Increasing the Effective Number of Neutrinos with Decaying Particles

Ichikawa, Kazuhide; Kawasaki, Masahiro; Nakayama, Kazunori; Senami, Masato; Takahashi, Fuminobu

doi:10.1063/1.2823816

Cited by 17 publications

(28 citation statements)

References 47 publications

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“…The model is specified by the mSUGRA parameter set augmented by one additional parameter, M 2 : 4) where M 1 = M 3 ≡ m 1/2 , but M 2 is allowed to be free (with either sign). We take m t = 171.4 GeV, in accord with recent mass determinations [29].…”

Section: Jhep10(2007)088mentioning

confidence: 99%

Mixed higgsino dark matter from a large SU(2) gaugino mass

Baer

Mustafayev

Summy

et al. 2007

J. High Energy Phys.

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We observe that in SUSY models with non-universal GUT scale gaugino mass parameters, raising the GUT scale SU(2) gaugino mass |M 2 | from its unified value results in a smaller value of −m 2Hu at the weak scale. By the electroweak symmetry breaking conditions, this implies a reduced value of µ 2 visà vis models with gaugino mass unification. The lightest neutralino can then be mixed Higgsino dark matter with a relic density in agreement with the measured abundance of cold dark matter (DM). We explore the phenomenology of this high |M 2 | DM model. The spectrum is characterized by a very large wino mass and a concomitantly large splitting between left-and right-sfermion masses. In addition, the lighter chargino and three light neutralinos are relatively light with substantial higgsino components. The higgsino content of the LSP implies large rates for direct detection of neutralino dark matter, and enhanced rates for its indirect detection relative to mSUGRA. We find that experiments at the LHC should be able to discover SUSY over the portion of parameter space where mg < ∼ 2350 − 2750 GeV, depending on the squark mass, while a 1 TeV electron-positron collider has a reach comparable to that of the LHC. The dilepton mass spectrum in multi-jet + ℓ + ℓ − + E miss T events at the LHC will likely show more than one mass edge, while its shape should provide indirect evidence for the large higgsino content of the decaying neutralinos.

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Section: Jhep10(2007)088mentioning

confidence: 99%

Mixed higgsino dark matter from a large SU(2) gaugino mass

Baer

Mustafayev

Summy

et al. 2007

J. High Energy Phys.

View full text Add to dashboard Cite

show abstract

“…It should be noticed that it may also open the decay mode of gravitino into axino and axion [63], and this newly produced non-thermal axions serve as the additional radiation energy density [64], which speeds-up the Hubble expansion and changes the result of BBN especially the 4 He abundance. In terms of the effective number of neutrinos N ν , the success of BBN requires ∆N ν 1 at the beginning of BBN 6 .…”

Section: B Gravitinos From Modulus Decaymentioning

confidence: 99%

Baryon asymmetry in a heavy moduli scenario

Kawasaki

Nakayama

2007

Phys. Rev. D

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In some models of supersymmetry breaking, modulus fields are heavy enough to decay before BBN. But the large entropy produced via moduli decay significantly dilutes the preexisting baryon asymmetry of the universe. We study whether Affleck-Dine mechanism can provide enough baryon asymmetry which survives the dilution, and find several situations in which desirable amount of baryon number remains after the dilution. The possibility of non-thermal dark matter is also discussed. This provides the realistic cosmological scenario with heavy moduli.

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“…Therefore, the Universe must have become radiation dominated at some point after inflation, but we do not know when that transition occurred, nor do we know how the Universe evolved between inflation and the onset of radiation domination. The existence of the cosmic neutrino background provides the most robust constraint on the temperature of the Universe when it became radiation dominated: this reheat temperature must exceed 3 MeV to generate the neutrinos required to produce the observed abundances of light elements [4][5][6][7] and the observed power spectra of anisotropies in the cosmic microwave background and large-scale density perturbations [8,9]. The vast difference between 3 MeV and the theorized energy scale of inflation leaves a tremendous gap in our understanding of the thermal history of the Universe.…”

Section: Introductionmentioning

confidence: 99%

The dark matter annihilation boost from low-temperature reheating

Erickcek

2015

Phys. Rev. D

185

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The evolution of the Universe between inflation and the onset of Big Bang Nucleosynthesis is difficult to probe and largely unconstrained. This ignorance profoundly limits our understanding of dark matter: we cannot calculate its thermal relic abundance without knowing when the Universe became radiation dominated. Fortunately, small-scale density perturbations provide a probe of the early Universe that could break this degeneracy. If dark matter is a thermal relic, density perturbations that enter the horizon during an early matter-dominated era grow linearly with the scale factor prior to reheating. The resulting abundance of substructure boosts the annihilation rate by several orders of magnitude, which can compensate for the smaller annihilation cross sections that are required to generate the observed dark matter density in these scenarios. In particular, thermal relics with masses less than a TeV that thermally and kinetically decouple prior to reheating may already be ruled out by Fermi-LAT observations of dwarf spheroidal galaxies. Although these constraints are subject to uncertainties regarding the internal structure of the microhalos that form from the enhanced perturbations, they open up the possibility of using gamma-ray observations to learn about the reheating of the Universe.

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Increasing the Effective Number of Neutrinos with Decaying Particles

Cited by 17 publications

References 47 publications

Mixed higgsino dark matter from a large SU(2) gaugino mass

Mixed higgsino dark matter from a large SU(2) gaugino mass

Baryon asymmetry in a heavy moduli scenario

The dark matter annihilation boost from low-temperature reheating

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