Could new measurements of the way subatomic particles known as muons interact with magnetic fields hint at physics beyond the Standard Model? <\/p>
On 10 August, an international collaboration of experimentalists at the Fermi National Laboratory (Fermilab), on the outskirts of Chicago, USA, announced an updated measurement of the way muons interact with a magnetic field (more on this later). <\/p>
The update was eagerly awaited, largely because previous measurements disagreed with the predictions of the Standard Model<\/a> of particle physics. The discrepancy has led to talk of a possible fifth force of nature. So, what would that mean, and what did the update tell us?<\/p> There are four known fundamental forces.<\/p> Gravity is described by relativity. The Standard Model of particle physics contains the other three. A fifth force would be something beyond this, and as such would be a huge breakthrough in our understanding of the physics behind the world we live in.<\/p> Physicists are hungry for such a breakthrough because, while the Standard Model is a beautiful way of explaining a vast array of phenomena, it is not a complete \u2018Theory of Everything\u2019. <\/p> For example, as mentioned above, it does not contain gravity \u2013 and, in fact, relativity and the Standard Model are inconsistent at very high energies. Any measurement that does not agree with the current theory would be seen as a clue to what a bigger and hopefully better \u2013 in the sense of being more explanatory \u2013 theory might be.<\/p> Muons are fundamental particles, according to the Standard Model. That means they are one of the basic building blocks of matter. They are very much like electrons, but are 210 times heavier. <\/p> They carry electric charge, and they have angular momentum \u2013 known as spin \u2013 which means they have a tiny magnetic moment \u2013 an axis with a North and a South pole like a bar magnet, or the Earth.<\/p> The experiment at Fermilab corrals billions of muons into a storage ring, governed by very precisely calibrated electric and magnetic fields, and measures how their magnetic axes wobble, or precess, as they travel around the ring.<\/p> Read more about physics:<\/strong><\/p> These wobbles can be calculated very precisely in the Standard Model. The calculations involve so-called \u2018virtual\u2019 particles, which aren\u2019t directly observed but which influence the results by making fleeting appearances in quantum<\/a> loops.<\/p> If the measurements don’t line up with the prediction, that could be a sign that there is some unknown particle appearing in these loops. <\/p> One favoured candidate to explain that would be the carrier of a fifth force. This would be equivalent of a photon (which carries the electromagnetic force), but would not be part of the Standard Model.<\/p> The updated measurement confirms the previous value at significantly higher precision, and is an impressive achievement. But there are two big issues to be resolved before we could say we have discovered a fifth force.<\/p> Firstly, the measurement is so precise it challenges the precision of the theory. The discrepancy is based on a widely agreed combination of theoretical calculations, but there are some newer predictions which are closer to the measurement than this \u2013 and not all predictions are consistent with each other.<\/p> These differences may themselves be a sign of some interesting new physics, but they certainly need to be resolved before we can be sure we are seeing any kind of fifth force.<\/p> The second issue is more subtle but more exciting. If the discrepancy is confirmed, we will be sure there is something new going on. However, we won’t be sure exactly what it is!<\/p> The ideal outcome would be that the discrepancy would inform new theoretical ideas, and these would lead to new predictions \u2013 for example, of how we might find the particle that carries the new force, if that’s what it is.<\/p> The final confirmation would then come from building an experiment to directly discover that particle \u2013 much like the ideas of Brout, Englert and Higgs were only finally vindicated by the discovery of the Higgs boson.<\/p> There are other experiments making measurements that challenge the Standard Model. Several discrepancies exist in various measurements from experiments at the CERN<\/a> Large Hadron Collider (LHC), for example.<\/p> But some such discrepancies are bound to happen just by chance as we explore new physics territory, and many apparent anomalies have gone away as we collect more data and understand the experiments better.<\/p> There will be an even more precise update from Fermilab in due course, and the LHC will also be collecting a lot more data over the next few years. Physicists working there will continually be watching for discrepancies that don’t go away, based on a multitude of new and more precise measurements.<\/p> However, the muon magnetic moment is one of the longest-standing and most significant discrepancies between any measurement and the Standard Model \u2013 the measurement itself is very unlikely to be wrong now.<\/p> This means that if the theory predictions get sorted out, this could be the first strong evidence for something new and beyond the Standard Model; possibly a fifth force of nature!<\/p> Read more<\/strong>:<\/p> Could new measurements of the way subatomic particles known as muons interact with magnetic fields hint at physics beyond the Standard Model? <\/p>\n","protected":false},"author":24,"featured_media":32756,"template":"","categories":[1,29],"acf":{"readingTimeMinutes":"5"},"uagb_featured_image_src":{"full":["https:\/\/c01.purpledshub.com\/uploads\/sites\/42\/2023\/08\/how-one-particle-could-unlock-the-universes-mysterious-fifth-force.jpg",1200,800,false],"thumbnail":["https:\/\/c01.purpledshub.com\/uploads\/sites\/42\/2023\/08\/how-one-particle-could-unlock-the-universes-mysterious-fifth-force-150x150.jpg",150,150,true],"medium":["https:\/\/c01.purpledshub.com\/uploads\/sites\/42\/2023\/08\/how-one-particle-could-unlock-the-universes-mysterious-fifth-force-300x200.jpg",300,200,true],"medium_large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/42\/2023\/08\/how-one-particle-could-unlock-the-universes-mysterious-fifth-force-768x512.jpg",768,512,true],"large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/42\/2023\/08\/how-one-particle-could-unlock-the-universes-mysterious-fifth-force-1024x683.jpg",800,534,true],"1536x1536":["https:\/\/c01.purpledshub.com\/uploads\/sites\/42\/2023\/08\/how-one-particle-could-unlock-the-universes-mysterious-fifth-force.jpg",1200,800,false],"2048x2048":["https:\/\/c01.purpledshub.com\/uploads\/sites\/42\/2023\/08\/how-one-particle-could-unlock-the-universes-mysterious-fifth-force.jpg",1200,800,false]},"uagb_author_info":{"display_name":"importmanagerhub@sprylab.com","author_link":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/author\/importmanagerhubsprylab-com\/"},"uagb_comment_info":0,"uagb_excerpt":"Could new measurements of the way subatomic particles known as muons interact with magnetic fields hint at physics beyond the Standard Model?","_links":{"self":[{"href":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/wp-json\/wp\/v2\/rss_feed\/32755"}],"collection":[{"href":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/wp-json\/wp\/v2\/rss_feed"}],"about":[{"href":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/wp-json\/wp\/v2\/types\/rss_feed"}],"author":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/wp-json\/wp\/v2\/users\/24"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/wp-json\/wp\/v2\/media\/32756"}],"wp:attachment":[{"href":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/wp-json\/wp\/v2\/media?parent=32755"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/wp-json\/wp\/v2\/categories?post=32755"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}What are the four fundamental forces?<\/h2>
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What are Muons?<\/h2>
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What could the fifth force of nature be?<\/h2>
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