Cosmic neutrino background search experiments as decaying dark matter detectors

We consider theories in which the generation of neutrino masses is associated with the breaking of an approximate global lepton number symmetry. In such a scenario the spectrum of light states includes the Majoron, the pseudo-Nambu Goldstone boson associated with the breaking of the global symmetry. For a broad range of parameters, the Majoron decays to neutrinos at late times, after the cosmic neutrinos have decoupled from the thermal bath, resulting in a secondary contribution to the cosmic neutrino background. We determine the current bounds on this scenario, and explore the possibility of directly detecting this secondary cosmic neutrino background in experiments based on neutrino capture on nuclei. For Majoron masses in the eV range or below, the neutrino flux from these decays can be comparable to that from the primary cosmic neutrino background, making it a promising target for direct detection experiments. The neutrinos from Majoron decay are redshifted by the cosmic expansion, and exhibit a characteristic energy spectrum that depends on both the Majoron mass and its lifetime. For Majoron lifetimes of order the age of the universe or larger, there is also a monochromatic contribution to the neutrino flux from Majoron decays in the Milky Way that can be comparable to the diffuse extragalactic flux. We find that for Majoron masses in the eV range, direct detection experiments based on neutrino capture on tritium, such as PTOLEMY, will be sensitive to this scenario with 100 gram-years of data. In the event of a signal, the galactic and extragalactic components can be distinguished on the basis of their distinct energy distributions, and also by using directional information obtained by polarizing the target nuclei.

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“…Note added: While this paper was being completed, we received Ref. [47], which discusses ideas similar to those considered here.…”

Section: Discussionmentioning

confidence: 99%

Detecting a secondary cosmic neutrino background from Majoron decays in neutrino capture experiments

Chacko

Geller

2019

Phys. Rev. D

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“…In order to derive the neutrino capture rate including such cosmological effects, we begin by considering the scattering amplitude for the process in Eq. (22). Since we are interested in the reaction at an energy much lower than the weak boson masses, the approximate four-Fermi interaction process can be used to calculate the amplitude.…”

Section: Precise Neutrino Capture Rate Including Cosmological Effectsmentioning

confidence: 99%

“…It would also test if they were produced less in very low reheating scenarios [16][17][18][19][20][21]; if their spectra and energy densities were modified by the decay of a heavy particle into neutrinos (see e.g. [22][23][24][25]); or if some dark radiation contributes to N eff .…”

Section: Introductionmentioning

confidence: 99%

Precise capture rates of cosmic neutrinos and their implications on cosmology

2021

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We explore the potential of measurements of cosmological effects, such as neutrino spectral distortions from the neutrino decoupling and neutrino clustering in our Galaxy, via cosmic neutrino capture on tritium. We compute the precise capture rates of each neutrino species including such cosmological effects to probe them. These precise estimates of capture rates are also important in that the would-be deviation of the estimated capture rate could suggest new neutrino physics and/or a non-standard evolution of the universe. In addition, we discuss the precise differences between the capture rates of Dirac and Majorana neutrinos for each species, the required energy resolutions to detect each neutrino species and the method of reconstruction of the spectrum of cosmic neutrinos via the spectrum of emitted electrons, with emphasis on the PTOLEMY experiment.

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“…The most promising method 2 of direct detections of the CνB is neutrino capture on β-decaying nuclei [49,50], in particular on tritium target [51][52][53][54][55], via the inverse β-decay process, ν i + 3 H → e − + 3 He (see refs. [56][57][58][59][60][61] for studies of physics beyond the SM via cosmic neutrino capture on tritium). This method has at least two merits: (i) this process includes no threshold energy, (ii) thanks to the energy injection of cosmic neutrinos, its energy of emitted electrons appears above the β-decay endpoint, 3 H → νi + e − + 3 He.…”

Section: Introductionmentioning

confidence: 99%

Unstable cosmic neutrino capture

Akita

Lambiase

Yamaguchi

2022

J. High Energ. Phys.

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Future direct observations of the Cosmic Neutrino Background (CνB) have the potential to explore a neutrino lifetime, especially in the region of the age of the universe, t0 = 4.35 × 1017 s. We forecast constraints on neutrino decay via capture of the CνB on tritium, with emphasis on the PTOLEMY-type experiment. In addition, in some cases of invisible neutrino decay into lighter neutrinos in the Standard Model and invisible particles, we can constrain not only the neutrino lifetime but also the masses of the invisible particles. For this purpose, we also formulate the energy spectra of the lighter neutrinos produced by 2-body and 3-body decays, and those of the electrons emitted in the process of the detection of the lighter neutrinos.

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Cosmic neutrino background search experiments as decaying dark matter detectors

Cited by 27 publications

References 56 publications

Detecting a secondary cosmic neutrino background from Majoron decays in neutrino capture experiments

Detecting a secondary cosmic neutrino background from Majoron decays in neutrino capture experiments

Precise capture rates of cosmic neutrinos and their implications on cosmology

Unstable cosmic neutrino capture

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