Did we discover a new force of nature? New results from CERN
Results suggest beauty quarks decay into electrons and muons at different rates
New results
While the result was tantalizing, it wasn’t conclusive. All measurements come with a certain degree of uncertainty or “error”. In this case there was only around a one in 1,000 chance that the result was down to a random statistical wobble – or “three sigma” as we say in particle physics parlance.
One in 1,000 may not sound like a lot, but we make a very large number of measurements in particle physics and so you might expect a small handful to throw up outliers just by random chance. To be really sure that the effect is real, we’d need to get to five sigma – corresponding to less than a one in a million chance of the effect being down to a cruel statistical fluke.
To get there, we need to reduce the size of the error, and to do this we need more data. One way to achieve this is simply to run the experiment for longer and record more decays. The LHCb experiment is currentlybeing upgradedto be able to record collisions at a much higher rate in future, which will allow us to make much more precise measurements. But we can also get useful information out of the data we’ve already recorded by looking for similar types of decays that are harder to spot.
This is what my colleagues and I have done. Strictly speaking, we never actually study beauty quark decays directly, since all quarks are always bound together with other quarks to make larger particles. The March study looked at beauty quarks that were paired up with “up” quarks. Our result studied two decays: one where the beauty quarks were paired with “down” quarks and another where they were also paired with up quarks. That the pairing is different shouldn’t matter, though – the decay that’s going on deep down is the same and so we’d expect to see the same effect, if there really is a new force out there.
And that is exactly what we’ve seen. This time, muon decays were only happening around 70% as often as the electron decays but with a larger error, meaning that the result is about “two sigma” from the standard model (around a two in a hundred chance of being a statistical anomaly). This means that while the result isn’t precise enough on its own to claim firm evidence for a new force, it does line up very closely with the previous result and adds further support to the idea that we might be on the brink of a major breakthrough.
Of course, we should be cautious. There is some way to go still before we can claim with a degree of certainty that we really are seeing the influence of a fifth force of nature. My colleagues are currently working hard to squeeze as much information as possible out of the existing data, while busily preparing for the first run of the upgraded LHCb experiment. Meanwhile, other experiments at the LHC, as well as theBelle 2 experiment in Japan, are closing in on the same measurements. It’s exciting to think that in the next few months or years a new window could be opened on the most fundamental ingredients of our universe.
This article byHarry Cliff, Particle physicist,University of Cambridge, is republished fromThe Conversationunder a Creative Commons license. Read theoriginal article.
Story byThe Conversation
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