Workbook

137
E-815 (Bernstein / Shaevitz) Precision Measurements ofNeutrino Neutral
CmTent Interactions Using a Sign-SelectedBeam
Adelphi, Cincinnati, Columbia, Fermilab,
Kansas State, Oregon, Rochester, Xavier
IStatus: No Data YetI
A major physics goal of the 1990's will be precision tests of the
electroweak sector of the Standard Model. The Standard Model makes definite
predictions which can be confirmed or refuted with sufficiently precise
measurements. Comparing the value of sin 2 9w measured in e+e- collisions at
the ZO pole, at hadron colliders, and in deep-inelastic neutrino-nucleon
scattering tests the radiative corrections to the Standard Model and allows us
to search for physics beyond it.
E-815 (NuTeV) will exploit the full power of the high-energy, highintensity
Tevatron neutrino beam to significantly improve the precision of the
measurements of the electroweak parameters. The new sign-selected beam
will enable us to measure neutrino and anti-neutrino interactions separately.
This has two significant advantages: (1) previously limiting systematic errors
can be eliminated or reduced, and (2) sign-selection will provide the first
precision measurement of p. The value of p, the ratio of neutral-to-charged
current coupling strengths, reflects the structure of the Higgs sector so a
precise determination of p is a powerful probe of the nature of electroweak
unification. Furthermore, both p and sin 29w are radiatively corrected by mt in
a known way. Hence before the discovery of the top quark, the electroweak
measurements can predict its mass; after mt has been directly measured,
requiring consistency between the predicted and measured values is a
stringent test ofthe Standard Model.
NuTeV will yield a measurement of (1) sin 29w with an expected error of
o(sin 29w) = ±0.0025 (statistical and systematic errors combined), and (2) p with
an error of ±0.0054, a factor of six improvement over existing data. These
errors can be compared to measurements of mt or Mw; the corresponding
error on mt is 30 GeV/c 2 and only 130 MeV/c 2 on Mw, competitive with the
expectations from the collider measurements. The vN measurements have a
unique dependence on the radiative corrections and are the only
measurements which directly determine both sin 29w and p.
Neutrino-nucleon scattering has always been a rich source of
information on the structure of nucleons and tests of QeD and NuTeV will
build on that tradition. We will use our experience from E-744/E-770 to reduce
the systematic errors on as and AQCD through the use of an extensive test beam
program for calibrating the apparatus. E-744/E-770 has already provided the
best measurement of as(Mz); NuTeV can reduce that error by nearly a factor of
two. In addition, the sign-selected beam will allow us to make more precise