Super-K sees its first neutrino from T2K!


February 25, 2010: The T2K experiment in Japan has recorded its first long-baseline neutrino event in the Super-Kamiokande detector. It was announced this morning by a press release from KEK, the Japanese high energy physics laboratory.  In this experiment, a beam of neutrinos is created at the new J-PARC accelerator facility in Tokai, Japan and sent 295 km to the Super-Kamiokande detector. The experiment plans to study, for the first time, the appearance of electron neutrinos from a quantum mechanical flavor oscillation of muon neutrinos. A graphical display of the first event, recorded on February 24, 2010, is shown here and below. This events marks the true start of running for the T2K experiment.

You can read the press release here

The Super-Kamiokande experiment is a giant underground water Cherenkov experiment in Mozumi, Japan, 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 ultrapure water.  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 with K2K ("KEK to Kamioka"), a beam of artificial neutrinos sent 250 km through the Earth to Super-K from the KEK accelerator laboratory in Mozumi, Japan.  The beam neutrinos "went missing" after their sub-Japan flight 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 last unknown neutrino oscillation parameter, "θ13".  The signature of non-zero θ13 is a tiny amount of electron neutrino appearance in a beam of muon neutrinos.  The T2K (Tokai to Kamioka) experiment will provide a beam about 100 times more intense than K2K.

The T2K collaboration consists of 508 physicists from 62 institutes in 12 countries (Japan, South Korea, Canada, the United States, the United Kingdom, France, Spain, Italy, Switzerland, Germany, Poland, and Russia).  The experiment consists of a new neutrino beam-line using the recently constructed 30 GeV synchrotron at the J-PARC laboratory in Tokai, Japan, a set of near detectors constructed 280m from the neutrino production target, and the Super-Kamiokande detector in western Japan.

After traveling 295 km underneath Japan, a neutrino interacted with the giant Super-K detector, and was recorded by its light detectors.

Duke Professors Kate Scholberg and  Chris Walter have worked for more than 10 years on the Super-K and T2K experiments. Current Duke University participants in the experiment also include postdoc Roger Wendell, and graduate students Josh Albert and Taritree Wongjirad.

A graphical view of the event recorded by the Super-Kamiokande detector.