在低 x 区间确定纵向质子结构函数 F_L

presented at momentum transfers $8.5 \leq Q^2 \leq 35 GeV^2$ and large inelasticity $y = 0.7$, i.e. for the Bjorken-x range $0.00013 \leq x \leq 0.00055$。Using a next-to-leading order QCD fit to the structure function F_2 at lower y values, the contribution of F_2 to the measured cross section at high y is calculated and, by subtraction, the longitudinal structure function F_{L} is determined for the first time with an average value of $F_L=0.52 \pm 0.03 (stat)^{+0.25}_{-0.22}$ (syst) at $Q^2=15.4 GeV^2$ and $x=0.000243$。