| DATE: |
2004-09-07 11:00 - |
| PLACE: |
Building No.4,3F RM345 |
| TITLE: |
Pentaquark Baryons in String Theory |
| CONTACT: |
Tango |
| SPEAKER: |
Prof. Akio Sugamoto (Ochanomizu University) |
| LANGUAGE: |
Japanese |
| ABSTRACT: |
Recently observed Pentaquark baryons Theta^{+} and Xi^{--} are studiedin the dual gravity theory of QCD. By developping a general formulation useful to study the branched string web in the curved space, simple mass formulae of the Pentaquark baryons are derived in the Maldacena\\\'s prototype model for a supersymmetric QCD and a more realistic model for the ordinary QCD. Even though the approximations adopted here in deriving these formulae are extremely naive, the prediction of the masses is not too bad. For example, in the QCD like model, we have the quark masses and the pentaquark masses as follows: m_u=m_d=313-312 MeV, m_s=567-566 MeV, and M(Theta)=1,577-1,715 MeV, M(Xi)=1,670-1,841 MeV. In this model one extra dimension is compactified with the mass scale of 2-5 MeV, which is necessary to break supersymmetries. The decay processes of pentaquarks are also examined considering the recombination of strings, for which we gives a naive discussion on how we can obtain the decay width of O(1) MeV. Therefore, this direction of study is promising towards the explanation of the observed masses of Pentaquarks and of their extremely narrow decay widths. To approach the more reliable mass formulae, a preliminary sketch of how the spin, the hyperfine interaction and the parity are considered in the string picture. [Refs: hep-ph/0404019, hep-ph/0405259]
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