OPERA tau neutrino candidate event 11143018505

Of the two secondary vertices, one has 2-prongs and occurs in the same lead plate of the neutrino vertex, after a flight length of $103$~$\mu$m, while the other one exhibits a kink after a flight length of $1160$~$\mu$m.</p><p>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.

The energy of the neutrino interaction was measured to be $23.2$~GeV/c.</p><p>The most probable interpretation for this event is a $\nu_\tau$ charged-current interaction with charmed hadron production. Other possibilities like a neutral-current $\nu_{\mu}$ interaction with associated charm production were discarded with a good significance using a multivariate analysis method. The most discriminating variables used were the lepton-hadron transverse angle and the daughter momentum.

With respect to the non $\tau$-charm hypothesis, the observed event has a very low probability, about $10^{-4}$, which corresponds to a significance of 3.5$\sigma$.</p>