Comment on "Mass and K Lambda coupling of N*(1535)"

TL;DR

This paper clarifies that the previously reported mass shift of N(1535) due to K Lambda coupling is actually a change in its bare mass, not its Breit-Wigner mass, impacting interpretations in constituent quark models.

Contribution

It corrects a misconception by showing the mass shift pertains to the bare mass, not the Breit-Wigner mass, influencing theoretical models of nucleon excitations.

Findings

The Breit-Wigner mass of N(1535) remains unchanged.

The mass shift is attributed to the bare mass of N(1535).

Clarifies the interpretation of mass shifts in nucleon resonances.

Abstract

It is argued in [1] that when the strong coupling to the K Lambda channel is considered, Breit-Wigner mass of the lightest orbital excitation of the nucleon N(1535) shifts to a lower value. The new value turned out to be smaller than the mass of the lightest radial excitation N(1440), which effectively solved the long-standing problem of conventional constituent quark models. In this Comment we show that it is not the Breit-Wigner mass of N(1535) that is decreased, but its bare mass. [1] B. C. Liu and B. S. Zou, Phys. Rev. Lett. 96, 042002 (2006).