An international team of physicists from the STAR collaboration at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory has made a breakthrough in understanding the fundamental properties of matter and antimatter. The scientists have observed for the first time an exotic antinucleus, which consists of four antimatter particles – two antineutrons, one antihyperon, and one antiproton. The new type of nucleus is called antihyperhydrogen-4, and its detection confirms the existence of rare and exotic objects. It should be noted that the RHIC collider recreates the conditions of the early Universe, providing a unique opportunity to study the asymmetry between matter and antimatter in the Universe. Sounds complicated, right? Let's get to it!
Scientists have observed antihyperhydrogen-4 for the first time, opening up new horizons in particle physics. Image: bnl.gov
The asymmetry of matter and antimatter is one of the main unsolved problems in physics. It is assumed that the asymmetry arose in the first fractions of a second after the Big Bang.
Contents
- 1 Antimatter and antimatter
- 2 Antihyperhydrogen-4
- 3 Research results
- 4 The significance of the discovery for science
- 5 Future research
- 6 Why were Russian scientists restricted from accessing the LHC?
Antimatter and Antimatter
Matter that consists of antiparticles – “mirror images” of a number of elementary particles with the same spin and mass – is called antimatter. And although the Universe is believed to be made of matter, not antimatter, both were probably present in equal quantities in the cosmic expanses during the Big Bang about 14 billion years ago.
Antimatter, in turn, consists of antiparticles, which are not stably formed in nature (to date, antimatter has not been detected in our Galaxy or beyond). For this reason, the nuclei of antimatter atoms are synthesized by scientists and consist of antiprotons and antineutrons, and the shells are made of positrons.
The asymmetry of matter and antimatter is one of the main problems of modern science. Image: interestingengineering.com
Thus, in order to study the asymmetry of matter and antimatter in the Universe, physicists must first discover new antimatter particles. This is the logic followed by the authors of a new study published in the journal Nature.
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The experiment was carried out at the RHIC collider to collide gold nuclei at energies reaching 200 GeV per nucleon. These high-energy collisions create conditions similar to those that existed in the first microseconds after the Big Bang and generated quark-gluon plasma – a state of matter where quarks and gluons did not bind into the usual protons and neutrons.
Recall that The Relativistic Heavy Ion Collider (RHIC) is one of the few accelerators in the world capable of accelerating heavy ions to relativistic speeds, recreating the conditions of the early Universe.
The international research group that specializes in studying the properties of strongly interacting matter at high energies at RHIC is the STAR collaboration.
Antihyperhydrogen-4
As part of the experiment, scientists were able to observe antihyperhydrogen-4 for the first time– an exotic antimatter hypernucleus (hypernuclei are nuclei that contain hyperons, particles that include at least one strange quark). It is the heaviest antimatter hypernucleus discovered to date.
The authors of the new study also looked for specific signatures of the decay of antihyperhydrogen-4. It should be noted that the decay of this unstable nucleus leads to the formation of antihelium-4 and a positively charged pion (π⁺). Antihelium-4, as the paper says, “was previously detected by the STAR collaboration, which helped in identifying new events.”
Antihyperhydrogen-4 consists of an antiproton, two antineutrons, and an antilambda hyperon (antihyperon). Image: futurezone.at
Needless to say, finding and observing antihyperhydrogen-4 was a huge challenge. In fact, according to Brookhaven National Laboratory physicist Lijuan Ruan, “it’s only by luck that the four constituent particles — an antiproton, two antineutrons, and an antihyperon — can emerge from the collision close enough to form an antinucleus.”
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The team also analyzed the tracks of billions of collisions to look for rare events consistent with the decay of antihyperhydrogen-4. Each antihelium-4 emerging from a collision could be associated with hundreds or even thousands of positive pions.
A lot of pions are produced during the RHIC collision. Image: theconversation.com/
The main task for scientists was to find pairs of particles whose trajectories intersect at one point — the top of the decay, which has certain characteristics.
Results of the study
Despite the fact that the Big Bang should have created equal amounts of matter and antimatter, the observable Universe consists of matter. Understanding the causes of this imbalance is one of the main tasks of modern physics, — the authors of the new study said.
After careful analysis, the physicists found 22 events, of which about 6.4 could be explained by “background” noise. This means that about 16 events correspond to real decays of antihyperhydrogen-4. This statistical significance allowed the team to conduct a direct comparison of the properties of matter and antimatter.
Antihyperhydrogen-4 is the key to unraveling the mysteries of the Universe. Image: techno-science.net
The researchers also compared the “lifetime” of antihyperhydrogen-4 with its material analogue, hyperhydrogen-4, and compared pairs of hypertriton and antihypertriton. The results obtained in the experiment showed that the lifetimes of these pairs are almost identical, which corresponds to the predictions of the Standard Model of particle physics.
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The importance of the discovery for science
The discovery, as its authors note, indicates that, with the exception of opposite electric charges, antimatter has the same properties as matter. But since our Universe consists mainly of matter, the reasons for this imbalance still remain a mystery. Fortunately, the discovery of antihyperhydrogen-4 provides a new tool for studying asymmetry.
The results of the experiment also confirm predictions that the properties of antimatter should be a mirror image of the properties of matter.
The detection of 16 real events involving antihyperhydrogen-4, with an expected background noise of 6.4 events, gives high confidence in the results of the experiment. Image: giantfreakinrobot.com
If we were to see a violation of this symmetry, we would have to revise many of our ideas about physics. The fact that the symmetry holds strengthens confidence in existing theories, said Emily Duckworth of Kent State University.
The results of the new study also open up opportunities for further research into heavier antimatter nuclei and hypernuclei, which could lead to a deeper understanding of the strong interaction and the processes observed in extreme conditions such as the interior structure of neutron stars.
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Future research
In the future, the STAR collaboration team plans to continue research in this area using more sophisticated detection and data analysis methods. The ability to create and observe more complex antimatter structures could lead to new discoveries in nuclear physics and cosmology.
Dr. Hao Qiu from the Institute of Modern Physics believes that further study of the asymmetry between matter and antimatter requires the discovery of new antimatter particles. He emphasizes that the results of the new study are a major step forward in the experimental study of antimatter.
In the future, these studies may help to solve one of the greatest mysteries of the Universe – why it consists mainly of matter, not antimatter. Image: physicsworld.com
Overall, the authors of the scientific work have once again confirmed the correctness of existing models and made a big step forward in experimental studies of antimatter.
Earlier, scientists came closer to understanding why there is less antimatter in the Universe than matter. Details – here!
It should also be noted that the historic observation of antihyperhydrogen-4 confirms fundamental principles of physics and opens up new avenues for research, demonstrating the capabilities of modern technologies and the importance of international cooperation in achieving breakthrough results.
Why were Russian scientists restricted from accessing the LHC?
The importance of international cooperation, which the authors of the new study talk about, is unfortunately not obvious to everyone today. Recently, the European Organization for Nuclear Research (CERN), which operates the Large Hadron Collider, decided to sever its last ties with physicists from Russian scientific organizations starting January 1, 2025.
Thus, CERN is closing access to its research projects for Russian scientists. CERN employees confirmed this information to The Insider journalists, clarifying that the restriction applies not only to Russian citizens, but also to scientists of all nationalities who collaborate with Russian institutes.
The Large Hadron Collider is a unique particle accelerator. Scientists from all over the world work with it. Image: britannica.com
According to the rules, which will come into force on December 1, 2024, Russian scientists who have not previously participated in CERN projects will not be able to collaborate with the European institute as of January 1, 2025.
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The only exception is the current contracts between CERN and JINR, which will not be terminated. This means that those Russian scientists who are already working on joint projects at CERN will be able to continue their research.
We are being excluded from international collaborations that we have been part of for many years. For example, my colleague who has worked at ALICE for 30 years will have to resign. No one is fired, but access is denied. This is a heavy blow. I would describe it as the destruction of the entire Russian field of experimental high-energy physics. After all, these researchers were at the forefront of modern science, working at CERN, and now they are being kicked out of there, deprived of access to experimental facilities and the global scientific community. CERN is the only place in the world where such research is possible. The Large Hadron Collider is the only one of its kind. Without access to it, there is no science, – a Russian physicist who took part in scientific experiments at CERN told The Insider.
Russian scientists from Russian scientific organizations will be denied the opportunity to work at the LHC from January 1, 2025. Image: i.guim.co.uk
Another Russian physicist working at CERN claims that the decision will not benefit the European organization:
This decision deals two blows, and both are detrimental to science as a whole. On the one hand, Russian scientists are deprived of the opportunity to continue work that has already taken significant resources and years of their lives; young physicists are deprived of the opportunity to conduct research in one of the most advanced laboratories in the world within the framework of established scientific schools. On the other hand, the departure of Russian research groups will weaken the areas of their work at CERN.
CERN justifies its decision by the fact that Russian researchers belong to state universities whose rectors supported the Russian Federation's policy towards Ukraine. At the same time, the organization notes that if a scientist from Russia gets a job, say, at an Italian research center, they will cooperate with him.
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The decision taken by the European Organization for Nuclear Research causes serious damage not only to Russian, but also to world science: without international cooperation, the most important discoveries for humanity are simply impossible.