New ways to decay

This plot shows one of the new ways for B0s mesons to decay. The decay appears on this mass plot as the red bump (J/ψ K-Star).

Particles can be rather particular about how they choose to decay. Though some particles may have hundreds of choices available to them, these particles typically have just a few ways that they prefer over all others. Despite having such strong preferences, particles do occasionally decay in one of their less preferred ways.

CDF scientists have recently studied this process for the B0s meson. Recently, we have looked at 5.9 inverse femtobarns of data and have identified two new ways in which the B0s meson can decay. Given that this is not the preferred decay chain, this type of discovery is only possible with the large data samples now available that allow us to look for these rare decay modes.

Before anyone can claim a discovery or in this case, an observation of one of these rare decay modes, they have to demonstrate that they are able to make physics measurements of objects that physicists have seen and obtain answers comparable to that knowledge. Only then will the particle physics community acknowledge this rare finding as being plausible. For this analysis, a common particle that physicists can use as a benchmark and is quite similar to the B0s is the B0 meson. One of the decay modes for the B0 is into particles called the J/ψ and the K-Star meson, while a second decay mode is the J/ψ and K-short meson. These two decay modes from this B0 particle are identical to the decay modes of the B0s particle that we are interested in. The B0 thus makes an ideal test subject.

The figures show very large peaks at a mass of 5.28 GeV/c2, which is the decay of the B0. This meson has been measured precisely by a number of experiments and was one of our test subjects. The small red peaks in the figure above at 5.36 GeV/c2 represent about 150 events in one of these newly observed rare decay modes. (A second figure shows 65 events.) Each of these new decay modes is rather rare— less than 1 in every 50,000 B0s mesons will decay in these newly identified ways.

Scientists can now investigate the properties of these newly identified objects to see if they behave the way we expect them to. These investigations will help us better understand the weak force and thus the world we live in. Learn more.

Edited by Andrew Beretvas

Individuals involved in this analysis include: From left, Kevin Pitts, Ben Carls, Olga Norniella (all from the University of Illinois).