Bibliographic record
Abstract
We explore the big-bang nucleosynthesis (BBN) constraint on heavy neutrino that is a mixture of gauge-singlet fermion and active neutrinos in the Standard Model. We work in the minimal model with only two parameters, the heavy neutrino mass m 4 and the mixing parameter | U a 4 | 2 , where a = e , μ , or τ stands for the active neutrino flavor. We show that both the early Universe production mechanism and decay products of the heavy neutrino are determined by m 4 and | U a 4 | 2 , with little room for further assumptions. This predictability allows us to present a portrait of the entire BBN excluded parameter space. As a novel result, we derive the lower boundary of the BBN exclusion in the | U a 4 | 2 versus m 4 parameter space. Our analysis includes various effects including temporary matter domination, energy injections in the form of charged mesons, photons, and light neutrinos. The BBN constraint is complementary to the terrestrial search for heavy neutrinos (heavy neutral leptons) behind the origin of neutrino masses and a portal to the dark sector.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.003 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.003 |
| Open science | 0.001 | 0.002 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.008 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".