Accelerator Neutrino Neutron Interaction Experiment

The Accelerator Neutrino Neutron Interaction Experiment, abbreviated as ANNIE, is a proposed water Cherenkov detector experiment designed to examine the nature of neutrino interactions. This experiment will study phenomena like proton decay, and neutrino oscillations, by analyzing neutrino interactions in gadolinium-loaded water and measuring their neutron yield. Neutron Tagging plays an important role in background rejection from atmospheric neutrinos. By implementing early prototypes of LAPPDs (Large Area Picosecond Photodetector), high precision timing is possible. The suggested location for ANNIE is the SciBooNE hall on the Booster Neutrino Beam associated with the MiniBooNE experiment. The neutrino beam originates in Fermilab where The Booster delivers 8 GeV protons to a beryllium target producing secondary pions and kaons. These secondary mesons decay to produce a neutrino beam with an average energy of around 800 MeV. ANNIE will begin installation in the summer of 2015. Phase I of ANNIE, mapping the neutron background, completed in 2017. The detector is being upgraded for full science operation (so-called Phase II) which is expected to begin late 2018. The Accelerator Neutrino Neutron Interaction Experiment, abbreviated as ANNIE, is a proposed water Cherenkov detector experiment designed to examine the nature of neutrino interactions. This experiment will study phenomena like proton decay, and neutrino oscillations, by analyzing neutrino interactions in gadolinium-loaded water and measuring their neutron yield. Neutron Tagging plays an important role in background rejection from atmospheric neutrinos. By implementing early prototypes of LAPPDs (Large Area Picosecond Photodetector), high precision timing is possible. The suggested location for ANNIE is the SciBooNE hall on the Booster Neutrino Beam associated with the MiniBooNE experiment. The neutrino beam originates in Fermilab where The Booster delivers 8 GeV protons to a beryllium target producing secondary pions and kaons. These secondary mesons decay to produce a neutrino beam with an average energy of around 800 MeV. ANNIE will begin installation in the summer of 2015. Phase I of ANNIE, mapping the neutron background, completed in 2017. The detector is being upgraded for full science operation (so-called Phase II) which is expected to begin late 2018. ANNIE will be run using the Booster Neutrino Beam (BNB) which runs at 7.5 Hz, with roughly 4 x 1012 protons-on-target per spill. These are delivered in 81 bunches over 1.6 microseconds per spill to a target 100 meters upstream in the SciBooNE hall. The beam, in neutrino mode, is 94% pure muon neutrinos with a flux peak energy at around 700 MeV. The water target used by ANNIE is a cylindrical volume 3.8 m long and 2.3 m in diameter encased by a plastic liner and aluminum enclosure. The target is to be instrumented by 60 to 100 eight-inch photomultiplier tubes. Part of the iron-scintillator sandwich detector used to track the direction of daughter muons in the SCiBooNE target, called the Muon Range Detector (MRD), could be used by ANNIE. The MRD will be modified by replacing 10 or the 13 layers of scintillator with resistive plate chambers (RPCs). This upgrade will allow centimeter-level precision at each layer. Moreover, the RCPs are capable of withstanding a 1 T magnetic field. Such an applied field could someday be added to ANNIE in order to achieve charge-spin reconstruction in the MRD. This would also allow momentum reconstruction at the highest event energies. Given the few-meter scale of the detector, it would be possible to achieve timing based reconstruction of events using information from the Cherenkov radiation produced during events in the detector. In order to achieve the necessary picosecond time resolution, ANNIE intends to use early commercial prototypes of Large Area Picosecond Photodetectors (LAPPDs). Large Area Picosecond Photodetectors are (8 in. x 8 in. x 0.6 in) MCP photodetectors. While common PMTs are single pixel detectors, LAPPDs are able to resolve the position and time of single photons within a single detector with time and space resolutions higher than 3 mm and 100 picoseconds accordingly. Initial Monte Carlo simulations show that using LAPPDs of this accuracy would allow ANNIE to operate as a tracking detector with track and vertex reconstruction resolution on the order of a few centimeters. These detectors are in their final stages of development. The use of a directed neutrino beam allows the reconstruction of the initial neutrino energy and therefore total momentum transfer during the interaction. ANNIE examines the interactions between neutrinos and nuclei in water with the aim of producing measurements of final state neutron abundance as a function of total momentum transfer. Neutron capture is aided by the solvated gadolinium salts which have high neutron capture cross sections and emit around 8MeV in gamma radiation upon absorption of a thermalized neutron. Characterization of neutron yield in proton decay background events, which are predominantly encountered in atmospheric neutrino interactions in large water Cherenkov Detectors like Super-Kamiokande, would help increase confidence in the observation of proton-decay-like events. By studying the neutron yield, the events captured in the fiducial volume may be separated between a variety of charged-current (CC) and neutral Current (NC) event types. The ability to tag neutrons in the final state will also allow ANNIE to test specific nuclear models for validity in neutrino interactions. In neutrino made, the mode in which the beam is predominantly neutrinos, neutron multiplicity is expected to be lower for CC interactions. This can be used to distinguish electron neutrino oscillation candidates from backgrounds such as neutral pion or photon production. Additionally, ANNIE will look for appearance of electron neutrinos in the beam-line. Proton decay is a prediction of many grand unification theories. ANNIE will characterize the neutron yield of events that generate signatures similar to those of proton decay in water Cherenkov detectors. The two channels of proton decay that are of interest to ANNIE, and most popular among GUTs are: The former is the preferred decay channel in minimal SU(5) and SO(10) GUT models while the second is typical of supersymmetric GUTs where dimension-5 operators induce decays that require a strange quark. Super-Kamiokande has shown a minimum limit above 1034 years.