Super-K is getting ready for some new neutrinos!
 
 
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.
 
In 2001, an accident at Super-K -- a chain reaction implosion of
phototubes after a routine phototube replacement upgrade-- destroyed two thirds of the light sensors.  The surviving ones, along with available new ones, were redistributed around the detector (now with acrylic shell protection).  "Super-K II" with half of the original PMT density ran from 2003 to 2005.  Over the winter of 05/06, Super-K's phototubes were fully replenished.  Duke personnel spent many weeks in Japan working on the full reconstruction of Super-K. Duke's particular responsibility was replacement of Tyvek (a white reflective material) in the outer part of the detector.
 
A fully rebuilt "Super-K III" has been running since mid-2006,
and the first analyses of the new data are underway.
 
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, starting in 2009.  In preparation for T2K, Super-K is undergoing an electronics upgrade, and a software revamp as well. Postdocs Maxim Fechner and Naho Tanimoto are playing key roles in this upgrade.
 
The T2K experiment will comprise the beam, the Super-K detector at 295 km, plus two near detectors.  One detector 280 m from the neutrino source will characterize the neutrinos before they fly off to
Super-K. An additional detector 2 km from the source with a water
Cherenkov detector, fine-grain tracker, and muon ranger components,
will observe a flux nearly identical to that at Super-K.  This "2km"
detector effort is being led on the US side by Prof. Walter.
 
The observation of non-zero θ13 is the first step for answering
the question of CP (charge conjugation-parity) violation in neutrinos. It's now well known that processes involving quarks violate CP symmetry; it's suspected that the same is true for leptons (such as
neutrinos), but leptonic CP violation is as yet unobserved.  We hope
that understanding of CP violation, along with knowledge of the other neutrino parameters, may lead to insight into the question of the observed matter-antimatter asymmetry of the universe.  The long-term program of Super-K and the T2K long baseline neutrino beam  experiment aims to answer these questions.
Duke Super-K members Prof. Chris Walter, Postdoc Naho Tanimoto, grad student Roger Wendell and Prof. Kate Scholberg rest a moment floating in the center of Super-K after the intense rebuild effort during the winter of 05/06.
 
We use small colored magnets coded with a shift number on magnetic tags with our names to keep track of who is currently in the mine for safety reasons.
 
Graduate student Roger Wendell hangs in the side of the detector with Prof. Scholberg while installing reflective material.
News on the SK Rebuild
Prof. Chris Walter was in charge of installing reflective tyvek covering on the outside of Super-K.  The work was done by team of researchers and graduate students from Duke and Boston.
 
The workers had one day off a week.  One week they traveled up into the snowy mountains to learn how to make noodles from a Japanese Soba master.
The 2KM detector is an extension to T2K which will  add to the power of the experiment to make one of the most important measurements in neutrino physics today..
 
- “To learn to mix the flour correctly takes three years.”