CERN confirms transformation of extremely rare particles, hints at new physics: ScienceAlert

At CERN’s particle collider, a rare event brings us excitingly close to the edge of new physics.

Of years of operation what is known as NA62 experienceparticle physicist Cristina Lazzeroni of the University of Birmingham in the UK and her colleagues have now established, observed and measured the decay of a charged kaon particle into a charged pion and a pair of neutrinos and antineutrinos. The researchers presented their findings in A CERN Symposium.

It’s exciting stuff. The reason the team has been relentlessly pursuing this very specific type of decay channel for more than a decade is that it is what is known as a “golden” channel, meaning that it is not only incredibly rare, but well predicted by complex mathematics. Composition of the standard model of physics.

This rarity and precision make it an extremely sensitive measure for discovering new physics. However, it was only by collecting an incredible amount of data covering countless particle collisions that the team was able to confirm their discovery as being accurate according to the famous book.Five sigma“Standard of statistical certainty.

“This challenging analysis is the result of excellent teamwork, and I am extremely proud of this new result.” Lazzerone says.

Kaons consist of a combination of a quark and a different antiquark particle associated with the strong force, which rapidly decays in a unique way that physicists describe as “strange‘. This strange property made it a useful tool in determining the rules by which particles should generally behave.

Producing coons is not particularly difficult, if you have the right equipment. Using the Super Proton Synchrotron at CERN, researchers fired a beam of high-energy protons at a fixed beryllium target. This produces a secondary beam of about a billion particles per second, about 6% of which are some type of charged kaon.

Counters do not have a long life; They form and decay in one-hundredth of a millionth of a second. So, in that secondary ray, the decay of the kaon is constantly occurring, generally transforming into a very heavy cousin of the electron called the muon, and Neutrino.

However, in about 13 out of every 100 billion kaons that decay, the result is an antineutrino, a neutrino, and an unstable particle made of another flavor of quark and an antiquark called a pion.

“Kaons and pions are particles that contain quarks,” Lazzrino told ScienceAlert. The fact that quarks are of different types (up, down, strange, charm, beautiful, top) is called flavor.

“The rarity of this decay has to do with the fact that there is a change in the flavor of the Z quarks Bosun It is produced by Pune and Neutrinos. “This can only happen through a fairly complex process, hence its rarity.”

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The scale of kaon decay needed to observe this process is astronomical, but that is not the end of the challenges involved. Neutrinos are notoriously difficult to detect as they are, and they and their antineutrino partner will annihilate almost immediately; For the NA62 experiment, researchers made no attempt to detect a neutrino-antineutrino pair.

It’s just the charged pion, or “pi+”, that is the needle, in the middle of a huge haystack of decay of other charged kaons (K+).

“All the other K+ decays that we want to eliminate are called background, and they have detectable particles. The challenge is to detect them.” everyone “From it and always, so when we see K+ to pi+ and nothing else, we are sure that we have not lost anything, and that is really the signal,” Lazzerino explained.

That’s why, when the team reported their first set of results in 2019, they weren’t at the five-sigma level of statistical certainty they found. And now they have reached that threshold.

Now that the decay channel has been created, researchers can move on to looking for any anomalies that might indicate new physics. The kaon-to-pion number and neutrino/antineutrino decay observed by the team are higher than 8.4 per 100 billion predicted by the standard modelbut it is still within the uncertainty parameters.

In order to find new physics, a higher deviation in the number of decays must be observed.

“the Standard form Feedback prediction has been very good so far, but we know it is bound to have flaws. Like it doesn’t include a model for Dark matterAnd the matter is- Antimatter The imbalance is an order of magnitude too small in relation to what is needed to represent the universe. In general, we expect new physics to emerge. What it is exactly, is unknown. “But in general we expect new particles (and forces) to exist,” Lazzeroni said.

“NA62 has already collected more data, and will continue for another three years. With the totality of the data, we will be able to determine whether it is consistent with the Standard Model.”

How wonderfully sexy.

The team presented its results in CERN Symposium.