Date Thesis Awarded
Honors Thesis -- Access Restricted On-Campus Only
Bachelors of Science (BS)
The Standard Model predicts that neutrinos are massless particles, but the observation of neutrino oscillations between their three existing flavor states is only possible if they possess a small mass. Such mysteries offer exciting opportunities for searches for physics beyond the Standard Model (BSM). Precision neutrino oscillation experiments are one such way to probe neutrino oscillations and search for BSM, but the measurements taken by these experiments are reliant on neutrino interaction models, which introduce a large source of uncertainty. The MINERvA experiment was designed to study neutrino-nucleus interactions on 5 nuclear targets to better constrain these models and subsequently improve the measurements made by neutrino oscillation experiments. This work details an analysis conducted using data from MINERvA to calculate the double differential cross section as a function of longitudinal and transverse muon momentum for inclusive charged current muon neutrino interactions on 3 of the nuclear targets - iron, lead, and carbon. The steps for such a calculation were as follows. Using a medium-energy dataset in which the incident neutrino has an energy between about 2-10 GeV, a series of cuts were applied to obtain a sample of signal events that included both data and simulated Monte Carlo (MC) events. The MC had 2.01E20 protons-on-target (POT), which corresponded to 3,689,661 neutrino events before cuts, while the data had 4.15E19 POT, which corresponded to 1,280,685 events before cuts. The cuts applied were on both the muon kinematics, which were required for reconstruction of the produced muon, and on the material and target within the detector. Then, the background contamination was removed from the signal using a process called sideband fitting that utilized MC simulated events in the regions just outside the nuclear targets to estimate the background and scale the MC appropriately to fit the data. After this, the sources of background interactions, including neutral current and wrong flavor charged current interactions, can be directly subtracted out. An iterative unfolding process was then performed to remove detector smearing effects and ensure that the true transverse and longitudinal momentum values are being properly reconstructed. Lastly, efficiency corrections were applied to account for the true signal events that the detector missed, and the result is normalized with respect to the neutrino flux, the number of target nuclei within the detector, and width of the momentum bins. The resulting cross sections for both data and MC were plotted. Despite large uncertainties, both systematic and statistical, the resulting MC cross sections tended to underestimate the data, which is consistent with previous results. In particular, in regions of low transverse momentum, which are dominated by quasi-elastic and 2p2h interactions, and regions of high momentum, which are dominated by true deep inelastic scattering interactions, the discrepancy between the data and the MC seems to increase. However, running over a larger dataset, in addition to more careful consideration of the uncertainties, will improve the precision of the measurements and allow for more detailed conclusions to be drawn, as well as comparison with different neutrino interaction models. Thus will ultimately help improve those models and the understanding of neutrino interactions.
Hawkins, Sarah M., "Inclusive Double Differential Muon Neutrino CC Cross Sections on Various Nuclear Targets in MINERvA" (2023). Undergraduate Honors Theses. William & Mary. Paper 2006.
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