The Deep Underground Neutrino Experiment (DUNE) partnership has successfully published their first scientific article based on information obtained with the ProtoDUNE single-phase detector situated at CERN’s Neutrino Platform.
According to the results, the single-phase detector is performing at an efficiency of more than 99%. This finding makes it the largest as well as the best-performing liquid-argon time projection chamber so far.
The team’s findings are currently being used by scientists to further improve their experimental methods and prepare for the development of the international Deep Underground Neutrino Experiment at the Long-Baseline Neutrino Facility—an advanced neutrino experimental program hosted by Fermilab of the Department of Energy in the United States.
These first results are great news for us. They show that the ProtoDUNE-SP detector works even better than anticipated. Now we are ready for the construction of the first components for the DUNE detector, which will feature detector modules based on this prototype, but 20 times larger.
Stefan Söldner-Rembold, Co-Spokesperson, Deep Underground Neutrino Experiment
Söldner-Rembold is also a professor at the University of Manchester.
DUNE is a striving global experiment that will quantify the characteristics of neutrinos, which are minute fundamental particles. Despite being the most abundant matter particles in the universe, neutrinos seldom interact with other kinds of particles, and as a result, they are very difficult to analyze.
At least three different kinds of neutrinos exist in nature, and, each second, 65 billion of these particles travel through every square centimeter of the Earth. But while traveling, neutrinos tend to do something unusual—they convert from one form to another.
According to scientists, such neutrino oscillations—and also oscillations in which antimatter neutrinos are involved—may help answer some of the fundamental questions in the field of physics, for example, the observed asymmetry of matter and antimatter in the universe. Furthermore, DUNE will search for neutrinos from supernovae and look for unusual subatomic processes, like proton decay.
“ProtoDUNE-SP shows that we can scale up this type of technology to the size and resolution we need to finally put neutrinos under a very powerful microscope,” stated Marzio Nessi, a coordinator of the CERN Neutrino Platform.
Accurate measurement of such oscillations will not only limit but also rule out certain hypothetical models, and will provide new opportunities to find and investigate rare subatomic phenomena.
However, to obtain such accurate measurements, investigators require extremely large, consistent, and sensitive detectors.
The ProtoDUNE results show that we have designed a detector that will allow us to reach our science goals in DUNE.
Elizabeth Worcester, Scientist, Brookhaven National Laboratory, Department of Energy
Worcester is also the DUNE physics coordinator.
DUNE has been specifically developed to demonstrate the exact nature of neutrino oscillations by firing a powerful ray of neutrinos from Fermilab close to Chicago via 1,300 km (800 miles) of earth and into four massive subterranean detector modules based 1.5 km deep at the Sanford Underground Research Facility located in South Dakota.
A pair of ProtoDUNE detectors deployed at CERN—one based on a dual-phase liquid-argon technology and the other based on a single-phase technology—represents a key step toward constructing the massive DUNE detector modules, each containing 17,000 tons of liquid argon.
The DUNE Technical Design Report is the blueprint for building these modules. This report was published in February 2020.
At CERN, DUNE investigators from across the world made use of cosmic rays and a test beam of 800-GeV to assess the advanced ProtoDUNE-SP detector. The CERN’s SPS accelerator fired the test beam that traveled through a couple of individual targets to produce beams of protons, electrons, and other kinds of particles. Particle detectors, which were based just outside the ProtoDUNE-SP detector, quantified the identity and energy of such test-beam particles before they penetrated the ProtoDUNE-SP detector.
Fragile planes of wires within the detector interspersed with photon detectors integrated into 800 tons of transparent, liquid argon. When an interaction occurs between a passing particle and the argon, it displaces loose electrons that are pulled by a high-voltage electric field across many meters to the wire planes proximal to the walls of the detector.
Using the signal on the wires, investigators produced a 3D image of the trajectory of the particle and can establish both its identity and energy.
By comparing this information from within the ProtoDUNE-SP detector to the familiar characteristics of the original test-beam particle, the team was able to accurately calibrate the apparatus and optimize the intricate reconstruction software.
Similar to how the quality of a photo differs considerably on the basis of the quality of a photographer’s editing software and camera, the quality of physics data is only as good as the detector and its reconstruction equipment.
Researchers working on the ProtoDUNE-SP director have learned from previous neutrino experiments and have attained a level of performance that was not possible before. All the data of the detector contains slight differences, known as noise, that can, at times, prove hard to differentiate from the signals produced by particles.
This is a general issue encountered in all physics experiments, and investigators are constantly thinking of novel means to enhance data quality using a combination of decreasing the amount of noise and increasing the strength of the signal.
In the first DUNE article, investigators have demonstrated how they were able to obtain a signal-to-noise ratio of 50 to 1, which was formerly unfeasible to obtain for liquid-argon time projection chambers. The team also assessed the reliability of the detector and observed that over 99% of its 15,360 detector channels are working as predicted.
If some channels in a detector don’t work, scientists get gaps in their data. Data analysis tools can help close those gaps, but there is a limit. The number of inactive channels in ProtoDUNE is less than 1%, giving us highly efficient event reconstruction. ProtoDUNE-SP shows that we can reach and exceed our physics goals.
Tingjun Yang, DUNE Collaborator, Fermilab, Department of Energy
Yang has also headed the ProtoDUNE data analysis.
Abi, B., et al. (2020) First results on ProtoDUNE-SP liquid argon time projection chamber performance from a beam test at the CERN Neutrino Platform. Journal of Instrumentation. doi.org/10.1088/1748-0221/15/12/P12004.