• NuTeV result: sin2thw= 0.22773 +/- 0.00135 (stat) +/- 0.00093 (syst)
  which is ~3 sigma above the standard model prediction of 0.2227 +/- 0.00037

• 2004 NuTeV Talks:
  • M. Shaevitz, talk on "Electroweak Measurements at NuTeV: Are Neutrinos Different?", Stockholm Symposium on Neutrino Physics, August 2004
  • K.S. McFarland talk on "Status of the NuTeV Electroweak Anomaly" at PEP04 (From Zero to Z0 Workshop), May 12, 2004
  • P. Spentzouris talk on "Strange Sea Asymmetry Results from NuTeV" at DIS04, April 16, 2004
  • D. Mason talk on "New Strange Sea Results from NuTeV" at Moriond QCD, March 31, 2004

• Recent NuTeV Papers and Publications:
  • Moriond QCD proceedings, D. Mason et al., "New Strange Asymmetry Results from NuTeV", hep-ex/0405037
  • Zeuthen EW workshop proceedings: K.S. McFarland and S-O. Moch, hep-ph/0306052
  • NuInt01 proceedings: K.S. McFarland et al., Nucl. Phys. Proc. Suppl. 112, 226 (2002)
  • PIC02 proceedings: K.S. McFarland et al., hep-ex/0210010
  • Response to Miller/Thomas comment on shadowing: G.P. Zeller et al., hep-ex/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

• Topics:
  • NLO QCD Corrections
  • Electroweak Radiative Corrections
  • Strange Sea Asymmetry
  • Isospin Violation
  • Nuclear Shadowing
  • Other Nuclear Effects
  • Electron Neutrino Content in the Beam
  • Supersymmetry
  • Other Beyond the Standard Model Effects
  • Global Fits to the Data

• 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 re-evaluated 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
    • B. Dobrescu and K. Ellis, hep-ph/0310154
    • S. Kretzer, M.H. Reno, hep-ph/0307023
    • K. McFarland and S. Moch, hep-ph/0306052
    • S. Davidson et al., JHEP 0202:037 (2002), hep-ph/0112302

• Electroweak Radiative Corrections:
  • NuTeV analysis relies on a single calculation of EW radiative corrections (the only corrections currently available) - by Bardin and Dokuchaeva (JINR-E2-86-260); 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 Baur-Wackeroth is also in progress
    • O. Brein, B. Kock, and W. Hollik, hep-ph/0408331 <-- considers loop effects in MSSM
    • A.B. Arbuzov and D. Yu Bardin, hep-ph/0407203
    • K.P.O. Diener, hep-ph/0311122
    • K.P.O. Diener, S. Dittmaier, W. Hollik, Phys. Rev. D69, 073005 (2004), hep-ph/0310364
    • S. Davidson et al., JHEP 0202:037 (2002), hep-ph/0112302

• Strange Sea Asymmetry:
  • NuTeV can internally constrain strange sea from dimuon data, and has evaluated the possibility of a strange sea asymmetry in a variety of ways:
    • NLO dimuon (P. Spentzouris DIS 2004 talk): consistent with zero asymmetry (this work performed in collaboration with Amundson, Kretzer, Olness, and Tung who kindly provided us with necessary tools)
    • NLO dimuon (D. Mason ICHEP 2002 talk): consistent with zero asymmetry
    • LO dimuon ( Phys. Rev. D65, 111103 (2002)): weakly negative asymmetry using NuTeV iron PDFs
    • LO dimuon result (M. Goncharov et al. Phys. Rev. D64, 112006 (2001)): consistent with zero asymmetry

    NLO NuTeV strange sea asymmtry appears to be consistent with the measured asymmetry at LO. Both tend towards a negative s-sbar asymmetry at the lowest x bin data points. Neither yield the large positive s-sbar asymmetry obtained by CTEQ. Enforcing number sum rule and use of CTEQ evolution code (which separately evolves s and sbar) do not appear to have a large effect on the NuTeV results. NuTeV is currently working with CTEQ to resolve differences between their two differing results.

  • update of BPZ fits shown by B. Portheault at DIS03 consistent with no asymmetry

  • CTEQ global fit suggests possibility of a positive strange sea asymmetry; CTEQ has a range of global fits with different assumptions yielding -0.001 < [S-] < 0.004, which implies a large uncertainty in NuTeV sin2thw: -0.005 < delta sin2thw < 0.001

  • Also see NuTeV/CTEQ discussion in neutrino seesion at WIN03
    • B. Ma, hep-ph/0412324 -- ignores experimental constraints from dimuon data (author has been contacted by NuTeV on this point; author says this will be subject of a longer paper currently in preparation)
    • J. Alwall, hep-ph/0412286
    • M. Wakamatsu, hep-ph/0411203 NLO Moriond results and ignores limits on the strange sea excess at high x in Phys. Rev. D64, 112006 (2001)
    • Y. Ding, R. Xu, and B. Ma, hep-ph/0408292 <-- doesn't agree with NuTeV dimuon measurement of separate s and sbar
    • J. Alwall and G. Ingelman, hep-ph/0407364
    • B. Portheault, hep-ph/0406226
    • Y. Ding and B. Ma, hep-ph/0405178
      • NuTeV has indicated to authors that their calculation would be more clear if they used more recent data available on s-sbar and and its effect on NuTeV sin2thw
    • S. Catani et al., hep-ph/0404240, hep-ph/0406338 <-- perturbative generation of asymmetry at NNLO
    • F. Olness et al., hep-ph/0312323, hep-ph/0311064
    • S. Kretzer et al., hep-ph/0312322, hep-ph/0408287
    • G.P. Zeller et al., hep-ex/0203004

• 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 1-1.5 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)
    • M. Gluck, P. Jimenez-Delgado, E. Reya, hep-ph/0501169 -- radiatively generated isospin violation
    • F.M. Steffens and K. Tsushima, hep-ph/0408018 -- charge symmetry violation at very large x
    • J.T. Londergan and A.W. Thomas, hep-ph/0407247
    • A.D. Martin et al. (MRST global fit), hep-ph/0411040, hep-ph/0308087
    • J.T. Londergan and A.W. Thomas, hep-ph/0303155
    • J.T. Londergan and A.W. Thomas, hep-ph/0301147

• 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
    • S.J. Brodsky, hep-ph/0412101, hep-ph/0411056
    • S.J. Brodsky et al., SLAC-PUB-9677 (Aug 2004)
    • G.P. Zeller et al., hep-ex/0207052
    • G.A. Miller and A.W. Thomas, hep-ex/0204007

• Other Nuclear Effects:
  • NuTeV does take into account the neutron excess in our target and nuclear cross section effects (via extracting NuTeV-specific 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 well-known 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 re-evaluated 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, hep-ph/0412425 -- global study of nuclear structure functions
    • S. Kumano et al., hep-ph/0412284, hep-ph/0412307, hep-ph/0307105, hep-ph/0209200
    • S.A. Kulagin, hep-ph/0409057, hep-ph/0406220 and hep-ph/0301045, Phys. Rev. D67, 091301 (2003)
    • S. Kovalenko et al., hep-ph/0207158
    • K.S. McFarland et al., Nucl. Proc. Suppl. 112, 226 (2002)

• Electron Neutrino Content in the NuTeV Beam:
  • recent BNL-E865 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, hep-ex/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=10-100 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))
    • J.S. Ma et al. hep-ex/0501011 -- can a 3+2 oscillation model explain NuTeV?
    • C. Giunti and M. Laveder, hep-ph/0202152

• 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)
    • A. Kurylov, M.J. Ramsey-Musolf, S. Su, hep-ph/0309027
    • K.S. Babu and J.C. Pati, hep-ph/0203029 (ESSM SO(10))
    • S. Davidson et al., JHEP 0202:037 (2002), hep-ph/0112302

• Other Beyond the Standard Model Effects:
  • model building around the NuTeV result is challenging
    • R.N. Mohapatra et al., "Theory of Neutrinos", hep-ph/0412099 (prt of APS neutrino study - see Chapter VIII B, page 29+ for NuTeV discussion)
    • G. Prezeau et al., "Neutrino Mass Constraints on mu-decay and pi^0-->nu nubar", hep-ph/0409193
    • M.A. Perez, "Two Body Z' Decays in the Minimal 3-3-1 Model", hep-ph/0402156, Phys. Rev. D69, 115004 (2004)
    • E. Ma, "Different G_F and sin2thw for Different Processes", hep-ph/0306218
    • E. Nardi et al., "On the Neutrino Vector and Axial Vector Charge Radius", hep-ph/0212266 and hep-ph/0210137
    • X. Li and E. Ma, "Gauge Model of Quark-Lepton Nonuniversality", hep-ph/0212029
    • E. Ma and D.P. Roy, "Anomalous Neutrino Interaction, Muon g-2, and Atomic Parity Nonconservation", hep-ph/0111385
    • S. Davidson et al., "Old and New Physics Interpretations of the NuTeV Anomaly", JHEP 0202:037 (2002), hep-ph/0112302

• Precision Electroweak Data Global Fits and Summaries
  • T. Takeuchi and W. Loinaz, hep-ph/0410201
  • J. Erler and P. Langacker, hep-ph/0407097 -- 2004 Review of Particle Properties
  • J.H. Field, hep-ex/0407040
  • G. Altarelli, hep-ph/0406270
  • J. Erler and M. Ramsey-Musolf, hep-ph/0404291
  • W. Loinaz, N. Okamura, T. Takeuchi, and L.C.R. Wijewardhana, hep-ph/0403306, hep-ph/0210193, Phys. Rev. D67, 073012 (2003)
  • M. Chanowitz, Phys. Rev. D66, 073002 (2002), hep-ph/0304199

last updated on March 4, 2005
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