OPERA tau neutrino candidate event 12123032048, OPERA collaboration
Cite as: OPERA collaboration (2018). OPERA tau neutrino candidate event 12123032048. CERN Open Data Portal. DOI:10.7483/OPENDATA.OPERA.CJ94.4RWQ
Dataset Derived OPERA CERN-SPS
This neutrino interaction occurred on May $2^{nd}$ 2012 in a brick located in the 8$^{th}$ wall of the first super-module. An isolated, penetrating track was reconstructed in the electronic detectors: the particle was recorded in 24 Target Trackers planes and crossed 6 Resistive Plate Chamber planes before stopping in the spectrometer. Its range corresponded to 1650~g/cm${^{2}}$ of material, larger than the threshold of 660~g/cm${^{2}}$ set to identify the particle as a muon. Therefore, the event was classified as 1$\mu$.
The scanning of the interface emulsion films of the interaction brick was performed around the electronic detector prediction of the muon track and 6 tracks were found, one matching the muon direction. A converging pattern was also found, thus satisfying the conditions for event validation and brick film development. After the event location procedure, the position of the vertex was found to be between the 38$^{th}$ and 39$^{th}$ emulsion films, well inside the brick, 3.3 radiation lengths from its downstream face. All tracks possibly related to the interaction were searched for in the brick within an angular acceptance defined by ${\tan\theta=3}$.
The primary vertex consists of two tracks: the ${\tau}$ lepton candidate and a hadron track having a distance of closest approach of ${(0.5\pm 0.5)}$~${\mu}$m. The ${\tau}$ lepton decay occurred after a flight length of ${(376\pm 10)}$~${\mu}$m in the plastic base of the first film immediately downstream of the primary vertex.
The decay particle shows a kink angle of ${(245\pm 5)}$~mrad and an impact parameter of ${(93.7\pm 1.1)}$~${\mu}$m w.r.t.~the primary vertex and it is compatible with the muon track reconstructed in the electronic detectors.The other primary track has been classified as a hadron by the momentum-range correlation; its interaction in the downstream brick was reconstructed, without any visible charged particle track attached at the interaction point.
The muon momentum at the interaction vertex was accurately estimated from the range of the particle in the electronic detector: a Kalman filter-based algorithm yielded a value of p${_\mu = (2.8\pm 0.2)}$~GeV/c, compatible with the value found using measurements based on the emulsion data and MCS: ${3.1^{+0.9}_{-0.5}}$~GeV/c. For the charge measurement, the bending of the track in the magnetised iron was used. In this case, four Resistive Plate Chamber (RPC) hits were available, while no hits could be recorded by the Precision Tracker planes. A fit was performed with a straight line in the non-magnetized region (Target Tracker hits) and with a parabola in the magnetized region (RPC hits). The parabolic part was meant to approximate the circular trajectory. The fit gave a parabola with the concavity towards the bottom, corresponding to a radius of ${\sim 85}$~cm. Given the direction of the magnetic field, this is compatible with a negative charge with a significance of~${5.6\sigma}$.
An electromagnetic shower produced by a ${\gamma}$-ray and pointing to the primary vertex was also observed, having energy of ${3.1^{+0.9}_{-0.6}}$~GeV. Its probability to be attached to the secondary vertex is less than ${10^{-3}}$. The energy of this neutrino interaction was measured to be $(6.8^{+0.9}_{-0.6})$~GeV/c.
This event was interpreted as a $\nu_{\tau}$ charged-current interaction with the $\tau$ lepton decaying into a muon. A detailed description of the event is given in 10.1103/PhysRevD.89.051102.
Electronic detector data for tau neutrino appearance studies
This event is part of OPERA Emulsion Detector tau appearance datasetVariable | Description |
---|---|
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 |
Demobbed-viewer is a JavaScript application developed for the CERN Open Data Portal. The application is supposed to visualise neutrino interaction events registered in the OPERA experiment.
At present OPERA open data sample includes four sub-samples (a sub-sample to display can be specified in the left part of the toolbar):
- the "nuTau" sub-sample (Electronic detector data + Emulsion data) includes 10 tau neutrino candidate events observed by OPERA in the CNGS neutrino beam.
- the "nuMu" sub-sample (Electronic detector data + Emulsion data) includes 817 events used in the study of charged hadron multiplicities in charged-current neutrino-lead interactions in the OPERA detector.
- the "nuE" sub-sample (Electronic detector data + Emulsion data) includes 19 electron neutrino candidate events registered in the OPERA detector.
- the "charm" sub-sample (Electronic detector data + Emulsion data) includes 50 charm decay candidate events registered in the OPERA detector.
Opera hybrid experimental setup (described in detail here) included Electronic detectors (ED) for real-time detection of neutrino interactions and nuclear emulsions for precision analysis of neutrino event topologies. The ED provided positions of hits in two perpendicular planes: XZ (top view) and YZ (side view). By default, only ED information is displayed in the Demobbed-viewer. After analysis of the ED data the unit of OPERA target (lead-emulsion or ECC brick) that most probably contained the neutrino interaction vertex was extracted from the detector and its emulsion data were analysed as well. 3D view of reconstructed emulsion data can be opened in the ECC display (see description below).
Brief description of available button actions:
/ - go to the previous/next event (if any) in the selected sub-sample. Also the event Id can be specified directly in the nearest edit box.
- reload the currently displayed event.
/ - zoom in/out. Please note that the default (whole detector) views of the ED display can't be zoomed out.
- move the XZ and YZ camera views to the vertex brick. ECC brick that contains the primary neutrino interaction vertex will be shown (an appropriate zooming will be adjusted automatically). The vertex position as well as projections of muon and some long hadron tracks found in the emulsion will be displayed as well.
- move the XZ and YZ camera views and adjust zooming in order to display the whole neutrino event region.
- show the whole detector region (default option).
, , , and - move the ED display camera views, correspondingly, up, down, left, and right.
The ECC display view can be rotated or moved with help of the left or right mouse buttons, correspondingly.
, , or - show the default XZ, YZ, or XY view of the event in the ECC display.
/ - stretch/compress the ECC view in the vertical (Y) direction.
- start/accelerate animated rotation of the ECC event around the Y (vertical) axis. This button can be clicked several (but not so many!) times.
- decelerate animated rotation of the ECC event. In order to stop the rotation this button has to be clicked the same number of times as the "accelerating" button has been clicked before.
A browser-based event display for visualisation of open data of the OPERA experiment.
This application uses d3.js and three.js libraries. The code is available on the GitHub repository.
Contributors: S. Dmitrievsky (JINR, Dubna, Russia), G. Tsanaktsidis (CERN, Geneva, Switzerland), M. Vidal (CERN, Geneva, Switzerland).
These OPERA event data files can be visualised using the online OPERA event display
The open data are released under the Creative Commons CC0 waiver. Neither the experiment(s) ( 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.