The Role of Baryon Number Conservation in Measurements of Fluctuations

Understand

I discuss the role and impact of net-baryon number conservation in measurements of net proton fluctuations in heavy-ion collisions.

• I show that the magnitude of the fluctuations is entirely determined by the strength of two particle correlations.
• At LHC and top RHIC energy, this implies the fluctuations are proportional to the integral of the balance function (BF), $B^{p\bar p}$ of protons and anti-protons, while in the context of the RHIC beam energy scan (BES), one must also account for correlations of "stopped" protons.
• The integral of $B^{p\bar p}$ measured in a $4\pi$ detector depends on the relative cross-sections of processes yielding $p\bar p$ and those balancing the proton baryon number via the production of other anti-baryons.