Three months ago, physicists at the world’s largest particle accelerator found the first signs of a particle heavier than the Higgs boson.
Now, hints of this mysterious new particle at the Large Hadron Collider (LHC) has just got more convincing.
While it falls short of the accuracy needed to be able to announce a discovery, it does make the reading more statistically significant – and that has got scientists excited.
Unexplained by current models, the particle’s existence might lead to the discovery of a whole new set of particles and possibly even a fifth fundamental force.
In data produced last December at the LHC in Geneva, two separate measurements found what looked like a particle six times heavier than the Higgs boson.
If it turns out to be real, and not just a blip in the measurements, this would be a huge discovery.
‘It would be something completely beyond the Standard Model, and the tip of an iceberg of a large new set of particles,’ Professor John Ellis, theoretical physicist at Kings College London told MailOnline, ‘if it exists!’
Two of the detectors, ATLAS and CMS, were searching for new physics by counting particle decays that ended up in two photons.
Measuring photons is a good method for detecting new physics because photons are easy to detect and physicists know what to expect in terms of results from background events.
They both separately saw photons with a combined energy of 750 GeV.
The excess of photons seen by the CMS experiment has become slightly more significant, due to a mew analysis reported today at a conference in La Thuile, Italy.
When particles decay into photons, they release energy equivalent to their mass multiplied by the speed of light squared.
The data used in the latest CMS analysis is 23 per cent larger as it includes collisions from early in the LHC’s run last year.
‘The good news is, we now we have almost as much data as ATLAS,’ says James Olsen, CMS physics coordinator and a physicist at Princeton University in New Jersey.
Nature reports that the CMS team re-calibrated the full data set, which caused the statistical significance of the CMS bump to go up from 1.2 to 1.6 sigma.
When scientists talk about sigma levels, they are describing how far their observations are from where they might expeced.
A 1-sigma observation meaning that they would expect 32 per cent of future observation to be at least as far away as what they have seen.
ATLAS also had its data re-analysed and now sees a 1.9 sigma excess at 750 GeV, according to a report in the Guardian.
While this is an improvement, it still falls short of physicists’ threshold for a discovery, which is 5 sigma, or a chance of around three in 10 million that the signal is a fluke.
This new particle, if it exists, has not been predicted by the Standard Model, so would open up physicists to a whole new unexplored world and could lead to the discovery of a new set of particles.
The Standard Model claims everything in the universe is made from the most basic building blocks called fundamental particles, that are governed by four forces: gravity, electromagnetic, weak nuclear and strong nuclear.
The forces work over different ranges and have different strengths.
This new particle, if it exists, would not fit into the description given by the Standard Model and so would lead to a whole new area of particle physics for them to explore.
Some have suggested it might even lead to the discovery of a fifth fundamental force.
‘This is possible, but there must at least be a set of unknown particles to explain how this new particle decays, and probably how it is produced,’ said Ellis.
This development is exciting because the Standard Model has left some questions unanswered for years, so scientists are keen to break free of it and find new theories.
It can’t explain gravity, for example, because it is incompatible with our best explanation of how gravity works – general relativity, nor does it explain dark matter particles.
The quantum theory used to describe the small particles in the world, and the general theory of relativity used to describe the larger objects world, are also difficult to reconcile.
Nobody has managed to make the two mathematically compatible in the context of the Standard Model.
According to the Big Bang theory, matter and antimatter were created in equal amounts at the start of the universe and so they should have annihilated each other totally in the first second or so of the universe’s existence.
This means the cosmos should be full of light and little else.
But because it isn’t there must have been a subtle difference in the physics of matter and anti-matter that has left the universe with a surplus of matter and that makes up the stars we see, the planet we live on and ourselves.
But the observations seen so far are not enough to confirm the existence of a particle.
The CERN physicists need to make sure the observations were not just down to chance, so it comes down to collecting much more data and waiting to see if the particle is spotted again.
Some remain unconvinced.
‘Indeed, I don’t see yet statistically convincing bumps that would point to the existence of a new particle in the LHC data,’ Professor Patrick Janot, working on the CMS detector at CERN told MailOnline.
The LHC will start making more collisions next month, and the results that might confirm or refute the existence of this particle will be available by summer.
‘You will hear solid statements in summer,’ said Janot, ‘when a lot more data than in 2015 are accumulated at 13 TeV.’