K_short meson
One of the most amazing characteristics of science is reproducibility, i.e., experimental results can be reproduced by independent tests. So, the first thing to check in any physics experiment is to see if you can reproduce what older, well tested, experiments have found running in similar conditions. CMS did this very quickly last November when it presented its beautiful di-photon resonance peak, but the story does not end there.
Since December, CMS has taken advantage of the technical stop scheduled for the LHC in order to improve the reliability for the cooling system in the end-caps of the detector and, meanwhile, physicists have put a lot of effort in analyzing the data gathered during those few weeks of operation, mostly at 900 GeV of energy.
The results are quite fantastic. I mean, ok, we know these particles (resonances) for quite some time now (most of them have been known for more than 40 years) and we can easily “google” them and obtain all their information, but to see them coming alive in our detector is probably only second to experiencing the actual discovery. To make this succint, we know now that our detector is capable of reconstructing, with an astonishing precision, the invariant mass of many mesons and baryons [“vintage” Kaon (short) resonance is shown in the plot as an example!!], such as pions, eta mesons, kaons, lambda baryons, etc, that were seen and studied many years ago by different experiments around the world. Seeing these beloved resonances is not only cool, but they are necessary to calibrate the detector and to be in a much better shape for the next round of operations of the LHC, which will happen most likely in middle February. Stay tuned, the next big thing will be seeing Z/W bosons, for example, and from then a plethora (hopefully) of new and exciting physics (particles).
Edgar Carrera (Boston University)
