24 research outputs found
Numerical Approach to Multi Dimensional Phase Transitions
We present an algorithm to analyze numerically the bounce solution of
first-order phase transitions. Our approach is well suited to treat phase
transitions with several fields. The algorithm consists of two parts. In the
first part the bounce solution without damping is determined, in which case
energy is conserved. In the second part the continuation to the physically
relevant case with damping is performed. The presented approach is numerically
stable and easily implemented.Comment: 18 pages, 8 figures; some comments, a reference and a table adde
Production of Gravitational Waves in the nMSSM
During a strongly first-order phase transition gravitational waves are
produced by bubble collisions and turbulent plasma motion. We analyze the
relevant characteristics of the electroweak phase transition in the nMSSM to
determine the generated gravitational wave signal. Additionally, we comment on
correlations between the production of gravitational waves and baryogenesis. We
conclude that the gravitational wave relic density in this model is generically
too small to be detected in the near future by the LISA experiment. We also
consider the case of a "Standard Model" with dimension-six Higgs potential,
which leads to a slightly stronger signal of gravitational waves.Comment: 29 pages, 7 figures; published version, some comments adde
Supersonic Electroweak Baryogenesis: Achieving Baryogenesis for Fast Bubble Walls
Standard electroweak baryogenesis in the context of a first order phase
transition is effective in generating the baryon asymmetry of the universe if
the broken phase bubbles expand at subsonic speed, so that CP asymmetric
currents can diffuse in front of the wall. Here we present a new mechanism for
electroweak baryogenesis which operates for supersonic bubble walls. It relies
on the formation of small bubbles of the symmetric phase behind the bubble
wall, in the broken phase, due to the heating of the plasma as the wall passes
by. We apply the mechanism to a model in which the Higgs field is coupled to
several singlets, and find that enough baryon asymmetry is generated for
reasonable values of the parameter space
Electroweak baryogenesis
Electroweak baryogenesis (EWBG) remains a theoretically attractive and
experimentally testable scenario for explaining the cosmic baryon asymmetry. We
review recent progress in computations of the baryon asymmetry within this
framework and discuss their phenomenological consequences. We pay particular
attention to methods for analyzing the electroweak phase transition and
calculating CP-violating asymmetries, the development of Standard Model
extensions that may provide the necessary ingredients for EWBG, and searches
for corresponding signatures at the high energy, intensity, and cosmological
frontiers.Comment: 42 pages, 13 figures, invited review for the New Journal of Physics
focus issue on 'Origin of Matter
Excluding Electroweak Baryogenesis in the MSSM
In the context of the MSSM the Light Stop Scenario (LSS) is the only region
of parameter space that allows for successful Electroweak Baryogenesis (EWBG).
This possibility is very phenomenologically attractive, since it allows for the
direct production of light stops and could be tested at the LHC. The ATLAS and
CMS experiments have recently supplied tantalizing hints for a Higgs boson with
a mass of ~ 125 GeV. This Higgs mass severely restricts the parameter space of
the LSS, and we discuss the specific predictions made for EWBG in the MSSM.
Combining data from all the available ATLAS and CMS Higgs searches reveals a
tension with the predictions of EWBG even at this early stage. This allows us
to exclude EWBG in the MSSM at greater than (90) 95% confidence level in the
(non-)decoupling limit, by examining correlations between different Higgs decay
channels. We also examine the exclusion without the assumption of a ~ 125 GeV
Higgs. The Higgs searches are still highly constraining, excluding the entire
EWBG parameter space at greater than 90% CL except for a small window of m_h ~
117 - 119 GeV.Comment: 24 Pages, 4 Figures (v3: fixed typos, minor corrections, added
references
TeV physics and the Planck scale
Supersymmetry is one of the best motivated possibilities for new physics at
the TeV scale. However, both concrete string constructions and phenomenological
considerations suggest the possibility that the physics at the TeV scale could
be more complicated than the Minimal Supersymmetric Standard Model (MSSM),
e.g., due to extended gauge symmetries, new vector-like supermultiplets with
non-standard SU(2)xU(1) assignments, and extended Higgs sectors. We briefly
comment on some of these possibilities, and discuss in more detail the class of
extensions of the MSSM involving an additional standard model singlet field.
The latter provides a solution to the problem, and allows significant
modifications of the MSSM in the Higgs and neutralino sectors, with important
consequences for collider physics, cold dark matter, and electroweak
baryogenesis.Comment: 17 pages, 5 figures. To appear in New Journal of Physic
The Higgs vacuum uplifted: revisiting the electroweak phase transition with a second Higgs doublet
The existence of a second Higgs doublet in Nature could lead to a cosmological first order electroweak phase transition and explain the origin of the matter-antimatter asymmetry in the Universe. We explore the parameter space of such a two-Higgs-doublet-model and show that a first order electroweak phase transition strongly correlates with a significant uplifting of the Higgs vacuum w.r.t. its Standard Model value. We then obtain the spectrum and properties of the new scalars H0, A0 and H± that signal such a phase transition, showing that the decay A0 → H0Z at the LHC and a sizable deviation in the Higgs self-coupling λhhh from its SM value are sensitive indicators of a strongly first order electroweak phase transition in the 2HDM
Gravitational wave production by collisions: more bubbles
We re-examine the production of gravitational waves by bubble collisions during a first-order phase transition. The spectrum of the gravitational radiation is determined by numerical simulations using the 'envelope approximation'. We find that the spectrum rises as f3.0 for small frequencies and decreases as f-1.0 for high frequencies. Thus, the fall-off at high frequencies is significantly slower than previously stated in the literature. This result has direct impact on detection prospects for gravity waves originating from a strong first-order electroweak phase transition at space-based interferometers, such as LISA and BBO. In addition, we observe a slight dependence of the peak frequency on the bubble wall velocity