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News from Super-Kamiokande

Twenty years after the start of Super-Kamioande

2016/4/1

Today, twenty years have passed since we officially started Super-Kamiokande (SK) data-taking at midnight on April 1st, 1996. A copy of the log book and a photograph taken when we started the operation is shown below. We celebrated the start in the Kamioka mine surrounding the first spokesperson, Prof. Yoji Totuska.

Fig1; At midnight on April 1st, 1996 the first spokesperson, Prof. Yoji Totsuka started Super-Kamiokande data-taking. The collaborators celebrate the start in the Kamioka mine.

Fig.2; The log book of the first official run. "Run1000 Started by Totsuka-san! It works!"

A lot of things have happened in twenty years. In 1998 it was shown that neutrinos have mass by observing neutrino oscillations in SK’s atmospheric neutrino data. This achievement led to Prof. Kajita’s Nobel Prize in 2015. In 2001 oscillations of solar neutrinos were also discovered, in 2004 the first long baseline accelerator experiment (the K2K experiment) confirmed neutrino oscillations, and in 2011 the T2K experiment discovered the third oscillation mode. On the other hand, in 2001 about 60% of SK’s photomultipliers (PMTs) were destroyed by an accident. Because of that we operated the detector with half the usual number of PMTs from 2002 to 2005. In 2006 we fully recovered the detector, and since then we have been operating the detector stably. We are greatly indebted to various associated organizations and their people for this long successful operation of SK. We would like to deeply thank them for their support.

Super-K will continue observation for further discoveries. If a supernova happens in our galaxy, SK would detect many thousands of neutrino events; they would reveal a detailed explosion mechanism. Also, we plan to detect the neutrinos emitted from past supernovae from the beginning of the universe by improving the detector. The T2K experiment plans to investigate the difference between neutrino and anti-neutrino oscillations.

We would appreciate your continued cooperation in the exciting years to come.

On April 1st, 2016
Super-Kamiokande Spokesperson
Masayuki Nakahata