Testing the MSW effect in SN Explosion with Neutrino Event Rates

Kwang-Chang Lai², Chun Sing Jason Leung^1*, Guey-Lin Lin¹

¹Institute of Physics, National Chiao Tung University, Hsinchu, Taiwan
²Centre for General Education, Chang Gung University, Taoyuan, Taiwan

* Presenter:Chun Sing Jason Leung, email:jasonleung.py04g@g2.nctu.edu.tw

Flavor transitions in supernova neutrinos are yet to be determined. We present a method to probe whether or not the Mikheyev-Smirnov-Wolfenstein effects occur as SN neutrinos propagate outward from the SN core by investigating time evolutions of neutrino event rates for different favors in neutrino detectors. As the MSW effect occurs, the ν_e flux swaps with the ν_x flux, which represents any one of ν_μ, ν_τ, and their correspoinding anti-neutrinos, either fully or partially depending on the neutrino mass hierarchy. During the neutronization burst, the ν_e emission evolves in a much different shape from the emissions of ν_e and ν_x while the latter two evolve in a similar pattern. Meanwhile, the luminosity of the the ν_e emission is much larger than those of the anti-ν_e and ν_x emissions while the latter two are roughly equal. As a consequence, the time-evolution pattern of the ν_eAr event rates in the absence of the MSW effect will be much different from that in the occurrence of the MSW effect, in either mass hierarchy. With the simulated SN neutrino emissions, the ν_eAr and IBD event rates are evaluated. The cumulative event rates of ν_eAr and IBD are calculated with different SN simulations up to 100 ms. We show that the time evolutions of this cumulative rates can effectively determine whether MSW effects really occur for SN neutrinos or not.

Keywords: MSW Effect, Neutrino Oscillation, JUNO, DUNE