A Super Neutrino Beam Proton Driver

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A Super Neutrino Beam (Proton Driver)
at Brookhaven National Laboratory for a Very
Long Baseline Neutrino Oscillation
Experiment allowing the Precise Measurement
of Mixing Parameters and CP Violating Effects
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Physics Importance of Neutrino Oscillations
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Physics Goals of theVery Long Baseline Neutrino
Program

• We introduce a plan to provide the following
  goals in a single facility
• Precise determination of the oscillation
  parameters ?m322 and sin22?23
• Detection of the oscillation of ?? ? ?e and
  measurement of sin22?13
• Measurement of ?m212 and sin22?12 in a ?? ? ?e
  appearance mode, can be made even if the value of
  ?13 is zero
• Verification of matter enhancement and the sign
  of ?m322
• Determination of the CP-violation parameter ?CP
  in the neutrino sector
• The use of a single neutrino super beam source
  and half-megaton neutrino detector will optimize
  the efficiency and cost-effectiveness of a full
  program of neutrino measurements. If the value
  of sin22?13 happens to be larger than 0.01, then
  all the parameters, including CP-violation can be
  determined.

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BNL ??Homestake Super Neutrino Beam
Homestake
Base line 2540 km Max depth 128 km
BNL
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Advantages of a Very Long Baseline and A Wide
Band Beam

• The dominant term governing the oscillations is
  sin2(?m322 L / 4E)
• Longer Length allows oscillations to be seen at
  higher Energy
• Cross sections are larger and energy resolutions
  are better at higher Energy
• A broad band beam allows coverage of multiple
  oscillation periods and observation of a distinct
  oscillation signature
• The multiple node structure alows ?m322 to be
  precisely measured by a wavelength rather than an
  amplitude (reducing systematic errors)

Expected Number of nm CC QE events and
background from non-QE
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Baseline Length and Neutrino Energy

• For a fixed phase angle, e.g. ?/2, the ratio of
  distance to energy is fixed (see sloped lines in
  Figure)
• The useful neutrino energy range in a beam
  derived from a proton production source is
  restricted
• below 1 GeV by Fermi mom. in the target nucleus
• above 8 GeV by inelastic ? interactions
  background
• These conditions prescribe a needed baseline of
  greater than 2000 km from source to detector
• By serendipity, the distance from BNL to the
  Homestake Mine in Lead, SD is 2540 km

Location in energy and distance of the (2n1)p/2
oscillation nodes
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VLB Application to Measurement of ?m322

• Comparison of the BNL-VLB experiment after a
  5-year measurement with the present
  Super-Kamiokande atmospheric-n results and those
  expected from 3 years of MINOS data
• Dm322 will be measured with a statistical
  precision of 1
• Can limit sin22q23 gt 0.99 at 90 confidence
  potential to observe non-maximal mixing
• There is no other plan, worldwide, to employ the
  VLB method due to a combination of target power
  and geography.
• Other planned experiments can't achieve the VLB
  precision.

Expected sensitivity to nm disappearance
parameters. (systematics do not include absolute
energy scale)
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?e Appearance Measurements

• A direct measurement of the appearance of ?? ?
  ?e is important the VLB method competes well
  with any proposed super beam concept
• For values gt 0.01, a measurement of sin22?13 can
  be made (the current experimental limit is 0.12
  assuming the SK best fit point)
• For most of the possible range of sin22?13, a
  good measurement of ?13 and the CP-violation
  parameter ?CP can be made by the VLB experimental
  method

Expected event rate of ne CC QE events and
background from single p0
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?e Appearance Measurements (Cont.)

• Even if sin22?13 0, the current best-fit value
  of ?m212 7.3x10-5 induces a ?e appearance
  signal
• The size of the ?e appearance signal above
  background depends on the value of ?m212
• The figure indicates the range of possible
  measured values for the ?e yields above
  background for various assumptions of the final
  value of ?m212

Expected ne CC QE event rate and background given
sin22q13 0.
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Mass-ordering and CP-violation Parameter ?CP

• The CP-violation parameter ?CP can be measured
  in the VLB exp.
• It is relatively insensitive to the value of
  sin22?13
• The mass-ordering of the neutrinos will be
  determined in the VLB exp
• ?1 lt ?2 lt ?3 is the natural order
• but ?1 lt ?3 lt ?2 is still possible
• Experimentally VLB can determine which is the
  case using the effects of matter on the higher
  energy neutrinos
• Only n running is needed. Anti-n running will
  improve result.

Expected sensitivity to dCP and sin22q13 with
only n running