Reanalysis of the Four-Quark Operators Relevant to \Lambda_b Lifetime from QCD Sum Rule

TL;DR

This paper reanalyzes the mbda_b lifetime using QCD sum rules, incorporating additional vacuum condensates, alternative quark-hadron duality, and deviations from vacuum saturation to improve theoretical predictions.

Contribution

It introduces new elements into the QCD sum rule analysis, including more condensates and duality assumptions, to refine the mbda_b lifetime estimate.

Findings

Calculated mbda_b lifetime ratio mbda_b/bel B^0 = 0.83  0.04

Determined the hadronic parameter r to be 3.6  0.9 with \u03ba_1=4

Results are consistent with experimental measurements.

Abstract

\Lambda_b matrix element of four-quark operator relevant to its lifetime is reanalyzed by QCD sum rule. The new ingredients introduced are that (1) more vacuum condensates are considered; (2) different quark-hadron duality is adopted; and (3) the possible deviation from the vacuum saturation assumption for the four quark condensates is considered. With \kappa_1=4 the related hadronic parameter r is calculated to be 3.6 \pm 0.9, and the lifetime ratio \tau(\Lambda_b)/\tau(B^0) = 0.83 \pm 0.04, which is consistent with the experimental data.