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Title: Suppression of the neutralino relic density with supersymmetric CP violation

Abstract

We study pair annihilations of the neutralino dark matter in the minimal supersymmetric standard model with CP violation. We consider the case that the Higgsino mass and the trilinear scalar couplings have CP-violating phases of order unity, taking a scenario that the scalar fermions in the first two generations are much heavier than those in the third generation to avoid a severe constraint from experimental limits on electric dipole moments. It is found that, when the lightest neutralino ({chi}) is binolike, the cross sections of the W-boson pair production {chi}{chi}{yields}W{sup +}W{sup -} and the lightest Higgs boson pair production {chi}{chi}{yields}H{sub 2}{sup 0}H{sub 2}{sup 0} for nonrelativistic neutralinos can be significantly enhanced by the phase of the Higgsino mass. The relic density of the neutralino can be considerably suppressed by this effect. However, even this suppression is not enough to make binolike dark matter consistent with a cosmological constraint. We also discuss the effect of CP violation on the positron flux from neutralino pair annihilations in the galactic halo.

Authors:
 [1]
  1. Department of Physics, College of Science and Technology, Nihon University, 1-8-14, Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8308 (Japan)
Publication Date:
OSTI Identifier:
20776684
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. D, Particles Fields; Journal Volume: 73; Journal Issue: 3; Other Information: DOI: 10.1103/PhysRevD.73.035005; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ANNIHILATION; COUPLING; CP INVARIANCE; CROSS SECTIONS; DENSITY; ELECTRIC DIPOLE MOMENTS; HIGGS BOSONS; NONLUMINOUS MATTER; PAIR PRODUCTION; POSITRONS; REST MASS; SCALARS; STANDARD MODEL; SUPERSYMMETRY; W MINUS BOSONS; W PLUS BOSONS

Citation Formats

Nihei, Takeshi. Suppression of the neutralino relic density with supersymmetric CP violation. United States: N. p., 2006. Web. doi:10.1103/PhysRevD.73.035005.
Nihei, Takeshi. Suppression of the neutralino relic density with supersymmetric CP violation. United States. doi:10.1103/PhysRevD.73.035005.
Nihei, Takeshi. Wed . "Suppression of the neutralino relic density with supersymmetric CP violation". United States. doi:10.1103/PhysRevD.73.035005.
@article{osti_20776684,
title = {Suppression of the neutralino relic density with supersymmetric CP violation},
author = {Nihei, Takeshi},
abstractNote = {We study pair annihilations of the neutralino dark matter in the minimal supersymmetric standard model with CP violation. We consider the case that the Higgsino mass and the trilinear scalar couplings have CP-violating phases of order unity, taking a scenario that the scalar fermions in the first two generations are much heavier than those in the third generation to avoid a severe constraint from experimental limits on electric dipole moments. It is found that, when the lightest neutralino ({chi}) is binolike, the cross sections of the W-boson pair production {chi}{chi}{yields}W{sup +}W{sup -} and the lightest Higgs boson pair production {chi}{chi}{yields}H{sub 2}{sup 0}H{sub 2}{sup 0} for nonrelativistic neutralinos can be significantly enhanced by the phase of the Higgsino mass. The relic density of the neutralino can be considerably suppressed by this effect. However, even this suppression is not enough to make binolike dark matter consistent with a cosmological constraint. We also discuss the effect of CP violation on the positron flux from neutralino pair annihilations in the galactic halo.},
doi = {10.1103/PhysRevD.73.035005},
journal = {Physical Review. D, Particles Fields},
number = 3,
volume = 73,
place = {United States},
year = {Wed Feb 01 00:00:00 EST 2006},
month = {Wed Feb 01 00:00:00 EST 2006}
}
  • We study the neutralino relic density and the neutralino-proton elastic scattering cross sections in the minimal supersymmetric standard model (MSSM) with CP-violating phases. We include all the final states to the neutralino pair annihilation cross section at the tree level, taking into account the mixing between the CP-even and CP-odd neutral Higgs fields. We show that variations of the relic density and the elastic scattering cross sections with the CP-violating phases are significant. In particular, interferences between the major contributions in the neutralino annihilation cross section can cause considerable enhancement of the relic density.
  • We calculate the relic density of dark matter in the MSSM with CP violation. We analyze various scenarios of neutralino annihilation: the cases of a b-ino, b-ino-W-ino and b-ino-Higgsino LSP, annihilation through Higgs, as well as sfermion coannihilation scenarios. Large phase effects are found--on the one hand, due to shifts in the masses; on the other hand, due to modifications of the couplings. Taking special care to disentangle the effects in masses and couplings, we demonstrate that the presence of CP phases can have a significant influence on the neutralino relic abundance. Typical variations in {omega}h{sup 2} solely from modificationsmore » in the couplings are O (10%-100%), but can reach an order of magnitude in some cases.« less
  • We discuss the lower bound to the lightest Higgs boson H{sub 1} in the minimal supersymmetric extension of the standard model with explicit CP violation, and the phenomenology of the lightest relic neutralino in the same scenario. In particular, adopting the CPX benchmark scenario, we find that the combination of experimental constraints coming from LEP, thallium electric dipole moment measurements, quarkonium decays, and B{sub s}{yields}{mu}{mu} decay favors a region of the parameter space where the mass of H{sub 1} is in the range 7 GeV < or approx. M{sub H{sub 1}} < or approx. 10 GeV, while 3 < ormore » approx. tan{beta} < or approx. 5. Assuming a departure from the usual grand unified theory relation among gaugino masses (|M{sub 1}|<<|M{sub 2}|), we find that through resonant annihilation to H{sub 1} a neutralino as light as 2.9 GeV can be a viable dark matter candidate in this scenario. We call this the CPX light neutralino scenario and discuss its phenomenology showing that indirect dark matter searches are compatible with the present experimental constraints, as long as m{sub {chi}}< or approx. M{sub H{sub 1/2}}. On the other hand, part of the range m{sub {chi}} > or approx. M{sub H{sub 1/2}} which is allowed by cosmology is excluded by antiproton fluxes.« less
  • We discuss ILC measurements for a specific MSSM scenario with CP phases, where the lightest neutralino is a good candidate for dark matter, annihilating efficiently through t-channel exchange of light staus. These prospective (CP-even) ILC measurements are then used to fit the underlying model parameters. A collider prediction of the relic density of the neutralino from this fit gives 0.116<{omega}h{sup 2}<0.19 at 95% C.L. CP-odd observables, while being a direct signal of CP violation, do not help in further constraining {omega}h{sup 2}. The interplay with (in)direct detection of dark matter and with measurements of electric dipole moments is also discussed.more » Finally we comment on collider measurements at higher energies for refining the prediction of {omega}h{sup 2}.« less