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NuTeV Anomaly & Strange-Antistrange Asymmetric Sea. Bo-Qiang Ma Department of Physics, Peking University August 16, 200 4, talk at ICHEP04, Beijing. ?. In collaboration with Yong Ding PLB590(2004)216 hep-ph/0405178. Outline. The NuTeV anamoly and Paschos-Wolfenstein relation

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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


Outline
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


Weinberg angle from nuetrino dis nutev anamoly
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


  • The Paschos-Wolfenstein relation

  • The assumptions for the P-W relationship

    a isoscalar target

    b charge symmetry

    c symmetric strange and antistrange distributions


  • 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


  • 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)


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) )


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



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/0404240, S.Catani et al.


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



Strange antistrange asymmetry in phenomenological analyses
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


A brief comment
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


Modified p w relationship
Modified P-W relationship

  • The cross section for neutrino-nucleon DIS

    a for neutral current interaction


b for charged current interaction

  • The structure functions of neutral current



-

  • The modified P-W relation


Strange antistrange asymmetry
Strange-antistrange asymmetry

  • In light-cone baryon-meson fluctuation model

  • The dominant baryon-meson configuration for s-sbar






The probabilities for meson baryon fluctuation
The probabilities for meson-baryon fluctuation

  • General case

  • Our case

Brodsky & Ma, PLB381(96)317

Ma, Schmidt, Yang, EPJA12(01)353



The results for
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


The results
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


S x sbar x asymmetry
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


A further chiral quark model study
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.


Summary
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


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