Einstein wins again! Quarks obey relativity laws, Large Hadron Collider finds

Illustration of protons colliding, creating a shower of elementry particles, including the top quark. (Image credit: Robert Lea (created with Canva))

Is there a time of day or night at which nature's heaviest elementary particle stops obeying Einstein's rules? The answer to that question, as bizarre as it seems, could tell scientists something very important about the laws of physics governing the cosmos.

In a first-of-its-kind experiment conducted at the world's most powerful particle accelerator, the Large Hadron Collider (LHC), scientists have attempted to discover if the universe's heaviest elementary particle — a particle not composed of other smaller particles — always obeys Einstein's 1905 theory of special relativity.

More specifically, the team operating the LHC's Compact Muon Solenoid (CMS) detector wanted to know if one of the rules upon which special relativity is built, called "Lorentz symmetry," always holds for top quarks.

Lorentz symmetry states that the laws of physics should be the same for all observers who aren't accelerating. That means that the results of an experiment should be independent of the orientation of the experiment, or the speed at which it runs.

Quark around the clock!

Quarks are the particles in the standard model of particle physics that bind together and comprise particles like protons and neutrons.

There are six "flavors" of quark with increasing masses: up, down (found in protons and neutrons), charm, strange, top, and bottom. The heaviest of these is the top quark, possessing around the same mass as a gold atom (about 173 giga-electronvolts).

The Standard Model of physics is the most accurate theory of the universe to date. — A diagram shows the particles of the standard model of particle physics. (Image credit: Cush/Wikimedia Commons)

The CMS researchers reasoned that, if the collisions between protons accelerated to near-light-speeds in the LHC depend on orientation, then the rate at which top-quark pairs produced by such events should vary with time.

That is because, as Earth rotates, the direction of the proton beams generated for particle collisions in the powerful particle accelerator changes. Thus, the direction of the top quarks created by such collisions should change, too.

Wildly, that means that the number of quarks created should depend on what time of day the collisions occur!

image showing two metallic cylinders inside a particle accelerator — An image of the CMS detector at CERN's Large Hadron Collider (Image credit: CERN)

Thus, if there is a preferred direction in space-time and signs of Lorentz symmetry breaking, there should be a deviation from a constant rate of top quark pair production in the LHC dependent on the time of day the experiment is conducted!

Using data from Run 2 of the LHC, which was conducted between 2015 and 2018, the CMS collaboration found no such deviation.

That means that they found no sign of Lorentz symmetry breaking, and thus no evidence of top quarks defying Einstein no matter what way proton beams are orientated (or what time of day collisions occurred).

So, Einstein's theory of relativity is safe around the clock. Well, for now, at least.

—A tiny, wobbling muon just shook particle physics to its core

—A strange new Higgs particle may have stolen the antimatter from our universe

The upgraded LHC's third and more powerful operating run began in 2022 and is set to conclude next year. The team will look for signs of Lorentz symmetry breaking in higher-energy proton-proton collisions.

"The results pave the way for future searches for Lorentz symmetry breaking based on top-quark data from the third run of the LHC," the CMS collaboration wrote. "They also open the door to scrutiny of processes involving other heavy particles that can only be investigated at the LHC, such as the Higgs boson and the W and Z bosons."

The team's research was published at the end of 2024 in the journal Physics Letters B.

Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at: community@space.com.

Robert Lea is a science journalist in the U.K. whose articles have been published in Physics World, New Scientist, Astronomy Magazine, All About Space, Newsweek and ZME Science. He also writes about science communication for Elsevier and the European Journal of Physics. Rob holds a bachelor of science degree in physics and astronomy from the U.K.’s Open University. Follow him on Twitter @sciencef1rst.

More about science astronomy

An incredible image of a mystery blue spiral that appeared in the skies over Europe on Monday (March 24). This image was captured by Daniel Puchalski from Poland.

Mysterious blue spiral spotted over European skies. What was it? (photos)

NASA’s James Webb Space Telescope observed Herbig-Haro 49/50, an outflow from a nearby still-forming star, in high-resolution near- and mid-infrared light. The young star is off to the lower right corner of the Webb image.Intricate features of the outflow, represented in reddish-orange color, provide detailed clues about how young stars form and how their jet activity affects the environment around them. A chance alignment in this direction of the sky provides a beautiful juxtaposition of this nearby Herbig-Haro object (located within our Milky Way) with a face-on spiral galaxy in the distant background. Image released on March 24, 2025.

'Cosmic tornado' swirls in breathtaking new James Webb Space Telescope image

Artist impression of ESA's Gaia satellite observing the Milky Way. The background image of the sky is compiled from data from more than 1.8 billion stars. It shows the total brightness and colour of stars observed by Gaia released as part of Gaia’s Early Data Release 3 (Gaia EDR3) in December 2020.

So long, Gaia: Europe officially retires prolific star-mapping space telescope

See more latest

32 Comments Comment from the forums

Unclear Engineer

I am still wondering how a quark can be a "fundamental" particle when the combination of 2 down quarks and 1 up quark (a neutron) can become a combination of one down quark and 2 up quarks ( a proton) by emitting an electron, which is also supposed to be a "fundamental" particle that is not composed of quarks at all, and quarks are not supposedly containing electrons.

Typically, I see something like this from https://en.wikipedia.org/wiki/Quark :
"A quark of one flavor can transform into a quark of another flavor only through the weak interaction, one of the four fundamental interactions in particle physics. By absorbing or emitting a W boson, any up-type quark (up, charm, and top quarks) can change into any down-type quark (down, strange, and bottom quarks) and vice versa. This flavor transformation mechanism causes the radioactive process of beta decay, in which a neutron (n) "splits" into a proton (p), an electron (e−) and an electron antineutrino (νe) (see picture). This occurs when one of the down quarks in the neutron (udd) decays into an up quark by emitting a virtual W− boson, transforming the neutron into a proton (uud). The W− boson then decays into an electron and an electron antineutrino."

For me, that indicates something entirely different from "building blocks" when a quantum physicist says "fundamental particle".

Reply
Robert Lucien Howe

The result here is interesting but not really a surprise.. At speeds slower than light Special Relativity passes every test.

Its predictions for physics at speeds faster than light are a very different matter but there is currently still no real way to test that..
Reply
danR

I am still wondering how a quark can be a "fundamental" particle when the combination of 2 down quarks and 1 up quark (a neutron) can become a combination of one down quark and 2 up quarks ( a proton) by emitting an electron, which is also supposed to be a "fundamental" particle that is not composed of quarks at all, and quarks are not supposedly containing electrons.
For me, that indicates something entirely different from "building blocks" when a quantum physicist says "fundamental particle".

The decay emits the electron, not the quark. Conservation laws require the mass/energy, charge, and whatnot be preserved in Nature's bookkeeping. Nuclear reactions aren't like chemical reactions where, say, hydrogen evolves from zinc and hydrochloric acid.

The electron was never there in the first place. The decay process fashions it out of the inventory of whole cloth, the aforementioned attributes. Search Google Images, "Feynman Diagram" . Eg. electron and positron emitting gamma photon, thence quarks and gluon, none of which were components of the fundamental electron or positron from the outset.
Reply
Unclear Engineer

I can read that thought process, but I don't agree with it.

As I said, the concept of "fundamental particle" has devolved into "we don't know how to split this particle with the theories and technology at our disposal right now", and nothing more than that meaning.

If quantum theorists believe that they can get an electron out of "nothing" without getting a positron out of that same "nothing" at the same time, then what is their problem ginning up a solution to the obvious lack of antimatter in our current universe that is consistent with the Big Bang Theory?

Yes, the theory that "explains" beta decay and positron decay and electron capture by nuclei does conserve the parameters currently combined into the Standard Model of quantum mechanics. But, that model also postulates all sorts of things that are just not "explained" in a manner that makes sense to people not confined to that particular box of thought processes.
Reply
notsomuch

Unclear Engineer said:
I can read that thought process, but I don't agree with it.

As I said, the concept of "fundamental particle" has devolved into "we don't know how to split this particle with the theories and technology at our disposal right now", and nothing more than that meaning.

If quantum theorists believe that they can get an electron out of "nothing" without getting a positron out of that same "nothing" at the same time, then what is their problem ginning up a solution to the obvious lack of antimatter in our current universe that is consistent with the Big Bang Theory?

Yes, the theory that "explains" beta decay and positron decay and electron capture by nuclei does conserve the parameters currently combined into the Standard Model of quantum mechanics. But, that model also postulates all sorts of things that are just not "explained" in a manner that makes sense to people not confined to that particular box of thought processes.
Don't think of particles as being like rocks. They are 100% energy. Not solid or any sort of similar way to think about them.
Reply
Helio

As for relativity, I was hoping to see a result to indicate some evidence of length contraction. The only example of it has come from accelerators. A flattened particle, apparently, best explains what’s observed. Otherwise, all the tons of other evidence favors time dilation, AFAIK.

I find it curious that one must choose to use either time dilation or length contraction, but not both, in calculating the time to, say, Proxima Centauri.
Reply
Unclear Engineer

How theorists think about "particles" is also part of the issue. We can all agree that when we try to measure subatomic "things", we see properties that look like particles under some conditions and like waves under other conditions. But, we really have not idea how waves can exist without being in some sort of medium that they displace to create forces.

The Michaelson-Morley experiment to detect our motion through such a medium showed that we cannot detect motion through any sort of medium in space through which photons propagate. But, that does not mean that there is no such medium, and the Lorenz transformations of Special Relativity provide a mathematical solution to the observation by making the measurements of time and length dependent on the differences in (constant) speed between observers.

So, the quantum theorists use the concept of "fields" that are everywhere in space all of the time to propose that "particles" are really only energy that vibrates fields in particular ways. And, they have a pantheon of various fields and vibrations to explain what they find with high energy collisions between various "particles".

My only point is that we really don't fully understand what we are talking about. And, further, we have problems with combining that theory with astronomy observations and the General Theory of Relativity, which does quite a good job of matching astronomy observations - except perhaps for the observations of galactic object speeds, which seem to require more matter than we can detect (currently).

The BBT ties to bridge the existing gap between General Relativity and quantum mechanics so as to be able to extrapolate the apparent expansion of the universe backward in time to a single point (or wimps out at the Planck radius). But, we really don't have the answers to fundamental questions such as how those theories can explain the dominance of regular matter over antimatter in the universe today, among other important unexplained problems. Which is why I brought up the issue of beta decay seeming to not fit the idea of certain particles really being "fundamental".

So, there are plenty of people who are not "sold" on the current forms of the Standard Model or the Big Bang Theory. My thinking is that we are probably missing something important, so I support the research to look for things that might answer some of these questions.

What I don't support is the incessant writing of articles that states things "are" what the theories say they think they are. My point is that we need to constantly be aware of the differences between what we actually can demonstrate with observations and what we postulate are the explanations for the underlying physics that produce those observations. We will make progress faster if we don't fall into the trap of believing what we assume, so that we discard the thinking about other potential explanations.
Reply
Helio

Unclear Engineer said:
My only point is that we really don't fully understand what we are talking about. And, further, we have problems with combining that theory with astronomy observations and the General Theory of Relativity, which does quite a good job of matching astronomy observations - except perhaps for the observations of galactic object speeds, which seem to require more matter than we can detect (currently).
But astronomers are detecting regions of DM around a countless number of galaxies, large and small, and in clusters (e.g. Bullet cluster).

These are indirect observations, but they are almost as good as direct observations given the magnitude of their effects.

Unclear Engineer said:
The BBT ties to bridge the existing gap between General Relativity and quantum mechanics so as to be able to extrapolate the apparent expansion of the universe backward in time to a single point (or wimps out at the Planck radius).
I favor the view that grander theories are required to go beyond what I see as the BBT. The GUT (Grand Unified Theory) is one example. Many too often try to extrapolate the physics in BBT into the realm of metaphysics or pseudoscience, which is beyond the boundaries of BBT. Since the "bang" is found in this no-man's land, it's not hard to see why people stretch BBT a little too far, but a better label for the BBT has yet to emerge.

Unclear Engineer said:
My thinking is that we are probably missing something important, so I support the research to look for things that might answer some of these questions.
Yes, there should be a great deal to learn about the regions prior to t=1E-12 sec, where hard evidence begins to turn to mush. But that just means the BBT should come with limits of prior origins, just as Darwin's theory was sound even though it offered no explanation for the origin of life.

Unclear Engineer said:
We will make progress faster if we don't fall into the trap of believing what we assume, so that we discard the thinking about other potential explanations.
Yes, all the more reason to assign labels for the areas differing in our confidence.
Reply
Robert Lucien Howe

Helio said:
"I find it curious that one must choose to use either time dilation or length contraction, but not both, in calculating the time to, say, Proxima Centauri."
I think in this case the two are directly equivalent - they produce the same result. Choosing both mechanisms together would add the two together producing a wrong result.
So it could be said that in either you get the other for free - but I may be wrong.
Reply
Helio

Robert Lucien Howe said:
I think in this case the two are directly equivalent - they produce the same result. Choosing both mechanisms together would add the two together producing a wrong result.
So it could be said that in either you get the other for free - but I may be wrong.
Since they are likely mutually exclusive then there is no free compliment, I think.

The oddity of this is that we think in terms of what is real. If space actually contracts with relativistic speeds, then if we say time also changes at these speeds, then it too must be factored into the equation. Yet we can't easily do this without some serious math contortions.

We can make a ham sandwich or a cheese sandwich, but for some reason, we can't make a ham and cheese sandwich? ;)
Reply

Show more comments

Get the Space.com Newsletter

Quark around the clock!