Main Injector Experiment for ν-A, or MINERνA, is a neutrino scattering experiment which uses the NuMI beamline at Fermilab. MINERνA seeks to measure low energy neutrino interactions both in support of neutrino oscillation experiments and also to study the strong dynamics of the nucleon and nucleus that affect these interactions.
Name
MINERvA's name combines several things. "MI" stands for the Main Injector, a Fermilab accelerator that provides high-energy protons which are targeted to create the neutrino beam. "NER" comes from "Neutrino ExpeRiment." The conventional symbol for the neutrino is the Greek letter nu, which resembles a lowercase "v". Finally, "A" represents the mass number of the target material. MINERvA studies neutrino interactions with several materials, in particular helium, carbon, iron or lead, each having a different value of A.
Physicists describe these interactions where a neutrino collides with a nucleus as a "nu-A interaction," but spell MINERvA with a Roman "v" and pronounce it with a "v". The name also evokes Minerva, the Roman goddess of wisdom.
Status
The experiment that became MINERvA was proposed to Fermilab by two separate groups in 2002. MINERvA's detector was assembled 107 meters underground, in a portion of the same hall that housed the Near Detector of the MINOS experiment. The first detector module was completed in early 2006, and the first events were observed by the partially assembled detector in April 2009. MINERvA started taking data regularly in November 2009 with a partially complete detector, and started taking data with the full detector in March 2010.
At times, the NuMI beamline would provide either neutrino or antineutrino beams, tuned to particular energies. MINERvA acquired data in both a low energy (peaked at ~2.5 GeV) tune and a medium energy (peaked at ~6 GeV) tune. The physics run was completed in February 2019. Years of data analysis have followed.
Approximately 65 scientists collaborate on MINERvA. As of the end of 2022, 51 students had earned their Ph.D.s for MINERvA-related work, and 32 students had earned Master's Degrees. The scientific co-spokespersons of the MINERvA experiment are Prof. Laura Fields of University of Notre Dame and Prof. Deborah Harris of York University.
Detector
The detector used for the MINERνA experiment is made of many layers of parallel scintillator strips. Each strip is connected to a photomultiplier tube which is used to detect the amount of energy deposited into the strip. The orientation of the strips varies from layer to layer so that three-dimensional information about where particles interact with the strip can be determined. The detector consists of a middle region, the active tracker, which is made of just the scintillator strips, and is surrounded by scintillator strips interspersed with lead and iron absorbers to provide surrounding calorimetry. Upstream of the active tracker is a nuclear target region of scintillator strips in which passive targets of liquid helium, carbon, water, iron, and lead are interspersed in order to allow comparisons of interactions of neutrinos in different materials.
Scientific Results
MINERvA has published results on a wide variety of topics related to neutrino interactions and on other aspects of accelerator neutrino experiments.
Neutrino Flux Measurements
In order to measure neutrino interaction probabilities, MINERvA has needed to precisely understand the flux of incoming neutrinos. Through techniques such as studying the precisely predicted but rare interactions of neutrinos on atomic electrons, improving the simulation of the production of neutrinos in the beamline, and studying the most elastic interactions of neutrinos, MINERvA has been able to predict its flux with a fractional uncertainty of approximately 4%. MINERvA's techniques provide a proof of principle for applications expected to result in higher precision in future experiments.