Dark matter, there is new hope for research

Dark matter

A few years ago, at the Large Hadron Collider (LHC) - the largest particle accelerator in the world, located at CERN in Geneva - the team of physicist Ivan Vorobyev  began producing an exotic form of antimatter known as antihelium. Antimatter is the name by which the mysterious substance is known that destroys itself when it comes into contact with normal matter, while antihelium represents the antimatter equivalent of a classic atom of helium, the chemical element with which they are filled the balloons. Although no human being has ever found a particle of antihelium in nature on Earth, this substance could be the key to solving one of the greatest mysteries of physics: the nature of dark matter .

Although on our planet it is a rare substance, physicists believe that antihelium could be present in abundance in our galaxy, where it is formed from the decay of dark matter, an invisible substance that appears to make up 85 percent of the matter in the universe. On Monday, December 12, Vorobyev's team announced that it had generated about 18,000 antihelium nuclei and, more importantly, that it had calculated the likelihood that ground-based detectors would catch the substance drifting in space, which could indicate the presence of dark matter. .

The experiment

Between 2016 and 2018, Vorobyev's team collided more than a billion particles inside the approximately 27-kilometer ring that makes up the lhc. The collisions recreated by the scientists involved two types of particles: on the one hand a collision between protons and on the other a collision between lead ions, which break apart to form a myriad of new particles, including pions, kaons and other protons. Several petabytes of data, stored on thousands of portable hard drives, were needed to record the results. Subsequently, the team of scientists started sifting through the information: " We filtered only the part that was interesting for us ", explains Vorobyev, a member of the collaborative experiment Alice (acronym of A large ion collider experiment ), which led the project.

Specifically, Vorobyev's team focused on a version of the antiparticle known as antihelium-3, made up of two antiprotons and an antineutron. The team wasn't the first to create antihelium-3: Scientists first observed the antiparticle in 1970 after producing it inside a collider. Although it forms naturally on our planet, antimatter is usually composed of light particles, such as positrons (antimatter's equivalent of electrons), which have thousands of times less mass than antihelium. However, antihelium-3 is relatively heavy, and the heavier a particle of antimatter, the less likely it is to produce it.

The “signatures” of dark matter

Physicists have deduced the existence of dark matter from the gravitational influence it exerts on the rotation of galaxies, but they still don't know what the dark matter is made of. substance. Among the various hypotheses there are very heavy bodies such as black holes or extremely light objects, with a weight equivalent to 100 millionths of the mass of an electron. Twenty years ago, physicists first theorized that some dark matter particles — known as weakly interacting massive particles, or Wimps — could annihilate themselves upon contact with anti-dark matter, producing equal amounts of matter and antimatter. If the annihilating dark matter emitted antihelium, the presence of this antiparticle would represent an indication of its real existence.

In theory, physicists who are involved in researching dark matter could go hunting for matter or of the antimatter generated by the substance: " In many models, dark matter is its own antiparticle, or there are equal quantities of dark matter and anti-dark matter - says physicist Tim Linden of the University of Stockholm, Sweden, who participated in the LHC experiment – ​​In both cases, the annihilation of dark matter tends to generate equal numbers of antiparticles and particles."

However, even stars and other astrophysical bodies that do not have no connection to dark matter produce many particles of extraterrestrial matter, adds Linden, making it difficult to identify their origin. That said, antimatter particles detected in space are more likely to come from dark matter.

Enthusiasm around the possibility that antimatter represents a "signature" of dark matter has grown due to an announcement of some astrophysicists arrived in 2016 . At the time, the researchers in charge of the Alpha magnetic spectrometer (AMS), an instrumentation present on the International Space Station, reported that they had probably succeeded in detecting eight antihelium nuclei. Although the result was never formally released and researchers still refer to the recorded signal as "tentative," the announcement "inspired an effort to figure out how the signal got here, if it were real," he says. Linden.

Galvanized Industry

The LHC experiment and analysis are significant because they have fueled industry confidence in the possibility of detecting antihelium in space as a strategy to find dark matter. After producing the nuclei in the detector, Vorobyev's team analyzed the likelihood of the antihelium breaking up or annihilating with normal matter as it moved through the machine. The scientists then used the results to simulate a model of the Milky Way and estimate the likelihood that antihelium nuclei, originating from tens of thousands of light-years away, would reach Earth. Even if space is relatively empty, as the antihelium crosses the galaxy towards our planet there is still the possibility that these nuclei will be destroyed by colliding with clouds of gas.

The results are promising: " We have given that half [of the nuclei, ed.] will survive the journey to near-Earth detectors, ”explains Vorobyev. This means that there is a good chance that sooner or later antimatter detectors will be able to detect a traveling antihelium particle. The AMS, which recorded the alleged signals announced in 2016, hasn't stopped looking. At the end of 2023, a new instrument, the General antiparticle spectrometer, is expected to be launched into the Antarctic atmosphere and will be used to search for antihelium and other particles at an altitude of about 40 kilometers.

The new work it illustrates how tortuous and uncertain the scientific process can be. To address a question as broad as dark matter, theorists had to think about how researchers might detect it on Earth. Those responsible for the experiments then had to run tests such as Vorobyev's to verify the theorists' ideas. Astrophysicists, therefore, have built the tools to look for the signals left by antimatter. Now the strands are coming together, at least as far as antihelium-based dark matter research is concerned: "It's a great example of diverse communities coming together to try to find answers to really tough problems," Linden points out.

But these communities still have a lot of work ahead of them. Theorists like Linden are still trying to figure out how dark matter can generate antihelium. Astrophysicists must observe the signals of the substance coming from space and possibly verify that the antiparticles are in line with the predictions of dark matter theorists. The Alice experiment lays the groundwork for a new approach to solving the dark matter mystery, but there is still much more for physicists to explore.

This article originally appeared on sportsgaming.win UK.