文摘
Inclusive $ep$ double differential cross sections for neutral current deep inelastic scattering are measured with the H1 detector at HERA. The data were taken with a lepton beam energy of $27.6$ ?GeV and two proton beam energies of $E_p=460$ and 575 GeV corresponding to centre-of-mass energies of 225 and 252 GeV, respectively. The measurements cover the region of $6.5\times 10^{-4} \le x \le 0.65$ for $35\le Q^2 \le 800$ GeV $^2$ up to $y=0.85$ . The measurements are used together with previously published H1 data at $E_p=920$ GeV and lower $Q^2$ data at $E_p=460$ , $575$ and $920$ GeV to extract the longitudinal proton structure function $F_L$ in the region $1.5\le Q^2 \le 800$ GeV $^2$ .