Delta Gamma_d: A Forgotten Null Test of the Standard Model

TL;DR

This paper discusses Delta Gamma_d as a null test for the Standard Model, reviewing measurement methods and proposing a new approach to detect potential new physics effects.

Contribution

It introduces a novel method for measuring Delta Gamma_d, enhancing the potential to identify deviations from Standard Model predictions.

Findings

Standard Model predicts Delta Gamma_d below 1%

Proposed measurement approach improves sensitivity

Null test can reveal new physics if deviations are observed

Abstract

The recent measurement of an anomalous like-sign dimuon asymmetry by the D0 collaboration has prompted theoretical speculation on possible sources of physics beyond the Standard Model that may affect lifetimes and lifetime differences in neutral B meson systems. One observable that deserves closer attention is the width difference in the B_d system, Delta Gamma_d. Since the Standard Model prediction for this quantity is well below 1%, it serves as a "null test" whereby the measurement of a larger value would cleanly reveal the presence of new physics. Methods to measure Delta Gamma_d at current and future experiments are reviewed and an attractive new approach is proposed.