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NuTeV Anomaly v ersus Strange Antistrange Asymmetry

NuTeV Anomaly v ersus Strange Antistrange Asymmetry. Bo-Qiang Ma Department of Physics, Peking University June 17, 200 5 at Internal Conference on QCD and Hadronic Physics. ?.

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NuTeV Anomaly v ersus Strange Antistrange Asymmetry

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  1. NuTeV Anomaly versus Strange Antistrange Asymmetry Bo-Qiang Ma Department of Physics, Peking University June 17, 2005 at Internal Conference on QCD and Hadronic Physics ? In collaboration with S.J. Brodsky, X.-Q. Li, X.-B. Zhang, and Yong Ding, PLB590(2004)216 Yong Ding, Rong-Guang Xu, PLB607(2005)101 Yong Ding, Rong-Guang Xu, PRD71(2005) 094014

  2. Outline • The NuTeV anamoly and Paschos-Wolfenstein relation • A brief review on strange-antistrange asymmetry of the nucleon sea • The strange-antistrange asymmetry in the light-cone baryon-meson fluctuation mdel • The strange-antistrange asymmetry in the chiral quark model • Summary

  3. Weinberg (or weak mixing) Angle from Nuetrino DIS: NuTeV Anamoly • NuTeV Collaboration reported result, PRL88(02)091802 • Other electroweak processes • The three standard deviations could be an indication of new physics beyond standard model if it cannot be explained within conventional physics

  4. The Paschos-Wolfenstein relation • The assumptions for the P-W relationship a isoscalar target b charge symmetry or isospin symmetry between p and n c symmetric strange and antistrange distributions

  5. Non-isoscalar target correction a neutron excess correction(p<n) S. Kumano(PRD66:111301,2002), the correction issmall; S. A. Kulagin(PRD67:091301,2003), gave the correction is-0.004. b nuclear shadowing and anti-shadowing effect & EMC effect S. Kuvalenko, I. Schmit and J.J,Yang (杨建军）(PLB546:68,2002), correction varies from-0.00098to 0.00178; Brodsky-Schmidt-Yang (PRD70:116003,2004), talk by I.Schmidt at this conference J.W. QiuandI. Vitev(PLB587:52,2004), provideda modificationto the discrepancy;

  6. Charge symmetry violation a quark model E. Sather, (PLB274:433,1992) obtained the correction as of -0.002, which could reduce the discrepancy by 40% b twist two valence parton distributions J. T. Londergan and A.W. Thomas, (PLB558:132,2003; PRD 67:111901, 2003)) obtained the result which could remove roughly one-third of the discrepancy or with more large uncertainties

  7. other calculations about CSV B.-Q. Ma (PLB274:111,1992); C.J. BeneshandT. Goldman (PRC55:441,1997) R.M. DavidsonandM. Burkardt (PLB403:134,1997); C.J. BeneshandJ.T. Londergan (PRC58:1218,1998) C. Boros,et. al (PLB468:161,1999)

  8. non-perturbative method meson cloud model F. G. Cao (曹福广)and A. I. Signal (PRC62:015203,2000), found the CSV in both the valence quark distribution and the nucleon sea are smaller (below 1%) than most quark model predictions (2%-10%) and did not give the correction to the discrepancy

  9. Asymmetric strange-antistrange sea quark distributions meson cloud model: F. G. CaoandA.I. Signal, PLB559(03)229 it is concluded that the asymmetry of the strange and anti-strange issmalland could not affectthe discrepancy

  10. The Strange-Antistrange Asymmetry The strange quark and antiquark distributions are symmetric at leading-orders of perturbative QCD However, it has been argued that there is strange-antistrange distribution asymmetry in pQCD evolution at three-loops from non-vanishing up and down quark valence densities. S.Catani et al. PRL93(2004)152003

  11. Strange-Antistrange Asymmetryfrom Non-Perturbative Sources • Meson Cloud Model A.I. Signal and A.W. Thomas, PLB191(87)205 • Chiral Field M. Burkardt and J. Warr, PRD45(92)958 • Baryon-Meson Fluctuation S.J. Brodsky and B.-Q. Ma, PLB381(96)317

  12. The strange-antistrange asymmetry in a microscopic model X.Q.Li, X.B.Zhang, B.Q.Ma (PRD65 (01) 014003) there exists an obvious mass difference due to medium effect between strange and anti-strange quarks, as large as 10-100 MeV, which can produce more sbar at small x and more s at large x.

  13. Mechanism for s-sbar asymmetry _ \ s(x)=s(x)

  14. Strange-Antistrange Asymmetry in phenomenological analyses • V. Barone et al. Global Analysis, EPJC12(00)243 • NuTeV dimuon analysis, hep-ex/0405037 • CTEQ Global Analysis, F. Olnesset. al (hep-ph/0312323), With large uncertainties

  15. A brief comment More precision determinations of strange-antistrange asymmetry should be performed or some sensitive quantities should be used to measure the strangeness asymmetry

  16. Modified P-W relationship • The cross section for neutrino-nucleon DIS a for neutral current interaction

  17. b for charged current interaction • The structure functions of neutral current

  18. The structure functions of charged current

  19. - • The modified P-W relation

  20. strange-antistrange asymmetry • In light-cone baryon-meson fluctuation model • The dominant baryon-meson configuration for s-sbar

  21. Mechanism for S-Sbar asymmetry

  22. Proton wave functions

  23. The momentum distributions

  24. The probabilities

  25. The probabilities for meson-baryon fluctuation • General case • Our case Brodsky & Ma, PLB381(96)317 Ma, Schmidt, Yang, EPJA12(01)353

  26. The distributions for

  27. The results for • For Gaussian wave function • For power law wave function However, we have also very large Qv (around a factor of 3 larger) in our model calculation, so the ratio of S‾/Qv is reasonable

  28. The results B.-Q.Ma, Y. Ding, PLB590(2004)216 • For Gaussian wave function the discrepancy from 0.005 to 0.0033(0.0009) • For power law wave function the discrepancy from 0.005 to 0.0036(0.0016) Remove the discrepancy 30%-80% between NuTev and other values of Weinberg angle

  29. s(x)/sbar(x) asymmetry s(x)/sbar(x) could be compatible with data by by including some intrinsic strange sea contributions CCFR and NuTeV experimental analyses break net zero strangeness

  30. A Further Chiral Quark Model Study • A further study by using chiral quark model also shows that this strange-antistrange asymmetry has a significant contribution to the Paschos-Wolfenstein relation and can explain the anomaly without sensitivity to input parameters. R.Ding, R.-G.Xu, B.-Q.Ma, PLB607 (2005) 101

  31. The Effective Chiral Quark Model • Established by Weinberg, and developed by Manohar and Georgi, has been widely accepted by the hadron physics society as an effective theory of QCD at low energy scale. • Applied to explain the Gottfried sum rule violation by Eichten, Hinchliffe and Quigg, PRD 45 (92) 2269. • Applied to explain the proton spin puzzle by Cheng and Li, PRL 74 (95) 2872.

  32. Chiral Quark Model • The Lagrangian • Effective Lagrangian between GS bosons and quarks

  33. The Effective Chiral Quark Model

  34. Two different inputs of valence quark distributions 1、Constituent Quark Model： 2、CTEQ6parametrization

  35. The distributions of within the chiral quark model

  36. The distributions for

  37. R.Ding, R.-G.Xu, B.-Q.Ma, PLB607(2005)101 The results for different inputs within the effective chiral quark model • The results can remove the deviation at least 60%

  38. R.Ding, R.-G.Xu, B.-Q.Ma, PRD71(2005) 094014 The strange and antiatrange distributions within effective chiral quark model

  39. R.Ding, R.-G.Xu, B.-Q.Ma, PRD71(2005) 094014 The comparison for between the model calculation and experiment data The shadowing area is the range of NuTeV Collaboration, the left side is the result of the chiral quark model only, and the right side is with an additional symmetric strange sea contribution.

  40. Several works with similar conclusion • Ding-Ma, 30-80% correction PLB590 (2004) 216 • Alwall-Ingelman, 30% correction PRD70 (2004) 111505(R) • Ding-Xu-Ma, 60-100% correction PLB607 (2005) 101, PRD71 (2005) 094014 • Wakamatsu, 70-110% correction PRD71 (2005) 057504

  41. Summary • The effect due to strange-antistrange asymmetry might be important to explain the NuTeV anamoly or the NuTeV anomaly could be served as an evidence for the s-sbar asymmetry. • The calculated s-sbar asymmetry are compatiable with the data by including some additional symmetric strange quark contribution. • Reliable precision measurements are needed to make a crucial test of s-sbar asymmetry.

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