Cafe neutrino meeting minutes (12/14/09)
Present: E. Benedetto, A. Blondel, M.Diwan, F. Dufour, I. Efthymiopoulos, C. Hansen, J. Strait, E. Wildner, A. Zalewska
Neutrinos in the U.S. (J. Strait): .pdf
Next meeting: TBA
At Fermilab there exist 2 neutrino beams: BNB from the Booster beam and NuMI from the Main Injector. A third one (LBNE) is planned, pointing to South Dakota. For the BNB (Booster Neutrino Beam), the 8 GeV-proton beam power is typically 8 kW and can go up to 25 kW if the experiments which have higher priority (Collider and NuMI) are off. Neutrino energy peak is ~0.6 GeV. The BNB is used by MiniBooNE (at 541 m from target, can see also off-axis NuMI beam), SciBooNE and MicroBooNE (100 tons active volume, Liquid Argon TPC, ready for data-taking in 2013). For the NuMI beam (Neutrinos from the Main Injector), the 120 GeV-proton beam power is ~300 kW and will be upgraded to 700 kW after the Collider is switched-off. The neutrino energy is tunable in the range 3-12 GeV. It serves MINOS, NOvA and MINERvA. MINOS looks at νμ disappearance, baseline is 735 km, near detector on Fermilab site and 5 ktons magnetized-iron far detector in Soudan mines. NOvA will look at νe appearance. Far detector will be completed in 2013. Far detector is ~15 kT liquid scintillator, will look at 14 mrad off-axis, 2 GeV narrow-band beam. Near detector in Fermilab cavern will be at the same off-axis angle. NOvA will constrain the sin(θ13) sensitivity to 0.01. Mass hierarchy if θ13 is large enough. MINERvA is in Fermilab near cavern (on-axis) and will be completed next spring. Use high intensity beam, tunable energy, for cross-section measurements for neutrino oscillation experiments and a broad physics program of weak-interactions measurements. In addition, NuMI high intensity beams serves ArgoNeuT, a test experiment placed in front of MINOS near-detector for Liquid Argon TPC R&D, in operation during summer 2009-spring 2010. Finally, the proposed LBNE (Long Baseline Neutrino Experiment) will look at νe appearance with a ~1300 km baseline. The proton beam power will be 700 kW (upgrade of NuMI) and finally 2 MW (from ProjectX). It will be 100 kton Water Cherenkov or equivalent LAr TPC or a combination of the two.
Neutrino plans in the U.S (M. Diwan):
Milind discussed the neutrino oscillation program in the U.S., talking in particular about the LBNE proposal. His presentation from the CERN EP Seminar can be found here. Milind was very impressed (Slide37: "Convergence of interests") at a recent Workshop in Valencia by the High Energy Physics community interest in the &theta13 mixing angle, mass hierarchy and CP, for the Grand Unification Theory (GUT) scale implications. The existence of a neutrino mass would mean that neutrinos have a heavy partner >109 GeV (could LHC find it?). Moreover, θ13 could be of the same order of the Cabibbo angle and an analogy between the quark mixing matrix and the neutrino mixing matrix can be made. Accelerator and detector technology are almost ready for next step and thanks to new physics discoveries (? see Slide 7) we know the scale for the next experiments. Indeed, people used to push for experiments in the top-left corner of the plot, while we are in a region of higher mixing angle and lower mass difference. The size of the detectors should not be smaller than 100 ktons WC. In that case, with a 1 MW incident proton beam, there will be anyway detected ~20 events per year (Slide 42). In particular there is the proposal of the Long Baseline Nu Experiment (LBNE) from Fermilab to DUSEL at Homestake in South Dakota. The Black Hills are the perfect place at the right distance (1290 km) to host a detector, because they are a very ancient geological conformation, the rocks have low radioactivity and there were some old mines. Electron neutrino appearance spectra plots (Slides 48-49, done by Mary Bishai) have a peak at ~few GeV neutrino energy. According to whether normal or reversed hierarchy, respectively neutrino or anti-neutrino running is essential. In the plots, blue region represents beam background and red neutral-current background, which can be reduced to the same order of the beam background. Signal to background ratio is about ~2, at the peak. If Liquid Argon detector is used instead of Water Cherenkov, there is no neutral-current background. Sensitivity plots at 3 sigma (Slide 52) show that after 3+3years of operation the sensitivity for θ13, mass ordering and CP violation will be < 0.01. Full documentation can be found on this web page and in the References collected in Slide 67.