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When quark gluon plasma is created during heavy ion collisions, the QGP exists extremely briefly before hadronizing--the process where the QGP cools and quarks combine to form colorless hadrons. A similar hadronization process occurred shortly after the Big Bang, when temperatures cooled enough for protons and neutrons (and potentially their antiparticles) to form. Given that there exists a matter-antisymmetry in the universe, would a similar imbalance occur during the hadronization process that follows a heavy ion collision? Is it expected that if there exists a mechanism that caused the matter-antimatter asymmetry after the Big Bang, then we should observe the same on a smaller scale any time QGP hadonizes? Or is matter-antimatter asymmetry unrelated to the hadronization process?

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  • $\begingroup$ Have your read this? en.wikipedia.org/wiki/Baryon_asymmetry " Several competing hypotheses exist to explain the imbalance of matter and antimatter that resulted in baryogenesis. However, there is as of yet no consensus theory to explain the phenomenon, which has been described as "one of the great mysteries in physics". $\endgroup$
    – anna v
    Apr 18, 2023 at 4:57

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Given that there exists a matter-antisymmetry in the universe, would a similar imbalance occur during the hadronization process that follows a heavy ion collision?

Actually, it turns out that when systematically studying the ratio of particles to antiparticles from various collisions (heavy ion and $pp$) at the LHC over the last 30 or so years (and using the framework of the hadron resonance gas (HRG) model, a statistical model which describes the low temperature hadronic phase of QCD), indicates that as far as particle colliders are concerned, there is no particle/antiparticle asymmetry.

That is, the researchers found that the ratio of particles to antiparticles $\rightarrow 1$.

From the first paper above:

"The ratios of bosons and baryons get very close to unity indicating that the matterantimatter asymmetry nearly vanishes at LHC. The chemical potential calculated at this energy strengthens the assumption of almost fully matter-antimatter symmetry at LHC energy."

And from their conclusion:

"So far, it can be concluded that the future LHC heavy-ion program likely will produce antiparticle-to-particle ratios similar, when not entirely identical, to the ones measured in this current pp program. Secondly, the ratios obviously run very close to unity implying almost vanishing matter-antimatter asymmetry."

Is it expected that if there exists a mechanism that caused the matter-antimatter asymmetry after the Big Bang, then we should observe the same on a smaller scale any time QGP hadonizes?

There is no consensus on the mechanism itself thus far, so answering that would be opinion. In any event, we appear to have observed the opposite on a smaller scale.

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  • $\begingroup$ I would be curious how the error budget on the LHC’s dataset compares to the part-per-billion asymmetry observed by comparing the baryon density to the CMB. One does not do a part-per-billion experiment by accident. $\endgroup$
    – rob
    Apr 18, 2023 at 5:40
  • $\begingroup$ @rob I guess so. They did look at data spanning 30 years, so who knows how many data points they looked at. $\endgroup$
    – joseph h
    Apr 18, 2023 at 6:52

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