Jim Strait: Experimental Program at the Long Baseline Neutrino Facility
The US “P5 report” recently issued a recommendation for neutrino physics plans: to “form a new international collaboration to design and execute a highly capable long-baseline neutrino facility hosted by the US.”
The minimum requirements is an exposure of at least 120kt * MW * yr by the 2035 time frame, a 1.2MW upgradable beam power, and capability for making measurements of SN neutrino and proton decay.
The european strategy document also pointed out that CERN should develop a neutrino programme to pave the way for a substantial european role in future long-baseline experiments.
We have now what is the ELBNF: an experimental program in neutrino physics, nucleon decay, and astroparticle physics at the fermilab long baseline neutrino facility. It is a merger of previous efforts, to build, operate and exploit a 40kt LAr detector at the Sanford underground research facility, 1300km from Fermilab, with a high-granularity and precision near detector. It is a long term program of 25+ years.
The measurements will be test of CP violation in lepton sector, determine the ordering of neutrino masses, test the three-nu paradigm, and perform a broad set of neutrino scattering experiments. A letter of intent for the above program was signed by 142 institutions, with 527 signatures. Beam-based oscillation physics is the core of the program.
The expected sensitivity to the mass hierarchy and CP violation goes beyond 3-sigma for reachable exposures in kilotons times megawatts times years of operation easily, for the mass hierarchy 5-sigma are easily surpassed.
For the far detector, the discussion is ongoing between a single or a dual phase liquid-argon TPC. The near detector is a key part of the program. There is a fine-grained tracker surrounded by a 4-pi electromagnetic calorimeter and outer muon detectors; another is a high-pressure GAr TPC with a downstream electromagnetic calorimeter. These designs will have to be studied to determine which gives the best performances.
Jim Strait then showed and discussed several pictures of the detectors, the source, the target, the focusing structure, and the planned beam power upgrade that will lead the power to 1.2MW and beyond. If you are interested in these I suggest you to give a look at his slides (available at the conference web site).
The US DOE is very supportive of the aggressive status being laid out. To support the funding required, the DOE has called for a “CD-1 refresh” review in July this year for the whole LBNF and ELBNF enterprise. It will review new cost and schedule estimates and management plans.
In summary, a new global collaboration has formed. The organization is taking shape rapidly. Strong support from the DOE, and the next few months will be crucial to form the collaboration and to define the international governance.
In the discussion following the presentation, Luca Stanco commented that to control systematics one should have equal technology for the near and far detector, and he was surprised that this is not envisioned in the present plan. The speaker replied that beam intensity is so high that the near detector would suffer pile-up issues. The impact of systematics has not been fully studied yet.