# Baryonic density in collision experiments

Does anyone know any way of estimating the net baryon density in collision experiments, e.g. in LHC, RHIC, or the upcoming ones at GSI-FAIR?

I have comes across many hand-waving arguments, sample -

1. Electron-positron colliders start with $\rho_B = 0$, and since conservation laws have to respected, matter and anti-matter must be produced in equal amounts. Hence, barring inhomogeneities, LHC is essentially in the $\rho_B \approx 0$ regime.

2. Antikaon-proton interaction is known to be attractive, through various model-dependent calculations, so if we have a ${\bar K}-p$ collision experiment, it shall involve the formation of quasi-matter having a larger density than usual, and hence, via these kind of reactions, GSI-FAIR plans to study QCD matter at high densities (especially in the Compressed Baryonic Matter experiment), while it remains inaccessible at LHC.

(Please correct me if the hand waving is inappropriate.) I am wondering, if there is any way of making this a little more calculation oriented, though I understand that a fully rigorous calculation would be very difficult. (I don't want that, too.)

Also, is it possible to have any model-independent answers, since model-dependent answers can be found with a bit of googling, e.g. Phys. Rev. C 72, 034613 (2005), which even has the evolution of these densities in lead-lead collisions. Though these calculations are the order of the day, model-independent calculations, if possible, teach you much more.

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The answer is no, imo. Either you develop a model that you can calculate which will be fairly complicated as it is many body on many body scattering ( arxiv.org/abs/1205.0579 ), or you hand wave. –  anna v Jun 1 '14 at 7:31
@ anna v - Thanks, at least some one responded. I completely buy the fact that a rigorous calculation is very complicated. But since you are an experimentalist in particle physics (if I'm right), you are in good position to assess these arguments. Is my understanding of FAIR's high density experimentation correct? Is this the right hand-waving argument for how these guys plan to reach all these fantastic densities ($\sim 4$ times the nuclear saturation density). Thanks :) –  The Dark Side Jun 1 '14 at 10:37
you have to give me a link for this GSI-Fair proposal. I cannot find one. –  anna v Jun 1 '14 at 11:25
Thanks. I'll edit the question and put the link over there. –  The Dark Side Jun 3 '14 at 6:24
@annav it's the top search result for GSI FAIR ;-) –  David Z Jun 3 '14 at 6:29