Measurement of the Proton Structure Function F_2 and \sigma_{tot}^{\gamma^* p} at Low Q^2 and Very Low x at HERA

A measurement of the proton structure function F_2(x,Q^2) is presented in the kinematic range 0.045 GeV^2 < Q^2 < 0.65 GeV^2 and 6*10^{-7} < x < 1*10^{-3}. The results were obtained using a data sample corresponding to an integrated luminosity of 3.9pb^-1 in e^+p reactions recorded with the ZEUS detector at HERA. Information from a silicon-strip tracking detector, installed in front of the small electromagnetic calorimeter used to measure the energy of the final-state positro...

The results of a measurement of the proton structure function F_2(x,Q^2)and the virtual photon-proton cross section are reported for momentum transfers squared Q^2 between 0.35 GeV^2 and 3.5 GeV^2 and for Bjorken-x values down to 6 10^{-6} using data collected by the HERA experiment H1 in 1995. The data represent an increase in kinematic reach to lower x and Q^2 values of about a factor of 5 compared to previous H1 measurements. Including measurements from fixed target experi...

The proton structure function F_2(x,Q^2) is measured in inelastic QED Compton scattering using data collected with the H1 detector at HERA. QED Compton events are used to access the kinematic range of very low virtualities of the exchanged photon, Q^2, down to 0.5 GeV^2, and Bjorken x up to \sim 0.06, a region which has not been covered previously by inclusive measurements at HERA. The results are in agreement with the measurements from fixed target lepton-nucleon scattering ...

We report on a measurement of the proton structure function $F_2$ in the range $3.5\times10^{-5}\leq x \leq 4\times10^{-3}$ and 1.5 ${\rm GeV^2} \leq Q^2 \leq15$ ${\rm GeV^2}$ at the $ep$ collider HERA operating at a centre-of-mass energy of $\sqrt{s} = 300$ ${\rm GeV}$. The rise of $F_2$ with decreasing $x$ observed in the previous HERA measurements persists in this lower $x$ and $Q^2$ range. The $Q^2$ evolution of $F_2$, even at the lowest $Q^2$ and $x$ measured, is consist...

The proton structure function F2 has been measured in the range 0.045 GeV2 < Q2 < 0.65 GeV2 and 6*10**-7 < x < 1*10**-3 using 3.9 pb-1 of ep->eX reactions recorded with the ZEUS detector in 1997. The analysis is based on data from the Beam Pipe Calorimeter (BPC) and the Beam Pipe Tracker (BPT). Compared to our previous analysis, the BPT permits improved background suppression and better control of systematic uncertainties, allowing the extension of the kinematic region of the...

The data collected with the H1 and ZEUS detectors during the running period 1994-99 are used to give an experimental review on the proton structure functions and the neutral current and charged current large Q^2 cross sections in e^\pm p scattering at HERA.

Measurements of proton structure functions made in neutral and charged current interactions at HERA are discussed, covering four-momentum transfers Q^2 from about 0.5 GeV^2 to 30000 GeV^2. The results include the rise of the structure function F2 towards small x and electro-weak effects at high Q^2. QCD fits made by the H1 and ZEUS collaborations provide both, parton densities with uncertainties, and precise alpha_s determinations.

In the following article we describe our measurement of the proton structure function $F_2$ and of the gluon momentum density $xg$ in $ep$ collisions with the ZEUS detector at HERA in 1993. The results for $F_2$ confirm our measurement from the previous year but with much higher statistics and show a strong rise towards small $x$. The gluon momentum density $xg$ is measured for the first time in a range from $ 4 \cdot 10^{-4} < x < 10^{-2}$ at a value of $Q^2 = 20$~GeV$^2$.

Preliminary results on a measurement of the proton structure function F_2 are reported for momentum transfers squared Q^2 between 1.5~GeV^2 and 5000 GeV^2 and for Bjorken x between 5.10^{-5} and 0.32 using data collected by the HERA experiments H1 and ZEUS in 1994. F_2 increases significantly with decreasing x, even in the lowest reachable Q^2 region. The data are well described by a Next to Leading Order QCD fit, and support within the present precision that the rise at low ...

Using 3.9 $pb^{-1}$ of data from ep $\ra$ eX interactions recorded using the ZEUS detector in 1997,the proton structure function, F$_2$, has been measured in the range 0.015 GeV$^2$ $<$ Q$^2 <$ 0.65 GeV$^2$ and $6 \times 10^{-7} < x < 1 \times 10^{-3}$. The analysis is based on data taken incorporating new detector components. Compared with the previous analysis, these components allow improved background suppression and better control of systematic uncertainties, extending t...