{"id":374540,"date":"2026-04-11T12:49:10","date_gmt":"2026-04-11T12:49:10","guid":{"rendered":"https:\/\/www.newsbeep.com\/nz\/374540\/"},"modified":"2026-04-11T12:49:10","modified_gmt":"2026-04-11T12:49:10","slug":"new-particle-mass-measurement-deepens-quantum-mystery","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/nz\/374540\/","title":{"rendered":"New particle mass measurement deepens quantum mystery"},"content":{"rendered":"

Physicists have measured the mass of one of the universe\u2019s basic building blocks, the W boson particle. The new calculation, made at the Large Hadron Collider (LHC) near Geneva, could help solve a niggling mystery about this particle\u2019s mass<\/a>.<\/p>\n

About 80 times heavier than protons, W bosons<\/a> are among the heaviest of nature\u2019s fundamental particles, which can\u2019t be broken down into smaller bits. They carry the weak force, which allows other particles to morph from one type to another in processes such as the radioactive decay of uranium to lead and the nuclear fusion of hydrogen to helium.<\/p>\n

A 2022 measurement of the W boson\u2019s mass made by the Collider Detector at Fermilab (CDF) experiment at the Fermi National Accelerator Laboratory\u2019s (Fermilab\u2019s) Tevatron collider was the most precise to date. And it suggested that the mass differed significantly from the prediction of the Standard Model<\/a>\u2014the ruling theory of particle physics. If correct, that meant that something strange was going on with the particles governing radioactivity and with the rules of physics.<\/p>\n

Sign up for Today in Science, a free daily newsletter from Scientific American and join a community of science-loving readers.<\/a><\/p>\n

The 2022 measurement had been the most precise to date. The new measurement, however, nearly matches its precision\u2014but agrees with the Standard Model<\/a>. Leaders of the new study, which was conducted at the LHC\u2019s Compact Muon Solenoid (CMS) experiment, say it reassures them that their basic understanding of the W boson is likely on track. \u201cWhile it would have been thrilling to confirm the CDF result, what I really wanted was to publish a result that will stand the test of time,\u201d says Massachusetts Institute of Technology physicist Kenneth Long, a co-author of the new study. \u201cI think most physicists today will be placing their bets on the standard model, and I think our measurement is a big reason for that.\u201d<\/p>\n

The puzzle isn\u2019t fully solved yet, though. \u201cWhile I congratulate CMS on their valiant effort, any conclusions at this stage are certainly premature,\u201d says Duke University physicist Ashutosh Kotwal, who co-authored the CDF analysis. \u201cClearly, both CDF and CMS cannot be correct.\u201d The CDF team derived its mass measurement using six different methods and studied various ways the W boson might decay to smaller particles. \u201cCMS, on the other hand, is just getting started, with their first publication containing only one of these six methods,\u201d Kotwal says.<\/p>\n

The Standard Model has been enormously successful in describing the world of fundamental particles, but scientists know it isn\u2019t complete. It doesn\u2019t include, for instance, the mysterious dark matter that physicists believe is ubiquitous in the cosmos or the dark energy that seems to be accelerating the universe\u2019s expansion. If researchers can find a discrepancy between the model\u2019s predictions and reality, it could point the way toward expanding the theory to more fully describe nature.<\/p>\n

\u201cI think we all expect the Standard Model to truly \u2018break\u2019 one day,\u201d Long says. \u201cBut this measurement means that one of the more enticing (and striking) hints that the Standard Model wasn\u2019t working now seems more like an experimental anomaly than a theoretical insufficiency. It means we have to keep looking harder and perhaps in different places to find these cracks.\u201d<\/p>\n

According to the LHC\u2019s new measurement, the W boson weighs 80,360.2 \u00b1 9.9 mega-electron-volts (MeV), roughly 160,000 times the mass of the electron, which has about 0.5 MeV. That figure is squarely within Standard Model\u2019s predictions.<\/p>\n

The LHC speeds up protons to nearly the speed of light and then crashes them together. The energy of the collision spawns many new particles, including\u2014sometimes\u2014W bosons. The experiment can\u2019t measure W bosons directly because they disappear after only 10\u2013 24 seconds of existence. But they often decay into a pair of particles called a neutrino and a muon (a heftier version of an electron).<\/p>\n

The neutrino is nearly as elusive as the W boson, but CMS can study muons very precisely. By carefully measuring the energy and momentum of muons produced in about 100 million collisions thought to have created W bosons, the physicists arrived at their new mass estimate. The finding was published on April 8 in the journal Nature<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"Physicists have measured the mass of one of the universe\u2019s basic building blocks, the W boson particle. The…\n","protected":false},"author":2,"featured_media":374541,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[24],"tags":[195439,195438,195436,4436,20816,111,139,69,2905,393,13094,147,195437],"class_list":{"0":"post-374540","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-physics","8":"tag-cdf","9":"tag-collider-detector-at-fermilab","10":"tag-fundamental-particles","11":"tag-large-hadron-collider","12":"tag-measurement","13":"tag-new-zealand","14":"tag-newzealand","15":"tag-nz","16":"tag-particle-physics","17":"tag-physics","18":"tag-radioactive-decay","19":"tag-science","20":"tag-the-standard-model"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/374540","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/comments?post=374540"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/374540\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media\/374541"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media?parent=374540"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/categories?post=374540"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/tags?post=374540"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}