2023-10-18 15:00  P7F Seminar Room

[Journal Club] Supernova neutrino oscillations : Beyond two flavors

Dr. Madhurima Chakraborty

 A core-collapse supernova (SN) explosion is one of the gigantic stellar events. It is accompanied with the release of a huge number (∼ 10^58 ) of MeV energy neutrinos which carry major portion of the total gravitational energy released. The search for the actual cause of this huge explosion is currently into extensive research. The current hydrodynamical simulations provide a hint towards neutrinos being the driving factor. These neutrinos, being weakly interacting and the major energy carrier act as the direct probe of the complex nuclear processes going on inside the SN core. Thus, this is an interesting field of study. The neutrinos are known to change their flavor from one to another due to the different flavor and mass eigenstates and the process is known as neutrino oscillations. From the detection point of view, it is essential to understand the oscillations undergone by them while travelling from the SN to the detector as their signatures will be imprinted on the neutrino signal. Due to the high density of neutrinos in a supernova medium, in addition to the usual Mikheyev-Smirnov-Wolfenstein effect, another phenomenon known as collective oscillations take place due to the neutrino-neutrino interaction in the dense medium. They have been further classified into slow and fast oscillations depending on the growth rates of these instabilities. The fast conversions grow at the scale of the large neutrino-neutrino interaction strength (10^5 km^(−1)) of the dense SN core. The slow collective modes, on the other hand grow at a slower rate as they are driven by the smaller vacuum oscillation frequencies (10^0 km^(−1)). In the literature, these flavor conversions have been exclusively studied in the standard two flavor scenario (three species). We carry out the linear and nonlinear study of the collective fast oscillations beyond the two flavor scenario (six species), i.e., taking into account all the three flavors of neutrinos and their antineutrinos. In my talk, I will discuss the three flavor results which demonstrate the incompleteness of the standard two flavor case and thus emphasizes on the need to go beyond the simplistic approximation of the three species while studying fast flavor oscillations.