28 research outputs found
Dark Matter Gravitinos and Baryons via Q-ball decay in the Gauge-Mediated MSSM
We show that late Q-ball decay in the MSSM with gauge-mediated SUSY breaking
can provide a natural source of non-thermal NLSPs which subsequently decay to
gravitino dark matter without violating nucleosynthesis constraints. To show
this, we perform a global analysis of Q-ball formation and decay in
Affleck-Dine baryogenesis for a d = 6 (u^{c}d^{c}d^{c})^2 flat direction of the
gauge-mediated MSSM. A general phenomenological potential for the
flat-direction is studied and the Q-ball decay properties are obtained as a
function of its parameters. The corresponding gravitino mass necessary to
account for dark matter is then determined for the case of stau NLSPs. The
decay temperature depends on the charge of the Q-balls, which is determined by
the fragmentation of the AD condensate. Different fragmentation scenarios are
considered, and the final non-thermal NLSP density from Q-ball decay and NLSP
annihilation is determined. Particular care is taken to establish that NLSPs
from Q-ball decay become homogeneous and non-relativistic prior to
annihilation. The gravitino mass necessary for dark matter is naturally
consistent with the theoretical gravitino mass in the gauge-mediation model.Comment: 16 pages, LaTeX, 2 figure
Affleck-Dine dynamics and the dark sector of pangenesis
Pangenesis is the mechanism for jointly producing the visible and dark matter
asymmetries via Affleck-Dine dynamics in a baryon-symmetric universe. The
baryon-symmetric feature means that the dark asymmetry cancels the visible
baryon asymmetry and thus enforces a tight relationship between the visible and
dark matter number densities. The purpose of this paper is to analyse the
general dynamics of this scenario in more detail and to construct specific
models. After reviewing the simple symmetry structure that underpins all
baryon-symmetric models, we turn to a detailed analysis of the required
Affleck-Dine dynamics. Both gravity-mediated and gauge-mediated supersymmetry
breaking are considered, with the messenger scale left arbitrary in the latter,
and the viable regions of parameter space are determined. In the gauge-mediated
case where gravitinos are light and stable, the regime where they constitute a
small fraction of the dark matter density is identified. We discuss the
formation of Q-balls, and delineate various regimes in the parameter space of
the Affleck-Dine potential with respect to their stability or lifetime and
their decay modes. We outline the regions in which Q-ball formation and decay
is consistent with successful pangenesis. Examples of viable dark sectors are
presented, and constraints are derived from big bang nucleosynthesis, large
scale structure formation and the Bullet cluster. Collider signatures and
implications for direct dark matter detection experiments are briefly
discussed. The following would constitute evidence for pangenesis:
supersymmetry, GeV-scale dark matter mass(es) and a Z' boson with a significant
invisible width into the dark sector.Comment: 51 pages, 7 figures; v2: minor modifications, comments and references
added; v3: minor changes, matches published versio
Affleck-Dine Baryogenesis, Condensate Fragmentation and Gravitino Dark Matter in Gauge-Mediation with a Large Messenger Mass
We study the conditions for successful Affleck-Dine baryogenesis and the
origin of gravitino dark matter in GMSB models. AD baryogenesis in GMSB models
is ruled out by neutron star stability unless Q-balls are unstable and decay
before nucleosynthesis. Unstable Q-balls can form if the messenger mass scale
is larger than the flat-direction field Phi when the condensate fragments. We
provide an example based on AD baryogenesis along a d = 6 flat direction for
the case where m_{3/2} \approx 2 GeV, as predicted by gravitino dark matter
from Q-ball decay. Using a phenomenological GMSB potential which models the Phi
dependence of the SUSY breaking terms, we numerically solve for the evolution
of Phi and show that the messenger mass can be sufficiently close to the
flat-direction field when the condensate fragments. We compute the
corresponding reheating temperature and the baryonic charge of the condensate
fragments and show that the charge is large enough to produce late-decaying
Q-balls which can be the origin of gravitino dark matter.Comment: 9 Pages, 3 Figures, additional discussion of fragmentation. Version
published in JCA
New Q-ball Solutions in Gauge-Mediation, Affleck-Dine Baryogenesis and Gravitino Dark Matter
Affleck-Dine (AD) baryogenesis along a d=6 flat direction in gauge-mediated
supersymmetry-breaking (GMSB) models can produce unstable Q-balls which
naturally have field strength similar to the messenger scale. In this case a
new kind of Q-ball is formed, intermediate between gravity-mediated and
gauge-mediated type. We study in detail these new Q-ball solutions, showing how
their properties interpolate between standard gravity-mediated and
gauge-mediated Q-balls as the AD field becomes larger than the messenger scale.
It is shown that E/Q for the Q-balls can be greater than the nucleon mass but
less than the MSSM-LSP mass, leading to Q-ball decay directly to Standard Model
fermions with no MSSM-LSP production. More significantly, if E/Q is greater
than the MSSM-LSP mass, decaying Q-balls can provide a natural source of
non-thermal MSSM-LSPs, which can subsequently decay to gravitino dark matter
without violating nucleosynthesis constraints. The model therefore provides a
minimal scenario for baryogenesis and gravitino dark matter in the
gauge-mediated MSSM, requiring no new fields.Comment: 13 pages, 9 figures. Some corrections and additional discussion.
Version published in JCA
Condensate cosmology in O'Raifeartaigh models
Flat directions charged under an R-symmetry are a generic feature of
O'Raifeartaigh models. Non-topological solitons associated with this symmetry,
R-balls, are likely to form through the fragmentation of a condensate, itself
created by soft terms induced during inflation. In gravity mediated SUSY
breaking R-balls decay to gravitinos, reheating the universe. For gauge
mediation R-balls can provide a good dark matter candidate. Alternatively they
can decay, either reheating or cooling the universe. Conserved R-symmetry
permits decay to gravitinos or gauginos, whereas spontaneously broken
R-symmetry results in decay to visible sector gauge bosons.Comment: 29 pages, 5 figures. Comments and references added, accepted for
publication in JHE
Visible and dark matter from a first-order phase transition in a baryon-symmetric universe
The similar cosmological abundances observed for visible and dark matter
suggest a common origin for both. By viewing the dark matter density as a
dark-sector asymmetry, mirroring the situation in the visible sector, we show
that the visible and dark matter asymmetries may have arisen simultaneously
through a first-order phase transition in the early universe. The dark
asymmetry can then be equal and opposite to the usual visible matter asymmetry,
leading to a universe that is symmetric with respect to a generalised baryon
number. We present both a general structure, and a precisely defined example of
a viable model of this type. In that example, the dark matter is atomic as well
as asymmetric, and various cosmological and astrophysical constraints are
derived. Testable consequences for colliders include a Z' boson that couples
through the B-L charge to the visible sector, but also decays invisibly to dark
sector particles. The additional scalar particles in the theory can mix with
the standard Higgs boson and provide other striking signatures.Comment: 26 pages, comments and references added, JCAP versio
The Physics of Q-balls
In this thesis we investigate the stationary properties and formation process
of a class of nontopological solitons, namely Q-balls. We explore both the
quantum-mechanical and classical stability of Q-balls that appear in
polynomial, gravity-mediated and gauge-mediated potentials. By presenting our
detailed analytic and numerical results, we show that absolutely stable
non-thermal Q-balls may exist in any kinds of the above potentials. The latter
two types of potentials are motivated by Affleck-Dine baryogenesis, which is
one of the best candidate theories to solve the present baryon asymmetry. By
including quantum corrections in the scalar potentials, a naturally formed
condensate in a post-inflationary era can be classically unstable and fragment
into Q-balls that can be long-lived or decay into the usual baryons/leptons as
well as the lightest supersymmeric particles. This scenario naturally provides
the baryon asymmetry and the similarity of the energy density between baryons
and dark matter in the Universe. Introducing detailed lattice simulations, we
argue that the formation, thermalisation and stability of these Q-balls depend
on the properties of models involved with supersymmetry breaking.Comment: Ph.D. thesis, University of Nottingham, 156 pages (2009), Advisor:
Edmund J. Copelan