arXiv subjects

Pomita Ghoshal

Publications and source records attributed to Pomita Ghoshal.

22 records · Page 2Linked to original sources

arXiv2007

Mass Hierarchy Determination via future Atmospheric Neutrino Detectors

We study the problem of determination of the sign of Delta m^2_{31}, or the neutrino mass hierarchy, through observations of atmospheric neutrinos in future detectors. We consider two proposed detector types : (a) Megaton sized water Cerenkov detectors, which can measure the survival rates of nu_μ+ \barν_μand nu_e + \barν_e and (b) 100 kton sized magnetized iron detectors, which can measure the survival rates of ν_μand \barν_μ. For energies and path-lengths relevant to atmospheric neutrinos, these rates obtain significant matter contributions from P_{μe}, P_{μμ} and P_{ee}, leading to an appreciable sensitivity to the hierarchy. We do a binned χ^2 analysis of simulated data in these two types of detectors which includes the effect of smearing in neutrino energy and direction and incorporates detector efficiencies and relevant statistical, theoretical and systematic errors. We also marginalize the χ^2 over the allowed ranges of neutrino parameters in order to accurately account for their uncertainties. Finally, we compare the performance of both types of detectors vis a vis the hierarchy determination.

hep-ph↗

arXiv2006

Earth Matter Effects at Very Long Baselines and the Neutrino Mass Hierarchy

We study matter effects which arise in the muon neutrino oscillation and survival probabilities relevant to atmospheric neutrino and very long baseline beam experiments. The inter-relations between the three probabilities P_{μe}, P_{μτ} and P_{μμ} are examined. It is shown that large and observable sensitivity to the neutrino mass hierarchy can be present in P_{μμ} and P_{μτ}. We emphasize that at baselines of > 7000 Km, matter effects in P_{μτ} can be large under certain conditions. The muon survival rates in experiments with very long baselines thus depend on matter effects in both P_{μτ} and P_{μe}. We indicate where these effects are sensitive to θ_{13}, and identify ranges of E and L where the event rates increase with decreasing θ_{13}, providing a handle to probe small θ_{13}. The effect of parameter degeneracies in the three probabilities at these baselines and energies is studied in detail. Realistic event rate calculations are performed for a charge discriminating 100 kT iron calorimeter which demonstrate the possibility of realising the goal of determining the neutrino mass hierarchy using atmospheric neutrinos. It is shown that a careful selection of energy and baseline ranges is necessary in order to obtain a statistically significant signal, and that the effects are largest in bins where matter effects in both P_{μe} and P_{μτ} combine constructively. Under these conditions, upto a 4σsignal for matter effects is possible (for Δ_{31}>0) within a timescale appreciably shorter than the one anticipated for neutrino factories.

hep-ph↗

arXiv2005

Probing the Neutrino Mass Hierarchy via Atmospheric $ν_μ+ \bar ν_μ$ Survival Rates in Megaton Water Cerenkov Detectors

The neutrino mass hierarchy, presently unknown, is a powerful discriminator among various classes of unification theories. We show that the $ν_μ + \barν_μ$ survival rate in atmospheric events can provide a novel method of determining the hierarchy in megaton water Cerenkov detectors. For pathlength and energy ranges relevant to atmospheric neutrinos,this rate obtains significant matter sensitive variations not only from resonant matter effects in $P_{μe}$ but also from those in $P_{μτ}$. We calculate the expected muon event rates in the case of matter oscillations with both natural and inverted hierarchy.We identify the energy and pathlength ranges for which resonant matter effects can lead to observable differences between the above two cases. We also estimate the exposure time required to observe this difference and determine the sign of $Δ_{31}$ in a statistically significant manner.

hep-ph↗

arXiv2004

Large Matter Effects in ${ν_μ\to ν_τ}$ Oscillations

We show that matter effects change the ${\rm {ν_μ\to ν_τ}}$ oscillation probability by as much as 70% for certain ranges of energies and pathlengths. Consequently, the ${\rm {ν_μ\to ν_μ}}$ survival probability also undergoes large changes. A proper understanding of $ν_μ$ survival rates must consider matter effects in $P_{μτ}$ as well as $P_{μe}$. We comment on a) how these matter effects may be observed and the sign of $Δ_{31}$ determined in atmospheric neutrino measurements and at neutrino factories and b) how they lead to heightened sensitivity for small $θ_{13}$.

hep-ph↗