Dark Matter Particles May Be Fewer Due to Effect of "Dilaton"

Research at King's College, London that is published in BioMed Central shows that theories of the properties of dark matter may be generating models that overestimate the role of supersymmetry neutralinos by neglecting the influence of dilatons.

Dilatons are hypothetical particles predicted by superstring supersymmetry models. Dilatons have zero mass and zero spin. Their importance in physics relates to the attempts by scientists to develop a theory of everything, that includes all the four universal forces--gravity, weak nuclear force, strong nuclear force and electromagnetic force--and all universal particles, known and as yet unknown.

Neutralinos are a more well known hypothetical particle that is also predicted by superstring supersymmetry models--one of the attempts at developing a theory of everything. Superstring supersymmetry models state that all Standard Model matter particles have partner "shadow" force carrier particles with the same quantum number but different energic spin, with the reverse also being true: every "shadow" particle has a matter particle. In other words, there is a one-on-one, two-directional relationship between matter particles and corresponding shadow force carriers. For example, for every matter particle called a quark there is a shadow force carrier called a squark.

At a second, later singular point in time, matter and energy ceased interacting with each other. This moment came when the universe had cooled down enough to allow electrons and protons to bond to form hydrogen atoms, which are the first of the visible matter atoms. At this time--the time of the forming of matter--the density of dark matter particles such as the neutralino--which are as yet unidentified and only hypothesized--was "frozen," left in a fixed state without further interaction with matter particles except through gravity. This frozen density of dark matter is referred to as the relic abundance.

Dark matter is fundamentally different from luminous visible matter, called baryonic matter. Dark matter particles give off no light or heat; they do not reflect electromagnetic radiation the way baryonic matter does and are invisible to modern telescopes, although new telescopes are being developed that could be used to help detect dark matter. Dark matter appears to interact with normal visible matter only through gravity, being decucible by its effects on baryonic bodies.

This relates to the composition of dark matter and how the dilaton effects the neutralio. The results of the research done at King's College show that the effects of the presence of dilatons on the mass of neutralinos in dark matter is such that the amount, or relic abundance, of dark matter left over from the early universe may contain a lesser mass of neutralinos than present models indicate. In other words, dilatons may reduce the relic abundance of the stable neutrino dark matter particle as compared to the abundance predicted in standard cosmology theories.in the universe is thought to have been created at one singular moment in time. Matter and energy then interacted with each other. Dark matter particles were in existence at this time along with the particles that would later become visible matter particles.

The King's College researchers arrived at this conclusion through a partial collaboration with John Ellis of CERN, Vasiliki Mitsou of Instituto de Fisica Corpuscular (IFIC) in Valencia, scientists from King's College and colleagues from Athens and Texas, studied an individual term in an equation, called the Boltzman equation. This term describes the evolution of hot matter density as the universe cooled down.

Based on their new calculation model, the researchers say that the neutralino relic abundance is reduced in mass by as much as a factor of ten. The reduction shown in their model is due to the effects of the dilaton.

Additionally, the relic abundance of visible, ordinary baryonic matter is only slightly reduced from standard model predictions, which means that the new model agrees with the current predictions of total mass of the universe

Most physicists believe that dark matter particles and dark energy make up approximately 96 percent of all matter in the universe, with approximately22 percent being dark matter and 74 percent being dark energy, with about only 4 percent being ordinary visible matter.

For particle physics, these findings are relevant for future searches in colliders such as the Large Hadron Collider, which is due to start up at CERN in May of 2008. It is these unseen, yet predicted dark matter particles that LHC's four experiments are designed to detect. The search may be advanced by the results of Mavromatos' team's new model.

"Dilaton could affect abundance of dark matter particles," BioMed Central.