Preliminary Results on the Experimental Investigation of the Structure Functions of Bound Nucleons

TL;DR

This paper reports preliminary experimental findings on how the structure functions of bound nucleons differ from free ones, revealing unexpected differences in longitudinal and transverse modifications that challenge existing models.

Contribution

It provides new measurements of the ratio R for nuclei and deuterium, showing that nuclear modifications are different for longitudinal and transverse structure functions, contrary to prior expectations.

Findings

Nuclear modifications of structure functions differ for longitudinal and transverse components.

Measured R_A is less than R_D, contrary to some theoretical predictions.

Results suggest the need to revise models of the EMC effect.

Abstract

We present preliminary results on an experimental study of the nuclear modification of the longitudinal ($\sigma_L$) and transverse ($\sigma_T$) structure functions of nucleons bound in nuclear targets. The origin of these modifications (commonly referred as as the EMC effect) is not fully understood. Our measurements of R= $\sigma_L / \sigma_T$ for nuclei ($R_A$) and for deuterium ($R_D$) indicate that nuclear modifications of the structure functions of bound nucleons are different for the longitudinal and transverse structure functions, and that contrary to expectation from several theoretical models, $R_A< R_D$.