arXiv subjects

Ali Ajmi

Publications and source records attributed to Ali Ajmi.

5 recordsLinked to original sources

arXiv2020

Matter vs Vacuum oscillations in Atmospheric Neutrinos

Atmospheric neutrinos travel very long distances through earth matter. It is expected that the matter effects lead to significant changes in the neutrino survival and oscillation probabilities. Initial analysis of atmospheric neutrino data by the Super- Kamiokande collaboration is done using the vacuum oscillation hypothesis, which provided a good fit to the data. In this work, we did a study to differentiate the effects of vacuum oscillations and matter modified oscillations in the atmospheric neutrino data. We find that magnetized iron detector, ICAL at INO, can make a 3 sigma discrimination between vacuum oscillations and matter oscillations, for both normal and inverted hierarchies, in ten years.

hep-ph↗

arXiv2017

Physics Potential of the ICAL detector at the India-based Neutrino Observatory (INO)

The upcoming 50 kt magnetized iron calorimeter (ICAL) detector at the India-based Neutrino Observatory (INO) is designed to study the atmospheric neutrinos and antineutrinos separately over a wide range of energies and path lengths. The primary focus of this experiment is to explore the Earth matter effects by observing the energy and zenith angle dependence of the atmospheric neutrinos in the multi-GeV range. This study will be crucial to address some of the outstanding issues in neutrino oscillation physics, including the fundamental issue of neutrino mass hierarchy. In this document, we present the physics potential of the detector as obtained from realistic detector simulations. We describe the simulation framework, the neutrino interactions in the detector, and the expected response of the detector to particles traversing it. The ICAL detector can determine the energy and direction of the muons to a high precision, and in addition, its sensitivity to multi-GeV hadrons increases its physics reach substantially. Its charge identification capability, and hence its ability to distinguish neutrinos from antineutrinos, makes it an efficient detector for determining the neutrino mass hierarchy. In this report, we outline the analyses carried out for the determination of neutrino mass hierarchy and precision measurements of atmospheric neutrino mixing parameters at ICAL, and give the expected physics reach of the detector with 10 years of runtime. We also explore the potential of ICAL for probing new physics scenarios like CPT violation and the presence of magnetic monopoles.

physics.ins-det↗

arXiv2015

Improving the hierarchy sensitivity of ICAL using neural network

Atmospheric neutrino experiments can determine the neutrino mass hierarchy for any value of $δ_{CP}$. The Iron Calorimeter (ICAL) detector at the India-based Neutrino Observatory can distinguish between the charged current interactions of $ν_μ$ and $\barν_μ$ by determining the charge of the produced muon. Hence it is particularly well suited to determine the hierarchy. The hierarchy signature is more prominent in neutrinos with energy of a few GeV and with pathlength of a few thousand kilometers, $\textit{i.e.}$ neutrinos whose direction is not close to horizontal. We use adaptive neural networks to identify such events with good efficiency and good purity. The hierarchy sensitivity, calculated from these selected events, reaches a $3 σ$ level, with a $Δχ^2$ of 9.

physics.ins-det↗

arXiv2015

Energy and Direction Estimation of Neutrinos in muonless events at ICAL

In this paper, we study events without identifiable muon tracks in the Iron Calorimeter detector at the India-based Neutrino Observatory. Such events are dominated by high energy (E$_ν>$1 GeV) $ν_e$ charged current interactions, which have been studied only in a few experiments so far. The charged particles, produced in these neutrino interactions, give rise to a set of hits in the detector. We attempt to reconstruct the energy and the direction of the neutrino in such events. We study the energy distribution for a given pattern of hits of these events and find that the Landau distribution provides a good fit. % The parameters of the fit can be correlated to the energy of the neutrino. We define two kinematic variables based on the hit distribution and use them to determine the cosine of the polar angle of the neutrino direction ($\cos θ$). There is a moderate correlation between these variables and the $\cos θ$. These provide us enough information to prepare calibration charts for looking up the energy and direction of the incident neutrino.

physics.ins-det↗

arXiv2015

Muonless Events in ICAL at INO

The primary physics signal events in the ICAL at INO are the $ν_μ$ charged current (CC) interactions with a well defined muon track. Apart from these events, ICAL can also detect other types of neutrino interactions, i.e. the electron neutrino charged current interactions and the neutral current events. It is possible to have a dataset containing mostly $ν_e$CC events, by imposing appropriate selection cuts on the events. The $ν_μ$ CC and the neutral current events form the background to these events. This study uses the Monte Carlo generated neutrino events, to design the necessary selection cuts to obtain a $ν_e$ CC rich dataset. An optimized set of constraints are developed which balance the need for improving the purity of the sample and having a large enough event sample. Depending on the constraints used, one can obtain a neutrino data sample, with the purity of $ν_e$ events varying between 55% to 70%.

physics.ins-det↗