The nuMSM, leptonic asymmetries, and properties of singlet fermions

By M. Shaposhnikov. 2008

260 citations recorded by the source corpus.

We study in detail the mechanism of baryon and lepton asymmetry generation in the framework of the νMSM (an extension of the Standard Model by three singlet fermions with masses smaller than the electroweak scale). We elucidate the issue of CP-violation in the model and define the phase relevant for baryogenesis. We clarify the question of quantum-mechanical coherence, essential for the lepton asymmetry generation in singlet fermion oscillations and compute the relevant damping rates. The range of masses and couplings of singlet leptons which can lead to successful baryogenesis is determined. The conditions which ensure survival of primordial (existing above the electroweak temperatures) asymmetries in different leptonic numbers are analysed. We address the question whether CP-violating reactions with lepton number non-conservation can produce leptonic asymmetry below the sphaleron freeze-out temperature. This asymmetry, if created, leads to resonant production of dark matter sterile neutrinos. We show that the requirement that a significant lepton asymmetry be produced puts stringent constraints on the properties of a pair of nearly degenerate singlet fermions, which can be tested in accelerator experiments. In this region of parameters the νMSM provides a common mechanism for production of baryonic matter and dark matter in the universe. We analyse different fine-tunings of the model and discuss possible symmetries of the νMSM Lagrangian that can lead to them.

Subfields: Artificial Intelligence, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/9904dee3225379645c1fff92611b32afc974a380

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Citations in the corpus

Sterile neutrino Dark Matter (2018, background): “Resonant production ¥ The presence of lepton asymmetry makes this production much more effective – resonant production Shi Fuller’98 Laine, Shaposhnikov’08 ¥ To be effective this mechanism requires lepton asymmetry of the order nν−nν̄s & 10 −6 (compare with ηB = nb−nb̄ s ∼ 10 −10) ¥ Typically, one e”
The Phenomenology of Right Handed Neutrinos (2013, background): “νMSM comes at the price of a ”ﬁne tuning” in the mass splitting of two RH neutrinos: M2 and M3 have to be equal to a level of precision ∼ 10−13 [231]. This degeneracy may be related to new symmetries [158, 540], but cannot be explained in the framework of the νMSM itself. The tuning mainly arises fr”
Leptogenesis (2008, unknown): “If they succeed in establishing the Majorana nature of the light neutrinos,(25) this will strengthen our confidence that the seesaw mechanism is at the origin of the neutrino masses and, most importantly, will (24)The opposite result would not disprove sphaleron physics: see [283, 284] for a model i”
Dark Matter, Baryogenesis and Neutrino Oscillations from Right Handed Neutrinos (2012, background): “y the Majorana relations Nc I = NI and νi= νci. The matrix UN diagonalises the sterile neutrino mass matrix MN deﬁned below. The entries of the matrix θdetermine the active-sterile mixing angles. 4In [6] the notation is slightly diﬀerent and the letter “N I” does not denote mass eigenstates. 5 The n”
Thermal production of ultrarelativistic right-handed neutrinos: complete leading-order results (2012, methodology): “ remains far below the equilibrium density. This is the case in scenarios where the asymmetry is generated via oscillations between the right-handed 3Results for the broken phase can be found in Ref. [8]. The production rate in the low temperature regime has recently been calculated at next-to-leadi”
The Long-Baseline Neutrino Experiment: Exploring Fundamental Symmetries of the Universe (2013, background): “Different considerations indicate that their mass should be in the region of O(1) GeV [290].”
The Role of Sterile Neutrinos in Cosmology and Astrophysics (2008, background): “rement restricts the masses of N 2,3 to the 1 − 100 GeV region. A detailed analysis of this condition, accounting for numerical factors and complicated ﬂavor structure of asymmetry was carried out in [44]. It leads to a constraint marked “BAU”, shown in Fig. 1 (right panel) on the mass-mixing angle ”
Lyman-alpha constraints on warm and on warm-plus-cold dark matter models (2008, background): “Notice that this production channel is always present (although it may be subdominant, see below).”