Emulsion data for track multiplicity

Description

The dataset was extracted from the official OPERA data repository. It contains 817 muon neutrino interactions with the lead target where a muon was reconstructed in the final state. This happens in the so-called charged-current interactions of a muon neutrino. For this data sample, the Collaboration performed a dedicated analysis, with a detailed classification of all particles produced at the neutrino interaction on top of the muon. Indeed, in a muon neutrino interaction with the nucleons of the lead target, different hadrons are produced: the so-called shower hadrons and nuclear fragments produced in the break-up and in the evaporation of the target nucleus. The detailed study of the multiplicity of the hadrons produced provides insights on the mechanism of the hadronic shower formation. This data record contains the information of the neutrino interaction vertices including all the emulsion tracks produced in the interactions. The location of the neutrino interaction and the measurement of the trajectories of all the particles produced is the final step of the event analysis, after the identification of the neutrino interaction bricks done with the electronic detector data. The tracks include nuclear fragments moving both forward and backward. The available information includes minimum ionisation tracks produced in the hadronic shower, heavy ionising particles produced in the nuclear break-up and evaporation.

Dataset characteristics

Dataset semantics

How were these data selected?

Events stored in this dataset were selected by requiring that a muon was reconstructed in the final state. On top of this requirement, they were randomly selected in three physics runs taken in 2010, 2011 and 2012, in order to collect a sample close to 800 events, statistically sufficient to perform the multiplicity studies. This subset was analysed aiming at a detailed study of the multiplicity of charged particles produced in neutrino interactions as an important input to models of the hadronic shower generation.

How were these data validated?

During the data taking, all the runs recorded by OPERA are certified as good for physics analysis if the trigger and all sub-detectors show the expected performance. Moreover, the time stamp of the event should lie within the gate open by the CNGS beam signal. The data certification is based first on the offline shifters evaluation and later on the feedback provided by all sub-detector experts. Based on the above information, stored in a specific database, the Data Quality Monitoring group verifies the consistency of the certification and prepares an ascii file of certified runs to be used for physics analysis. For this specific data record, dedicated calibration procedures are performed to align the emulsion films each other and with the electronic detectors. These procedures with the corresponding results are saved in a dedicated database where data quality experts certify the results and prepare files to be used for the track and vertex reconstruction, thus being available for physics analysis.