Fast flavor conversion of neutrinos Tobias Stirner Introduction - PowerPoint PPT Presentation

Introduction Neutrino Collider Conclusions Fast flavor conversion of neutrinos Tobias Stirner

Introduction Neutrino Collider Conclusions Why do neutrinos oscillate?

Introduction Neutrino Collider Conclusions Why do neutrinos oscillate? Two bases for fields: � µ 1 � � φ e � • massive µ ( x ) = and flavor φ ( x ) = µ 2 φ τ • related via SO(2) mixing matrix φ ( x ) = ˆ U µ ( x ) → propagating dof � = interacting dof mixing is environment dependent oscillation length in vacuum: L ∼ 10km in high neutrino density: L ∼ 1m

Introduction Neutrino Collider Conclusions Equation of Motion description with Wigner transform � D � S d 3 y e − i k · y φ x − y x + y � � � φ † � � ρ ( x , k , t ) = ˆ ≡ 2 2 S ∗ 1 − D √ d 3 q Hamiltonian ˆ � k 2 + ˆ M 2 + ρ − ˆ � � � H = 2 G F ˆ ¯ (1 − cos θ qk ) ρ (2 π ) 3 � � ˆ Liouville equation i ( ∂ t + v · ∂ x ) ˆ ρ = H , ˆ ρ interpretations: particle transport & wave equation

Introduction Neutrino Collider Conclusions Two beams assume: flavor correlation small S ≪ 1 � d v ′ → i ( ∂ t + v · ∂ x ) S v = − 4 π (1 − cos θ ) G v ′ S v ′ G v : particle content simplification: 2 beams in 1 + 1d parameters: velocities ( ↿ ↾ , ↿ ⇂ ) & particle content ( ν, ¯ ν ) look for unstable regions in dispersion relation ω ( k ) → ω or k complex in S ∼ e − i( ω t − k · x )

ω ω Introduction Neutrino Collider Conclusions Stable cases parallel v , only ν no excluded regions → completely stable k antiparallel v , only ν gap in ω modes with small energy damped k

ω ω Introduction Neutrino Collider Conclusions Instable case parallel v , ν and ¯ ν gaps in ω and k convective instability k antiparallel v , ν and ¯ ν gap in k absolute instability k

Introduction Neutrino Collider Conclusions Conclusions • oscillation is a misleading term • self-interactions can cause complex regions in dispersion relation • depending on the gaps different instabilities arise

Introduction Neutrino Collider Conclusions Bibliography • Izaguirre et al.: ”Fast Pairwise Conversion of Supernova Neutrinos: A Dispersion-Relation Approach”, arXiv:1610.01612 • Capozzi et al: ”Fast flavor conversion of supernova neutrinos: Classifying instabilities via dispersion relations”, arXiv:1706.03360 • TS et al.: ”Liouville term for neutrinos: Flavor structure and wave interpretation”, arXiv:1803.04693