arXiv:hep-th/0005149·v2·High Energy Physics — Theory
Width and Partial Widths of Unstable Particles
P.A. Grassi (New York U.)🇺🇸 · B.A. Kniehl (Hamburg U.)🇩🇪 · A. Sirlin (New York U.)
Abstract
In the gauge theory context, a definition of branching ratios and partial widths of unstable particles is proposed that satisfies the basic principles of additivity and gauge independence. A simpler definition, similar to the conventional one, is examined in the Z^0-boson case. In order to establish contact with experiment, we show that it leads to a peak cross section that justifies the expression used by the LEP Electroweak Working Group through next-to-next-to-leading order, provided that the pole rather than the on-shell mass and width of the Z^0 boson are employed.
Comments: 8 pages, LaTex, no figures, macros included, A more complete theoretical discussion and applications to the Z^0 peak cross section are included