In the course of proton collisions in the LHC at CERN, physicists Claude Amsler, Vincenzo Chiochia and Ernest Aguiló from the University of Zurich's Physics Institute managed to detect a baryon with one light and two heavy quarks. The particle Xi_b^* comprises one "up," one "strange" and one "bottom" quark (usb), is electrically neutral and has a spin of 3/2 (1.5). Its mass is comparable to that of a lithium atom. The new discovery means that two of the three baryons predicted in the usb composition by theory have now been observed.
The discovery was based on data gathered in the CMS detector, which the University of Zurich was involved in developing. The new particle cannot be detected directly as it is too unstable to be registered by the detector. However, Xi_b^* breaks up in a known cascade of decay products. Ernest Aguiló, a postdoctoral student from Professor Amsler's group, identified traces of the respective decay products in the measurement data and was able to reconstruct the decay cascades starting from Xi_b^* decays.