This image shows the first cosmic ray event recorded in the MicroBooNE TPC on Aug. 6. Credit: MicroBooNE
A school bus-sized detector packed with 170 tons of liquid argon has seen its first particle footprints. On Aug. 6, MicroBooNE, a liquid-argon time projection chamber recorded images of the tracks of cosmic muons, particles that shower down on Earth when cosmic rays collide with nuclei in our atmosphere.
“This is the first detector of this size and scale we’ve ever launched in the U.S. for use in a neutrino beam, so it’s a very important milestone for the future of neutrino physics,” said Sam Zeller, co-spokesperson for the MicroBooNE collaboration.
Picking up cosmic muons is just one brief stop during MicroBooNE’s expedition into particle physics. The centerpiece of the 3 detectors planned for Fermilab’s Short-Baseline Neutrino program, or SBN, MicroBooNE will pursue the much more elusive neutrino, taking data about this weakly interacting particle for about 3 yrs. When beam starts up in October, it will travel 470 meters and then traverse the liquid argon in MicroBooNE, where neutrino interactions will result in tracks that the detector can convert into precise 3D images. Scientists will use these images to investigate anomalies seen in an earlier experiment called MiniBooNE, with the aim to determine whether the excess of low-energy events that MiniBooNE saw was due to a new source of background photons or if there could be additional types of neutrinos beyond the 3 established flavors.
One of MicroBooNE’s goals is to measure how often a neutrino that interacts with an argon atom will produce certain types of particles. A 2nd goal is to conduct R&D for future large-scale LArTPCs. MicroBooNE will carry signals up to 2.5 meters across the detector, the longest drift ever for a LArTPC in a neutrino beam. This requires a very high voltage and very pure liquid argon. It is also the 1st time a detector will operate with its electronics submerged in liquid argon on such a large scale. All of these characteristics will be important for future experiments such as the Deep Underground Neutrino Experiment, or DUNE, which plans to use similar technology to probe neutrinos.
“The field has chosen liquid argon as its future technology, and all eyes are on us to see if our detector will work.” http://www.fnal.gov/pub/today/archive/archive_2015/today15-08-12.html
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