Fermilab E815 (NuTeV) is scheduled to run in the next fixed target run at Fermilab in early 1996 using the same Lab E neutrino detector as was used in FNAL E744/E770. The primary physics goal of the experiment is to measure the quantity
to a precision of . This factor of 2-3 improvement over the current best measurement in scattering translates into an equivalent W-mass error of 100-150 MeV/, and a limit on the top mass of MeV/. This precision will be comparable to that achieved by the collider programs at SLC/LEP and D0/CDF in terms of testing the standard model of elementary particle physics. Once the magnitude of the top mass is pinned down at Fermilab, the precision neutrino measurement of will provide valuable and in some cases, unique, constraints on the existence of extra bosons, mirror type fermions, and other physics processes beyond the standard model.
The feature of the experiment that permits this increased precision is a new high intensity sign-selected neutrino beam. One can appreciate the point of this beam most simply by considering the quantity
where in the standard model, at tree level. The part of the cross section that depends on the ``sea-quark'' distributions is the same for neutrinos and anti-neutrinos; thus, the quantity depends only on the well-measured valence quark distributions. The theoretically troublesome part of the cross section that is due to , where s and c are strange and charmed quarks, respectively, does not contribute to . The uncertainty associated with charged-current charm production has been the dominant systematic error in previous neutrino determinations of the weak mixing angle. The E815 experiment will be able to make the first significant measurement of because its new beam design permits clean separation of from while providing enough intensity to maintain small statistical errors. The new beam also helps to reduce other systematic errors in the weak mixing angle measurement.
The scheduled two year run using the higher intensity of the upgraded Tevatron, coupled with an improved calibration procedure for the calorimeter and muon spectrometer, enhances the opportunities for E815 to make significant measurements of the QCD scale parameter , the charm mass , the fraction of strange quark sea in the proton , the CKM matrix element , and the size of the charmed quark sea in the proton ; and to probe for exotic physics sources related to transitions or flavor-changing neutral current production of charmed quarks. The expected precision on different physics quantities in E815 is given in the accompanying table.
Table 1: Comparisons of the precision on different physics measurements for different data samples (The errors shown in parentheses are statistical only).