NuTeV Anomaly & Strange-Antistrange Asymmetric Sea

1. NuTeV Anomaly & Strange-Antistrange Asymmetric Sea Bo-Qiang Ma Department of Physics, Peking University August 16, 2004, talk at ICHEP04, Beijing ? In collaboration with Yong Ding PLB590(2004)216 hep-ph/0405178

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 • Summary

3. Weinberg 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 in conventional physics

4. The Paschos-Wolfenstein relation • The assumptions for the P-W relationship a isoscalar target b charge symmetry 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; S. Davidsonet. al(JHEP,0202: 037,2002), no exactly correction.) b nuclear shadowing and anti-shadowing effect (S. Kuvalenko, I. Schmit and J.J,Yang (杨建军）(PLB546:68,2002), gave the correction changes its sign from-0.00098to 0.00178; J. W, QiuandI. Vitev(hep-ph/0401062), providing2%for the discrepancy) c EMC effect

6. Charge symmetry violation Perturbative method a quark model (E. Sather, (PLB274:433,1992)) obtained the correction is -0.002, which could reduce the discrepancy40%) b twist two valence parton distributions (J. T. Londergan and A. W. Thomas, (PLB558:132,2003;PRD 67:111901, 2003)) obtained the result should remove roughly one-third of the discrepancy)

7. c comparing the structure functions (C. Boros, J. T. LonderganandA. W. Thomas (PRL81:4075,1998;PRD59:074021,1999) thought the CSV in the nucleon seais predominant andmuch larger than the valence quarks) d 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. hep-ph/0404240, S.Catani et al.

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. Mechanism for S-Sbar asymmetry _ \ s(x)=s(x)

13. 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

14. 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

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

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

17. 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 • 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.

31. Summary • Checked the influence due to strange-antistrange asymmetry and derived the modified Paschos-Wolfenstein relation • Conclude that the correction due to the strange-antistrange asymmetry might be important to explain the NuTeV anamoly