The Super-K detector
Super-Kamiokande is a 50~kiloton water Cherenkov detector located at the Kamioka Observatory of the Institute for Cosmic Ray Research, University of Tokyo. It was designed to study neutrino oscillations and carry out searches for the decay of the nucleon. The Super-K experiment began in 1996 and in the ensuing years of running has produced extremely important results in the fields of atmospheric and solar neutrino oscillations, along with setting stringent limits on the decay of the nucleon and the existence of dark matter and astrophysical sources of neutrinos. Perhaps most crucially, Super-K for the first time definitively showed that neutrinos have mass and undergo flavor oscillations.
This facility is in the Mozumi mine of the Kamioka Mining Company in Gifu prefecture, in the Japanese alps. Super-K consists of two concentric, optically separated water Cherenkov detectors contained in a stainless steel tank 42 meters high and 39.3 meters in diameter, holding a total mass of 50,000 tons of water. The inner detector is comprised of 11,146 Hamamatsu~R3600 50~cm diameter photomultiplier tubes (PMTs), viewing a cylindrical volume of pure water 16.9~m in radius and 36.2~m high.
The COHERENT collaboration aims to measure CEvNS (Coherent Elastic Neutrino-Nucleus Scattering) using the high-quality pion-decay-at-rest neutrino source at the Spallation Neutron Source in Oak Ridge, Tennessee. The SNS provides an intense flux of neutrinos in the few tens-of-MeV range, with a sharply-pulsed timing structure that is beneficial for background rejection. The CEvNS process is cleanly predicted in the Standard Model and its measurement provides a Standard Model test; furthermore, the process is involved in supernova explosion processes and supernova neutrino detection. It also represents a background floor for dark matter direct detection. In the long term, precision measurement of CEvNS will address questions of nuclear structure. We aim to deploy multiple detector technologies in a phased approach.
The Deep Underground Neutrino Experiment /Long-Baseline Neutrino Facility (DUNE/LBNF) will send a beam of neutrinos 1300 km from Fermilab to a large liquid argon detector underground in South Dakota to explore neutrino oscillations. It will also hunt for a burst of supernova neutrinos and search for nucleon decay.
The Large Synoptic Survey Telescope (LSST) project is a giant survey telescope that will be located in Chile and is designed to make a three
dimensional survey of the entire visible sky. The LSST Dark Energy Science Collaboration will examine billions of galaxies and try to determine the nature of the mysterious “Dark Energy” which is unaccountably causing the universe to be pushed apart at a faster and faster rate.
The LSST will open a whole new field of observational cosmology by collecting an unprecedented amount of data and addressing some of the most fundamental questions we have about space-time including the nature of gravity, dark energy, dark matter and inflation. In 2010 a panel convened by the National Research Council for the National Academy of Sciences ranked LSST as its top priority for the next large ground-based astronomical facility. LSST will survey the entire visible sky with a level detail and distance that has never been achieved before
Summer student Ben Izatt created the Super-KAVE, a 3D immersive visualization in the DiVE of the Super-Kamiokande detector. You can fly around the detector, look at photomultiplier tube hits in time or charge mode, see the Cherenkov cone, and turn different particles on and off. Here’s a video, by Dave Zielinski, and here’s a supernova simulation.
The Super-KAVE event display
Josh and Chris after the defense
Josh has successfully defended his dissertation, and graduated from Duke University with a PhD in physics. His dissertation, on electron neutrino appearance at T2K, was defended in March, and the graduation ceremonies were held in May, 2012. He will be continuing his research into the nature of neutrinos with a postdoc for Indiana University, working on the Enriched Xenon Observatory experiment.
Roger is in Canada. He is spending six weeks working on the HALO experiment. Underground in asia got boring so he is checking out the north american underground.
A T2K candidate electron neutrino event
After many years of work in T2K we are excited to report our first indications of electron neutrino appearance!
Read more on Chris Walter’s website here.
Read the official T2K press release here and the Duke Today story here.
The T2K experiment is a “long-baseline” neutrino experiment where neutrinos are produced in an accelerator north of Tokyo and then shot across Japan to the Super-Kamiokande detector underneath the Japanese Alps. Super-Kamiokande is a giant underground water Cherenkov experiment, designed to capture neutrinos from the Sun and sky: the 11,000 inner detector photomultiplier tubes (PMTs) record photons from the charged products of neutrino interactions in the ultra-pure water. In the T2K experiment, Super-K acts at the far target of the neutrino beam.
In 1998, Super-K showed that muon neutrinos produced by cosmic ray collisions in the Earth’s atmosphere “disappear” by changing to almost-invisible tau flavor: the neutrinos “oscillate” from one flavor to another by interference of mass states. Such flavor change is only possible if neutrinos have mass. Neutrino masses and the parameters which govern neutrino flavor oscillation are deeply connected to both fundamental particle physics and cosmology. Over the next few years, the Super-K atmospheric neutrino result was confirmed by other experiments. The beam neutrinos “went missing” in exactly the numbers expected, and with exactly the expected energy dependence predicted by the oscillation hypothesis.
The next physics quest for Super-K is the search for the unknown neutrino oscillation parameter, “Theta _13” as part of the T2K experiment. The signature of non-zero Theta_13 is a tiny amount of electron neutrino appearance in a beam of muon neutrinos. The T2K experiment is designed to measure this parameter by looking for muon neutrinos produced in an accelerator at the JPARC center north of Tokyo to transform into electron neutrinos after they travel 295 km across Japan. Since this is a very small effect, a powerful beam is needed to create just a few of these events.
In the latest T2K results, the accelerator made a beam pulse of neutrinos over two million times. Six events consistent with an electron neutrino were observed, although only 1.5 events would have been seen if muon neutrinos don’t oscillate into electron neutrinos. The probability that the observation is just due to a chance fluctuation is less than 1%.
Super-K is located near Toyama city in Japan. In fact, Toyama is a sister city of Durham . Home to Toyama bay, firefly squid and excellent Buri, you can be there in a short 20 hours from Durham!
Members of the group make frequent trips to the experiment and some are based there. We have been and are involved in both the physical construction and maintenance of the experiment, and data analysis from both Super-K and T2K.