Quenched spectrum with staggered fermions

Abstract

We present results for the spectrum of QCD in the quenched approximation using staggered fermions at $\beta =5.7, 6.0, \mathrm{and} 6.2$. We use extended wall sources, which give a better projection onto the ground state, and allow us to study many nonlocal pion and $\rho$ states, as well as the $\Delta$ baryon. Staggered flavor-symmetry breaking reduces dramatically from $\beta =5.7\mathrm{} \mathrm{to} 6.2$. For $\beta =6\mathrm{}$, the ratio $\frac{m_N}{m_{\rho }}$ lies significantly below 1.5 for $m_q<m_s$. At $\beta =6\mathrm{}$ we study finite-volume effects using ${16}^3$×40 and ${24}^3$×40 lattices. We reanalyze our old data at $\beta =6.2\mathrm{}$ and resolve the problem of the anomalously light scalar state.