ones which affect the energy and zenith angle spectrum of the neutrinos, make a rather drastic reduction of the sensitivity of PINGU. We also study the prospects of measuring the octant of θ23 in the long baseline experiments T2K and NOνA in conjunction with the reactor experiments. We study this for two configurations of NOνA and T2K and make a comparative analysis of them. With just 3 years of statistics, PINGU would have an octant sensitivity of more than 3σ C.L. for sin2θ23 < 0.419 and sin2θ23 > 0.586 if we add the reactor data and if normal hierarchy is true. On addition of the data from T2K and NOνA, the sensitivity improves so that we have an octant sensitivity at the 4σ C.L. for sin2θ23 < 0.426 and sin2θ23 > 0.586 if normal hierarchy is true. Even a 5σ significance for the right octant can be expected if sin2θ23(true) < 0.413 for the true normal hierarchy. The sensitivity for the true inverted hierarchy is lower and we expect a 3σ sensitivity of the octant of θ23 for sin2θ23(true) < 0.43 and > 0.585 from the combined data set for this case.

Prospects of indirect searches for dark matter at INO

The annihilation of Weakly Interactive Massive Particles (WIMP) in the centre of the sun could give rise to neutrino fluxes. We study the prospects of searching for these neutrinos at the upcoming Iron CALorimeter (ICAL) detector to be housed at the India-based Neutrino Observatory (INO). We perform ICAL simulations to obtain the detector efficiencies and resolutions in order to simulate muon events in ICAL due to neutrinos coming from annihilation of WIMP in the mass range