REVIEW
Asymmetric Sneutrino Dark Matter and the Omega(b)/Omega(DM) Puzzle
High Energy Physics - Phenomenology · Submitted 7 Oct 2004 · 21 references
Pith's verdict: A modest, checkable paper: the new content is the sneutrino-to-baryon asymmetry ratio A/A_bary = k/3 to k/6 and the asymmetric relic-density scan, and both hold up; the equilibrium assumptions the reader worried about are fine, the thin spots are the single-point scan and the flavor constraint.
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Referee report
The paper
The paper claims
The paper argues that if dark matter carries the same conserved quantum number as baryons, it inherits the baryon asymmetry, so the two cosmic densities are linked rather than independently set by unrelated physics.
The reading
What carries the argument
The load-bearing device is chemical equilibration: for every interaction in equilibrium among particle species, the chemical potentials satisfy a linear relation, and the asymmetry in number density of a species with mass below the temperature is $n - n̄ = g T^2 μ/6$. Applying this to the Standard Model plus $k$ light right-handed neutrino and sneutrino supermultiplets, the authors reduce the independent potentials to three and obtain $B = 6 T^2 μ_{u_L}$ for baryons and $S = 2k T^2 μ_{ν_L}/3$ for sneutrinos, so the ratio $A/A_{bary}$ is fixed by counting and by the non-perturbative sphaleron relation $3μ_{u_L} + μ_{ν_L} = 0$. The second device is the modified relic-density formalism for an asymmetric two-species relic, in which the antiparticle's contribution is weighted by a depletion factor $e^{-x}/(e^{-x}+A)$ inside the thermal integrals, interpolating between the standard two-species result and the asymmetry-limited floor $Ω h^2_{min} = Ω h^2_{bary} (A/A_{bary})(m/m_{bary})$.
Extended reading notes
Core claim
The central claim is that in the mixed sneutrino variant of the MSSM, where light neutrino masses come from higher-dimensional supersymmetry-breaking terms, the sneutrino is a viable asymmetric dark matter candidate whose abundance is tied to the baryon abundance. The argument has two halves. First, a chemical-potential analysis of the plasma above the electroweak phase transition, using the $B+L$ anomaly together with $SU(2)_W$ and $U(1)_Y$ gaugino interactions and the $O(m_W)$ trilinear $A$-terms that connect left- and right-handed sneutrinos, forces the sneutrino and baryon asymmetries into a fixed ratio, $1/3 > A/A_{bary} > 1/6$ for one light right-handed sneutrino supermultiplet. Second, feeding that asymmetry into the relic-density calculation changes the answer: the antisneutrino population is depleted early, so annihilation no longer erases the surviving particles, and the relic density is pushed from the symmetric result toward the asymmetry-limited floor set by the same number that fixes the baryon density. The authors compute the relic density including $s$-channel $Z$ exchange, $t$-channel neutralino and chargino exchange, and Higgs exchange, and show that the region of sneutrino mass and mixing angle compatible with the WMAP dark matter density is substantially enlarged once $A/A_{bary} = 1/6$ is imposed.
Load-bearing premise
The whole chain rests on the distributing interactions — electroweak sphalerons, gaugino interactions, and the $O(m_W)$ $A$-terms linking left- and right-handed sneutrinos — staying in chemical equilibrium down to the electroweak phase transition and then switching off, with the phase transition assumed first order.
Editorial extensions
If this is right
- The near-coincidence of $Ω_b$ and $Ω_{dm}$ becomes a consequence of a shared quantum number rather than a coincidence, with the dark matter mass naturally near a few times the proton mass, around 30 GeV in the simplest case.
- The WMAP-compatible region of mixed-sneutrino parameter space widens well beyond the narrow strip found without an asymmetry, extending to masses above 70 GeV where the symmetric calculation overproduces dark matter.
- The sneutrino flavor becomes a discriminant: a muon- or tau-flavored candidate produces a solar muon flux of order $10^{-12}\,\mathrm{cm}^{-2}\,\mathrm{s}^{-1}$ that conflicts with Super-Kamiokande and MACRO, while an electron-flavored candidate escapes those bounds.
- The asymmetry need not originate in a high-scale mechanism: the authors note that TeV-scale resonant leptogenesis in the same model could supply it, making the origin and the sharing of the asymmetry part of one story.
- Because R-parity is retained and the lightest superpartner is the mixed sneutrino, the mixing angle and mass that control the relic density also control collider signatures, giving the scenario a target at the LHC.
Reading between the lines
- The mechanism is not specific to sneutrinos: any weak-scale dark matter particle carrying $B-L$ and annihilating efficiently with its own antiparticle would land in the same place, so the sneutrino is a worked example of a broader class rather than a unique prediction.
- If the ratio $A/A_{bary}$ really is fixed by equilibration rather than by the unknown CP phases, the dark matter mass is pinned to roughly $m_{bary} \times Ω_{dm}/Ω_b$, so a firmly established asymmetric candidate much heavier than that would need extra entropy production or a different charge assignment to stay consistent.
- The large elastic scattering cross section the authors cite as a liability for standard sneutrino dark matter becomes a virtue here: the same low-mass window that the asymmetry opens should be reachable by direct detection and by solar capture searches, so the scenario is testable in more than one channel.
- The prediction depends on the $B-L$-breaking scale entering only through the small neutrino masses, so improved neutrino mass and mixing measurements, particularly the ordering, indirectly constrain how weakly the shared symmetry can be broken without spoiling the ratio.
Original abstract
The inferred values of the cosmological baryon and dark matter densities are strikingly similar, but in most theories of the early universe there is no true explanation of this fact; in particular, the baryon asymmetry and thus density depends upon unknown, and {\it a priori} unknown and possibly small, CP-violating phases which are independent of all parameters determining the dark matter density. We consider models of dark matter possessing a particle-antiparticle asymmetry where this asymmetry determines both the baryon asymmetry and strongly effects the dark matter density, thus naturally linking $\Omega_{\rm{b}}$ and $\Omega_{\rm{dm}}$. We show that sneutrinos can play the role of such dark matter in a previously studied variant of the MSSM in which the light neutrino masses result from higher-dimensional supersymmetry-breaking terms.
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
The inferred values of the cosmological baryon and dark matter densities are strikingly similar, but in most theories of the early universe there is no true explanation of this fact; in particular, the baryon asymmetry and thus density depends upon unknown, and {\it a priori} unknown and possibly small, CP-violating phases which are independent of all parameters determining the dark matter density. We consider models of dark matter possessing a particle-antiparticle asymmetry where this asymmetry determines both the baryon asymmetry and strongly effects the dark matter density, thus naturally linking $\Omega_{\rm{b}}$ and $\Omega_{\rm{dm}}$. We show that sneutrinos can play the role of such dark matter in a previously studied variant of the MSSM in which the light neutrino masses result from higher-dimensional supersymmetry-breaking terms.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | The inferred values of the cosmological baryon and dark matter densities are strikingly similar, but in most theories of the early universe there is no true explanation of this fact; in particular, the baryon asymmetry and thus density depends upon unknown, and {\it a priori} unknown and possibly small, CP-violating phases which are independent of all parameters determining the dark matter density. | background 0.66 | 0.05 | 0.04 | asserted 0.98 |
| s1 | We consider models of dark matter possessing a particle-antiparticle asymmetry where this asymmetry determines both the baryon asymmetry and strongly effects the dark matter density, thus naturally linking $\Omega_{\rm{b}}$ and $\Omega_{\rm{dm}}$. | contribution 0.98 | 0.59 | 0.55 | asserted 0.78 |
| s2 | We show that sneutrinos can play the role of such dark matter in a previously studied variant of the MSSM in which the light neutrino masses result from higher-dimensional supersymmetry-breaking terms. | contribution 0.90 | 0.86 | 0.31 | asserted 1.00 |
What was examined, and what was not
- arXiv listing abstract v2
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Figures
Figures reproduced from arXiv:hep-ph/0410114 by the authors.
References
How the literature uses it
69 arXiv papers cite this in 77 sentences
Papers citing it · 33 sentences without a confident label
Cites it as background 42 papers
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As for the DM candidates, by noticing that it is the number density difference between particles and anti-particles that induces the photon birefringence, we are led to consider the asymmetric DM (ADM) scenario [ref] (For reviews of ADM models, see Refs [ref] and references therein), in which all the observed DM density in the Universe is solely composed of fermionic DM particles without its anti-particle counterparts.
Cosmic Birefringence from Neutrino and Dark Matter Asymmetries · Introduction · 0.83
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Asymmetric DM candidates were put forward in [ref] as technibaryons, in [ref] as Goldstone bosons, and subsequently in many diverse forms [ref] .
Light Asymmetric Dark Matter on the Lattice: SU(2) Technicolor with Two Fundamental Flavors · Introduction · 0.99
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Most recent papers discussed the asymmetric Dark Matter models [ref] .
Abundance of Asymmetric Dark Matter in Brane World Cosmology · Introduction · 0.99
Discussion
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