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| Home > Publications database > Combination of the inclusive DIS $e^{\pm}p$ cross sections from HERA, QCD and EW analyses and the need for low-$Q^2$ higher-twist corrections |
| Book/Report/Dissertation / PhD Thesis | PUBDB-2017-00798 |
; ;
2017
Verlag Deutsches Elektronen-Synchrotron
Hamburg
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Please use a persistent id in citations: doi:10.3204/PUBDB-2017-00798
Report No.: DESY-THESIS-2017-004
Abstract: A combination of the inclusive lepton-proton cross sections from the ZEUS and H1 experiments is presented. The data are combined taking into account correlations of the systematic uncertainties of the measurements. The resulting combined inclusive neutral- and charged-current e ± p cross sections derived from ∼1 fb^−1 of data, cover the kinematic region of 0.045 ≤ Q^2 ≤ 50000 GeV^2 and 6 · 10 −7 ≤ x_Bj ≤ 0.65. The combined data is an unique legacy of the HERA collider and the core of any parton-density-function extraction.The parton distribution functions are essential ingredients in the evaluation of QCD predictions for the high-energy processes, studied at modern proton colliders. The methodology of HERAPDF fits is used as an ansatz for the global QCD fit. The charm- and beauty-quark mass parameters in the analyses at next-next-to-leading order were found to be M_c^opt = 1.43 GeV and M_b^opt = 4.5 GeV, respectively. HERAPDF2.0 sets give reasonable DIS data description.The effect of higher-twist corrections on the DIS structure functions was studied. The twist-4 corrections were introduced to the F_2 and F_L structure functions. A minimal improvement in the data description was found for the F_2 correction. The introduction of a higher-twist correction to the F_L structure function improved the QCD fit quality by up to ∆χ^2 = 47, predominantly affecting the low-x_Bj and low-Q^2 regions. The twist-4 correction causes an unphysical rise of the predicted F_L in the low x_Bj region. The results indicate a need for further investigations.The electroweak parameters and PDFs are determined simultaneously using the HERA inclusive cross sections together with information on the lepton beam polarisation. The vector- and axial-vector couplings of the u- and d-type quarks to the Z^0 boson are determined simultaneously. The u-type quark couplings were found to be a_u = 0.532 +0.107 −0.063,v_u = 0.144 +0.066 −0.058 , which are the most precise measurements from data from a single collider. The measurements are consistent with the SM predictions and expected to contribute significantly to the world-average values. The mass of the W boson was found to be M W = 80.68 +0.38 −0.28 GeV. The weak mixing angle was measured to be sin^2θ_W (M_Z) = 0.2252 +0.0013 −0.0011 . The sin^2θ_W was also measured for the first time over a range of Q^2, namely [200, 50000] GeV^2. The measurements were found to be consistent with the world average.Studies of the inner surface of 9-cell Nb superconducting RF cavities are presented. Optical inspections of a large number of cavities were performed with the OBACHT system. Profilometry studies of surface defects were done by inspecting rubber “replica” on a 3D optical/laser scanning microscope. Contamination agents of the cavities from the fabrication process were studied using X-ray spectroscopy. The obtained information may be used to improve the future cavity production.
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