B Quark Gluon Plasma In the Presence of Charged Leptons?

metastable

It is my understanding that a state of matter known as quark-gluon plasma has been produced artificially and studied in various labs. How is the presence of varying densities of charged leptons such as electrons thought to influence the behavior of any naturally occurring examples of quark gluon plasma, past or present?

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Staff Emeritus
How is the presence of varying densities of charged leptons such as electrons thought to influence the behavior of any naturally occurring examples of quark gluon plasma, past or present?
Not at all.

metastable

In a cooling, naturally occurring quark gluon plasma, are any metastable interactions or states allowed between up quarks & electrons that would ordinarily be prohibited by color confinement?

vanhees71

Gold Member
The nice thing of leptons (and also photons) in the context of heavy-ion collisions is that for them the medium is transparent. Thus one can neglect "final-state interactions". When produced they leave the fireball practically completely unperturbed.

Thus they are the only probes of the hot and dense medium that carry information over the whole history of the fireball evolution. Of particular importance are lepton-antilepton pairs (socalled dileptons, i.e., electron-positron or muon-antimuon pairs). Their spectral shape is directly related with the in-medium autocorrelation function of the electromagnetic current of the strongly interacting matter. Among other things they thus give some hint about the spectral properties of the light vector mesons, $\rho$, $\omega$, and $\phi$ and the related change of their spectral properties in the context of the chiral phase transition (in the socalled "low-mass range", ie., invariant masses of the dileptons below the $\phi$ peak).

In the intermediate-mass range at high collision energies (top SPS and RHIC energies, LHC) one has a unstructured piece in the spectrum (as already in the vacuum, which is given by $\mathrm{e}^+ + \mathrm{e}^- \rightarrow \text{hadrons}$). The main sources of dileptons there are (a) thermal radiation from the QGP and (b) correlated $\text{D}$-$\bar{\text{D}}$ (and particularly at the LHC also $\text{B}$ -$\bar{\text{B}}$) decays. If one is able to subtract this open-heavy-flavor component (as was possible in the NA60 experiment on dimuons at the SPS), one has a clear signal from the QGP, and since the invariant-mass spectrum is unaffected by the Doppler-blueshift from the flow of the medium, it's a direct space-time-weighted average of the temperature reached. Already at the SPS this mean temperature is above the pseudo-critical temperature, which is a clear indication that already at the SPS a QGP has been formed.

For some pedagogical introduction, see my presentations prepared for some graduate-student lecture weeks in recent years:

https://th.physik.uni-frankfurt.de/~hees/hgs-hire-lectweek18/index.html
https://th.physik.uni-frankfurt.de/~hees/hgs-hire-lectweek17/
https://th.physik.uni-frankfurt.de/~hees/hqm-lectweek14/index.html

metastable

https://th.physik.uni-frankfurt.de/~hees/publ/habil.pdf

...in the hadronic world isospin symmetry is only slightly broken. This is due to the fact that a large part of the mass of hadrons like the nucleons is dynamically generated by the strong interaction, and thus the observed isospin-symmetry breaking can be considered as a small perturbation which is due to the difference in the bare up- and down-quark masses (which, however, are small compared to the typical hadron-mass scale of around 1 GeV) and the electromagnetic interaction. Thus in the hadronic world the isospin symmetry is valid to a much higher accuracy than suggested by the large difference of the small up- and down-quark masses in the QCD Lagrangian...
https://th.physik.uni-frankfurt.de/~hees/publ/habil.pdf

Thank you for your answer. My understanding is too basic to understand all the equations, but I was reading this part about the bare up and down quark masses, and how they are small compared to the hadron mass scale, which reminded me why I was asking about this to begin with. I was told in another thread there are ordinarily no metastable interactions between multiple electrons and multiple up quarks, because of color confinement. But in a quark gluon plasma, I understand color confinement breaks down. I understand it is thought we've observed quark gluon plasma on earth through heavy ion collisions, but how would this plasma be expected to behave in conditions similar to those present during inflation? Compared to ion collision quark gluon plasma, was inflation quark gluon plasma thought to persist over a longer time scale, and if so, during this longer time scale, without color confinement to prevent such interactions, is it conceivable under such conditions 4 up quarks and 3 electrons could occupy a small enough space for a long enough time to interact as a composite particle with the same charge and perhaps, being an odd number of particles, have other similar properties, such as 1/2 spin, to a down quark?

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"Quark Gluon Plasma In the Presence of Charged Leptons?"

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