Super-fast quarks as a probe of the origin of the EMC effect

Four decades after the initial publication showing the EMC effect, we still do not have a well-accepted understanding of what effect, or combination of effects, drives the suppression of the high-x quark distributions in nuclei. Because the x dependence is universal, while the A dependence is weak, many models can approximately reproduce the main EMC effect measurements. Several new observables have been proposed to better understand the origin of the EMC effect, including measurements of the spin and flavor dependence of the EMC effect, and detailed studies of the anomalous A dependence in light nuclei.

Another option is to examine the EMC effect at x>1 by measuring the distribution of super-fast quarks, where a single nucleon carries more longitudinal momentum than carried by an average proton in the nucleus. While most models show extremely small nuclear effects in the deuteron in the conventional EMC effect region, many of these show much larger effects at x>1. In addition, different classes of models motivated the observation of a correlation between the EMC effect and short-range correlations give very different predictions for x>1, providing a unique sensitivity. I will review existing and recently taken data from Hall C at Jefferson Lab, as well as future measurements and the EIC and/or at an energy-upgraded Jefferson Lab, which will be able to make clean and decisive measurements providing new and unique insight into the EMC effect.