Chirality and reliability of baryon QCD sum rules

The QCD sum-rule method has been widely used in studying various baryon properties. For a given problem, there is usually more than one sum rule and they all do not work equally well. In this paper, we point out that chirality plays an important role in determining the reliability of a baryon sum rule. The contributions of positive- and negative-parity excited baryon states partially cancel each other in the chiral-odd sum rules, but add up in the chiral-even sum rules. As such, the chiral-odd sum rules are generally more reliable than the chiral-even sum rules. This allows one to identify the more reliable sum rules and use them in extracting the ground-state baryon property of interest. This is illustrated in an explicit example. copyright 1997 The American Physical Society