arXiv subjects

Mohammad Nizam

Publications and source records attributed to Mohammad Nizam.

5 recordsLinked to original sources

arXiv2024

Long-Distance Signal Propagation in AC-LGAD

We investigate the signal propagation in AC-LGAD (aka RSD), which are LGAD with a common N+ layer and segmented AC-coupled readout contacts, by measuring response to IR laser TCT on a large selection of AC-LGAD with strip readout. The interest for this topic derives from the realization that while large charge sharing between neighboring strips is essential for good position resolution, large sharing beyond the next neighbor generates background signals which in general are detrimental to the sensor goal of low occupancy. Using AC-LGAD with strip readout produced by Hamamatsu Photonics (HPK), we evaluate the effects of a variety of sensor properties, including geometrical parameters (strip length, width), process parameters like the N+ layer resistivity, the coupling capacitance, and the thickness of the bulk on the signal sharing and the position resolution.

hep-ex↗

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↗

arXiv2020

Tensions between the appearance data of T2K and NOvA

The long baseline neutrino experiments, T2K and NOvA, have taken significant amount of data in each of the four channels: (a) $ν_μ$ disappearance, (b) $\barν_μ$ disappearance (c) $ν_e$ appearance and (d) $\barν_e$ appearance. There is a mild tension between the disappearance and the appearance data sets of T2K. A more serious tension exists between the $ν_e$ appearance data of T2K and the $ν_e / \barν_e$ appearance data of NOvA. This tension is significant enough that T2K rules out the best-fit point of NOvA at $95\%$ confidence level whereas NOvA rules out T2K best-fit point at $90\%$ confidence level. We explain the reason why these tensions arise. We also do a combined fit of T2K and NOvA data and comment on the results of this fit.

hep-ph↗

arXiv2019

Hadron energy estimation from Atmospheric neutrino events

The ICAL at INO is designed to mainly observe the muons produced in the charged current interactions of atmospheric muon neutrinos and anti-neutrinos. The track of the muon is reconstructed using the hits they produce in the detector. From this track, the charge, the energy and the direction of the muon are estimated, which are used to do oscillation physics analysis. In a large fraction of events, a number of hadrons are also produced in addition to the muons. The charged hadrons also leave hits in the detector which can be utilized to estimate the hadron energy. In this work, we study the relation between hadron hits, defined to be the difference between the total number of hits and the muon track hits, and the hadron energy. We find that a non-negligible number of baryons are produced in atmospheric neutrino interactions. For E(had) < 5 GeV, almost all the hadron energy is carried by these baryons. Finally, we formulate a procedure by which the hadron energy can be estimated from the number of hadron hits.

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↗