{"id":32843,"date":"2025-07-29T22:24:07","date_gmt":"2025-07-29T22:24:07","guid":{"rendered":"https:\/\/www.newsbeep.com\/ca\/32843\/"},"modified":"2025-07-29T22:24:07","modified_gmt":"2025-07-29T22:24:07","slug":"when-light-waves-collide-something-incredible-happens-study-finds","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/ca\/32843\/","title":{"rendered":"When light waves collide something incredible happens, study finds"},"content":{"rendered":"

The magnetic moment of the muon\u2014a tiny property of a tiny particle\u2014has long puzzled physicists. Experiments and theory haven\u2019t quite matched up, leaving open the thrilling possibility of discovering \u201cnew physics\u201d beyond the Standard Model<\/a>. Now, fresh insights into a subtle quantum effect could help close that gap, or at least tighten the constraints around it.<\/p>\n

At the heart of this puzzle lies light-by-light scattering, a quantum process where particles of light, or photons, briefly transform into other particles. Ordinarily, light waves pass through each other without any trouble. But when quantum mechanics is involved, something strange happens: photons<\/a> can interact through the creation of virtual particles that pop in and out of existence. These fleeting particles, though invisible, leave a measurable imprint on other particles.<\/p>\n

One of those affected is the muon, a heavier cousin of the electron. How the muon \u201cwobbles\u201d in a magnetic field\u2014its so-called anomalous magnetic moment\u2014depends in part on these tiny interactions. The muon’s magnetic behavior, often described using the formula a\u03bc = (g\u20132)\u03bc \/ 2, has been the subject of years of high-precision experiments and theory. Even the tiniest deviation between the theoretical prediction and experimental result can hint at unknown physics.<\/p>\n

Light is scattered by light \u2013 via virtual particles. (CREDIT: Vienna University of Technology) <\/p>\n

That\u2019s why the upcoming results from the Fermilab experiment are so important. Scientists there are about to cut the experimental uncertainty in half, narrowing it from 22\u00d710\u207b\u00b9\u00b9 to roughly 11\u00d710\u207b\u00b9\u00b9. But with increased precision comes pressure. Theory must now meet that same level of detail, and one of the biggest obstacles is the hadronic light-by-light (HLbL) scattering contribution. It\u2019s a notoriously tricky piece to calculate, involving strong nuclear forces and a tangle of particle interactions<\/a>.<\/p>\n

A role for underestimated particles<\/p>\n

New work from a team at TU Wien in Vienna<\/a>, led by theoretical physicist Jonas Mager, highlights a group of particles that might have been seriously underrated in earlier models: tensor mesons.<\/p>\n

Mesons are composite particles made of a quark and an antiquark, and they come in several types. Tensor mesons are a particular class with a spin-2 configuration. These particles don\u2019t last long and are never seen directly, but they influence other particles in subtle ways. Their importance shows up when photons scatter off each other\u2014something that doesn\u2019t happen in classical physics but becomes possible in the quantum world due to virtual particles.<\/p>\n

Related Stories<\/p>\n

\u201cEven though these virtual particles cannot be observed directly, they have a measurable effect on other particles,\u201d says Mager. \u201cIf you want to calculate precisely how real particles behave, you have to take all conceivable virtual particles into account correctly. That’s what makes this task so difficult\u2014but also so interesting.\u201d<\/p>\n

When light scatters off light, a photon can briefly turn into a pair of particles, such as an electron and a positron<\/a>. These interact and annihilate, turning back into a photon. But if heavier virtual particles like mesons appear in the process, the calculations become even more complicated.<\/p>\n

Earlier models included tensor mesons, but they were treated with heavy simplifications. A recent study showed that not only is their contribution larger than previously thought\u2014it may even carry the opposite sign, meaning it influences the final results in a completely different direction.<\/p>\n

The tensor mesons can be mapped onto five-dimensional gravitons, for which Einstein’s theory of gravity makes clear predictions. (CREDIT: Shutterstock) Closing the short-distance gap<\/p>\n

In the language of quantum chromodynamics (QCD), short-distance constraints (SDCs) describe what happens when photons involved in scattering carry large virtual energies. One important condition, known as the Melnikov-Vainshtein (MV) constraint<\/a>, has already been shown to be satisfied in a framework called holographic QCD (hQCD), thanks to contributions from an infinite series of axial vector mesons.<\/p>\n

But that\u2019s only part of the story. A different constraint, the symmetric longitudinal SDC, wasn\u2019t fully matched. In fact, hQCD models showed it was met only about 81% of the way using axial vector mesons alone. This left a sizable chunk unexplained.<\/p>\n

Here\u2019s where tensor mesons<\/a> come in. Unlike the axial types, the full tower of tensor mesons in holographic QCD contributes specifically to the symmetric constraint, not the MV one. When these are added in, the gap closes neatly.<\/p>\n

This match also agrees well with experimental data from BELLE and aligns with recent dispersive analysis, which carefully examines real-world scattering data. It turns out that tensor mesons add a large positive boost to the muon\u2019s magnetic moment from low-energy regions (below 1.5 GeV), with diminishing returns at higher energies.<\/p>\n

Comparison of singly virtual tensor TFFs for helicity \u03bb=2 with Belle data. (CREDIT: Physical Review Letters) A holographic trick<\/p>\n

Describing the strong force at play inside mesons is no easy feat. Conventional calculations work best only in certain limits, often missing out on intermediate interactions. To sidestep this, the team at TU Wien turned to an unconventional but powerful technique called holographic QCD.<\/p>\n

This method maps our usual four-dimensional physics into a five-dimensional gravitational model<\/a>, where Einstein\u2019s equations can be used more directly. It\u2019s not science fiction\u2014it\u2019s a mathematical shortcut inspired by string theory, and it works remarkably well for some types of quantum problems.<\/p>\n

\u201cThe tensor mesons can be mapped onto five-dimensional gravitons, for which Einstein’s theory of gravity makes clear predictions,\u201d says TU Wien\u2019s Anton Rebhan. By shifting the problem into a space with more dimensions, some of the trickiest calculations become manageable. Once solved, the answers are converted back into normal four-dimensional space.<\/p>\n

Using this method, the team could show that tensor mesons naturally fill in the missing pieces in the HLbL puzzle. The result? A theoretical prediction that fits much better with both experimental data and numerical simulations from lattice QCD\u2014another complex tool that uses supercomputers to model quark interactions<\/a> from first principles.<\/p>\n

Contribution of tensor mesons to the symmetric longitudinal SDC: Q4\u02c6 \u03a01(\u2212Q2,\u2212Q2,\u2212Q2) with full tensor bulk to-bulk propagator. (CREDIT: Physical Review Letters) Toward new physics\u2014or not?<\/p>\n

All of this refinement matters because physicists are trying to detect new physics at the tiniest scales. The Standard Model describes most of what we know about the quantum world\u2014but not all of it. Gravity, dark matter<\/a>, and many open questions still sit outside its reach.<\/p>\n

The magnetic moment of the muon offers a rare testing ground. Any deviation from the Standard Model\u2019s prediction could hint at unknown forces or particles. The discrepancy has shrunk recently, largely thanks to improved lattice QCD results for hadronic vacuum polarization\u2014the leading source of uncertainty. But HLbL scattering remains a stubborn second.<\/p>\n

By digging into the underestimated role of tensor mesons and using advanced tools like hQCD, researchers are chipping away at this last major uncertainty. Their work doesn\u2019t just sharpen the current theory\u2014it also ensures that when experimental data from Fermilab<\/a> arrives, physicists will be ready to interpret what it means. Whether it confirms the Standard Model or cracks it wide open, every piece of the puzzle counts.<\/p>\n","protected":false},"excerpt":{"rendered":"The magnetic moment of the muon\u2014a tiny property of a tiny particle\u2014has long puzzled physicists. Experiments and theory…\n","protected":false},"author":2,"featured_media":32844,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[24],"tags":[49,48,314,66],"class_list":{"0":"post-32843","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-physics","8":"tag-ca","9":"tag-canada","10":"tag-physics","11":"tag-science"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts\/32843","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/comments?post=32843"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts\/32843\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/media\/32844"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/media?parent=32843"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/categories?post=32843"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/tags?post=32843"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}