27 March 2013 – INFN – OPERA observed a third neutrino tau.
The OPERA international experiment at the INFN Gran Sasso Laboratory (Italy) has observed a third neutrino tau candidate from “flavour” oscillation. The “muon-type” neutrino produced at CERN in Geneva arrived at the Gran Sasso laboratory as a “tau” neutrino. An extremely rare event observed only twice before, in 2010 and in 2012.
The data analysis will be pursued for two more years searching for other tau neutrinos that could definitely prove this very rare phenomenon.
The first LHC protons run ends with new milestone | CERN press office.
– extracts from the article –
To put this into context, of the 6 million billion proton-proton collisions generated by the LHC, the ATLAS and CMS experiments have each recorded around 5 billion collisions of interest over the last three years. Of these, only around 400 produced results compatible with the Higgs-like particle whose discovery was announced in July.
During the last few days, the space between bunches has been successfully halved, achieving the design specification of 25 nanoseconds rather than the 50 nanoseconds used so far. Halving the bunch spacing allows the number of bunches in the beam to be doubled. A record number of 2748 bunches was recorded in each beam last weekend, almost twice as many as the maximum reached previously in 2012, but at the injection energy of 450 GeV and without collisions. Several hours of physics were then performed with up to 396 bunches in each beam, spaced by 25 nanoseconds, each beam being accelerated to the energy of 4 TeV.
The luminosity, a crucial parameter measuring the rate of collisions of an accelerator, has reached a value of 7.7×10^33cm-2s-1, more than twice the maximum value obtained in 2011 (3.5×10^33cm-2s-1). The collision energy was increased from 7 TeV in 2011 to 8 TeV in 2012.
At the beginning of 2013, the LHC will collide protons with lead ions before going into a long maintenance stop until the end of 2014. Running will resume in 2015 with increased collision energy of 13 TeV and another increase in luminosity.