Sketch of neutrino statement for Strategy
Long Baseline Neutrino studies at accelerator-made neutrino beams
Abstract
Measuring the neutrino mass hierarchy, the leptonic CPV phase and the unitarity properties of the
neutrino mixing matrix is a decisive task for accelerator neutrino beams.
R&D towards very high performance and purity beam technologies, such as a neutrino factory or a
betabeam , is in full swing and must continue.
Before then, possibilities of further short term progress with the present CNGS technology do exist
and …. .
V0.0 Alain Blondel 23-12-2011 v0.1 AB, 17-03-2012
1. New horizons opened by neutrino masses – what it could point to. Dedicated wording on neutrino
mass hierarchy, CP violation, precise verification of 3X3 framework, possible existence of sterile
neutrinos within accessible reach of experiments, fundamental aspect of quantum nature of neutrino
oscillations.
2. Complemetarity with nearby field of neutrinoless double beta decay and other means of
measurements of neutrino masses; implications of neutrino leptonic CP for leptogenesis, dark matter,
mass generation mechanism, quark-lepton universality and unification. (allude to proton decay?)
3. measurements accessible to accelerator neutrino experiments and why they are providing unique and
critical information. How far should they be pushed – it is a long term program. Given the importance of
the field, continuation of experiments with discovery potential in Europe is a must: European physicists
can thus express their own ideas and creativity better with real chance of discovery.
Priorities
4. Present experiments on the CNGS beam should be continued. What has been learned. Tau
appearance and speed of neutrino measurements should be continued to conclusion by the two
experiments. Be clear that because of particular baseline and set-up (no near detector), the future
should develop around larger detectors and longer, or shorter, baseline with near detector. Engaged
R&D on future facilities (MICE experiment, experiments to demonstrate beta beam) should be continued
until successful completion.
5. In order to plan the next step one should take stock of present status, lessons learned from existing
facility, from participation in experiments abroad, and from the design studies that have been going on
now for several years (here give references back to 1998)
6. projects planned in the world comprise MINOS +, NOvA, DUSEL, short baseline ideas in the US, T2K,
T2HK. Scopes and uncertainties.
6’. Do we have in Europe, in the short term, a real chance of discovery of the neutrino mass hierarchy
and of the CPV phase? Given the fact that sin2(2theta13) is large, of the order of 0.1.
The present several hundred KW CNGS technology is extremely successful. The only option to continue
in Europe experimentation, with an experiment which is feasible in a reasonable time, filling thus the
gap before a NuFact or Betabeam, is with that technology.
This can be the existing line or a new line.
1) existing CNGS line: a dedicated GS workshop will take place in May. It will presumably address
questions like:
What physics reach does the 732 Km baseline permit and what effort that implies?
Is it necessary/ possible to equip the line with a near detector site?
Are the modifications necessary to lower the present very high energy of the beam feasible?
How large a detector can be housed either in the existing lab or in possible extension?
2) new CNGS-like line: a specific proposal has been emerging, in the LAGUNA-LBNO DS, for a new North
area neutrino beam line line, heading to detectors in a new underground lab at Pyhasalmi (CN2PY) 2300
Km away . This should foresee from the start a near detector location.
Its longer baseline is unique among presently discussed project.
Assuming operation in 2023, its physics reach could include after two years a more than 3 sigma
sensitivity to the mass hierarchy (MH), with 100% coverage in delta CP, and after ten years a
measurement of delta CP at +- 15 degrees ( 1 sigma) at 10 degrees. NB By the same time, Nova will have
at most a 30% coverage for delta CP, with three sigma sensititivity for MH.
It would be based on an incremental approach both for detector construction and beam intensity and
also a longer term prospective with continuation to a neutrino factory
It would have complementarity with the road map emerging in another field (LENA, Li-Argon detectors
for p decay and low energy neutrinos pushed by ASPERA)
Questions
What is the optimal defintion of the incremental steps in detector mass and beam intensity?
What is the added value of a large liquid scintillator deector to measurements with a neutrino beam?
2a) Following path 2), a second beam line on surface is also being considered as a first step that would
allow to perform short baseline physics: searches for sterile neutrino, cross-section measurements,
providing also a site for neutrino detector R&D
Questions
What is the timescale? What is its additional cost?
…………..
The next step should be … maintains the community healthy, with a large range of possibility and a real
chance of discovery. The existence of a possible long baseline in Europe is unique in this regard. Develop
briefly the C2PY, the reach in mass hierarchy, the reach in sterile neutrinos search. Empahasize that it
can do a mass hierarchy determination quite rapidly, and that it can evolve into a more powerful beam
(NF) and thus offers a long term vision.
7. At the same time the facility proposed can perform short baseline physics: cross-section
measurements, near detector function and exploration of sterile neutrino possibilities
8. insist on the importance of the ancillary experiments (SHINE, possible muon storage ring for (nu_e
/nu_mu and C.C.)cross-section measurements.
9. continuation of R&D experiments for long term facility vision in particular MICE neutrino factory
design study.
10. The Beta beam design study that is really specific to Europe. Should the efforts in other parts of the
world towards CP violation with a very large Water Cherenkov not bear fruit, there would be a beautiful
opportunity. Comments on energy baseline and feasibility at CERN.