A new probe of relic neutrino clustering using cosmogenic neutrinos

We present the first comprehensive discussion of constraints on the cosmic neutrino background (CνB) overdensity, including theoretical, experimental and cosmological limits for a wide range of neutrino masses and temperatures. Additionally, we calculate the sensitivities of future direct and indirect relic neutrino detection experiments and compare the results with the existing constraints, extending several previous analyses by taking into account that the CνB reference frame may not be aligned with that of the Earth. The Pauli exclusion principle strongly disfavours overdensities ην ≫ 1 at small neutrino masses, but allows for overdensities ην ≲ 125 at the KATRIN mass bound mν ≃ 0.8 eV. On the other hand, cosmology strongly favours 0.2 ≲ ην ≲ 3.5 in all scenarios. We find that direct detection proposals are capable of observing the CνB without a significant overdensity for neutrino masses mν ≳ 50 meV, but require an overdensity ην ≳ 3 × 105 outside of this range. We also demonstrate that relic neutrino detection proposals are sensitive to the helicity composition of the CνB, whilst some may be able to distinguish between Dirac and Majorana neutrinos.

Section: Jcap01(2023)003mentioning

confidence: 99%

Limits on the cosmic neutrino background

Bauer

Shergold

2023

“…The conceivability of such values is discussed in [21]. An alternative method to observe or constrain CNB overdensities with future neutrino detectors was studied in [22]. 2 The history of our Milky Way galaxy is believed to be filled with such accretion and merger events [30].…”

Section: Jcap11(2023)038mentioning

confidence: 99%

Influence of local structure on relic neutrino abundances and anisotropies

Zimmer,

Correa,

Ando

2023

Gravitational potentials of the Milky Way and extragalactic structures can influence the propagation of the cosmic neutrino background (CNB). Of particular interest to future CNB observatories, such as PTOLEMY, is the CNB number density on Earth. In this study, we have developed a simulation framework that maps the trajectories of relic neutrinos as they move through the local gravitational environment. The potentials are based on the dark matter halos found in state-of-the-art cosmological N-body simulations, resulting in a more nuanced and realistic input than the previously employed analytical models. We find that the complex dark matter distributions, along with their dynamic evolution, influence the abundance and anisotropies of the CNB in ways unaccounted for by earlier analytical methods. Importantly, these cosmological simulations contain multiple instances of Milky Way-like halos that we employ to model a variety of gravitational landscapes. Consequently, we notice a variation in the CNB number densities that can be primarily attributed to the differences in the masses of these individual halos. For neutrino masses between 0.01 and 0.3 eV, we note clustering factors within the range of 1 + 𝒪(10-3) to 1 + 𝒪(1). Furthermore, the asymmetric nature of the underlying dark matter distributions within the halos results in not only overdense, but intriguingly, underdense regions within the full-sky anisotropy maps. Gravitational clustering appears to have a significant impact on the angular power spectra of these maps, leading to orders of magnitude more power on smaller scales beyond multipoles of ℓ = 3 when juxtaposed against predictions by primordial fluctuations. We discuss how our results reshape our understanding of relic neutrino clustering and how this might affect observability of future CNB observatories such as PTOLEMY.GitHub: our simulation code will be made visiblehere.

“…At present, KATRIN [19] has set the leading laboratory bound on the CνB density, and there are other ongoing experimental efforts such as PTOLEMY [20]. The constraints on the profiles of dark matter and cosmic neutrinos JCAP02(2024)029 impact the physics interpretation of respective direct detection results, insofar as the density at the position of the experiment may be much larger than the value that is usually assumed (see, e.g., [8,21,22]).…”

Section: Introductionmentioning

confidence: 99%

OSIRIS-REx constraints on local dark matter and cosmic neutrino profiles

Tsai,

Eby,

Arakawa

et al. 2024

We derive purely gravitational constraints on dark matter and cosmic neutrino profiles in the solar system using asteroid (101955) Bennu. We focus on Bennu because of its extensive tracking data and high-fidelity trajectory modeling resulting from the OSIRIS-REx mission. We find that the local density of dark matter is bound by ρ DM ≲ 3.3 × 10-15 kg/m3 ≃ 6 × 106 ρ̅DM, in the vicinity of ∼ 1.1 au (where ρ̅DM ≃ 0.3 GeV/cm3). We show that high-precision tracking data of solar system objects can constrain cosmic neutrino overdensities relative to the Standard Model prediction n̅ν, at the level of η ≡ n ν/n̅ν ≲ 1.7 × 1011(0.1 eV/mν ) (Saturn), comparable to the existing bounds from KATRIN and other previous laboratory experiments (with mν the neutrino mass). These local bounds have interesting implications for existing and future direct-detection experiments. Our constraints apply to all dark matter candidates but are particularly meaningful for scenarios including solar halos, stellar basins, and axion miniclusters, which predict overdensities in the solar system. Furthermore, introducing a DM-SM long-range fifth force with a strength α̃D times stronger than gravity, Bennu can set a constraint on ρ DM ≲ ρ̅DM(6 × 106/α̃D). These constraints can be improved in the future as the accuracy of tracking data improves, observational arcs increase, and more missions visit asteroids.