Friday, 20 January 2006 - h. 15:00 

Auditorium B. Touschek

  T. Walcher


The Form Factors of the Nucleon at Small Momentum Transfer


The form factors of the nucleon encode information about the microscopic structure of the nucleon. This structure is thought as a many body system of the elementary constituents quarks and gluons.

However, it is well known that many body systems are producing effective degrees of freedom composed of the elementary constituents.
It will be argued that the new results on the form factors of the nucleon at small four momentum transfers show a direct indication of the pion cloud, a virtual degree of freedom of the nucleon used since a long time.

This phenomenological hint is in conflict with recent dispersion relation results. The conflict together with the dramatic deviation of the dispersion relations from the existing determinations of the form
factor of the neutron in the timelike region of the four momentum transfer shows that our understanding of the microscopic structure of the nucleon is incomplete. The inconsistency of dispersion relations with the experiments hints to some unknown physics.



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MCD, 5/1/06