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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


  • 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

(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


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

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

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.
  • 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