In all the PDF plots that I have seen so far (e.g. https://arxiv.org/abs/1111.5452 Fig. $3$ and $4$) the PDFs for sea or charm quarks contained only the strange or charm quark, but not the $\bar{s}$ or $\bar{c}$ quark. Since the sea quarks can only be created through the process $g\rightarrow c\bar{c}$ or $g\rightarrow s\bar{s}$, I was left wondering why that is the case?
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2$\begingroup$ They are identical to those of their quark, for normal target hadrons, no? $\endgroup$– Cosmas ZachosCommented Oct 5, 2021 at 20:18
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$\begingroup$ In the first sentence, did you mean to write "the PDFs for strange or charm quarks contained only the strange or charm quark"? $\endgroup$– Arturo don JuanCommented Dec 28, 2021 at 22:12
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1 Answer
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Exactly as Mr. Zachos said, if the hadron has no valence strange or charm (or top or bottom) quarks, then the quark and antiquark distributions will be identical by the reasoning you gave (that they only ever come in pairs).
For example, a proton has a valence structure of $|uud\rangle$. Therefore for the strange quark we'd have$f_{s/P}(x)=f_{\bar s / P}(x)$, and likewise for all the other heavy quarks.
answered Dec 28, 2021 at 22:18