ATLAS Collaboration Provides High-Precision Measurement of B0 Meson Lifetime
ATLAS Collaboration Provides High-Precision Measurement of B0 Meson Lifetime
The ATLAS collaboration at the Large Hadron Collider (LHC) has unveiled a new, high-precision measurement of the lifetime of the electrically neutral beauty (B0) meson, a particle composed of a bottom antiquark and a down quark.
B mesons, which consist of two quarks, one being a bottom quark, have been pivotal in advancing our understanding of rare and predicted phenomena. By studying these mesons, physicists have gained valuable insights into weak force interactions and heavy-quark bound state dynamics. The precise measurement of the B0 meson lifetime, which represents the average time it exists before decaying into other particles, is crucial for these studies.
In their latest study, the ATLAS collaboration investigated the B0 meson’s decay into an excited neutral kaon (K0) and a J/ψ meson. The J/ψ meson decays into a pair of muons, while the K0 meson decays into a charged pion and a charged kaon. This analysis used proton-proton collision data collected by the ATLAS detector during Run 2 of the LHC (2015–2018), with a substantial data set of 140 inverse femtobarns (equivalent to around 100 trillion proton-proton collisions).
The team measured the B0 meson lifetime as 1.5053 picoseconds (ps), with a statistical uncertainty of 0.0012 ps and a systematic uncertainty of 0.0035 ps. This new measurement is the most precise to date, surpassing previous results, including earlier measurements from ATLAS.
Achieving this level of precision required overcoming several experimental challenges, such as minimizing systematic uncertainties, performing detailed modeling, and refining detector alignment. Beyond the B0 meson’s lifetime, the ATLAS team also calculated its decay width—a fundamental parameter that reflects the particle’s instability. The decay width is inversely related to the particle's lifetime, in accordance with Heisenberg's uncertainty principle. The B0 meson’s decay width was measured at 0.664 inverse picoseconds (ps-1), with a total uncertainty of 0.004 ps-1.
The researchers also compared this result to a previous measurement of the decay width of the Bs0 meson, composed of a bottom quark and a strange quark. They found that the ratio of decay widths for the two mesons was consistent with unity, aligning with theoretical predictions from heavy-quark models. These precision measurements from ATLAS provide deeper insights into weak-force-mediated decays within the Standard Model and offer valuable data to refine future theoretical predictions.