Emulsion data for neutrino tau appearance studies, OPERA collaboration
Cite as: OPERA collaboration (2018). Emulsion data for tau neutrino appearance studies. CERN Open Data Portal. DOI:10.7483/OPENDATA.OPERA.PUKC.44V7
This dataset was extracted from the official OPERA data repository and it contains all the emulsion data information 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 the information of the neutrino interaction vertices including all the emulsion tracks produced in the observed interactions and decay. 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 reconstructed tracks include hadrons, nuclear fragments moving both forward and backward and electron pairs, muon and tau leptons.
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.
|amplL||PMT amplitude measured from the "left" side of a scintillator strip (in photo-electrons)|
|amplR||PMT amplitude measured from the "right" side of a scintillator strip (in photo-electrons)|
|amplRec||PMT amplitude reconstructed from the "left" and "right" side amplitudes of a scintillator strip taking into account light attenuation in a WLS fiber (in photo-electrons)|
|clLength||cluster length (in cm)|
|driftDist||drift distance (in cm)|
|enHad||energy of a hadron jet (in GeV)|
|enNeu||energy of a neutrino (in GeV)|
|enVis||visible energy (in MeV)|
|evID||event Id (10- or 11-digit number)|
|globPosX||X position of a vertex in the OPERA detector system of reference (in cm)|
|globPosY||Y position of a vertex in the OPERA detector system of reference (in cm)|
|globPosZ||Z position of a vertex in the OPERA detector system of reference (in cm)|
|muMom||momentum of a muon (in GeV/c)|
|posX||For Electronic Detector events, X position of a drift tube, RPC, Target Tracker hit in the OPERA detector system of reference (in cm). For Emulsion Detector events, X position of a track/vertex in the OPERA brick system of reference (in micrometers).|
|posX1||X position of the beginning of a line in the OPERA brick system of reference (in micrometers)|
|posX2||X position of the end of a line in the OPERA brick system of reference (in micrometers)|
|posY||For Electronic Detector events, Y position of an RPC hit in the OPERA detector system of reference (in cm). For Emulsion Detector events, Y position of a track/vertex in the OPERA brick system of reference (in micrometers).|
|posY1||Y position of the beginning of a line in the OPERA brick system of reference (in micrometers)|
|posY2||Y position of the end of a line in the OPERA brick system of reference (in micrometers)|
|posZ||For Electronic Detector events, Z position of a drift tube, RPC, Target Tracker hit in the OPERA detector system of reference (in cm). For Emulsion Detector events, Z position of a track/vertex in the OPERA brick system of reference (in micrometers).|
|posZ1||Z position of the beginning of a line in the OPERA brick system of reference (in micrometers)|
|posZ2||Z position of the end of a line in the OPERA brick system of reference (in micrometers)|
|primary||flag of a vertex: 1 - primary vertex; 0 - not primary vertex|
|slopeXZ||tangent of a track angle in XZ view|
|slopeYZ||tangent of a track angle in YZ view|
|timestamp||event time in milliseconds since 01/01/1970|
|trType||type of a track: 1 - muon; 2 - hadron; 3 - electron/positron; 8 - tau lepton|
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.
After the analysis of the electronic detector data, the selected brick is extracted from the detector, the so-called changeable-sheets (CS) emulsion film doublets are developed in a dark room and analysed with fully automated optical microscopes in order to complete the brick identification process. The pattern of tracks reconstructed in the CS doublets was used to either confirm the prediction of the electronic detectors or to trigger the extraction of neighbouring bricks. CS doublets were inspected by automatic optical scanning microscopes in two specialised scanning stations at the Gran Sasso INFN Laboratory in Italy and at Nagoya University in Japan. After finding a suitable pattern of tracks, the emulsion films of the identified brick were developed and their films were sent to dedicated scanning stations operating in different Institutes of the Collaboration. All the tracks found in the CS films were then followed inside the brick up to the neutrino interaction vertex. Finally, the neutrino interaction is fully reconstructed in the brick with a micrometric tri-dimensional accuracy after the analysis of a volume of 2 cm^3 surrounding the vertex. A total of 5603 fully reconstructed neutrino interactions were reconstructed in the 0mu and 1mu categories. A decay search procedure was carried out to detect the expected decay topologies of tau leptons produced in tau neutrino charged-current interactions. In this data sample, all the events show this decay topology. Finally, a kinematical analysis was performed to further reduce the background processes. As a result of this complex analysis chain, ten tau neutrino candidates were selected and their emulsion data is reported in this data record.
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 at 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.
The open data are released under the Creative Commons CC0 waiver. Neither OPERA nor CERN endorse any works, scientific or otherwise, produced using these data. All releases will have a unique DOI that you are requested to cite in any applications or publications.