What can Bs mesons tell us?

This plot depicts measurements from three different experiments as well as the Standard Model prediction. All three measurements agree with one another pretty well and none differ very much with the prediction.
Inside a neutral B meson, the bottom antiquark can emit a W boson and convert to a charm antiquark. The W boson decays into a charm quark and strange antiquark, resulting in the J/ψ and Φ final state.

Since the mid 1950s, scientists have known that there are certain instances in which matter can change to antimatter and back again. This change, or oscillation, occurs only inside subatomic particles called mesons, which contain one quark and one antimatter quark. Further, this matter-antimatter flip only occurs in a few select classes of mesons. Subatomic particles called neutral B mesons (Bs) contain a bottom quark and a strange antiquark. Through the vagaries of quantum mechanics, the bottom quark can become a strange quark at the same time as a strange antiquark can become a bottom antiquark. In these instances, the quark and antiquark contents have become reversed, matter becomes antimatter and then back to matter in a grand oscillation.

The theoretical details behind this are quite daunting, but the fact that this process changes matter to antimatter and back again makes it an ideal spot to study some fundamental questions. One of these questions is why our universe naturally consists of only matter when matter and antimatter are made in equal quantities in our experiments.

One particularly interesting decay of Bs mesons is the decay into two other mesons (J/ψ and Φ). This decay is sensitive to the underlying quantum mechanics that governs the behavior of all subatomic matter. If something exists that influences the oscillation, its effect will appear in the measurements of the Bs lifetime. The Standard Model predicts certain productions of this decay. If an experimental measurement of the decay differs from the Standard Model, if could be a clue as to why we don’t see antimatter in the universe.

DZero studied this decay, and the result showed some interesting disagreements with the Standard Model. While the measurements are nothing to get too excited about, they are worth further investigation. At a recent conference, the LHCb experiment presented their similar result, which is more precise than what either Tevatron experiments achieved. The most recent results from all three experiments (DZero, LHCb and CDF) agree reasonably well with each other and marginally with the Standard Model. These results now suggest that the discrepancy between the measurement and the Standard Model might have been a fluctuation but more data, both at the LHC and the Tevatron, should settle the matter.

Learn more here and here

Don Lincoln

These researchers performed this analysis.