
The Accelerator Neutrino Neutron Interaction Experiment (ANNIE) is an advanced R&D detector designed to measure the neutron yield of atmospheric neutrino interactions in gadolinium-doped water. The neutrino physics group at Iowa State is a leading institution on ANNIE, with both Prof. Sanchez and Prof. Wetstein having acted as spokespeople for the experiment. Prof. Krennrich and Prof. Weinstein bring valuable expertise in the areas of electronics and triggering to the experiment.
ANNIE is an advanced R&D detector designed to measure the neutron yield of atmospheric neutrino interactions in gadolinium-doped water. To accomplish this measurement, ANNIE will rely newly developed Large Area Picosecond Photodetectors (LAPPDs) and the development of novel experimental techniques. The first phase of ANNIE has recently completed data taking at Fermilab, with the second phase planned to begin soon.
Calibration of ANNIE
ANNIE comprises of several calibration sources to understand the detector. The ISU group makes contributions to each of these systems.
Americium-Beryllium: A radioactive source coupled to a scintillating crystal, which will allow a significant reduction in backgrounds and more efficient detection of neutron capture. In the Fall of 2020 the fist calibration was performed, being led by the group.
Standard Candle: A well defined gamma-emitting source with close proximity to the 4 top PMTs. The signal is the Compton scattering edge of the Cesium and Cobalt spectrums. The ISU group designed and developed the calibration trigger.
LED Water Transparency Monitoring: A set of 6 LEDS are stategically placed to monitor water transparency. Daily monitoring runs and reports were generated by the group, and were used to find the most efficient operating voltages for PMTs.
Laserball Timing Calibration: Each PMT is illuminated with a very fast light pulse, to achieve precise timing alignment of the PMTs to a sub-nanosecond spread. The group is responsible for the PiLaS laser which is used.
Neutrino Interaction Physics Analysis
The ANNIE collaboration has developed a suite of analysis tools with the objective of ensuring a prompt and efficient processing of the data upon the restart of the BNB beam. Some of these tools were utilized to generate the dataset that led to the results presented in the first ANNIE Phase II PhD thesis (Teal Pershing from UC Davis).

As co-convenor of the ANNIE analysis group, Dr. Fischer has played and continues to play a significant role in both the direction and implementation of this effort. With the main particle reconstruction tools now tested on simulated data, members of the ANNIE analysis group are already analyzing the upcoming data for beam commissioning purposes. In parallel, the data gathered during the neutron calibration campaign, prior to the start of the beam, is being analyzed with the goal of determining the neutron detection efficiency throughout the detector volume.
With the detector largely commissioned and the LAPPDs on the verge of deployment, we expect that a significant part of the ISU effort will shift to data analysis. The whole group from faculty to undergraduates will be involved in this data analysis.
Notable Recent Talks and Posters
- Sanchez, The Accelerator Neutrino Neutron Interaction Experiment, ICHEP 2020, August 2020
- Tiras, The Accelerator Neutrino Neutron Interaction Experiment, Fermilab Users Meeting 2020, August 2020
- Tiras, The ANNIE Experiment at Fermilab: Updates from the Physics Phase, APS, April, 2020