M.Kirby: Status of MicroBooNE
It all started with the LSND excess. The final published data from MiniBooNE shows an excess at low energy (0.2-0.5 GeV) both in neutrino and antineutrinos. So trying to understand the neutral pion misidentification rate, which is the main background in that energy region, is one of the motivations for MicroBooNE.
At Fermilab the booster neutrino beam starts from 8 GeV protons from the booster. The spectrum of produced neutrinos has a peak at 700 MeV, dominated by muon neutrinos, with contaminations from antineutrinos.
The first thing to do is then to measure the cross section of our Argon target for neutrinos. Quasi-elastic charged-current interactions dominate below 1 GeV, then at higher energy the resonance production (like Delta+ state) peaks at 2 GeV, and the deep inelastic scattering starts off at several GeV. MicroBooNE covers the energy region between few hundred MeV and 2 GeV. Cosmic rays are the main background, inducing space charge effects, but they are rejected with internal light collection and external cosmic taggers. The signal with parameters as from previous excesses would be quite visible after final analysis, with main backgrounds coming from electron neutrinos due to K decays and neutral current single-photon events.
MicroBooNE will also be sensitive to supernova explosions. Special data streams are used to cache unbiased, continuous readout. They expect 10-20 events for a 10 kPc supernova. They read out the TPC with 10 crates, un-triggered, writing continuously the data to disk. The buffer maintains the data for about a week, hence they can access it before overwriting it.
The detector is a 170Ton Liquid-Argon TPC building on the ICARUS technology. 89Ton active volume, 8256 readout wires in 3 anode planes. To improve the understanding of Argon cross sections, they aim at improving identification of final state particles. This is possible e.g. by detecting multi-proton events.
Recently a Horn in the booster neutrino beam, which has been in service since October 2004, and received over 400 million pulses, underwent clogging in the cooling lines. Being replaced with an updated design. They anticipate first protons on target before the July shutdown, possibly as early as first days in May.