high energy neutrino scattering results from nutev

PROCEEDINGS SUPPLEMENTS

ELSEVIER Nuclear Physics B (Proc. Suppl.) 118 (2003) 164-173 www.elscvier.comllocatc/npc

High Energy Neutrino Scattering Results from NuTeV D. Naples?‘, T. Adamsb, A. Altonb, S. AvvakumovC, L. de Barbarod, P. de BarbaroC, R. H. Bernsteine, A. BodekC, T. Boltonb, J. Brauf, D. Buchholzd, H. BuddC, J. Conrads, R. B. Druckerf, B. T. Flemings, J. Formaggios, R. Freyf, J. Goldman b, M. Goncharovb, D. A. Harri,+, J. H. Kims, S. Koutsoliotass, R. A. Johnsonh, M. J. Lamme, J. McDonalda, W. Marshe, D. Ma.sonf, K. S. McFarlandC, C. McNultys, P. Nienabere, V. Radescua, A. Romosans, W. K. Sakumotoc, H. Schellmand, M. H. Shaevitzs, P. Spentzouriss, E. G. Sterns, N. Suwonjandee h, N. Tobiene, M. Tzanova, A. Vaitaitiss, M. Vakilih, U. K. Yang”, J. Yue, G. P. Zellerd, E. D. Zimmermans

aUniversity of Pittsburgh, Pittsburgh, PA 15232.

bKansas State University, Manhattan, KS, 66506.

CUniversity of Rochester, Rochester, NY. 14627.

dNorthwestern University, Evanston, IL, 60208.

eFermi National Accelerator Laboratory, Batavia, IL 60510.

fUniversity of Oregon, Eugene, OR, 97403.

scolumbia University, New York, NY 10027.

hUniversity of Cincinnati, Cincinnati, OH 45221.

The NuTeV experiment at Fermilab has obtained a unique high statistics sample of neutrino and antineutrino interactions using a novel high-energy sign-selected neutrino beam. Recent results from this sample are presented including a precision measurement of the electroweak parameter sin’&, which is observed to be three standard deviations above the standard model prediction.

1. Introduction

Neutrino scattering offers a unique and compli- mentary probe of the Standard Model. Neutrino scattering can provide a precision test of the electroweak sector via neutral-current (NC) interactions, v(p)iV + v(p)X. Charged-current scattering (CC), @)N + p- (+1X, probes the strong interaction and nucleon structure through measurement of the structure functions and offers a direct probe of the strange content of the nucleon through the process, VAN + p-(+)cX.

The NuTeV experiment is a second generation neutrino deep inelastic scattering experiment using separate high-purity neutrino and antineutrino beams at Fermilab. Having both vp and VP beams allows NuTeV to use a new method, with

reduced theoretical uncertainty, to extract the on- shell weak-mixing angle. The beamline was also designed to reduce the source of the largest experimental uncertainty, the ye content of the beam. The high-purity beams can also be used to search for rare processes such as neutral current charm production: URN + v,,ci?X and Standard Model disallowed processes such as the lepton-number violating process p,e- -+ p-Fe.

2. NuTeV Detector and Sign-Selected Beam

NuTeV took data during the 1996-97 Fermi- lab fixed target run using the upgraded 690 ton CCFR neutrino detector. The NuTeV data sample consists of approximately 1.5 x lo6 (vcc) and

0920-5632/03/$ - see front matter 0 2003 Published by Elsevier Science B.V. doi:IO.l016/S0920-5632(03)01314-8

D. Naples et al. /Nuclear Physics B (PFVC. Suppl.) 118 (2003) 164-I 73 165

0.5 x lo6 (pp) neutral-current and charged-current interactions after fiducial cuts.

The NuTeV neutrino detector consists of a 3m x 3mx 20m target-calorimeter instrumented with scintillators after every 1Ocm of steel and with drift chambers for tracking every 20cm. Just downstream of the target-calorimeter is a mag- netized iron toroidal spectrometer used to measure the momentum of high-energy muons from an event. NuTeV also benefitted from a dedi- cated in-situ calibration beam used to determine the energy response of the calorimeter and spectrometer to hadrons, muons, and electrons and to map the response over the face of the detector. The energy scale of the calorimeter is known to 0.43% and that of the toriod spectrometer to 1%. The NuTeV detector and its calibration are described in detail in Reference [l].

The unique feature of the NuTeV experiment is its separate high-purity v,, and i7, samples obtained using the Sign-Selected Quadrupole Train (SSQT) beamline. A dipole magnet after the primary target allows the sign of secondaries produced in the target to be selected by the beam optics, focused, and steered into the decay-region. Neutrinos (or antineutrinos) are produced when sign-selected secondary pions and kaons decay in the 0.5 km decay region beginning 1.4 km upstream of the neutrino detector. Figure 1 shows the energy distributions of neutrinos interacting in the NuTeV detector, and contributions from u,‘s and the wrong-sign component in each mode. The interacted neutrino fraction from F(V) in v(F)-mode is 3 x lop4 (4 x 10d3). Electron neutrinos come primarily from K* + nOe*v, decays, (93% v-mode, 71% p-mode), whose rates and spectra are constrained by the sample of fully reconstructed up and ~~ charged-current events. The beam is designed to have poor acceptance for v,‘s produced in neutral kaon decays (Ki + 7r*erve), this allows improved knowledge of u, beam content. The v, fraction in the beam is -1.6%.

3. Electroweak Measurements

The determination of electroweak parameters from a variety of processes plays an important

NuTeV Neutrino Flux Prediction g 103 --~~~ ----

~“~‘I‘--?..- v a “o 102 *” ..-...,-J--‘“i . .- .i I

UJ 50 100 150 200 250 300 350 400 450 500

E, (GeV)

-F

w 50 100 150 200 250 300 350 400 450 500

L (GeV)

Figure 1. Energy spectrum of interacted neutrinos (top) and antineutrinos (bottom) at the NuTeV detector.

role in testing the Standard Model and can be used to constrain the Higgs mass and provide hints at possible new physics beyond the Stan- dard Model. Measurements of the weak mixing angle, sir? 8~) from neutrino scattering provide a test with comparable precision in determination of Mw as that obtained in collider measurements.

The ratio of neutral-current to charged-current cross sections, II”(R for v(p) scattering from an isoscalar target composed of u and d quarks can be written as [2]

R"(c) - ONC - 2 m - gL + TJ+g;,

'Tee

where T is the ratio of charged current cross sections for antineutrinos to neutrinos, (T = $&) and g& = UL,R + dL,R. At tree level in Cache standard model the quark couplings are given by gi = i-sin2Bw+isin4Bw andgi = isin4&. Previous measurements of sin2 BW from neutrino

166 D. Nuples et al. /Nuclear Physics B (Proc. Suppl.) 118 (2003) 164-173

scattering [3]-[5] h ave been limited by uncertainty in modeling the suppression of charged-current cross section due to the charm production process v,(?QN + p-(‘)cX (see Figure 4). Separate neutrino and antineutrino beams allow NuTeV to use the combination [6]:

R-=RY-rRF 1-T

=g; -9;.

R- reduces the sensitivity to cross section uncertainties, including those arising from charm production due to scattering off the strange and d quark seas. Charm production only contributes through scattering from valence d quarks which is both cabibbo suppressed and at high momentum fraction, 2.

3.1. Analysis and Results The measurement of sin2 0~ requires a separa-

tion of events into neutral-current and charged- current categories. vP charged current events are characterized by the presence of a muon in the final state which deposits energy in a large number of consecutive scintillation counters as it travels through the calorimeter. For inclu- sion in the event sample and event must have a minimum energy deposited in the calorimeter, ECAL >20 GeV. An event is classified as either a neutral or charged current candidate depending on its length which is defined to be the number of counters between the neutrino vertex location and the last consecutive counter with energy above a low threshold. Events that are longer than an energy dependent length cut, L cut, Lt = 16, 17, 18 for ECAL <55 GeV, 55< ECAL <lOO GeV, ECAL >lOO GeV, re- spectively) are charged current candidates (long events), and the remainder are neutral current candidates (short events). Ratios are formed for each sample h$$? = e. The measured ratios are, R& = 0.3916 f 0.0007 and Rr.p = 0.4050f0.0016.

There is approximately a 20%(10%) background from charged current events in the short V(V) event sample, caused by muons exiting the side of the detector or ranging out before Lcut counters. The small electron neutrino contamination in the beam also contributes a charged cur-

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14000

12000

10000

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6000

4000

2000

0

- Total MC cc MC '.4

1.05

0.7 15 20 25

10 20 30 40 50 60 70 80 length (counters)

Figure 2. Event length distributions in neutrino (top) and antineutrino (bottom) modes. The solid line shows the Monte Carlo model and the dashed line is the contribution from charged- current events in the short length region. The corner box shows the ratio of data to Monte Carlo in the region of Lcut (bands indicate lcr systematic uncertainty).

D. Naples et al. /Nuclear Physics B (Proc. Suppl.) I18 (2003) 164-l 73

rent background (5%) to the short events, in particular at high reconstructed energy, (&AL). The short sample sample is corrected for a measured small contribution from cosmic-ray muon induced events (0.9% v-mode, 4.7% P-mode). The largest contamination to the long event sample is 0.7% from punch through events in which a muon from a decay in the shower extends the event length beyond L,,t. The event length distributions for the data samples are shown in Figure 2. The plot shows good agreement in our modeling of the length distributions in the region of L,,t (la systematic uncertainty band is shown).

sin2 9~ can be extracted from R& and Rz.,, by comparison with a detailed Monte Carlo simulation which which takes into account effects of the cross sections, neutrino fluxes, and detector response. The simulation also includes the beam fraction of v,‘s obtained from a beamline simulation which has been tuned using the observable uP and q fluxes from the interacting charged- current neutrino sample. The value of sin2 LOW is determined from RExp after using R&,, which is insensitive to sin2 &I to obtain an input value for the slow-resealing charm mass parameter, m,. This method is equivalent to using R- for reduc- ing the systematic uncertainty from the charm mass. For further details of the analysis see Ref- erence [7].

NuTeV measures the value of the weak mixing angle to be:

sin2 8( on--.hell)

W = 0.2277 f 0.0013 f 0.0009 (syst)

-0.00022 . ( M,2,,-(175 GeV)’

( 50 GeV)2 )

+0.00032 . In ($$z)

where, the first error is statistical only and the small dependence on electroweak radiative correc- tions from M top and MHiggs are explicitly shown. The result is three standard deviations above the global electroweak fit prediction of 0.2227f0.0004 [8], however, it is in good agreement with previous neutrino-nucleon scattering measurements shown in Figure 3. The NuTeV measurement is statistics dominated and represents a factor of two im- provement over the previous best measurement. The largest systematic uncertainty, from model-

* 0.24

$/DOF=4.79/4 ~ /

P c 0.23 t / I I I

t . ; / 0.22

0.21 haded band shows fbm, t I I I I I I

FMMF E616 CDHS CHARM CUR NuTeV v Experiment

Figure 3. Measurements to date of sin2 0~ from neutrino-nucleon scattering. The NuTeV result shown at the right is in good agreement with previous measurements. The yellow band shows correlated uncertainty due to charm production (not present in NuTeV). Central values for the five earlier experiments have been corrected to m, = 1.38 GeV and for Mtop > h/r,.

ing of charm production, contributes 0.00047 to the experimental uncertainty.

The NuTeV on-shell weak mixing angle measurement can be related the to the physical gauge boson masses, sin2 8~ = 1 - $. Using Mt,,=175 GeV and M~i~,,=150 GeV, NuTeV obtains MW = 80.14 f 0.08 GeV, a result which is three standard deviations below the world average value of MW = 80.45 f 0.04 GeV. Note that the size of the NuTeV MW uncertainty is comparable to that of a single direct measurement.

A two-parameter fit to R& and R&, is performed to obtain effective quark couplings (9$d2> which include electroweak radiative effects. NuTeV obtains (gz’r)’ = 0.3001 f 0.0014 and (g$)2 = 0.0308 f 0.0011 which can be compared with the standard model predictions (giff)2 = 0.3042 and (gtff)2 = 0.0301 (with negli- gible errors). This determination of (gtff)” is 3~ below the standard model value while (g&ff)2 is in agreement.

168 D. Naples et al. /Nuclear Physics B (Proc. Suppl.) 118 (2003) 164-I 73

3.2. Interpretation In contrast to purely leptonic measurements

of the weak mixing angle, NuTeV uses neutrinos scattering off quarks in an iron target with a 5.67% neutron excess. Plausible target modeling effects that would affect the NuTeV measurement include symmetry breaking parton distribution functions (pdf’s) and nuclear dependence.

NuTeV corrects for its 5.67% target neutron excess but would be sensitive to isospin symmetry violating effects in proton and neutron quark &f’s (NuTeV assumes UP = dn and dp = un, and corresponding sea quark symmetries). Violations of isospin symmetry are predicted in some non- perturbative models [9]-[ll], however, the effect on NuTeV’s measurement can be determined and is small (6 sin2 8~ - 10m4) in these models [12]. NuTeV data cannot uniquely constrain this possibility. A global analysis of all data used to extract pdf’s is needed determine to what extent isospin symmetry violation is currently constrained.

NuTeV makes the additional assumption of symmetry in the strange quark seas s(z) = s(z). The prediction for R- is sensitive to this assumption [13]. Fits to NuTeV dimuon data (see section 4) directly constrain this possibility. NuTeV’s

leading order analysis yields s

z(s -S)dz =

-0.0027 f 0.0013 (a 20 effect in, the wrong di- rection to account for the discrepancy) [12]. It has been suggested that non-perturbative effects can generate a sizable sea asymmetry [14]-[16]. A next-to-leading order analysis is currently under way to further investigate this possibility.

Nuclear effects in neutrino interactions are also plausible, however, no convincing model has been proposed to explain the discrepancy. The vector meson dominance shadowing model proposed in [17], where nuclear shadowing is weaker for Z”- exchange than for W* exchange, in particular, has the wrong sign to account for the discrepancy. Furthermore, shadowing effects occur primarily at low-x, therefore, the effect would be reduced due to diminished sea quark sensitivity of R- [18].

NuTeV’s shift in measured sin2 Bw may also be interpreted as an indication of new physics outside of the standard model framework. The NuTeV result suggests a smaller left-handed

neutral-current coupling to quarks than expected, while the right-handed coupling agrees with the standard model prediction. This combination of features can be signaling new tree level physics which shifts primarily the left-handed coupling such as extra 2’ bosons [19]. While some models, such as E(6)-predicted 2’ bosons, are disfa- vored in the absence of significant mixing, the result can accommodate a sequential 2’ bosons con- tributing destructively through interference with the Z, having mass in the range l-l.5 TeV. For a more complete discussion of new physics inter- pretations see 1131 and [20].

4. Charged-current Charm Production

Neutrinos can be used to study the charm production process shown in Figure 4, vp(q)N + p-(+lcX, where charm in the final state is observed in the NuTeV detector through its decay to muon final states. Charm production from d quarks is cabibbo-suppressed and accounts for about half of events in v-mode and only 10% in p- mode, therefore, this process allows a direct probe of the strange content of the nucleon. In addition, the energy dependence of this process is sensitive the dynamics of heavy-quark production.

A unique signature for this process is provided by two final state muons of opposite sign in the event. With the sign-selected beam, NuTeV can assign the sign of the primary muon from the beam mode alone. This allows the requirement on muon charge measurement to be relaxed and and allows a reduction of minimum momentum threshold for accepted muons. The candidate event sample (“dimuon” events) consists of events having two oppositely charged muons (each with EP >5 GeV) and a hadron shower with EHAD >lO GeV. NuTeV’s charm production results are presented in two forms, first using the leading-order slow resealing model to extract model parameters which describe the strange sea and model the massive-charm production process, and secondly, a “model independent” measurement of the dimuon cross section is extracted.

Charm production can be described by the Leading order slow resealing model in which the

D. Naples et al. /Nuclear Physics B (Proc. Suppl.) 118 (2003) 164-l 73 169

Figure 4. Neutrino charged-current charm production.

cross section is factorized into three pieces,

d%(u,N + p-pfx) = d%(uJv + CX) dc dy dz 4 4/

xD(z) Bc(c 3 p+x).

The first term describes the parton level scattering process in terms of the quark momentum distributions and the slow resealing variable, < = z (1+ m2/Q2)(1 - z2M2/Q2). The second term describes the hadronization of the final state charm quark with z representing the fraction of the charm quark momentum carried by the charmed hadron, and the third term is the semi-muonic branching ratio for charmed hadrons. The leading-order parton level process can be written as,

d20(v,N + cX) = 2G:ME ( ’ - mf

2MEu.t )

dt & n(l+ Q2/M$J2

x b(L Q2) + d(J, Q2)1 2 b’d2 + stt, Q2)lK.[2] .

The corresponding process for p scattering can be obtained by replacing the quark distributions with their anti-quark partners.

e

Figure 5. Plots show Evls distributions for v (top) and i7 (bottom) dimuon event samples. Fit- ted contributions from the leading-order strange sea (blue) and from d-quark charm production (green) are shown. The punchthrough background is shown in black.

Figure 5 shows the distribution of the measured total visible energy in the event, EVIS = EILl + E,,2 + EHAD, for u and v dimuon production, where E,I,z are the energies of the two muons in the event, and EHAD is the energy of the hadron shower. Sensitivity to the charm threshold behavior and charm mass parameter, m,, are greatest at low EVIS. Fitted contributions from the leading-order strange sea and from d-quark charm production are shown. The main background (-15%)) from charged-current events with a muon produced from a decaying meson in the shower is also shown. XVTS. defined as

1 _I I

4E,1 &IS sinZeM1’2 xv1s = ~M(&+EHAD) ’ is shown in Figure 6. Sensitivity to the strange sea distribution is greatest at low xvrs.

The leading-order contribution from the strange sea is determined using the parameteri- zation,

s(x) = K ( > y (lmx)“.

170 D. Naples et al. /Nuclear Physics B (Pmt. Suppl.) I18 (2003) 164-173

chi2=14/15 v+ 5102

Figure 6. Plots show XVIS distributions for v (top) and p (bottom) dimuon event samples. Fit- ted contributions from the leading-order strange sea (blue) and from d-quark charm production (green) are shown. The punchthrough background is shown in black.

Fits to the level, n, and shape parameter, cr yield for s(z), ~(v)=O.38 f 0.08 and a(v)=-2.07 f 0.96, and for S(z), @)=0.39 f 0.06 and a(p)=- 2.43 f 0.45. The parametric form for s(x) and S(Z) plotted for the fitted parameters are shown in Figure 7. The extracted seas at leading order are -40% the size of the light quark seas and have no significant asymmetry. The fit also determines a value for m, = 1.33f0.19 GeV, and Collins-Spiller fragmentation parameter [21], c = 2.07 f 0.31.

The sample can also be used to extract a differential cross section for forward dimuon production in E,, x, and y bins. The raw sample is corrected through a deconvolution procedure for smearing and acceptance effects. The Ep2 > 5 GeV requirement selects primarily charm produced forward in the center-of-mass frame, for which acceptance effects should be well modeled by the leading-order fit description. The results are tabulated and presented in Reference [22]. The measured differential cross section can be

0.06

0.1 BGPAR hatched blue GRV dashed black CTEQ dashed red

0.06

X X

Figure 7. NuTeV leading-order strange (left) and anti-strange (right) seas from two parameter fit to level and shape in each mode assuming the form described in equation 1.

used to test charm production models after apply- ing hadronization and decay simulations to obtain the prediction for dimuon production as a function of E, x, and y with a E,z > 5 GeV requirement .

Because the leading-order strange sea is large it is expected that at next-to-leading (NLO) gluon initiated processes will contribute significantly 1231. In a next-to-leading order model differential dependence on charm rapidity, 77, and fragmentation variable, Z, must be described to predict neutrino dimuon production [24]. NuTeV is ex- tending this analysis to extract NLO cross sections and model parameters for comparison and to test &CD.

5. Neutral Current Charm production

Neutrinos can also be used to study charm production through the neutral current process described in Figure 8, URN + V~CEX. Neu- tral current charm production in the standard model occurs when a neutrino scatters off the nucleon charm sea. Final state charm is inferred in

D. Naples et al. /Nuclear Physics B (Proc. Suppl.) 118 (2003) 164-173

Figure 8. Neutrino neutral-current charm production.

NuTeV from the presence of a final state muon produced by charmed-hadron decay. The distinc- tive signature for this process is provided by the muon charge, which is opposite the sign expected for a charged-current event in the beam, for ex- ample a p+ in v-mode and a ~1~ in P-mode. (re- ferred to as a “wrong-sign” event).

v-mode, which has higher beam purity, is used to extract a signal, and v-mode is used to un- derstand and predict the backgrounds. The main background comes from charged-current neutrino events induced by impurities in the beam. The largest source of impurities are from “scraping” (50%) due to secondary interactions in the beamline after the sign-selection, and prompt decays, (primarily D and P) upstream of the sign- selecting dipole magnets. The beam sources are constrained by tuning the spectrum of wrong- signed events in P-mode. Further discrimina- tion is provided by the yvrs distribution of the sample, defined as yvrs = EHAD/(EHAD + I?,.,). The wrong-signed beam related component, P (in v-mode), is expected to be peaked at low yvrs characteristic of the (1 - Y)~ shape expected for charged-current F-N interactions. The signal in-

Figure 9. yvrs distribution for wrong-signed events in u-mode showing contributions from beam-related backgrounds (peaked at low-yvrs) and backgrounds from charged-current charm production process in which the primary lepton is undetected and K or K mesons decays. The signal (shaded) is peaked at high-yvrs.

duced events are expected to be peaked at high yvrs, corresponding the low Eb in the event; in this case the lepton at the primary vertex is a neutrino and the muon results from a charmed meson decay originating from the hadronic vertex. Figure 9 shows the yvrs distribution for expected contributions to background and for the signal shape. High-yvrs contributions to the background come from ucl or v, charged-current charm production in which the primary lepton is undetected, or from x or K mesons in neutral current showers decaying to muons.

The signal is fitted for a contribution from a boson-gluon fusion generated charm sea with a charm-mass-suppressed cross section determined by the fitted value of m = 1 40f0.83 c . o,38 GeV to be:

172 D. Nuples et al. /Nuclear Physics B (Pmt. Suppl.) 118 (2003) 164-l 73

e- ve e- Al.=2

ve

Figure 10. Two purely leptonic processes studied in NuTeV. neutrino-induced standard model allowed process, inverse muon decay, (left), and disallowed lepton number violating process (right).

at average E, = 154 GeV (see [25]). This is the first observation of a neutral-current charm production signal in neutrino scattering. The determination of m, is consistent with the value obtained from charged-current neutrino charm production (see section 4). In addition, the level of charm sea required to generate our signal is consistent with Fiharm measured in charged-lepton scattering [26].

6. Lepton Number Violation

NuTeV’s pure ~~ beam allows a search for the purely leptonic process, FPe- + P-V,. This lepton number violating, (AL = 2), process is forbidden in the standard model, however is allowed in models with multiplicative lepton number conservation [27] and other models (e.g. [28]). NuTeV can also measure the rate for the standard model allowed process, VPe- + p-u, (inverse muon decay, IMD), for comparison. Both processes are shown in Figure 10.

Events are selected with low hadronic energy, EHAD < 3 GeV, and muon PT given by P?(p) < 2m,E,. The right-sign event sample in v mode can be used to measure the rate for the IMD process. The cross section is found to be,

aIMD = 13.8 f 1.2 f 1.4 X 10-42cm2/GeV.

which is in good agreement with previous measurements [29]. A lepton-number violating signal

P: (GeV *)

15

10

5

n “0 0.25 0.5

P; (GeV *)

Figure 11. P+(p) of measured wrong-signed events in v-mode (left) and P-mode (right). A lepton number violating signal would appear as an excess in v-mode.

would appear as wrong-sign events in i7 mode. The primary background is from beam impurities through the process VPe- + p-v, and iTee- + p-FP,. Figure 11 shows the distributions of measured wrong-signed events in i? mode, the wrong-sign sample in Y mode is also shown for comparison. The expected background from beam impurities describes both samples well and a limit on the rate of the lepton-number violating process relative to the IMD-rate is obtained. The process is limited to

< 1.1% (Scalar coupling)

< 2.7% (V - A coupling)

This measurement [30] is currently the best from neutrino-electron scattering, however, more strin- gent limits come from muon decay [31].

6.1. Summary and Future The NuTeV experiment at Fermilab has per-

formed precision tests of the standard model using high-statistics samples of vP and q. The measured value of sin2 19w obtained is in agree-

D. Nuples et al. /Nuclear Physics B (Proc. SuppI,) 118 (2003) 164-l 73 173

ment with previous measurements from v-N scattering but is 3u below the standard model prediction. The high purity beams also allow the study of rare processes such as neutral-current charm production, purely leptonic v,(q)-electron scattering, and standard model charged-current charm production.

The charged-current vp and q data samples in NuTeV, currently being analyzed, will provide new information on parton structure and &CD. The sign-selected beam allows this sample to include high-inelasticity (y) events. The extended y range will allow lever arm to improve QCD and structure function measurements. The improved understanding of the absolute energy scale in NuTeV (approximately a factor of two), obtained using the in-situ precision calibration beam, will reduce systematic uncertainties in QCD measurements and the determination of os.

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