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Strangeness in the nucleon .

Strangeness in the nucleon. M.V. Polyakov. Bochum University. What is known about strangeness in the nucleon ? What is strange in the strange quark matrix elements? Heavy quark limit. Heavy-light duality for strangeness? Exclusive production as effective tool to excite sea.

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Strangeness in the nucleon .

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  1. Strangeness in the nucleon. M.V. Polyakov Bochum University • What is known about strangeness in the nucleon ? • What is strange in the strange quark matrix elements? • Heavy quark limit. Heavy-light duality for strangeness? • Exclusive production as effective tool to excite sea

  2. What is known about strangeness in the nucleon ? We learned that strange matrix elements of the type are nonzero ! Sigma-term and octet mass splitting Polarized DIS Neutrino DIS Strange vector FFs at t=-0.1 GeV^2 from parity violating electron scattering Neutrino DIS

  3. What is strange in this matrix elements ? That they are non-zero ? That they are large ? That they are small ? Signs? . It is problem only for naive QM Comparing to what ? Comparing to what? How picture of the nucleon would change if I change signs? How to explain? In QCD all matrix elements are of order unity. Hierarchy! From ~1 to ~1/1000 Let us consider the same matrix elements but for heavy quark

  4. Topological charge density fluctuations in QCD vacuum (cooled lattice) [Simulation by D. Leinweber]

  5. Heavy quark mass limit of matrix elements Nucleon‘s slice

  6. Heavy quark mass limit of matrix elements Schäfer, Teryaev, MVP `99 Franz, Goeke, MVP `00 Clear hierarchy of matrix elements !

  7. Hierarchy as for heavy quarks ?

  8. Moreover, substituting mass of strange quark to heavy mass expansion formulae we obtain: It looks like semiclassics is justified by other parameter as heavy quark mass !

  9. If to follow this conjucture we should expect: Why strange quarks in the nucleon behave semiclassically? Or in other words: it looks like the strange quarks „feel“ only gluon operators with low dimensions. To check such conjucture a knowledge of other strange matrix elements is needed!

  10. Some of strange matrix elements in various models Tables from Diehl, Feldmann, Kroll `08 It seems that all sea distributions of the same order.

  11. It looks like the strange quarks „feel“ only gluon operators with low dimensions. Interesting problem: perform calcultions of higher order expansion and require the these corrections are small. In this way you obtain relations between nucleon matrix elements of high dim. gluon operators ! Possible origin of the hierarchy is the „chiral“ origin of the nucleon sea – natural in the baryon as soliton picture. One of practical application sof the conjectured hierarchy: shape of C-odd strange parton distribution

  12. Hierarchy conjecture See e.g. Diehl, Feldmann, Kroll `08 has several zeros Implies that

  13. CTEQ analysis of parton distributions „Hierarchy conjecture“ can help to constrain the shapes

  14. Diehl, Feldmann, Kroll `08 Strange form factor is too large as compared to our „hierarchy conjecture“. One can tune shape of strange quark distribution to get ~1/10000 for strange FF.

  15. Possible origin of the hierarchy is the „chiral“ origin of the nucleon sea – natural in the baryon as soliton picture. Idea: in the picture of baryons as solitons quarks move in chiral mean-field which we can find requiring the strange vector FFs are anomalously small . In this way one finds chiral Lagrangian!

  16. It is also interesting to see how strange quark behaves in other baryons. For example, in hyperons ! For that hard exclusive production of strangeness is very useful!

  17. Production of anti-strangeness – a way to „turn“ sea quarks into valence

  18. We can design probes by our wish ! See e.g. Goloskokov, Kroll `08 Interesting interference phenomena ! Fun to catch on a collider ! Eides, Frankfurt, Strikman `98

  19. It is also interesting to see how strange quark behaves in other baryons. For example, in hyperons !

  20. Nondiagonal DVCS

  21. b a

  22. Restorable part of GPD is contained in M.V.P. ´07 A. Moiseeva+MVP ´08 Vanderhaeghen+MVP´08

  23. Illustration for Abel tomography How to restore 3D spherically symmetric object from its 2D „fotograph“ Abel, 1826

  24. Additional variables charachterizing meson +N See classification of N->meson +N GPDs In /Stratmann, MVP ´06/

  25. QCD string operator For tomography of DVCS amplitude and GPD quintessence function see Polyakov, PLB659 (2008) 542

  26. Advantage of QCD strings to excite exotic baryons Hard photon removes a quark from N at once The quark returns back New Narrow Nucleon N*(1685) Revealed in eta photoproduction /Kuznetsov, MVP, JETP Lett. 88 (2008) 399/ Strong colour field Strong reararngenemt of colour This is just one of examples of advantage of QCD string probe for studies of baryon excitations.

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