OPERA tau neutrino candidate event 12123032048

Name: OPERA tau neutrino candidate event 12123032048
Creator: OPERA collaboration
Published: 2018

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

Data recorded in 2012. Published in 2018.

Dataset Derived OPERA CERN-SPS

Description

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.

Related datasets

This event is part of OPERA Electronic Detector tau appearance dataset

Electronic detector data for tau neutrino appearance studies

This event is part of OPERA Emulsion Detector tau appearance dataset

Emulsion data for neutrino tau appearance studies

Dataset characteristics

1 event. 14 files. 7.6 KiB in total.

Dataset semantics

Variable	Type	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