Relic densities including Sommerfeld enhancements in the MSSM

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Abstract

We have developed a general formalism to compute Sommerfeld enhancement (SE) factors for a multi-state system of fermions, in all possible spin configurations and with generic long-range interactions. We show how to include such SE effects in an accurate calculation of the thermal relic density for WIMP dark matter candidates. We apply the method to the MSSM and perform a numerical study of the relic abundance of neutralinos with arbitrary composition and including the SE due to the exchange of the W and Z bosons, photons and Higgses. We find that the relic density can be suppressed by a factor of a few in a seizable region of the parameter space, mostly for Wino-like neutralino with mass of a few TeV, and up to an order of magnitude close to a resonance.

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A Theory of Dark Matter

Tracy Slatyer, Douglas P. Finkbeiner, Nima Arkani-Hamed … (2008)

We propose a comprehensive theory of dark matter that explains the recent proliferation of unexpected observations in high-energy astrophysics. Cosmic ray spectra from ATIC and PAMELA require a WIMP with mass M_chi ~ 500 - 800 GeV that annihilates into leptons at a level well above that expected from a thermal relic. Signals from WMAP and EGRET reinforce this interpretation. Taken together, we argue these facts imply the presence of a GeV-scale new force in the dark sector. The long range allows a Sommerfeld enhancement to boost the annihilation cross section as required, without altering the weak scale annihilation cross section during dark matter freezeout in the early universe. If the dark matter annihilates into the new force carrier, phi, its low mass can force it to decay dominantly into leptons. If the force carrier is a non-Abelian gauge boson, the dark matter is part of a multiplet of states, and splittings between these states are naturally generated with size alpha m_phi ~ MeV, leading to the eXciting dark matter (XDM) scenario previously proposed to explain the positron annihilation in the galactic center observed by the INTEGRAL satellite. Somewhat smaller splittings would also be expected, providing a natural source for the parameters of the inelastic dark matter (iDM) explanation for the DAMA annual modulation signal. Since the Sommerfeld enhancement is most significant at low velocities, early dark matter halos at redshift ~10 potentially produce observable effects on the ionization history of the universe, and substructure is more detectable than with a conventional WIMP. Moreover, the low velocity dispersion of dwarf galaxies and Milky Way subhalos can greatly increase the substructure annihilation signal.

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Dark matter self-interactions and light force carriers

Matthew Buckley, Patrick Fox (2010)

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Neutralino Relic Density including Coannihilations

J. Edsjö, P. Gondolo (1997)

We evaluate the relic density of the lightest neutralino, the lightest supersymmetric particle, in the Minimal Supersymmetric extension of the Standard Model (MSSM). For the first time, we include all coannihilation processes between neutralinos and charginos for any neutralino mass and composition. We use the most sophisticated routines for integrating the cross sections and the Boltzmann equation. We properly treat (sub)threshold and resonant annihilations. We also include one-loop corrections to neutralino masses. We find that coannihilation processes are important not only for light higgsino-like neutralinos, as pointed out before, but also for heavy higgsinos and for mixed and gaugino-like neutralinos. Indeed, coannihilations should be included whenever \(|\mu| \lsim 2 |M_1|\), independently of the neutralino composition. When \(|\mu| \sim |M_1|\), coannihilations can increase or decrease the relic density in and out of the cosmologically interesting region. We find that there is still a window of light higgsino-like neutralinos that are viable dark matter candidates and that coannihilations shift the cosmological upper bound on the neutralino mass from 3 to 7 TeV.

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Publication date Created: 11 October 2010

Publication date Updated: 2011-03-29

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DOI: 10.1007/JHEP03(2011)069

ArXiV ID: 1010.2172

SO-VID: c226bd46-1f10-4e4c-b8d8-9cd83df61956

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http://arxiv.org/licenses/nonexclusive-distrib/1.0/

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Journal reference JHEP 1103:069,2011

Comments 23 pages, 7 figures; table 1 corrected and rearranged, numerical results practically unchanged, matches published version

Relic densities including Sommerfeld enhancements in the MSSM

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Scholarly Publication Practices and Impact Factor Calculation and Manipulation

Most cited references 10

A Theory of Dark Matter

Dark matter self-interactions and light force carriers

Neutralino Relic Density including Coannihilations

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