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Meson cloud and nucleon strangeness: an update F.S. N., F. Carvalho, M. Nielsen University of São Paulo Brazil H. Forkel, F. Navarra, M. Nielsen, PRC 61,

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Presentation on theme: "Meson cloud and nucleon strangeness: an update F.S. N., F. Carvalho, M. Nielsen University of São Paulo Brazil H. Forkel, F. Navarra, M. Nielsen, PRC 61,"— Presentation transcript:

1 Meson cloud and nucleon strangeness: an update F.S. N., F. Carvalho, M. Nielsen University of São Paulo Brazil H. Forkel, F. Navarra, M. Nielsen, PRC 61, (2000) F. Carvalho, F. Navarra, M. Nielsen, PRC 72, (2005) New data: A4 (2004); SAMPLE (2004); HAPPEX (2005); G0 (2005) F. Carvalho, F. Navarra, M. Nielsen, (2006), in progress

2 Strange sea quarks in the nucleon: theory : pQCD theory : lattice QCD, CHPT, models Strange meson loops: “the meson cloud” p High Q 2 experiment: deep inelastic scattering Low Q 2 experiment: parity violating e - scattering at TJNAF p K K

3 Assumptions: Convergence of Fock-state expansion: lighter states dominate Multiloop contributions are suppressed Motivation New data: SAMPLE(04), HAPPEX(05), MAMI(05), G0(05) arbitrary cut-off parameter functional form Regularization with form factors: New strange meson: E791 (2001) m = 800 MeV

4 Meson Loops M = B = seagull terms ~ 30 diagrams Ward – Takahashi identity Decuplet baryons neglected Malheiro Melnitchouk (1997)

5 Calculation Feynman rules: vertices and propagators : Regularization with form factors from Bonn-Jülich or Nijmegen potential

6 Dynamics transition meson baryon meson photon meson Y. Oh, H. Kim, PRC (2006)

7 Couplings Nijmegen: Rijken, Stoks, Yamamoto (1999) (Nijmegen NSC97f) Y. Oh, H. Kim, PRC (2006)

8 Strange form factors

9 SAMPLE Strange magnetic form factor G M Forkel, Navarra, Nielsen, PRC (2000) PRL, 78, 3824 (1997) PRL, 84, 1106 (2000)

10 Carvalho, Navarra, Nielsen, (2006) Strange magnetic form factor G M GMGM Q2Q2 ( GeV 2 ) No

11 Forkel, Navarra, Nielsen, PRC (2000) HAPPEX PRL, 82, 1096 (1999)

12 Strange electric form factor G E Carvalho, Navarra, Nielsen, PRC (2005)

13 (2005) Carvalho, Navarra, Nielsen, PRC (2005) nucl-ex/ PRL, 93, (2004) PRL, 94, (2005) nucl-ex/

14 Carvalho, Navarra, Nielsen, PRC (2005)

15 “best” case“worst”case Including Carvalho, Navarra, Nielsen, (2006)

16 Q2Q2 ( GeV 2 ) “best” case “worst”case Carvalho, Navarra, Nielsen, (2006)

17 Summary and conclusion Meson cloud model with: Parameters: coupling constants and cut-offs: Decuplet states withwere not considered Calculation of the nucleon strange form factors 2000: marginal description of G M and G E only withsuppression:Nijmegen 2005: no description of G M, marginal description of G E for larger Q 2 and FF s : no agreement ! includingmarginal agreement!

18 Appendix Goity, Musolf (1996) K* - K transition m K = 495 MeVm K* = 895 MeVm  = 800 MeV Masses

19 Some references: W. Köpf, E. Henley (1994) W. Köpf, S.J. Pollock, E. Henley (1992) T. Cohen, H. Forkel, M. Nielsen (1993) M. Musolf, M. Burkardt (1993) H. Forkel, M. Nielsen, X. Jin, T. Cohen (1994) Barz, Forkel, Hammer, Navarra, Nielsen, Ramsey-Musolf (1998) H. Forkel, F. Navarra, M. Nielsen (2000) F. Carvalho, F. Navarra, M. Nielsen (2005) Data: A4 (2004); SAMPLE (2004); HAPPEX (2005); G0 (2005) Data: SAMPLE (1997); HAPPEX (1999) W. Melnitchouk, M. Malheiro (1997) ; (1999)...

20 K K B K * K * B K K * B Strange Dirac form factor F 1  K =  K* = 1.2 GeV

21 Strange Pauli form factor F 2 K K B K * K * B K K * B

22 Strangeness radius K K B K * K * B K K * B total

23 Strangeness magnetic moment  s total K K * B K * K * B K K B

24 Strangeness radius -1.59, , , , , 2.0

25 -1.59, , , , , 4.0 Strangeness magnetic moment  s

26 Strange magnetic form factor G M Carvalho, Navarra, Nielsen, PRC (2005)


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