A new method is employed to measure the neutral current cross section up to Bjorken-x values of one with the ZEUS detector at HERA using an integrated luminosity of 65.1 pb-1 for e+p collisions and 16.7 pb-1 for e-p collisions at sqrt{s}=318 GeV and 38.6 pb-1 for e+p collisions at sqrt{s}=300 GeV. Cross sections have been extracted for Q2 >= 648 GeV2 and are compared to predictions using different parton density functions. For the highest x bins, the data have a tendency to lie above the expectations using recent parton density function parametrizations.
The double differential cross section for the 96-97 E+ P NC scattering data.
The double differential cross section for the 96-97 E+ P NC scattering data.
The double differential cross section for the 96-97 E+ P NC scattering data.
Dijet production in deep inelastic ep scattering is investigated in the region of low values of the Bjorken-variable x (10^-4 < x < 10^-2) and low photon virtualities Q^2 (5 < Q^2 < 100 GeV^2). The measured dijet cross sections are compared with perturbative QCD calculations in next-to-leading order. For most dijet variables studied, these calculations can provide a reasonable description of the data over the full phase space region covered, including the region of very low x. However, large discrepancies are observed for events with small separation in azimuth between the two highest transverse momentum jets. This region of phase space is described better by predictions based on the CCFM evolution equation, which incorporates k_t factorized unintegrated parton distributions. A reasonable description is also obtained using the Color Dipole Model or models incorporating virtual photon structure.
Inclusive dijet cross section for a lower ET cut off of (5+0) GeV for the highest ET jet.
Inclusive dijet cross section for a lower ET cut off of (5+1) GeV for the highest ET jet.
Inclusive dijet cross section for a lower ET cut off of (5+2) GeV for the highest ET jet.
The inclusive e^+ p single and double differential cross sections for neutral and charged current processes are measured with the H1 detector at HERA. The data were taken in 1999 and 2000 at a centre-of-mass energy of \sqrt{s} = 319 GeV and correspond to an integrated luminosity of 65.2 pb^-1. The cross sections are measured in the range of four-momentum transfer squared Q^2 between 100 and 30000 GeV^2 and Bjorken x between 0.0013 and 0.65. The neutral current analysis for the new e^+ p data and the earlier e^- p data taken in 1998 and 1999 is extended to small energies of the scattered electron and therefore to higher values of inelasticity y, allowing a determination of the longitudinal structure function F_L at high Q^2 (110 - 700 GeV^2). A new measurement of the structure function x F_3 is obtained using the new e^+ p and previously published e^\pm p neutral current cross section data at high Q^2. These data together with H1 low Q^2 precision data are further used to perform new next-to-leading order QCD analyses in the framework of the Standard Model to extract flavour separated parton distributions in the proton.
The NC cross section DSIG/DQ**2. There is an additional 1.5 PCT normalization uncertainty.
The CC cross section DSIG/DQ**2. There is an additional 1.5 PCT normalization uncertainty.
The NC cross section DSIG/DX for Q**2 > 1000 GeV**2. There is an additional 1.5 PCT normalization uncertainty.
Jet production is studied in the Breit frame in deep-inelastic positron-proton scattering over a large range of four-momentum transfers 5 < Q^2 < 15000 GeV^2 and transverse jet energies 7 < E_T < 60 GeV. The analysis is based on data corresponding to an integrated luminosity of L_int \simeq 33 pb^(-1) taken in the years 1995-1997 with the H1 detector at HERA at a center-of-mass energy sqrt(s)=300 GeV. Dijet and inclusive jet cross sections are measured multi-differentially using k_perp and angular ordered jet algorithms. The results are compared to the predictions of perturbative QCD calculations in next-to-leading order in the strong coupling constant alphas.QCD fits are performed in which alphas and the gluon density in the proton are determined separately. The gluon density is found to be in good agreement with results obtained in other analyses using data from different processes. The strong coupling constant is determined to be alphas(MZ)=0.1186+-0.0059. In addition an analysis of the data in which both alphas and the gluon density are determined simultaneously is presented.
Inclusive single jet cross section as a function of ET and Q**2.. Data are analysed in the Breit frame using the inclusive kT alogrithm.
Inclusive dijet cross section as a function Q**2.. Data are analysed in the Breit frame using the inclusive kT alogrithm.
Inclusive di-jet cross section as a function of ET and Q**2.. Data are analysed in the Breit frame using the inclusive kT alogrithm.
The inclusive single and double differential cross-sections for neutral and charged current processes with four-momentum transfer squared Q^2 between 150 and 30,000 GeV2 and with Bjorken x between 0.0032 and 0.65 are measured in e^+ p collisions. The data were taken with the H1 detector at HERA between 1994 and 1997, and they correspond to an integrated luminosity of 35.6 pb^-1. The Q^2 evolution of the parton densities of the proton is tested, yielding no significant deviation from the prediction of perturbative QCD. The proton structure function F_2(x,Q^2) is determined. An extraction of the u and d quark distributions at high x is presented. At high Q^2 electroweak effects of the heavy bosons Z0 and W are observed and found to be consistent with Standard Model expectation.
The structure function, F2, and the reduced cross section, in NC DIS scattering at Q**2 from 150 to 30000 GeV**2 as a function if x and y. Also tabulated are the QED corrections to the data, which have already been applied. The individual corrections used to calculate F2 from the cross sections are given in the following table.
The various corrections to the cross sections used to calcuate the F2 values given in the previous table. See the text of the paper for more details.
The CC double differential cross section and the structure function term PHI(C=CC) - see text of the paper for details - at Q**2 from 150 to 1 5000 GeV**2 as a function of both x and y. Also tabulated are the QED corrections to the data, which have already been applied.
The e^+p charged-current deep inelastic scattering cross sections, $d\sigma/dQ^2$ for Q^2 between 200 and 60000 GeV^2, and $d\sigma/dx$ and $d\sigma/dy$ for Q^2 > 200 GeV^2, have been measured with the ZEUS detector at HERA. A data sample of 47.7 pb^-1, collected at a center-of-mass energy of 300 GeV, has been used. The cross section $d\sigma/dQ^2$ falls by a factor of about 50000 as Q^2 increases from 280 to 30000 GeV^2. The double differential cross section $d^2\sigma/dxdQ^2$ has also been measured. A comparison between the data and Standard Model (SM) predictions shows that contributions from antiquarks ($\bar{u}$ and $\bar{c}$) and quarks (d and s) are both required by the data. The predictions of the SM give a good description of the full body of the data presented here. A comparison of the charged-current cross section $d\sigma/dQ^2$ with the recent ZEUS results for neutral-current scattering shows that the weak and electromagnetic forces have similar strengths for Q^2 above $M^2_W, M^2_Z$. A fit to the data for $d\sigma/dQ^2$ with the Fermi constant $G_F$ and $M_W$ as free parameters yields $G_F = (1.171 \pm 0.034 (stat.) ^{+0.026}_{-0.032} (syst.) ^{+0.016}_{-0.015} (PDF)) \times 10^{-5} GeV^{-2}$ and $M_W = 80.8 ^{+4.9}_{-4.5} (stat.) ^{+5.0}_{-4.3} (syst.) ^{+1.4}_{-1.3} (PDF) GeV$. Results for $M_W$, where the propagator effect alone or the SM constraint between $G_F$ and $M_W$ have been considered, are also presented.
The differential cross section DSIG/DQ**2.
The differential cross section DSIG/DX.
The differential cross section DSIG/DY.
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