The Future of High-Energy Astrophysical Neutrino Flavor Measurements

Abstract

We critically examine the ability of future neutrino telescopes, including Baikal-GVD, KM3NeT, P-ONE, TAMBO, and IceCube-Gen2, to determine the flavor composition of high-energy astrophysical neutrinos, i.e., the relative number of νe, νµ, and ντ , in light of improving measurements of the neutrino mixing parameters. Starting in 2020, we show how measurements by JUNO, DUNE, and Hyper-Kamiokande will affect our ability to determine the regions of flavor composition at Earth that are allowed by neutrino oscillations under different assumptions of the flavor composition that is emitted by the astrophysical sources. From 2020 to 2040, the error on inferring the flavor composition at the source will improve from > 40% to less than 6%. By 2040, under the assumption that pion decay is the principal production mechanism of high-energy astrophysical neutrinos, a sub-dominant mechanism could be constrained to contribute less than 20% of the flux at 99.7% credibility. These conclusions are robust in the nonstandard scenario where neutrino mixing is non-unitary, a scenario that is the target of next-generation experiments, in particular the IceCube-Upgrade. Finally, to illustrate the improvement in using flavor composition to test beyond-the-Standard-Model physics, we examine the possibility of neutrino decay and find that, by 2040, combined neutrino telescope measurements will be able to limit the decay rate of the heavier neutrinos to below 1.8 × 10 −5 (m/eV) s −1 , at 95% credibility.

The Nonsymmetric Flavor Transition Matrix and the Apparent P violation

“…We note that a similar observation for the standard matrix A has been obtained in the recent Ref. [54]. (ii) For the neutron-decay source and muon-damping source, s S 23 , s S 12 can enlarge the region of the flavor ratio at Earth noticeably.…”

Matter effects on flavor transitions of high-energy astrophysical neutrinos based on different decoherence schemes

“…All the predicted regions are at the margin of the 2015 ICeCube 3σ constraint [54]. Considering the 2040 expected sensitivity on the flavor ratio [15,21], these regions would be precluded by the observations of the neutrino telescopes in the near future. (Ⅱ) ordering [53].…”

“…The region from Scheme I: Since the oscillation effect is not notable for Scheme II, this region is nearly identical to that from Scheme II. Nearly half of the area overlaps with the 2040 3σ credible region [15]. So Scheme I and II might work in the era of precise measurement of the flavor ratio.…”

“…With help of the synergetic observation of electromagnetic wave messengers, the promising sources of HANs are indicated [11][12][13][14]. Although considerable progress has been made in neutrino astronomy, there are several important problems to be solved: The uncertainty of flavor ratio measured at Earth is large [15,16]; No source of HANs is identified above the 5σ discovery threshold; How to explain the multi-messenger emission from the blazar TXS0506+056 is challenging [17][18][19]; The production mechanism of HANs is unclear.…”

Energy-Dependent Neutrino Mixing Parameters at Oscillation Experiments

“…As far as detection at IceCube is concerned, we fix Q 2 d = 10 3 GeV, for simplicity. The IceCube collaboration has released results [83,84] on the flavor composition of astrophysical neutrinos, an observable that is also one of the pillars of the forthcoming IceCube-Gen2 upgrade [85,86]. The initial flavor composition (ν e :ν µ :ν τ ) of O(PeV) neutrinos (note that, here, we do not distinguish between neutrinos and antineutrinos) from astrophysical neutrino sources is uncertain due to our poor knowledge of the nature of these sources and the mechanism behind neutrino production.…”