Neutrinos in supernovae, neutron stars, and in the early Universe may change flavor collectively and unstably, due to neutrino-neutrino forward scattering. We prove that, for collective instability ...to occur, the difference of momentum distributions of two flavors must change sign, i.e., there is a zero crossing. This necessary criterion, which unifies slow and fast instabilities, is valid for Hamiltonian flavor evolution of ultrarelativistic standard model neutrino occupation matrices, including damping due to collisions in the relaxation approximation. It provides a simple but rigorous condition for collective flavor transformations that are believed to be important for stellar dynamics, nucleosynthesis, and neutrino phenomenology.
Neutrinos, being the only fermions in the Standard Model of Particle Physics that do not possess electromagnetic or color charges, have the unique opportunity to communicate with fermions outside the ...Standard Model through mass mixing. Such Standard Model-singlet fermions are generally referred to as “sterile neutrinos”. In this review article, we discuss the theoretical and experimental motivation for sterile neutrinos, as well as their phenomenological consequences. With the benefit of hindsight in 2020, we point out potentially viable and interesting ideas. We focus in particular on sterile neutrinos that are light enough to participate in neutrino oscillations, but we also comment on the benefits of introducing heavier sterile states. We discuss the phenomenology of eV-scale sterile neutrinos in terrestrial experiments and in cosmology, we survey the global data, and we highlight various intriguing anomalies. We also expose the severe tension that exists between different data sets and prevents a consistent interpretation of the global data in at least the simplest sterile neutrino models. We discuss non-minimal scenarios that may alleviate some of this tension. We briefly review the status of keV-scale sterile neutrinos as dark matter and the possibility of explaining the matter–antimatter asymmetry of the Universe through leptogenesis driven by yet heavier sterile neutrinos.
Galaxy clusters are one of the most promising candidate sites for dark matter (DM) annihilation. We focus on DM ( chi ) with mass in the range of 10 GeV-100 TeV, annihilating through the channels chi ...chi arrow right mu super(+) mu super(-), chi chi arrow right nunu, chi chi arrow right tt, or chi chi arrow right nunununu, and forecast the expected sensitivity to the annihilation cross section into these channels by observing galaxy clusters at IceCube/KM3NeT. Optimistically, the presence of DM substructures in galaxy clusters is predicted to enhance the signal by 2-3 orders of magnitude over the contribution from the smooth component of the DM distribution. Optimizing for the angular size of the region of interest for galaxy clusters, the sensitivity to the annihilation cross section, left angle bracketsigmaupsilonright angle bracket of heavy DM with mass in the range of 300 GeV-100 TeV will be O(10 super(-24) cm super(3) s super(-1)) for full IceCube/KM3NeT live time of 10 years, which is about one order of magnitude better than the best limit that can be obtained by observing the Milky Way halo. We find that neutrinos from cosmic ray interactions in the galaxy cluster, in addition to the atmospheric neutrinos, are a source of background. We show that significant improvement in the experimental sensitivity can be achieved for lower DM masses in the range of 10-300 GeV if neutrino-induced cascades can be reconstructed to asymptotically = 5degrees accuracy, as may be possible in KM3NeT. We, therefore, propose that a low-energy extension "KM3NeT-Core," similar to DeepCore in IceCube, be considered for an extended reach at low DM masses.
Aidnogenesis via leptogenesis and dark sphalerons Blennow, Mattias; Dasgupta, Basudeb; Fernandez-Martinez, Enrique ...
The journal of high energy physics,
2011 3, Volume:
2011, Issue:
3
Journal Article
We study the fully nonlinear fast flavor evolution of neutrinos in 1 + 1 dimensions. Our numerical analysis shows that at late times, the system reaches an approximately steady state. Using the ...steady-state approximation, we analytically show that the spatial variation of the polarization vectors is given by their precession around a common axis, which itself has a motion reminiscent of a gyroscopic pendulum. We then show that the steady-state solution to the equations of motion cannot be separated in position and velocity-that is, the motion is not collective in the usual sense. However, the fast evolution allows spectral-swap-like dynamics leading to partial decoherence over a range of velocities, constrained by the conservation of lepton number(s). Finally, we numerically show that at late times, the transverse components of the polarization vectors become randomly oriented at different spatial locations for any velocity mode and lepton asymmetry.
Aidnogenesis via leptogenesis and dark sphalerons Blennow, Mattias; Dasgupta, Basudeb; Fernandez-Martinez, Enrique ...
The journal of high energy physics,
03/2011, Volume:
2011, Issue:
3
Journal Article
Peer reviewed
Open access
We discuss aidnogenesis,
1
i.e. the generation of a dark matter asymmetry, via new sphaleron processes associated to an extra non-abelian gauge symmetry common to both the visible and the dark ...sectors. Such a theory can naturally produce an abundance of asymmetric dark matter which is of the same size as the lepton and baryon asymmetries, as suggested by the similar sizes of the observed baryonic and dark matter energy content, and provide a definite prediction for the mass of the dark matter particle. We discuss in detail a minimal realization in which the Standard Model is only extended by dark matter fermions which form “dark baryons” through an SU(3) interaction, and a (broken) horizontal symmetry that induces the new sphalerons. The dark matter mass is predicted to be ∼ 6 GeV, close to the region favored by DAMA and CoGeNT. Furthermore, a remnant of the horizontal symmetry should be broken at a lower scale and can also explain the Tevatron dimuon anomaly.
Flavor-dependent neutrino emission is critical to the evolution of a supernova and its neutrino signal. In the dense anisotropic interior of the star, neutrino-neutrino forward scattering can lead to ...fast collective neutrino oscillations, which has striking consequences. We present a theory of fast flavor depolarization, explaining how neutrino flavor differences become smaller, i.e., depolarize, due to diffusion to smaller angular scales. We show that transverse relaxation determines the epoch of this irreversible depolarization. We give a method to compute the depolarized fluxes, presenting an explicit formula for simple initial conditions, which can be a crucial input for supernova theory and neutrino phenomenology.
Neutrinos in dense environments undergo collective pair conversions νeν¯e↔νxν¯x, where x is a nonelectron flavor, due to forward scattering off each other that may be a crucial ingredient for ...supernova explosions. Depending on the flavor-dependent local angular distributions of the neutrino fluxes, the conversion rate can be “fast,” i.e., of the order μ=2GFnν, which can far exceed the usual neutrino oscillation frequency ω=Δm2/(2E). Until now, this surprising nonlinear phenomenon has only been understood in the linear regime and explored further using numerical experiments. We present an analytical treatment of the simplest system that exhibits fast conversions, and show that the conversion can be understood as the dynamics of a particle rolling down in a quartic potential, governed dominantly by μ but seeded by slower subleading effects.
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