Summary of Work on Possible NuTeV Explanations

 2004 NuTeV Talks:
 Recent NuTeV Papers and
Publications:
 Moriond QCD proceedings, D. Mason et al., "New Strange Asymmetry
Results from NuTeV",
hepex/0405037
 Zeuthen EW workshop proceedings: K.S. McFarland and SO. Moch,
hepph/0306052
 NuInt01 proceedings: K.S. McFarland et al.,
Nucl. Phys. Proc. Suppl. 112, 226 (2002)
 PIC02 proceedings: K.S. McFarland et al.,
hepex/0210010
 Response to Miller/Thomas comment on shadowing: G.P. Zeller et
al.,
hepex/0207052
 Effect of PDF asymmetries: G.P. Zeller et al.,
Phys. Rev. D65,
111103 (2002)
 The NuTeV sin2thw result: G.P. Zeller et al.,
Phys. Rev. Lett. 88, 091802 (2002)
 G.P. Zeller thesis

NLO QCD corrections:
 NuTeV analysis is not strictly LO, so some of these effects
have been taken into account (ex. longitudinal SF)
 NLO corrections are expected to be small in R, but should be
reevaluated for NuTeV experimental cuts and analysis
 Davidson et al. first to point out this effect should be small
 NuTeV currently working with Fermilab theory group to implement
a full NLO model in the analysis

Electroweak Radiative Corrections:
 NuTeV analysis relies on a single calculation of EW radiative
corrections (the only corrections currently available)  by
Bardin and Dokuchaeva (JINRE286260); however
additional cross checks would be prudent
 Davidson et al. assert that higher order EW corrections do not
have any relevant impact on NuTeV discrepancy because higher order
corrections are usually related to large top mass, and g_L^2 has
limited sensitivity to Mtop
 Diener et al. calculation includes improved treatment of
initial state mass singularities; they investigate impact of
updated radiative corrections on NuTeV sin2thw. Several
assumptions were made on parameter/input/kinematic choices
employed in NuTeV radiative correction calculation. The analysis
is based on shifts in R^nu, but do some of these effects to
cancel in R? In addition to evaluating impact on R^nubar,
also need compute effect of new radiative corrections using
NuTeV experimental cuts and energy spectrum
 Deiner et al. and Arbuzov et al. have each recently
supplied NuTeV with versions of their radiative correction
code. NuTeV is working with both sets of authors to incorporate
their codes into the NuTeV Monte Carlo
 Additional calculation by BaurWackeroth is also in progress
 O. Brein, B. Kock, and W. Hollik,
hepph/0408331 < considers loop effects in MSSM
 A.B. Arbuzov and D. Yu Bardin,
hepph/0407203
 K.P.O. Diener,
hepph/0311122
 K.P.O. Diener, S. Dittmaier, W. Hollik, Phys. Rev. D69, 073005
(2004),
hepph/0310364
 S. Davidson et al., JHEP 0202:037 (2002),
hepph/0112302

Strange Sea Asymmetry:

Isospin Violation:
 NuTeV assumes exact isospin symmetry in the analysis
(d^p=u^n, u^p=d^n), but has investigated effect of several isospin
violation models on NuTeV results
( Phys. Rev.
D65, 111103 (2002))
 model calculations vary, but can produce a sizable
effect on NuTeV sin2thw extraction; major difference between
NuTeV estimates and those of Londergan et al. is that the former
evaluated isospin violation effect including diquark smearing
(source: E.N. Rodionov, A. W. Thomas, and J.T. Londergan, Mod.
Phys. Lett. A9, 1799 (1994)) while latter did not. Given that
model appears to be highly sensitive to choice of diquark
width in the final state, NuTeV has concluded that such models are
not very predictive
 MRST has performed a global analysis including possibility
of isospin violation with a particular functional form; weak
indication given by global fit
that isospin violating valence PDFs could potentially reduce
NuTeV discrepancy by 11.5 sigma, although range of allowed isospin
violation could also remove discrepancy altogether or make it
worse; conclusion is that existing data allows level of isospin
violation which could either solve NuTeV discrepancy or make it
worse
 more experimental data needed to constrain possible isospin
violation (i.e.
FNAL P906)

Nuclear Shadowing:
 August 2004: new paper by Brodsky et al.on nuclear
antishadowing (see below). The effect appears to reside
entirely in R^nubar (the NuTeV control sample), so this solution
does not appear to fit NuTeV's separate measurements of R^nu and
R^nubar. This explanation leaves us with a situation in
which both R^nu and R^nubar are nearly 3 standard deviations low.
NuTeV has requested that the authors provide us with
parametrizations of the effect on the quark distributions
(Figs 7,8) at a variety of different Q^2 values so that we
can include the effect in the NuTeV analysis and evaluate
the full effect
 Miller and Thomas assert that NuTeV discrepancy can "entirely be
accounted for or hugely enhanced" by a difference in shadowing
effects in NC versus CC interactions
 NuTeV points out that while differences in NC and CC shadowing
significantly affect R^nu and R^nubar (though such corrections
actually increase the discrepancy in NuTeV experimental R^nu,
R^nubar), they largely cancel and cannot induce a significant
shift in R^ and hence NuTeV sin2thw

Other Nuclear Effects:
 NuTeV does take into account the neutron excess in our target
and nuclear cross section effects (via extracting
NuTeVspecific PDFs on NuTeV target, assuming NuTeV cross section
model)
 however, if nuclear effects are process dependent
(i.e. not universal for NC and CC interactions), then
they could affect NuTeV's sin2thw extraction
 Kumano has fit nuclear target data to investigate possibility
of flavor dependent nuclear corrections (i.e. different
corrections for valence u and d quarks); interesting work but
effect is small (delta sin2thw = 0.0002 > 0.0005) since
mainly affects high x, low Q^2 region where there is little
NuTeV experimental data
 Kulagin has argued that treatement of the neutron excess
correction may well explain a large part of NuTeV discrepancy,
but neutron excess of NuTeV target is very wellknown from
detailed materical survey of the NuTeV target. Kulagin
also pointed out that NuTeV d/u uncertainty too small, as
a result NuTeV systematic has been reevaluated and
delta sin2thw = +/ 0.0003 is the new estimate.
Kulagin also concluded that Fermi motion, nuclear binding
corrections, and shadowing effects are small for NuTeV
 Kovalenko et al. have suggested that there may be no EMC effect
in CC, but expected EMC effect in NC at high x; however such
a possibility is strongly excluded by CCFR CC cross section
measurement (U.K. Yang et al.,
Phys. Rev. Lett.
86, 2742 (2001))
 S.A. Kulagin and R. Petti,
hepph/0412425  global study of nuclear structure
functions
 S. Kumano et al.,
hepph/0412284,
hepph/0412307,
hepph/0307105,
hepph/0209200
 S.A. Kulagin,
hepph/0409057,
hepph/0406220 and
hepph/0301045, Phys. Rev. D67, 091301 (2003)
 S. Kovalenko et al.,
hepph/0207158
 K.S. McFarland et al., Nucl. Proc. Suppl. 112, 226 (2002)

Electron Neutrino Content in the NuTeV Beam:
 recent BNLE865 measurement of K+e3 branching ratio is 6% higher
than the PDG value used in the NuTeV analysis; higher branching
ratio would INCREASE NuTeV discrepancy by roughly 1 sigma;
appears to be confirmed by recent KTeV, KLOE results
 Ed Blucher's FNAL wine and cheese
talk (new KTeV results)
 J. Thompson, D.E. Krauss,
hepex/0307053 (new BNL E865 Ke3 BR)
 Giunti and Laveder suggest that a P(nu_e > nu_s)=0.21+/0.07
at delta m^2=10100 eV^2 could explain the NuTeV result, but
it is not clear whether such oscillation parameters are consistent
with disappearance experiments (BUGEY, CHOOZ), and furthermore
NuTeV directly measures its nu_e content to a few percent:
NuTeV published results on numu > nue search (S. Avvakumov et
al. Phys. Rev.
Lett. 89, 011804 (2002))

Supersymmetry:
 it is difficult to explain NuTeV results in the framework of the
MSSM; SUSY corrections are typically positive and hence in the
wrong direction; however, could potentially be accounted for in
extended supersymmetric models (ala Babu/Pati)

Other Beyond the Standard Model Effects:
 model building around the NuTeV result is challenging
 R.N. Mohapatra et al., "Theory of Neutrinos",
hepph/0412099 (prt of APS neutrino study  see Chapter
VIII B, page 29+ for NuTeV discussion)
 G. Prezeau et al., "Neutrino Mass Constraints on mudecay
and pi^0>nu nubar",
hepph/0409193
 M.A. Perez, "Two Body Z' Decays in the Minimal 331 Model",
hepph/0402156, Phys. Rev. D69, 115004 (2004)
 E. Ma, "Different G_F and sin2thw for Different Processes",
hepph/0306218
 E. Nardi et al., "On the Neutrino Vector and Axial Vector Charge
Radius",
hepph/0212266 and
hepph/0210137
 X. Li and E. Ma, "Gauge Model of QuarkLepton Nonuniversality",
hepph/0212029
 E. Ma and D.P. Roy, "Anomalous Neutrino Interaction, Muon g2,
and Atomic Parity Nonconservation",
hepph/0111385
 S. Davidson et al., "Old and New Physics Interpretations
of the NuTeV Anomaly", JHEP 0202:037 (2002),
hepph/0112302

Precision Electroweak Data Global Fits and Summaries
 T. Takeuchi and W. Loinaz,
hepph/0410201
 J. Erler and P. Langacker,
hepph/0407097  2004 Review of Particle Properties
 J.H. Field,
hepex/0407040
 G. Altarelli,
hepph/0406270
 J. Erler and M. RamseyMusolf,
hepph/0404291
 W. Loinaz, N. Okamura, T. Takeuchi, and L.C.R. Wijewardhana,
hepph/0403306,
hepph/0210193, Phys. Rev. D67, 073012 (2003)
 M. Chanowitz,
Phys. Rev. D66, 073002 (2002),
hepph/0304199
last updated on March 4, 2005
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