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Register a new userPolarized deep inelastic scattering at low Bjorken x and resummation of logarithmic corrections, $ln^2(1/x)$
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B. Ziaja
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For an accurate description of the polarized deep inelastic scattering at low $x$ including the logarithmic corrections, $ln^2(1/x)$, is required. These corrections resummed strongly influence the behaviour of the spin structure functions and their moments. Results of the work of J. Kwiecinski and myself on this problem are reviewed.}
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In this thesis we consider the polarized deep inelastic scattering in the region of low values of Bjorken variable, $x$. We formulate the evolution equations for the unintegrated parton distributions which include a complete resummation of the double logarithmic contributions, $ln^2(1/x)$. Afterwards, these equations are completed with the standard LO and NLO DGLAP evolution terms, in order to obtain the proper behaviour of the parton distributions at moderate and large values of $x$. The equations obtained are applied to the following observables and processes: (i) to the nucleon structure function, $g_1$, in the polarized deep inelastic scattering, (ii) to the structure function of the polarized photon, $g_1^{gamma}$, in the scattering of a lepton on a polarized photon, and (iii) to the differential structure function, $x_J d^2g_1/dx_J dk_J^2$, in the polarized deep inelastic scattering accompanied by a forward jet. Case (iii) is proposed to be a test process for the presence and the magnitude of the $ln^2(1/x)$ contributions. For each process the consequences of including the logarithmic corrections are studied in a detail. After integrating out the structure function, $g_1$, the moments of the nucleon structure function are obtained. The contribution of the region of low $x$ to these moments is estimated, and then discussed in the context of the spin sum rules. Finally, some predictions for the observables, the asymmetry and the cross sections, in the processes (i)-(iii) are given. They are important to planned experiments with the polarized HERA and linear colliders, which will probe the region of low values of Bjorken $x$.
High transverse momentum pi^0 -mesons and charged particles are measured in deep inelastic e-p scattering events at low Bjorken-x taken with the H1 detector at HERA. The production of high-pt particles is strongly correlated to the emission of hard partons in QCD and is therefore sensitive to the dynamics of the strong interaction. For the first time the measurement of single particles has been extended to the region of small angles w.r.t. the proton remnant (forward region). This region is expected to be particularly sensitive to QCD evolution effects in final states. Results are presented as a function of Bjorken-x and x_i, the fraction of the incident protons energy carried by the particle, and are compared to different QCD models.
We present a first calculation of the heavy flavor contribution to the longitudinally polarized DIS structure function $g_1$, differential in the transverse momentum or the rapidity of the observed heavy antiquark $overline{Q}$. All results are obtained at next-to-leading order accuracy with a newly developed parton-level Monte Carlo generator that also allows one to study observables associated with the heavy quark pair such as its invariant mass distribution or its correlation in azimuthal angle. First phenomenological studies are presented in a kinematic regime relevant for a future Electron-Ion Collider with a particular emphasis on the sensitivity to the helicity gluon distribution. Finally, we also provide first NLO results for the full neutral-current sector of polarized DIS, i.e., including contributions from Z-boson exchange.
We use soft-collinear effective theory (SCET) to study the factorization properties of deep inelastic scattering in the region of phase space where 1-x = O(Lambda_{QCD/Q}). By applying a regions analysis to loop diagrams in the Breit frame, we show that the appropriate version of SCET includes anti-hard-collinear, collinear, and soft-collinear fields. We find that the effects of the soft-collinear fields spoil perturbative factorization even at leading order in the 1/Q expansion.
High Q^2 NC and CC cross-sections as measured at HERA can give information on two distinct areas of current interest. Firstly, supposing that all the electroweak parameters are well known, these cross-sections may be used to give information on parton distributions at high x and high Q^2. Secondly, supposing that parton distributions are well known, after evolution in Q^2 from the kinematic regime where they are already measured, these cross-sections can be used to give information on electroweak parameters in a process where the exchanged boson is `spacelike rather than `timelike. WG1 addressed itself to clarifying the limits of our present and possible future knowledge on both these areas.
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