Calibration techniques honed and ready for test beam data

The author Garrett Robinson (far left) and the ProtoDUNE-SP dQ/dx calibration team, from left: Glenn Horton-Smith, Tingjun Yang and Ajib Paudel. Photo: R. Hahn

Ajib Paudel and Glenn Horton-Smith, both of Kansas State University, and Tingjun Yang of Fermilab are practicing calibration techniques on ProtoDUNE-SP to get ready for the DUNE far detector. Building on the Monte Carlo methodology used by MicroBooNE, the group is running MC data samples of cosmic ray muon tracks in ProtoDUNE through an analysis that Paudel and Yang wrote to correct for nonuniformities in the detector volume.

The team’s calibration of ProtoDUNE-SP focuses on dQ/dx, which gives a measure of how much charge is lost as the ionization electrons drift to the anode. From this calibration they can generate the dE/dx values to find the energy loss per unit track length, which helps greatly in particle identification.

“One of the things we will be looking for in the ProtoDUNE analysis is the smallest number of muons it takes to get a good calibration,” said Horton-Smith. “The cosmic ray rates in the deep underground location of DUNE are so low that it will take months to get the same number of stopping muons in DUNE as we will get in minutes at ProtoDUNE. This low muon rate is good for getting the purest neutrino data at DUNE, but it’s a challenge for muon-based calibration. Seeing how reproducible the muon calibration is over months of ProtoDUNE operation will give us an idea of how well it could work over a decade or more of DUNE operation.”

The team faced a few challenges as they developed this analysis, for instance, determining how to remove background effectively from cosmic ray data, how to reconstruct broken tracks (sometimes a single track reconstructs as two or three separate ones), and how to exploit the very-low-rate sources of muons that will be apparent in the far detector a mile underground – coming from the neutrino beam and from atmospheric neutrino interactions.

“The advantage of LArTPCs is the high spatial and calorimetric resolution,” said Yang. “The technique we developed will allow us to make a reliable calorimetric measurement, which is essential to particle identification and energy measurement.”

The team has accomplished a lot so far.

“The fact that we can process the MC data through our entire system shows a really good level of preparation for getting the real data in August,” said Horton-Smith.

Garrett Robinson is a high school student doing a summer internship at Fermilab. Garrett hopes to study aerospace engineering when he gets to college.