Structure of Deep Inelastic Interaction in Gauge and String Theories

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In the present research project, we have investigated the new features of the deep inelastic interaction based on the framework of string/gauge duality. As a recent remarkable development in the string theory, there has been a discovery of the so-called AdS/CFT correspondence, which is a duality between the large N limit of the superconformal SU(N) gauge theory and supergravity/string theory in AdS spacetime. In this project we analyzed deep inelastic processes in the gauge as well as string theories and tried to clarify their structures. In the first year, we have carried out the calculation of the polarized virtual photon structure functions which can be measured in the future electron-positron collider experiments. We also computed the spin-dependent quark and gluon distribution functions inside the virtual photon. On the other hand, we investigated both polarized and unpolarized structure functions based on the AdS/CFT correspondence for the small-x region where the excited states … More contribute in the intermediate state, about which we talked at the JPS meeting. We also presented our results on the spin-dependent parton distributions in the virtual photon at the SPIN2003 held in August at Washington University. In the second year, we explored the target mass effects in the polarized photon structure functions. In the final year of the present project, we studied polarized photon structure function related to the axial anomaly as well as the physics at the colliders like LHC. So far the form factor and structure functions in the string theory are known to show the exponential behavior with respect to the scaling variable x as well as momentum transfer squared Q^2 but it shows power behavior in the case of string theory due to the warp factor arising from the AdS/CFT correspondence. We in fact examined the polarized structure function for the first time in this framework. We further calculated the next-to-next-leading order (NNLO) QCD correction to the firtst moment of the polarized structure function g_1^γ. We presented this result at the RADCOR2005 in October at Shonan International Village. We also studied deeply virtual Compton scattering off virtual photon. We had the discussion on the strong interaction effects at the future collider like LHC with the researcher at KEK. In the course of the present research, discussions and communications with the people in the related fields were very useful. Especially, we are very much indebted to the communications with the researchers at KEK, Yokohama National University, RIKEN and DESY. We have published our results at JPS meeting and the international workshops at the domestic as well as foreign research Institutes. These results have been published in the journals listed above. Less