2020-05-20 by OPERA Collaboration
The OPERA Collaboration has released two data samples for the CERN Open Data portal.
The OPERA experiment has discovered the transmutation of muon neutrinos into tau neutrinos along their flight from CERN to the INFN Gran Sasso laboratory (Italy) where they are caught, by observing ten tau neutrino candidates. While searching for tau neutrinos, the Collaboration has also deeply studied the interactions of muon and electron neutrinos, since the OPERA apparatus is unique in identifying all three types of neutrinos. A brief guide available here explains the event reconstruction process of the OPERA experiment. It also explains how the event samples published on the CERN Open Data portal were obtained from the raw data taken by the Collaboration.
One of the two data sets released today by the OPERA Collaboration contains the data, from both electronic detectors and scanned emulsion films, of 19 electron neutrino interactions. The other data set contains electronic detector and emulsion data of 50 muon neutrino interactions with the lead target where a charmed hadron is reconstructed in their final state.
Electron neutrino candidates have been used to study the oscillation parameters of the transmutation of muon neutrinos into electron neutrinos and to constraint the existence of non-active (so-called sterile) neutrinos.
Charmed hadrons, instead, constitute the main background source for the tau neutrino search, when the muon at the primary vertex is not detected. Indeed, due to fact that charmed hadrons and tau leptons have very similar masses and lifetimes, the topology is practically the same and could be misidentified when the muon is undetected. For these events the Collaboration has reported both the neutrino interaction and the charmed hadron decay vertices.
The two data samples released today add up to the already available samples: the tau neutrino candidates and a sample of muon neutrino interactions. Therefore, with the data released today, OPERA reports data belonging to all three neutrino species.