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We demonstrate that the large soft gluon logarithm is correctly factorized into the Balitsky–Kovchegov (BK) renormalization group equation by accurately connecting the NLO scattering kinematics to the rapidity scale of the dipole amplitude in the scattering. This brings the perturbative expansion under control and enables us to do precision comparisons between theory and data. We fit the initial condition of the BK evolution equation to HERA inclusive deep inelastic scattering data by combining of the NLO accuracy inclusive cross sections with beyond leading order BK evolution prescriptions. This results in the state-ofthe-art accuracy comparison between CGC theory and HERA data, and determination of the dipole amplitude initial shape which is a necessary input for all NLO CGC phenomenology. In the introductory part of this thesis, the effect of the NLO BK equation on the fits is assessed, and an alternative form for the NLO loop correction to the inclusive cross sections is derived which enables the consistent setting of the dipole amplitude rapidity scale in the NLO corrections. The underlying mechanism of diffraction in particle scattering is still unknown, with multiple competing pictures. Diffraction is studied in this thesis in the CGC formalism, and we calculate the tree-level qqg¯ NLO contribution to the diffractive deep inelastic scattering structure functions where the qqg¯ Fock state scatters off the target and becomes the diffractively produced system. This contribution has previously been known in the literature only in leading log(Q2 ) accuracy valid at large Q2 , and only for the structure function F D T . The qqg¯ contribution to both structure functions F D T and F D L are presented in full NLO accuracy.

The dissertation is published in JYU Dissertations series, number 444, Jyväskylä 2021, ISSN 2489-9003, ISBN 978-951-39-8893-7 (PDF). Link to publication:

M.Sc. Henri Hänninen defends his doctoral dissertation "Deep Inelastic Scattering in the Dipole Picture at Next-to-Leading Order" on 29 October 2021 at 12 noon. Opponent Professor Krzysztof Golec-Biernat (Polish Academy of Sciences, Poland) and Custos Professor Tuomas Lappi (Ä¢¹½Ö±²¥). The doctoral dissertation is held in English.

The audience can follow the dissertation in the lecture hall or online.

Link to the Zoom Webinar event (Zoom application or Google Chrome web browser recommended): 

Phone number to which the audience can present possible additional questions at the end of the event (to the custos): +358408054879