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What is the Loop Process Bργ?

The Loop Process Bργ is an example of a class of B meson decays involving a virtual quantum loop and the emission of a photon. Within the Standard Model, the loop involves the exchange particle mediating the weak interaction, the W boson, and virtual quarks dominated by the top quark. The most likely result of this process is the conversion of the b quark into an s quark, along with the photon. In rare cases, such as the example here, the b quark transforms into a d quark and a photon, resulting in a final state that characteristically contains no strange quark. Within the Standard Model, these kinds of processes give us access to the weak interaction properties of the top quark. However, being a loop process, there are many forms of new physics at high mass scales that could change the rate for such rare decays. The agreement with Standard Model predictions and the increasing precision of such measurements provides a long-term constraint on new physics.