The Madala candidate

A new, homegrown hypothesis that could shed some light on dark matter and black holes.

WITH THE OBSERVATION OF THE HIGGS BOSON at the Large Hadron Collider (LHC) of the European Organisation for Nuclear Research (CERN) in 2012, the Standard Model of physics was deemed complete. We finally have a working model to account for how matter acquired mass. How stuff in essence became, well, stuff. However, there is another elusive mystery that remains unsolved by the Standard Model: what on Earth is dark matter? Physicists from Wits working with the LHC’S data, believe they have discovered signs of another exotic particle that may shed light on the dark matter issue. Enter the Madala boson hypothesis.

THE BOSON BASICS  The High Energy Physics Group (HEP) at the University of Witwatersrand (Wits), led by Professor Bruce Mellado, formulated the Madala hypothesis in June 2015, based on a number of features witnessed in the proton-proton collision data collected during the first run of the LHC’S ATLAS and CMS experiments.  The features in the data were interpreted by the HEP team as potential evidence for the existence of a new scalar, the Madala boson, with a mass of around 270 giga electronvolts (GEV). In contrast, the Higgs boson has a mass of around 126 GEV.  If confirmed, the Madala boson could shed some light on the nature of dark matter. The Higgs boson interacts only with known matter, the stuff we can observe. But known matter makes up only around 4 per cent of the mass and energy of the universe. The heavier Madala boson appears, in theoretical modelling, to interact with dark matter.  A conservative statistical combination yielded a threesigma effect – signifying a fair degree of certainty that the boson exists.  The experiments at the LHC have since reported new results at the international conference ICHEP2016. The Madala hypothesis is not excluded by the new data.

DARK MATTER? Dark matter makes up around 27 per cent of the mass in the known universe. Scientists know dark matter exists because they can observe the effects of its gravitational force in the cosmos, but dark matter doesn’t appear to emit any kind of observable, measurable form of radiation or light. No one knows what dark matter actually is.

So what’s the story? “Physics today is at a crossroads similar to the times of Einstein and the fathers of quantum mechanics,” says Mellado in a statement issued by Wits.

“Classical physics failed to explain a number of phenomena and, as a result, it needed to be revolutionised with new concepts, such as relativity and quantum physics, leading to the creation of what we know now as modern physics, and the Higgs boson.

“As complete as it now is, the Standard Model can’t explain the existence or behaviour of dark matter – which is where the heavier Madala boson comes in (if it’s real).”

The Wits Madala project team consists of approximately 35 young South African and African students and researchers who are currently contributing to the understanding of the data coming out of the LHC experiments.

The universe is made of mass and energy. The mass that we can touch, smell and see, the mass that can be explained by the Higgs boson, makes up only 4 per cent of the mass-energy budget of the universe. The rest of the mass in the universe is simply unknown. The next big step for the physics of fundamental interactions now is to understand the nature of dark matter in the universe: what is it made of? How many different types of particles are there? How do they interact among each other? How does it interact with known matter? What can it tell us about the evolution of the universe?

“With the Madala hypothesis, predictions of striking signatures are made, that are now being pursued and scrutinised by the young scientists of the Wits HEP group,” says Mellado.

* The Madala hypothesis is exclusively the view of the Wits HEP group.

Above: One of the first heavy-ion collisions with stable beams recorded by ATLAS in November 2015. The tracks are reconstructed from hits in the inner tracking detector and are shown as orange arcs curving in the solenoidal magnetic field. The green...

Below: Workers assembling the ATLAS Semiconductor Tracker.

Left: The pictured collisions were recorded from the first so-called “stable beams” of 2016; data from which are used by CMS for physics analyses. This marked the beginning of the 2016 data-collection operation.