OPERA tau neutrino candidate event 9234119599, OPERA collaboration
Cite as: OPERA collaboration (2018). OPERA tau neutrino candidate event 9234119599. CERN Open Data Portal. DOI:10.7483/OPENDATA.OPERA.EERC.93LM
Dataset Derived OPERA CERN-SPS
This neutrino interaction occurred on August 22$^{nd}$ 2009 in a brick located in the 11$^{th}$ wall of the first super-module, well inside the target, being separated from the detector edge by 3 raws on top and 24 columns on the left. No muon was identified by the reconstruction of the data provided by electronic detectors.
The scanning of interface emulsion films, performed around the electronic detector predictions, revealed five tracks with a converging pattern: the brick films were then developed. By following up the tracks inside the brick, the neutrino interaction was found to be placed in the lead plate between the 18$^{th}$ and 19$^{th}$ emulsion films, 6.5 radiation lengths far from the downstream edge of the brick, thus providing sufficient length for the identification of electromagnetic showers inside the brick itself, without the need of extending the analysis to the downstream one. The interaction was fully reconstructed in the brick, looking for all tracks within the angular acceptance defined by $\tan\vartheta = 3$.
The primary neutrino interaction is defined by 7 tracks, one of which exhibits a visible kink of $(41\pm 2)$~mrad, after a path length of~${(1335\pm 35)}$~${\mu}$m. A kink is a sudden change of the track direction, as it happens when a particle decays. Therefore, the kink is the topological evidence for a particle decay when it produces only a charged particle in the final state. All tracks were classified as hadrons using their overall track length reconstructed along all the downstream available bricks, the topology at their end-point and the correlation between their momentum and range. One of these particles was identified as a proton and another one as a pion.
Two electromagnetic showers induced by ${\gamma}$-rays were located. The first one was originated from the secondary vertex, 2.2~mm downstream of it, and its energy was reconstructed to be 5.6~GeV. The probability that it pointed to the secondary vertex was estimated to be ${32\%}$, several orders of magnitude larger than any other interpretation. The second $\gamma$ induced shower, with a reconstructed energy of 1.2~GeV, was compatible with pointing to the secondary vertex, with a probability of ${82\%}$, 8 times larger than any other interpretation. The reconstructed energy of the neutrino interaction is $24.3$~GeV/c.
The invariant mass of the two $\gamma$-rays is $(120\pm 20(\textit{stat.})\pm 35(\textit{syst.}))$~MeV/c$^2$, supporting the hypothesis that they originate from a $\pi^0$ decay. Similarly the invariant mass of the charged decay product assumed to be a $\pi^-$ and of the two $\gamma$-rays amounts to $(640^{+125}_{-80}(stat.)^{+100}_{-90}(syst.))$~MeV/c$^2$, which is compatible with the $\rho$ particle mass. The $\rho$ particle has an average lifetime as short as $4 \times 10^{-24}$~s and it decays through strong interactions, without producing any visible displacement. The branching ratio of the decay mode $\tau\rightarrow\rho^{-}\nu_\tau$ is about 25$\%$.
This event was thus interpreted as a $\nu_{\tau}$ charged-current interaction with the $\tau$ lepton decaying into a $\rho^- \nu_{\tau}$ and the subsequent $\rho^- \rightarrow \pi^{-} \pi^0$ decay. A detailed description of the event is given in 10.1016/j.physletb.2010.06.022.
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.