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3  Neutrino Oscillations

The strongest evidence for neutrino oscillations comes from astrophysical observations of atmospheric neutrinos with Δ m322 = (1.6 - 4.0) × 10-3  eV2 and maximal mixing [4], and from solar neutrinos with Δ m212 = (3 -10) × 10-5  eV2 assuming the LMA solution [5]. The observation by the LSND experiment [6] will soon be re-tested at Fermilab by the mini-Boone [7] experiment. Therefore we will not discuss it further in this document. There are several accelerator based experiments (K2K, MINOS, and CNGS) [8, 9, 10, 11, 12] currently in the construction phase or taking data to confirm the atmospheric neutrino signatures for oscillations. There is now a consensus that there are four main goals in the field of neutrino oscillations that should be addressed soon with accelerator neutrino beams:
  1. Precise determination of Δ m322 and sin2 2 θ23 and definitive observation of oscillatory behavior.
  2. Detection of νµ→ νe in the appearance mode. If the measured Δ m2 for this measurement is near Δ m322 then this appearance signal will show that
    | Ue3 |
    2
     
     
    (= sin2θ13) from the neutrino mixing matrix in the standard parameterization is non-zero.
  3. Detection of the matter enhancement effect in νµ→ νe in the appearance mode. This effect will also allow us to measure the sign of Δ m322, i.e. which neutrino is heavier.
  4. Detection of CP violation in neutrino physics. The neutrino CP-violation in Standard Model neutrino physics comes from the phase multiplying sinθ13 in the mixing matrix. This phase causes an asymmetry in the oscillation rates νµ→ νe versus anti-νµ→ anti-νe.
In this report we describe how all of these goals can be achieved under reasonable assumptions for the various parameters using the new intense AGS based beam and the very long baseline of BNL to Homestake laboratory of 2540 km.

In Section 3 we estimate the event rates, backgrounds and oscillation signals. This section highlights the physics measurements achievable with the detector being proposed, focusing on its sensitivity to various oscillation parameters.

In Section 4 of this report we briefly describe the accelerator upgrade path to achieve a proton source with intensity greater than 1 MW.

In Section 5 we examine the conventional neutrino beam spectrum and the target-horn station.

In Sections 6 we summarize the report and give a breakdown of the expected costs.

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