Neutrino Propagation When Mass Eigenstates and Decay Eigenstates Mismatch

The next generation of water Cherenkov neutrino telescopes in the Mediterranean Sea are under construction offshore France (KM3NeT/ORCA) and Sicily (KM3NeT/ARCA). The KM3NeT/ORCA detector features an energy detection threshold which allows to collect atmospheric neutrinos to study flavour oscillation. This paper reports the KM3NeT/ORCA sensitivity to this phenomenon. The event reconstruction, selection and classification are described. The sensitivity to determine the neutrino mass ordering was evaluated and found to be 4.4$$\sigma $$ σ if the true ordering is normal and 2.3$$\sigma $$ σ if inverted, after 3 years of data taking. The precision to measure $$\varDelta m^2_{32}$$ Δ m 32 2 and $$\theta _{23}$$ θ 23 were also estimated and found to be $$85 . 10^{-6}~{\mathrm{eV}^{2}}$$ 85 . 10 - 6 eV 2 and $$(^{+1.9}_{-3.1})^{\circ }$$ ( - 3.1 + 1.9 ) ∘ for normal neutrino mass ordering and, $$75 . 10^{-6}~{\mathrm{eV}^{2}}$$ 75 . 10 - 6 eV 2 and $$(^{+2.0}_{-7.0})^{\circ }$$ ( - 7.0 + 2.0 ) ∘ for inverted ordering. Finally, a unitarity test of the leptonic mixing matrix by measuring the rate of tau neutrinos is described. Three years of data taking were found to be sufficient to exclude "Equation missing" event rate variations larger than 20% at $$3\sigma $$ 3 σ level.

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“…OscProb numerical computations are compatible with analytical expressions for neutrino decay in matter derived in refs [24,25]…”

supporting

confidence: 57%

Determining the neutrino mass ordering and oscillation parameters with KM3NeT/ORCA

Aiello¹,

Albert²,

Garre³

et al. 2022

Eur. Phys. J. C

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“…Analytic treatment of neutrino oscillation and decay in matter Dibya S. Chattopadhyay the Zassenhaus expansion, and compute the neutrino oscillation probabilities perturbatively in the mismatch parameter γ. Such a formulation has been used to treat propagation of invisibly decaying neutrinos in matter for the first time in [5].…”

Section: Pos(ichep2022)1241mentioning

confidence: 99%

“…(10) and (11), calculated up to 𝑂 ( γ). 𝐴)− cos 2𝜃 𝑚 + γ Δ𝑏 sin 2𝜃 𝑚 cos 𝜒 | 𝐴| 2 cos 2 2𝜃 𝑚 − 2 γ Δ𝑏 sin 2𝜃 𝑚 cos 2𝜃 𝑚 cos 𝜒 Im( 𝐴) − γ Δ𝑎 sin 2𝜃 𝑚 cos 𝜒 |𝐵| 2 sin 2 2𝜃 𝑚 + 2 γ sin 2𝜃 𝑚 Δ𝑎 sin 𝜒 + Δ𝑏 cos 2𝜃 𝑚 cos 𝜒The survival probability for 𝜈 𝛼 → 𝜈 𝛼 is given by[5]…”

mentioning

confidence: 99%

Analytic treatment of neutrino oscillation and decay in matter

Chattopadhyay¹,

Chakraborty²,

Dighe³

et al. 2022

Proceedings of 41st International Conference on High Energy Physics — PoS(ICHEP2022)

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We analyze invisible decay of neutrinos in the presence of oscillation and matter effects. The inclusion of decay can be accommodated by a non-Hermitian effective Hamiltonian, with the Hermitian component giving rise to oscillations, and the anti-Hermitian component leading to the invisible decay of neutrinos. We consider the possibility that the oscillation and decay matrix may not commute; in fact, in matter, they will invariably become non-commuting. This would lead to a mismatch between the effective mass eigenstates and the decay eigenstates. Employing a resummation of the Zassenhaus expansion, we develop a formalism for calculating the neutrino oscillation probabilities in the two-flavor scenario. This technique can easily be extended to three flavors.

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“…Finally, S. Goswami suggested an alternative approach for analytic treatment of neutrino decay and oscillation in matter [53,54]. It is emphasized that in the presence of decay the Hamiltonian is non-hermitian, hence decay eigenstates and mass eigenstates are not simultaneously diagonalisable by Unitary transformations [55].…”

Section: Pos(now2022)060mentioning

confidence: 99%

“…It is emphasized that in the presence of decay the Hamiltonian is non-hermitian, hence decay eigenstates and mass eigenstates are not simultaneously diagonalisable by Unitary transformations [55]. Subsequently, a formalism is developed for the two-flavor [53] and three-flavor [54] neutrino propagation through matter of uniform density with invisible neutrino decay. Neutrino oscillation probabilities are derived as perturbative expansions for different decay scenarios.…”

Section: Pos(now2022)060mentioning

confidence: 99%