Abstract
A measurement of the inclusive deep-inelastic neutral current e+p scattering cross section is reported in the region of four-momentum transfer squared, 12<=Q^2<=150 GeV^2, and Bjorken x, 2x10^-4<=x<=0.1. The results are based on data collected by the H1 Collaboration at the ep collider HERA at positron and proton beam energies of E_e=27.6 GeV and E_p=920 GeV, respectively. The data are combined with previously published data, taken at E_p=820 GeV. The accuracy of the combined measurement is typically in the range of 1.3-2%. A QCD analysis at next-to-leading order is performed to determine the parton distributions in the proton based on H1 data.
Highlights
A small source of background for this analysis arises from photoproduction events, in which the scattered positron escapes detection in the backward beam pipe while a particle from the hadronic final state mimics the positron
In order to ensure that the cluster is well contained in the SpaCal, the extrapolation of the associated backward drift chamber (BDC) track segment to the SpaCal plane is required to be within a distance from the beam line of rSpac < 73 cm
The uncorrelated errors arise from various efficiencies and the radiative corrections
Summary
The H1 detector [11, 12] was built and upgraded for the accurate measurement of inelastic ep interactions at HERA. The detector components most relevant to this measurement are the central tracker, the backward lead-scintillator calorimeter (SpaCal) [13] and the liquid argon calorimeter (LAr) [14]. The drift chambers and the CST are used for the measurement of tracks from the hadronic final state. The momenta of the tracks are determined and the event vertex is reconstructed. The polar angle of the scattered positron is determined by the planar backward drift chamber (BDC) and the vertex position. Its energy resolution√for electromagnetic energy depositions is δE/E ≈ 0.07/ E/GeV ⊕ 0.01. It provides a trigger based on the scattered positron energy. The LAr allows the hadronic final state to be reconstructed.
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