Recently, the theoretical particle physics community has discovered an unexpected new duality. This duality exists between two scattering processes that can occur in proton collisions.
Surprisingly, the connection between the two scattering processes tells us that while the Standard Model of particle physics explains the microscopic world of particles and their interactions, there are still things in its intricate detail that are not fully understood and mastered.
Whenever a surprise appears, it will naturally attract people's attention. The research paper was recently published in the Physical Review Letters.
Duality in physics
The concept of duality is not uncommon in physics, and it appears in different fields of physics. Perhaps the most famous duality is particle-wave duality in quantum mechanics.
The famous double-slit experiment showed that light can act like a wave, but it can also behave like a particle. When light acts in the form of waves, those "ripples" interfere, appearing at the crests of the waves, creating bright edges, while at the troughs they cancel out interference, leaving dark stripes, thus leaving a pattern of light and dark on the screen (figure B below).
Double-slit experiment. (Photo: S ren J. Granat, NBI)
But if we lower the intensity of the beam, emit only one photon at a time, and place a detector next to each slit to monitor a single photon, then this interference pattern will disappear and instead two thick light bars appear on the screen (as shown in Figure C above).
This is already very strange, but even more subversive is how we should understand it. In fact, light is both a wave and a particle, and at the same time it is not both. To be precise, we can look at the light entity in two ways, both waves and particles, and each corresponds to a mathematical description. Both have a very different set of intuitive ideas, but they still describe the same thing.
This is a classic case of duality, that is, it is a correspondence and connection between theories that appear to be different on the surface but lead to the same result.
Theory and experiment go hand in hand
In the new study, what the team found was a similar duality.
At LHC, scientists have conducted collision experiments with a large number of protons. Protons contain more fundamental particles, namely quarks and gluons responsible for transmitting strong forces, and it is gluons that "glue" the quarks together and bind them inside the protons.
The proton contains quarks and gluons (curves in the figure) responsible for transmitting strong forces, which bind the quarks inside the proton. (Figure/Principle)
Under the huge impact of the collision, two gluons from different protons can interact to produce new particles, such as the Higgs boson, thus forming an intricate pattern in the detector.
The research team mapped out these patterns, and the theoretical work related to the experiment was used to accurately describe what happened in mathematical terms, thus establishing a comprehensive representation and making predictions that could be compared with the results of the experiment.
The team made prediction calculations for two scattering processes, one of which was the scattering process of two gluons interacting to produce four gluons, and the other being the scattering process of two gluons interacting to produce a gluon and a Higgs boson.
The left side of the comic represents a scattering process involving the interaction of two gluons (green-yellow and blue-blue globules), which produces a gluon (red-purple) and a Higgs boson (white). The more complex scattering process in the right mirror is mapped out, which represents the scattering process of two gluons (green-yellow and blue-blue globules) interacting to produce four gluons (red-purple, red-yellow, blue-purple, and green-green). Black symbolizes that in a collision, many different fundamental interactions can occur, and we must sum up all the possibilities. According to heisenberg's uncertainty principle, we have no way of knowing exactly what is going on, so it is a "black box". (Photo: S ren J. Granat, NBI)
Surprisingly, while current calculations are not experimentally as tangible as the famous double-slit experiment, a clear mathematical map has emerged between the two that shows that they both contain the same information. The scientists found that, to some extent, the results of the two calculations were related. That is to say, the answer to how likely one scattering process is to occur is the likelihood that another scattering process will occur. This is a typical kind of duality.
The wonder of this duality is that scientists don't yet know why there is such a correlation between two different scattering processes. They synthesized predictions of two very different physical properties and then saw the relationship, but there was still a fog behind it.
Principles and applications of duality
For scientific research, surprise always means that there is something we know now but do not yet know, and the only way is to continue further research.
Since the discovery of the Higgs boson in 2012, the physics community hasn't found any sensational new particles. Now, the approach that many physicists are taking is to make very precise predictions of what is expected to happen, and then compare that prediction to very precise measurements to see if they can find biases there, hoping to find a path to new physics in this "crack."
It also means that we need a lot of precision, both experimentally and theoretically. As precision improves, calculations naturally become more difficult. Thus, this newly discovered duality may be some sort of computational "shortcut." But the premise of doing so is that physicists need to really understand it. This is also the next goal of the researchers.
#创作团队:
Compile: M ka
Typography: Wenwen
#参考来源:
https://nbi.ku.dk/english/news/news22/new-and-surprising-duality-found-in-theoretical--particle-physics/
#图片来源:
Cover image: Linda Rain 714, Flickr, CC BY
首图：Michael Tefft, Flickr, CC BY-NC-ND