Electronic detector data for tau neutrino appearance studies

Description

This dataset was extracted from the official OPERA data repository and it contains all the data of the electronic detectors for the ten tau neutrino candidates, identified after an extensive analysis that includes data from both electronic detectors and nuclear emulsion films after their digitization with fully automated optical microscopes. The observation of the tau neutrino appearance in a muon neutrino beam was the main goal of the OPERA experiment. This data record contains in particular all the electronic detector hits produced by the ten tau neutrino interactions in their propagation through the detector, except in the emulsion films. It includes hits in the scintillating target tracker, drift tubes and resistive plate chambers. The hits in the drift tubes and in the resistive plate chambers are used to reconstruct the muon track and measure its charge and momentum. The hits in the target tracker are used to predict the location of the neutrino interaction in the target units, the so-called bricks. This leads to the subsequent phase of the analysis where the neutrino interaction is located with micrometric accuracy and all tracks attached are measured.

For this tau neutrino data sample, the Collaboration performed a dedicated analysis, with a detailed classification of all particles produced at the neutrino interaction. Indeed, in a 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. Moreover, according to the flavour of the interacting neutrino, a corresponding lepton is produced. After a flight length of about 1 mm, the tau lepton produced in the interaction of tau neutrinos decays into one of the following channels: single hadron (49.5%), electron (17.8%), muon (17.7%) and three hadrons (15.0%).

The tau neutrino candidate events are also described separately.

Dataset characteristics

Dataset semantics

How were these data selected?

Events stored in this dataset were collected between 2008 and 2012. Events are classified as “1mu” if one track is tagged as a muon after the analysis of the electronic detectors data, “0mu” otherwise. In this sample “0mu” events and “1mu” events with a muon momentum lower than 15 GeV/c were selected since they are richer in terms of their possible tau neutrino content.

The events reported in this data set have also undergone a full tri-dimensional reconstruction of the neutrino vertex in the nuclear emulsion films. A total of 5603 fully reconstructed neutrino interactions were reconstructed in the 0mu and 1mu categories. A search for possible decay topologies was applied to this sample of 5603 events with a procedure explained in the description of the emulsion data. A final selection was performed by applying kinematical cuts which selected the ten events reported in this sample.

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. Calibration procedures taking into account the specific geometry of the target associated to each event are applied to raw data and they are converted into a root file for each event that is then used for physics analysis.