If you cast your mind back to your high school science days you’ll likely remember being taught certain things about atoms and what they’re made up of. The theories you were taught, things like the strong/weak forces and electromagnetism, form part of what’s called the Standard Model of particle physics. This model was born out of an international collaboration of many scientists who were looking to unify the world of subatomic physics and, for the most part, has proved extremely useful in guiding research. However it has its limitations and the Large Hadron Collider was built in order to test them. Whilst the current results have largely supported the Standard Model there is a growing cache of evidence that runs contrary to it, and the latest findings are quite interesting.
The data comes out of the LHCb detector from the previous run that was conducted from 2011 to 2012. The process that they were looking into is called B meson decay, notable for the fact that it creates a whole host of lighter particles including 2 leptons (called the tau lepton and the muon). These particles are of interest to researchers as the Standard Model makes a prediction about them called Lepton Universality. Essentially this theory states that, once you’ve corrected for mass, all leptons are treated equally by all the fundamental forces. This means that they should all decay at the same rate however the team investigating this principle found a small but significant difference in the rate in which these leptons decayed. Put simply should this phenomena be confirmed with further data it would point towards non-Standard Model particle physics.
The reason why scientists aren’t decrying the Standard Model’s death just yet is due to the confidence level at which this discovery has been made. Right now the data can only point to a 2σ (95%) confidence that their data isn’t a statistical aberration. Whilst that sounds like a pretty sure bet the standard required for a discovery is the much more difficult 5σ level (the level at which CERN attained before announcing the Higgs-Boson discovery). The current higher luminosity run that the LHC is conducting should hopefully provide the level of data required although I did read that it still might not be sufficient.
The results have gotten increased attention because they’re actually not the first experiment to bring the lepton universality principle into question. Indeed previous research out of the Stanford Linear Accelerator Center’s (SLAC) BaBar experiment produced similar results when investigating lepton decay. What’s quite interesting about that experiment though is that it found the same discrepancy through electron collisions whilst the LHC uses higher energy protons. The difference in method with similar results means that this discrepancy is likely universal, requiring either a new model or a reworking of the current one.
Whilst it’s still far too early to start ringing the death bell for the Standard Model there’s a growing mountain of evidence that suggests it’s not the universal theory of everything it was once hoped to be. That might sound like a bad thing however it’s anything but as it would open up numerous new avenues for scientific research. Indeed this is what science is built on, forming hypothesis and then testing them in the real world so we can better understand the mechanics of the universe we live in. The day when everything matches our models will be a boring day indeed as it will mean there’s nothing left to research.
Although I honestly cannot fathom that every occurring.
The spiral shape of a galaxy is an image that would be familiar to many of us but the story behind that shape is much less understood. We all know that gravity inexplicably pulls all matter together however if we were to weigh everything we could see it wouldn’t fully account for the resulting shapes and distributions we see throughout the universe. The missing mass is what is commonly referred to as Dark Matter, a theorized type of matter which is incredibly hard to detect directly yet must be pervasive throughout the universe due to its gravitational effects. However that might soon change if observations from our own parent star prove to be correct and we’ll be able to detect dark matter in our cosmic backyard.
The picture above is what’s known as the Bullet Cluster, the collision of 2 galaxy clusters with each other which is thought to provide some of the best evidence for dark matter. It’s theorized that in a collision of this nature the dark matter would avoid interaction with all the normal matter and would essentially race ahead. This theory is supported by the gravitational lensing observed between the two galaxies as without some form of dark matter the lensing would follow the matter consistently whereas here it appears to be ahead of its observable matter brethren. There’s still not enough evidence here to call it a direct detection of it, especially when other modified standard models can accommodate the effect readily enough.
However physicists at the University of Leicester in the UK have detected what could be the decay of dark matter particles coming from our sun which, if proven to be correct, would be the first direct detection of dark matter. The theory goes that axions, particles which were theorized to solve one of the more puzzling problems in quantum chromodynamics and are theorized to be a component of cold dark matter, are created in the sun and make their way to earth. Much like neutrinos they don’t interact with matter very often and thus race from the core at light speed, unimpeded by the sun’s great mass. When they reach our magnetic field however they decay into a x-ray photon which means that the level of background x-rays should be higher within the earth’s magnetic field. This is what the researchers have found and data from other orbital observatories seems to corroborate this.
Of course the theory is not without its problems, notably that the properties of the axion that they’re theorizing would be different to the one that’s predicted by the current model. There’s evidence to suggest this from other observations so in order to prove the theory one way or the other further analysis with that additional data will have to be taken into consideration. It’ll likely be years before we’ll have a definitive answer on this particular theory thanks to the large data sets that they’re working with but either result will provide some insight into where dark matter might be hiding.