REVIEW
Leptogenesis in Inflaton Decay
High Energy Physics - Phenomenology · Submitted 15 Jun 1999 · 26 references
Pith's verdict: A useful, honest consistency check that non-thermal leptogenesis survives the gravitino bound at TR ~ 10^8 GeV, though the 'fully consistent' wording leans on an uncomputed branching ratio.
T0 · AI review
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Referee report
The paper
The paper claims
The paper argues that the universe's matter–antimatter asymmetry can be generated by heavy Majorana neutrinos produced in inflaton decays, so that the reheating temperature can stay near $10^8$ GeV and the gravitino problem is avoided.
The reading
What carries the argument
The mechanism is the CP-violating decay asymmetry of the lightest heavy Majorana neutrino, $epsilon_1$, generated by interference between tree-level and one-loop diagrams. Using the see-saw relation and the measured atmospheric neutrino mass splitting, the authors reduce it to $epsilon_1$ approximately $(3 delta_eff/16 pi)(m_{nu 3} M_1 / langle H_u rangle^2)$, which is about $-10^{-6}$ for $M_1 = 10^{10}$ GeV. Combined with the non-thermal production rate, this gives a single constraint on the ratio of inflaton mass to heavy neutrino mass, $2 < m_phi/M_1 <$ roughly $100 Br$, which is the condition that ties the inflation model to the neutrino mass spectrum. The Froggatt-Nielsen charges in the lepton sector do the rest: they fix $M_1$ at either $10^{10}$ or $10^{13}$ GeV depending on the charge assigned to $N_1$, and each choice lands in the mass window of one of the two inflation models.
Extended reading notes
Core claim
The central result is a compact formula for the lepton-to-entropy ratio produced when the lightest heavy Majorana neutrino $N_1$ is made in inflaton decays: $n_L/s$ is approximately $-10^{-6} Br (T_R/10^{10}~GeV)(M_1/m_phi)$, where $Br$ is the inflaton branching ratio into the $N_1$ channel, $T_R$ the reheating temperature, $M_1$ the heavy neutrino mass and $m_phi$ the inflaton mass. Because $N_1$ decays almost immediately after being produced, its number density is fixed by the inflaton decay rather than by thermal equilibrium, and the asymmetry survives as long as $M_1$ exceeds roughly $100 T_R$. The authors then check two concrete supersymmetric inflation models. A topological inflation model gives $m_phi$ of order $10^{11}$ to $10^{12}$ GeV and $T_R$ near $10^8$ GeV, which with $M_1$ around $10^{10}$ GeV yields $n_L/s$ of order $-10^{-10}$. A hybrid inflation model gives $m_phi$ of order $10^{13}$ to $10^{15}$ GeV, which with $M_1$ around $10^{13}$ GeV yields the same asymmetry. Both values match the observed baryon asymmetry $n_B/s$ of roughly $(0.1$ to $1) imes 10^{-10}$ after the sphaleron conversion factor of about $-8/23$.
Load-bearing premise
The chain depends on the inflaton branching ratio into the lightest heavy neutrino being somewhere between about 0.01 and 1, and on the flavour charge of that neutrino being chosen so that its mass sits in the narrow window between one fiftieth and one half of the inflaton mass.
Editorial extensions
If this is right
- Leptogenesis survives the cosmological gravitino bound: the reheating temperature can be as low as $10^8$ GeV, roughly two orders of magnitude below what thermal leptogenesis with the same heavy-neutrino mass would require.
- Topological inflation with $m_phi$ of order $10^{11}$ to $10^{12}$ GeV and hybrid inflation with $m_phi$ of order $10^{13}$ to $10^{15}$ GeV both accommodate the observed baryon asymmetry, so the scenario does not single out one inflation model.
- The Froggatt-Nielsen charge of the lightest heavy neutrino selects which inflation model works: $M_1$ near $10^{10}$ GeV pairs with topological inflation and $M_1$ near $10^{13}$ GeV pairs with hybrid inflation.
- If the extra U(1) gauge symmetry of the hybrid model is identified with $B-L$, the inflaton decays mainly through Yukawa couplings to heavy neutrinos and the branching ratio into $N_1$ can be of order one, which is the most favourable case for the asymmetry.
- A lower inflaton mass near $10^{10}$ GeV, only slightly above $2 M_1$, could still give the observed asymmetry with $T_R$ as low as $10^6$ to $10^7$ GeV.
Reading between the lines
- The branching ratio $Br$ is the least constrained input in the chain: it is asserted to be of order 0.1 to 1 rather than computed from the Kähler-potential couplings $C_i$ and $C'_i$, so an explicit calculation of those couplings would convert the scenario from a consistent fit into a prediction.
- Because the asymmetry scales linearly with $Br$ and with $M_1/m_phi$, a modest suppression of either pushes the predicted $n_L/s$ below $10^{-10}$; this makes the scenario more sensitive to the inflaton-to-heavy-neutrino coupling than to the CP phase, which is already taken maximal.
- The same non-thermal production channel would let a heavy neutrino with mass far above the reheating temperature leave a cosmological trace, so the reheating temperature inferred from gravitino bounds does not by itself bound the heavy-neutrino mass scale.
- If the lightest heavy neutrino mass were eventually pinned by neutrino-oscillation data and leptonic CP violation to a value outside the $10^{10}$ to $10^{13}$ GeV window used here, the pairing with these two inflation models would break even though the general non-thermal mechanism would survive.
Original abstract
We study a leptogenesis via decays of heavy Majorana neutrinos produced non-thermally in inflaton decays. We find that this scenario is fully consistent with existing supersymmetric inflation models such as for topological or for hybrid inflation and the Froggatt-Nielsen mechanism generating hierarchies in quark and lepton mass matrices. The reheating temperature $T_R$ of inflation may be taken as low as $T_R \simeq 10^8$ GeV to avoid the cosmological gravitino problem.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
We study a leptogenesis via decays of heavy Majorana neutrinos produced non-thermally in inflaton decays. We find that this scenario is fully consistent with existing supersymmetric inflation models such as for topological or for hybrid inflation and the Froggatt-Nielsen mechanism generating hierarchies in quark and lepton mass matrices. The reheating temperature $T_R$ of inflation may be taken as low as $T_R \simeq 10^8$ GeV to avoid the cosmological gravitino problem.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We study a leptogenesis via decays of heavy Majorana neutrinos produced non-thermally in inflaton decays. | contribution 1.00 | 0.77 | 0.11 | asserted 0.87 |
| s1 | We find that this scenario is fully consistent with existing supersymmetric inflation models such as for topological or for hybrid inflation and the Froggatt-Nielsen mechanism generating hierarchies in quark and lepton mass matrices. | result 0.87 | 0.86 | 0.25 | asserted 0.68 |
| s2 | The reheating temperature $T_R$ of inflation may be taken as low as $T_R \simeq 10^8$ GeV to avoid the cosmological gravitino problem. | result 0.94 | 0.56 | 0.18 | hedged possibility 1.00 |
What was examined, and what was not
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References
How the literature uses it
64 arXiv papers cite this in 87 sentences
Papers citing it · 67 sentences without a confident label
Builds on it 1 paper
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Thus, we obtain a generalized bound for an arbitrary number of right–handed neutrinos: [equation] This is identical to the “weaker” version of the Davidson–Ibarra bound in [ref] , which was also found in Ref. [ref] .
The Seesaw with Many Right-Handed Neutrinos · Comments on Leptogenesis · 0.82
Compares with it 1 paper
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In contrast to the original model [ref] , the inflaton eventually falls into another vacuum determined by the soft SUSY breaking effects.
Disappearing Inflaton Potential via Heavy Field Dynamics · Introduction · 0.95
Cites it as background 16 papers
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Here a lepton asymmetry is generated (solely) from the decay of the lightest right–handed neutrino $N_1$, and the model parameters are chosen such that the measured squared mass differences and mixing angles of the light neutrinos are reproduced. $N_1$ can be produced either thermally [ref] or non–thermally (via inflaton decay) [ref] , depending on its mass and on the reheating temperature.
Parameter Space of Leptogenesis in Polynomial Inflation · Introduction · 0.92
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In the second class of models, the heavy Majorana neutrinos are produced nonthermally via inflaton decay [ref] , nonperturbative preheating [ref] , or other interactions [ref] .
Nonthermal leptogenesis via cosmological gravitational particle production is tested by inflationary gravitational waves · Introduction · 0.97
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The alternative possibility of non-thermal leptogenesis, either at reheating from inflaton decay [ref] , or at preheating [ref] allows for lower reheat temperatures than thermal leptogenesis.
Examining leptogenesis with lepton flavor violation and the dark matter abundance · Introduction · 0.91
Discussion
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