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

2 Outline The NuTeV anamoly and Paschos-Wolfenstein relationThe NuTeV anamoly and Paschos-Wolfenstein relation A brief review on strange-antistrange asymmetry of the nucleon seaA brief review on strange-antistrange asymmetry of the nucleon sea The strange-antistrange asymmetry in the light- cone baryon-meson fluctuation mdelThe strange-antistrange asymmetry in the light- cone baryon-meson fluctuation mdel SummarySummary

3 Weinberg Angle from Nuetrino DIS: NuTeV Anamoly NuTeV Collaboration reported result, PRL88(02) 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 is small ; S. A. Kulagin (PRD67:091301,2003), gave the correction is ; S. Davidson et. 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 to ; J. W, Qiu and I. Vitev (hep-ph/ ), providing 2% for the discrepancy) c EMC effect

6 Charge symmetry violation Perturbative method a quark model (E. Sather, (PLB274:433,1992)) obtained the correction is , which could reduce the discrepancy 40% ) 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. Londergan and A. W. Thomas (PRL81:4075,1998;PRD59:074021,1999) thought the CSV in the nucleon sea is predominant and much larger than the valence quarks) d other calculations about CSV (B. Q. Ma (PLB274:111,1992); C. J. Benesh and T. Goldman (PRC55:441,1997) R. M. Davidson and M. Burkardt (PLB403:134,1997); C. J. Benesh and J. 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. Cao and A.I. Signal, PLB559(03)229 it is concluded that the asymmetry of the strange and anti-strange is small and could not affect the discrepancy

10 The Strange-Antistrange Asymmetry 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/ , S.Catani et al.

11 Strange-Antistrange Asymmetry from 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/ CTEQ Global Analysis, F. Olness et. al (hep-ph/ ), 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

18

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 to (0.0009) For power law wave function the discrepancy from to (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