Performance of a liquid argon time projection chamber exposed to the CERN West Area Neutrino Facility neutrino beam

We present the results of the first exposure of a Liquid Argon TPC to a multi-GeV neutrino beam. The data have been collected with a 50 liters ICARUS-like chamber located between the CHORUS and NOMAD experiments at the CERN West Area Neutrino Facility (WANF). We discuss both the instrumental performance of the detector and its capability to identify and reconstruct low-multiplicity neutrino interactions.

Figure 1

A sketch of the experimental setup (top view). Relative sizes are not to scale.

Figure 2

The 50 liters Liquid Argon Time Projection Chamber.

Figure 3

Lifetime of the drifting electrons in the 50 liters Liquid Argon TPC at the CERN $\nu$ beam. The filling of the chamber with LAr was performed on the fourth of April 1997.

Figure 4

Example of the 3D reconstruction of a low-multiplicity ${\nu }_{\mu }$ CC event. The raw image from collection and induction wire planes (on top): Hits and 2D track projections have been identified. Three-dimensional view of the reconstructed event (bottom picture) embedded in a 3D recreation of the experimental setup described in Sec. 2.

Figure 5

(Top) The raw images of a high multiplicity event (${\nu }_{\mu }$ CC DIS) in the collection (left panel) and induction plane (right panel). Below, the 3D reconstruction of a high multiplicity event (${\nu }_{\mu }$ CC DIS) with eight primary particles. Two of them stop in LAr and are recognized as protons.

Figure 6

$dQ/dx$ of crossing muons. The distribution is fitted to a convoluted Landau-Gaussian distribution.

Figure 7

$dQ/dx$ as a function of the residual range for protons. Dots are direct measurements from the reconstructed hits of the proton tracks, while the points with errors bars are the estimated most probable of $dQ/dx$ for each bin of the residual range. Data is fitted with a Bethe-Bloch corrected by the detector response function (Birk’s law) in the hypothesis of pion (dashed line) and proton (full line).

Figure 8

(left) $dQ/dx$ as a function of the residual range for the reconstructed proton in the event shown in Fig. 4: continuous (dashed) line represents the expected behavior of protons (pions) in the detector. (right) $dE/dx$ distribution for the muon reconstructed in Fig. 4: data is fitted to a convoluted Landau-Gaussian distribution.

Figure 9

The raw image of a low-multiplicity event in the collection (left) and induction plane (right). The event is reconstructed as (${\nu }_{\mu }n\to {\mu }^{-}{\Delta }^{+}\to {\mu }^{-}p{\pi }^0$) with a mip leaving the chamber, an identified stopping proton and a pair of converted photons from the ${\pi }^0$ decay. When these photons escape from the chamber, the event is tagged as a “golden event.”

Figure 10

Distribution of the proton kinetic energy for the “golden sample” (squared marks). Dotted histogram represents the expectation from simulated Monte-Carlo QE events, while the hatched one represents the simulated background from non-QE events. Both contributions are summed in the filled histogram and normalized to the golden sample data.

Figure 11

Distribution of the muon energy and the muon transverse momentum for the “golden sample.” Dotted histogram represents the expectation from simulated Monte-Carlo QE events, while the hatched one represents the simulated background from non-QE events. Both contributions are summed in the filled histogram and normalized to the golden sample data.

Figure 12

Distribution of the missing transverse momentum (left) and acollinearity (right) for the “golden sample.” Dotted histogram represents the expectation from simulated Monte-Carlo QE events, while the hatched one represents the simulated background from non-QE events. Both contributions are summed in the filled histogram and normalized to the golden sample data. The dashed histograms show the expected distributions in case no nuclear effects are taken into account.