It is a first step to understand why we exist

The most elementary question that human beings ask ourselves since we are here is simply: why do we exist? According to the best theories about the origin of the universe, We should not be here. The Big Bang should have created identical amounts of matter and antimatter, which would have annihilated each other in an energy flash, leaving an empty cosmos. And yet, here we are, in a universe made of matter.

Short. The key to our existence lies in a subtle asymmetry, a small trap in the laws of physics that favored matter over antimatter. Now, the CERN LHCB team has announced the first observation of this asymmetry in the bariones, the particles that make up everything we see: stars, planets and ourselves. It is a milestone that we had been waiting for decades, and that after its Publication in Nature magazine Open a new and fascinating way to solve the mystery of our own existence.

The enigma of the material universe. The Soviet physicist Andréi Sájarov saw it clear in 1967. For the matter to prevail above the antimatter after the Big Bang (so that a universe like ours was born, in short) three conditions should be met, including the violation of the load-partner symmetry.

Load symmetry (c) means that if you change a particle for its antiparticle (for example, an electron for a positron), physical laws should not change. Parity symmetry (P) is like looking at the process in a real mirror, investing space coordinates. Combined symmetry load-partity (CP) implies that a physical process is indistinguishable from its “antimatter version” in the mirror.

If the CP symmetry were perfect, the balance between matter and antimatter would never have inclined. CP symmetry violation means that the cosmic mirror is slightly broken. Subject and antimatter do not behave exactly as specular reflexes.

The fundamental piece that was missing. This phenomenon had already been observed for the first time in 1964 in particles called inns, formed by a quark and an antiquark. But there was a key piece of puzzle: it had never been detected in the bariones, formed by three quarks. It was a key piece because ourselves are barionic matter: the protons and neutrons that constitute us are bariones.

An imperfect reflex. The CERN LHCB team, one of the great detectors of the great Hadron collider, specializes in studying particles that contain a type of heavy quark called “Beauty” or “Bottom”, in which the effects of the CP violation are expected to be more pronounced.

For this investigation, physicists focused on a specific particle: the Lambda B zero (λb0) barion, a kind of heavy cousin of the proton. Scientists analyzed billions of collisions In data from 2011 to 2018observing how this particle disintegrated in four lighter: a proton, a kaon and two pions (λb0 → pk –π+π−).

The key to the experiment was to compare the rate of this disintegration with that of its antimatter twin, the disintegration of the anti-barion lambda b zero (λˉb0 → pˉ k+π-π+). If the CP symmetry were perfect, both disintegrations would occur with the same frequency. But it is not so. The LHCB team measured a clear and statistically robust difference.

Are we facing new physics? The results have a statistical significance of 5.2 sigmas. In particle physics, an observation with more than 5 sigmas is considered a full -fledged discovery. It is the first time that a barion and its antibarion are observed do not behave identically. The mirror is broken, also for particles that form the tangible world.

This discovery is, in the first place, a spectacular confirmation of the standard particle physics model. This model, our most complete theory on the subject, predicts that CP violation must occur in both inns and bariones. The fact that it is finally seen in barions reinforces our current understanding of physics.

However, and here comes the most exciting, it is also the beginning of a new chapter. The observed violation is insufficient to explain the enormous mastery of the matter we see in the cosmos. There must be Another source of asymmetrysomething that the standard model does not contemplate. Physicists have confirmed that the universe does not deal equal to matter and barionic antimatter, but hunt continues.

Image | Cern

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