Dark Matter interpretation of the neutron decay anomaly

Струмиа, Алессандро

doi:10.1007/jhep02(2022)067

Cited by 26 publications

(22 citation statements)

References 52 publications

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“…This is a kind of generic feature in determining the relic via co-annihilations in which the mass difference between two particle species should be comparable to the temperature at the relevant epoch [8]. In particular, the freeze-out temperature of χ in the non-relativistic scenario turns out to be T F ∼ (m n − m χ ) ∼ O (10) MeV for m χ = 0.92 GeV. It is clear that this condition is not satisfied for the relativistic freeze-out scenario when the mass of χ is away from the neutron mass.…”

Section: Relic Density Constraintmentioning

confidence: 96%

“…n + χ p + e − , where χ is considered as a charge-neutral Dirac fermion. Such a process can be motivated by the lepto-quark mediator models [9] in solving B-physics anomalies as well as solving the neutron decay anomaly [10]. Moreover, the process considered here can be instrumental for detecting sub-GeV particles (DM or exotic neutrinos) on the betadecaying nuclear targets [11][12][13].…”

Section: Coannihilation With Neutronmentioning

confidence: 99%

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Revisiting big bang nucleosynthesis with a new particle species : effect of co-annhilation with neutrons

Ghosh¹

2022

Preprint

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In big bang nucleosynthesis (BBN), the light matter abundance is dictated by the neutron-to-proton (n/p) ratio which is controlled by the standard weak processes in the early universe. Here, we study the effect of an extra particle species (χ) which co-annihilates with neutron, thereby potentially changing the (n/p) ratio in addition to the former processes. We find a novel interplay between the co-annihilation and the weak interaction in deciding the (n/p) ratio and the yield of χ. At the initial stage of BBN for the large co-annihilation strength (G D ) in comparison to the weak coupling (G F ), more neutrons are removed from the thermal bath modifying the (n/p) ratio from its standard evolution. We find that the standard BBN prediction is restored for G D /G F 10 −1 , while the mass of χ being much smaller than the neutron mass. When the mass of χ is comparable to the neutron mass, we can allow large G D /G F values, as the thermal abundance of χ becomes Boltzmann-suppressed. Therefore, the (n/p) ratio is restored to its standard value via dominant weak processes in later epochs. We also discuss the viability of this new particle to be a dark matter candidate.

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Section: Relic Density Constraintmentioning

confidence: 96%

Section: Coannihilation With Neutronmentioning

confidence: 99%

Revisiting big bang nucleosynthesis with a new particle species : effect of co-annhilation with neutrons

Ghosh¹

2022

Preprint

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“…The results are τ n (tot) = 878.52 ± 0.46 s (N = 9 and S = 1.8) and τ n (beam) = 888.0± 2.0 s (N = 2 and S = 0.3) which clearly disagree. A priori, it would be possible to hypothesize an additional neutron decay channel, into particles that are not detected, which would shorten the total average lifetime -a possible way out recently attempted [36]. This would require an agreement between the prediction and the exclusive measurement, namely that of τ n (beam), which is not what is observed: the predicted value τ n (SM) agrees with τ n (tot), but not with τ n (beam).…”

Section: The Neutron Lifetime Constraintmentioning

confidence: 99%

An accurate evaluation of electron (anti-)neutrino scattering on nucleons

Ricciardi

Vignaroli

Vissani

2022

J. High Energ. Phys.

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“…The results are τ n (tot) = 878.52 ± 0.46 s (N = 9 and S = 1.8) and τ n (beam) = 888.0 ± 2.0 s (N = 2 and S = 0.3) which clearly disagree each other. A priori, it would be possible to hypothesize an additional neutron decay channel, into particles that are not detected, which shortens the total average lifetime -a possible way out recently attempted [35]. This would require an agreement between the prediction and the exclusive measurement, namely that of τ n (beam), which is not what is observed: the predicted value τ n (SM) agrees with τ n (tot), but not with τ n (beam).…”

Section: The Neutron Lifetime Constraintmentioning

confidence: 99%

An accurate evaluation of electron (anti-)neutrino scattering on nucleons

Ricciardi,

Vignaroli,

Vissani

2022

Preprint

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We discuss as accurately as possible the cross section of quasi-elastic scattering of electron (anti-) neutrinos on nucleons, also known as inverse beta decay in the case of antineutrinos. We focus on the moderate energy range from a few MeV up to hundreds of MeV, and which includes neutrinos from reactors and supernovae. We assess the uncertainty on the cross section, which is relevant to experimental advances and increasingly large statistical samples. We estimate the effects of second-class currents, showing that they are small and negligible for current applications. INTRODUCTIONThe cross section of the process νe + p → e + + n (IBD, from inverse beta decay), which enabled the first direct observation of (anti-)neutrinos [1], is still essential today at relatively low energies for detectors that are based on water or hydrocarbons, i.e., the most commonly used detectors such as scintillators or Cherenkov light detectors.The most accurate estimates available today were described about 20 years ago by Beacom and Vogel [2] and by Strumia and Vissani [3]. In this paper, we aim to update the discussion, in consideration of some general facts: 1) the importance of the reaction itself, 2) the experimental progress of neutrino detectors, 3) the progress relating to the parameters that determine the reaction itself, 4) to quantify the role of second-class currents (SCCs) [4], previously omitted, but which has been the subject of a recent debate [5][6][7].Furthermore, there is a specific quantitative point that deserves to be highlighted: it is important to update not only the value, but also the estimate of the uncertainty on the cross section of the IBD process. Indeed, the conservative estimate of the uncertainty at low energies on this IBD cross section, obtained in [3] is 0.4 %. This corresponds to a statistical error over 60,000 events and therefore it is potentially relevant in cases where the statistical sample is quite large. There are at least two cases of this type, which concern reactor antineutrinos (with typical energies of 3 MeV and up to 10 MeV) and those from supernovae (with typical energies of 20 MeV and perhaps up to 60-70 MeV). We discuss them below:• Reactor neutrino experiment Daya Bay [8] has collected 3.5 million events already. Similar considerations apply to the other reactor experiments with very high statistics. But also the future detector JUNO [9] designed to study events from distant reactors, with a very large fiducial volume, about 20 kiloton of scintillator liquid, expects to collect 83 events/day and therefore in 6 years will amount to a total of 180000 events.• As for the future galactic supernova, Super-Kamiokande (SK) will collect more than 5000 IBD events with a mass of 32.4 kiloton and for a typical galactic distance of 10kpc (see e.g. [10]), a number that scales with the

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Dark Matter interpretation of the neutron decay anomaly

Cited by 26 publications

References 52 publications

Revisiting big bang nucleosynthesis with a new particle species : effect of co-annhilation with neutrons

Revisiting big bang nucleosynthesis with a new particle species : effect of co-annhilation with neutrons

An accurate evaluation of electron (anti-)neutrino scattering on nucleons

An accurate evaluation of electron (anti-)neutrino scattering on nucleons

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