Journal of the Korean Physical Society

pISSN 0374-4884 eISSN 1976-8524


Particles and Nuclei

J. Korean Phy. Soc. 2011; 59(2): 217-223

Published online August 12, 2011

Copyright © The Korean Physical Society.

Pion Electromagnetic Form Factor and ¥ñ-meson Mass Shift at Finite Density

Seung-il Nam, Hyun-Chul Kim


We investigate the pion electromagnetic form factor and the mass dropping of the ¥ñ meson at finite density. We first calculate the pion electromagnetic form factor and the corresponding charge radii within the framework of the nonlocal chiral quark model from the instanton vacuum both at zero and finite densities. In order to relate the change in the pion charge radius to that of the ¥ñ-meson mass at finite density, we employ the vector-meson dominance for the pion electromagnetic form factor. The pion charge radius turns out to get larger as the quark chemical potential increases. As a result, the ¥ñ-meson mass falls off as the quark chemical potential grows and is found to drop by about 10% at normal nuclear matter density: m¥ñ*/m¥ñ ¡Ö 1 − 0.12 ¥ìB/¥ì0, which is compatible to the results of the measurement at the KEK recently.

Keywords: ¥ñ-meson mass shift, Finite density, Pion electromagnetic charge radius, Nonlocal chiral quark model, Instanton vacuum, ,