Subcategory: Physics (not Nanoscience)
Charles Marrder - University of Notre Dame
Co-Author(s): Dr. David Ernst, Vanderbilt University
Neutrinos are subatomic particles so light and weakly-interacting that trillions pass through one’s body every second, all while travelling near the speed of light. There are three known flavors of neutrinos electron, muon, and tau. According to the Standard Model, flavor is conserved, but recent experiments have found that neutrinos change their flavor even in vacuum, a phenomenon called ‘neutrino oscillations.’ Furthermore, various short baseline neutrino oscillation experiments have exhibited an anomaly in which the number of antineutrinos detected was significantly less than expected. Such an anomaly might suggest a fourth sterile neutrino. The existence of the sterile neutrino would represent a further departure from the Standard Model, thus revealing a fundamental misunderstanding of the electro-weak theory governing particle physics.
We sought to reanalyze the anomaly by computationally modelling four, total flux experiments (ROVNO91, ROVNO88-1I, ROVNO88-2I, and Bugey-4), which primarily measured the number of antineutrinos detected without varying prompt energies. Our models generate chi-square plots and exclusion curves by finding which mass squared difference and mixing angle values minimize the chi-square function, thereby predicting the likelihood that a sterile neutrino with certain parameters exists. These models currently yield chi-square results which favor the fourth neutrino. We are presently combining individual models to consolidate the chi-square results of each experiment while accounting for common errors arising from shared reactors or detectors. Doing so will yield more comprehensive predictions by including various experimental results. The combined results will eventually be compared with those of individual, operational models to check for consistency. Upon ascertaining the accuracy of the combined chi-square plots, the exclusion curves will be analyzed to deduce the sterile neutrino’s likelihood given certain parameters. Chi-square and exclusion results from the individual experiments and the data consolidation method used to combine them will contribute to the Vanderbilt Neutrino Theory Group?s efforts of reanalyzing twenty-one neutrino oscillation experiments via a single, global analysis model.
References: G. Mention et al., Phys. Rev. D 83, 073006 (2011). Th. A. Mueller, et al., Phys. Rev. C 83, 054615 (2011). P. Huber, Phys. Rev. C 84, 024617 (2011). F.P. An et al., Chinese Physics C 41, 013002 (2017).
Funder Acknowledgement(s): Thank you to Dr. David Ernst for serving as an excellent mentor and allowing me to conduct research with him. Thanks also to Alyce Dobyns and Ashley Brammer for accommodating me so kindly at Vanderbilt. Funding was provided by NSF to Dr. David Ernst and the Vanderbilt REU program.
Faculty Advisor: Dr. David Ernst, firstname.lastname@example.org
Role: I modified the existing computational models (which were written by Dr. Ernst and his past graduate students) to fit the experimental data given by the references. Then, I sought methods to combine the individual models for different experiments in hopes of consolidating their chi-square results and shared errors.