Sterile neutrino?
J Kleinfeller (Karlsruhe) presented options for future short and medium-baseline experiments, which should shed more light on the oscillation signal of electron to muon-neutrinos reported by LSND experiment at Los Alamos. This result implies either the existence of an additional, sterile neutrino or in a three-flavour oscillation scenario a reinterpretation of the solar and atmospheric neutrino data.
The updated KARMEN experiment at the UK Rutherford Appleton Laboratory, sensitive to the same type of oscillations, does not see a signal but cannot rule it completely out either. A definite answer might be given by new projects being proposed at Fermilab (MiniBoone) and perhaps at the CERN PS proton synchrotron.
A Suzuki (Sendei) showed that the research on reactor neutrinos enters a new phase with the ongoing Palo Verde project and plans for KamLAND, both aiming to detect neutrinos from different reactors simultaneously.
The deficit of solar neutrinos detected on Earth was discussed by G Ewan (Queen's, Ontario) who pointed out the importance of detecting neutral current interactions of these neutrinos one of the goals of the new SNO Sudbury Neutrino Observatory (Summer, page 1). Such measurements could provide the crucial information needed to nail down the origin of the solar neutrino deficit. The energy spectrum of solar neutrinos as being measured by the SuperKamiokande, SNO and Borexino experiments may help us to understand what happens to neutrinos on their way from the Sun to the Earth.
For the final day of the workshop, delegates left the now familiar brewery and went across the canal to the "Trippenhuis", the seat of the Royal Academy of Arts and Sciences. Here the convenors presented the highlights of the topical sessions while kinematical and quantum mechanical aspects of oscillations were covered by H J Lipkin (Weizmann).
In his summary M Spiro (Saclay) stimulated further discussion by raising such provocative questions as "Do we fully understand the production of atmospheric neutrinos?" and "Is there need for a long-baseline enterprise both in the US and in Europe?" These questions were addressed in the final plenary discussion together with other key issues how can we verify the LSND and Kamiokande results? What would be the best way to attack the problem of the solar neutrino deficit? What strategy should be followed to obtain the most complete answers? Are we ambitious enough in designing new beams? One important conclusion can already be drawn: the NOW'98 workshop saw the need for discussion between physicists from different neutrino experiments and it seems appropriate to organize a similar workshop in 1999. Meanwhile, discussions continue via the Internet, where the proceedings of the workshop can also be found at the link in the left-hand column.
The workshop was supported by the City of Amsterdam, the European Physical Society and Dutch scientific and industrial institutions, and was organized by the local NIKHEF laboratory.