First results on inclusive D0 and D* production in deep inelastic $ep$ scattering are reported using data collected by the H1 experiment at HERA in 1994. Differential cross sections are presented for both channels and are found to agree well with QCD predictions based on the boson gluon fusion process. A charm production cross section for 10GeV$~2\le Q~2\le100$GeV$~2$ and $0.01\le y\le0.7$ of $\sigma\left(ep\rightarrow c\overlinecX\right) = (17.4 \pm 1.6 \pm 1.7 \pm 1.4)$nb is derived. A first measurement of the charm contribution F2_charm(x,Q~2) to the proton structure function for Bjorken $x$ between $8\cdot10~{-4}$ and $8\cdot10~{-3}$ is presented. In this kinematic range a ratio F2_charm/F2= 0.237\pm0.021{+0.043\atop-0.039}$ is observed.
Inclusive D meson production cross sections. The second systematc error represents the model uncertainty.
Inclusive charm meson cross section averaged for the two processes. The second systematc error represents the model uncertainty.
Ratio of cross sections of D0 and D* production.
Properties of the hadronic final state in photoproduction events with large transverse energy are studied at the electron-proton collider HERA. Distributions of the transverse energy, jets and underlying event energy are compared to $\overline{p}p$ data and QCD calculations. The comparisons show that the $\gamma p$ events can be consistently described by QCD models including -- in addition to the primary hard scattering process -- interactions between the two beam remnants. The differential jet cross sections $d\sigma/dE_T~{jet}$ and $d\sigma/d\eta~{jet}$ are measured.
No description provided.
Additional overall systematic error of 26 pct.
Additional overall systematic error of 26 pct.
A contact interaction analysis is presented to search for new phenomena beyond the Standard Model in deep inelastic $e~\pm p \rightarrow e~\pm \, hadrons$ scattering. The data are collected with the H1 detector at HERA and correspond to integrated luminosities of $0.909 \ {\rm pb}~{-1}$ and $2.947 \ {\rm pb}~{-1}$ for electron and positron beams, respectively. The differential cross sections $d\sigma / dQ~2$ are measured in the $Q~2$ range bet\-ween $160 \ \GeV~2$ and $20,000 \ \GeV~2$. The absence of any significant deviation from the Standard Model prediction is used to constrain the couplings and masses of new leptoquarks and to set limits on electron--quark compositeness scales and on the radius of light quarks.
Additional overall normalization error of 3.5 pct due to systematic errors of the luminosity measurement.
Additional overall normalization error of 1.8 pct due to systematic errors of the luminosity measurement.
Photoproduction of 2-jet events is studied with the H1 detector at HERA. Parton cross sections are extracted from the data by an unfolding method using leading order parton-jet correlations of a QCD generator. The gluon distribution in the photon is derived in the fractional momentum range $0.04\le x_\gamma \le 1$ at the average factorization scale $75$ GeV$~2$.
No description provided.
No description provided.
Gluon density of the photon (alpha is the fine structure constant).
We present a study of J ψ meson production in collisions of 26.7 GeV electrons with 820 GeV protons, performed with the H1-detector at the HERA collider at DESY. The J ψ mesons are detected via their leptonic decays both to electrons and muons. Requiring exactly two particles in the detector, a cross section of σ(ep → J ψ X) = (8.8±2.0±2.2) nb is determined for 30 GeV ≤ W γp ≤ 180 GeV and Q 2 ≲ 4 GeV 2 . Using the flux of quasi-real photons with Q 2 ≲ 4 GeV 2 , a total production cross section of σ ( γp → J / ψX ) = (56±13±14) nb is derived at an average W γp =90 GeV. The distribution of the squared momentum transfer t from the proton to the J ψ can be fitted using an exponential exp(− b ∥ t ∥) below a ∥ t ∥ of 0.75 GeV 2 yielding a slope parameter of b = (4.7±1.9) GeV −2 .
No description provided.
No description provided.
QED background subtracted.
Cross sections are presented for the inclusive production of charged particles measured in electron-proton collisions at low Q 2 with the H1 detector at HERA. The transverse momentum distribution extends up to 8 GeV/ c . Its shape is found to be harder than that observed in p p collisions at comparable centre-of-mass energies √S γp ≈ √S p p ≈ 200 GeV , and also harder than in γp collisions at lower energies √ S γp ≈ 18 GeV. Results from quantum chromodynamics (QCD) calculations agree with the measured transverse momentum and pseudorapidity cross sections.
No description provided.
No description provided.
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