Measurement of Neutral-Current $K^{+}$ Production by Neutrinos using MINERvA

Neutral-current production of $K^{+}$ by atmospheric neutrinos is a background in searches for the proton decay $p\to K^{+}\overline{\nu }$. Reactions such as $\nu p\to \nu K^{+}\mathrm{\Lambda }$ are indistinguishable from proton decays when the decay products of the $\mathrm{\Lambda }$ are below detection threshold. Events with $K^{+}$ are identified in MINERvA by reconstructing the timing signature of a $K^{+}$ decay at rest. A sample of 201 neutrino-induced neutral-current $K^{+}$ events is used to measure differential cross sections with respect to the $K^{+}$ kinetic energy, and the non-$K^{+}$ hadronic visible energy. An excess of events at low hadronic visible energy is observed relative to the prediction of the neut event generator. Good agreement is observed with the cross section prediction of the genie generator. A search for photons from ${\pi }^0$ decay, which would veto a neutral-current $K^{+}$ event in a proton decay search, is performed, and a $2\sigma$ deficit of detached photons is observed relative to the genie prediction.

Figure 1

A neutral-current $K^{+}$ data candidate event in MINERvA shown in the $X\text{−}Z$ view. This event is the 13th neutrino interaction in beam spill 408, of run 2371, subrun 53. The small triangles represent time-stamped energy deposits in individual scintillator strips. A hypothesis for each particle track is given. The ${\mu }^{+}$ is delayed in time relative to the $K^{+}$. The track labeled as a pion is probably from ${\mathrm{\Sigma }}^{-}\to n{\pi }^{-}$ with an unobserved neutron; however, it could also be a $K^{-}$ track.

Figure 2

The range of the longest reconstructed track in the event excluding the $K^{+}$, in $\mathrm{g}/{\mathrm{cm}}^2$. The arrow shows selected events, with events to the right forming the CC-like sideband. The highest bin includes all events above $850\mathrm{g}/{\mathrm{cm}}^2$ and is not normalized by the bin width, and the lowest bin includes events in which the $K^{+}$ is the only reconstructed track.

Figure 3

The differential cross section as a function of $K^{+}$ kinetic energy $T_K$, compared to genie and neut. The inner (outer) error bars represent the statistical (total) uncertainty.

Figure 4

The differential cross section as a function of non-$K^{+}$ visible energy $E_{\mathrm{vis}}$, as defined in the text, compared to genie and neut. The inner (outer) error bars represent the statistical (total) uncertainty.