Lepton Flavor Asymmetries: from the early Universe to BBN
Fuente:
arXiv
Gespeichert in:
| Hauptverfasser: | , , , |
|---|---|
| Format: | Preprint |
| Veröffentlicht: |
2025
|
| Schlagworte: | |
| Online-Zugang: | |
| Tags: |
Tag hinzufügen
Keine Tags, Fügen Sie den ersten Tag hinzu!
|
| _version_ | 1866915382530408448 |
|---|---|
| author | Domcke, Valerie Escudero, Miguel Navarro, Mario Fernandez Sandner, Stefan |
| author_facet | Domcke, Valerie Escudero, Miguel Navarro, Mario Fernandez Sandner, Stefan |
| contents | Large primordial lepton flavor asymmetries with almost vanishing total baryon-minus-lepton number can evade the usual BBN and CMB constraints if neutrino oscillations lead to perfect flavor equilibration. Solving the momentum averaged quantum kinetic equations (QKEs) describing neutrino oscillations and interactions, we perform the first systematic investigation of this scenario, uncovering a rich flavor structure in stark contradiction to the assumption of simple flavor equilibration. We find (i) a particular direction in flavor space, $Δn_e \simeq -2/3 \, (-1) Δn_μ$ for normal (inverted) neutrino mass hierarchy, in which the flavor equilibration is efficient and primordial asymmetries are essentially unconstrained, (ii) a minimal washout factor, $Δn_e^2|_\mathrm{BBN} \leq 0.03 \, (0.016) \sum_αΔn_α^2|_{\mathrm{ini}}$ yielding a conservative estimate for the allowed primordial asymmetries in a generic flavor direction, and (iii) particularly strong or weak washout if one of the initial flavor asymmetries vanishes due to non-adiabatic muon- or electron-driven MSW transitions. These results open up the possibility of a first-order QCD phase transition facilitated by large lepton asymmetries as well as baryogenesis from large and compensated $Δn_e =- Δn_μ$ asymmetries. Our first-principles approach of deriving momentum averaged QKEs includes collision terms beyond the damping approximation, energy transfer between the neutrino and electron-photon plasma, and provides a fast and reliable way to investigate the impact of primordial lepton asymmetries at the time of BBN. We publicly release the Mathematica code COFLASY-M on GitHub which solves the QKEs numerically. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2502_14960 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Lepton Flavor Asymmetries: from the early Universe to BBN Domcke, Valerie Escudero, Miguel Navarro, Mario Fernandez Sandner, Stefan High Energy Physics - Phenomenology Cosmology and Nongalactic Astrophysics Large primordial lepton flavor asymmetries with almost vanishing total baryon-minus-lepton number can evade the usual BBN and CMB constraints if neutrino oscillations lead to perfect flavor equilibration. Solving the momentum averaged quantum kinetic equations (QKEs) describing neutrino oscillations and interactions, we perform the first systematic investigation of this scenario, uncovering a rich flavor structure in stark contradiction to the assumption of simple flavor equilibration. We find (i) a particular direction in flavor space, $Δn_e \simeq -2/3 \, (-1) Δn_μ$ for normal (inverted) neutrino mass hierarchy, in which the flavor equilibration is efficient and primordial asymmetries are essentially unconstrained, (ii) a minimal washout factor, $Δn_e^2|_\mathrm{BBN} \leq 0.03 \, (0.016) \sum_αΔn_α^2|_{\mathrm{ini}}$ yielding a conservative estimate for the allowed primordial asymmetries in a generic flavor direction, and (iii) particularly strong or weak washout if one of the initial flavor asymmetries vanishes due to non-adiabatic muon- or electron-driven MSW transitions. These results open up the possibility of a first-order QCD phase transition facilitated by large lepton asymmetries as well as baryogenesis from large and compensated $Δn_e =- Δn_μ$ asymmetries. Our first-principles approach of deriving momentum averaged QKEs includes collision terms beyond the damping approximation, energy transfer between the neutrino and electron-photon plasma, and provides a fast and reliable way to investigate the impact of primordial lepton asymmetries at the time of BBN. We publicly release the Mathematica code COFLASY-M on GitHub which solves the QKEs numerically. |
| title | Lepton Flavor Asymmetries: from the early Universe to BBN |
| topic | High Energy Physics - Phenomenology Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2502.14960 |