This paper presents an analysis of the inclusive properties of diffractive deep inelastic scattering events produced in $ep$ interactions at HERA. The events are characterised by a rapidity gap between the outgoing proton system and the remaining hadronic system. Inclusive distributions are presented and compared with Monte Carlo models for diffractive processes. The data are consistent with models where the pomeron structure function has a hard and a soft contribution. The diffractive structure function is measured as a function of $\xpom$, the momentum fraction lost by the proton, of $\beta$, the momentum fraction of the struck quark with respect to $\xpom$, and of $Q~2$. The $\xpom$ dependence is consistent with the form \xpoma where $a=1.30\pm0.08(stat)~{+0.08}_{-0.14}(sys)$ in all bins of $\beta$ and $Q~2$. In the measured $Q~2$ range, the diffractive structure function approximately scales with $Q~2$ at fixed $\beta$. In an Ingelman-Schlein type model, where commonly used pomeron flux factor normalisations are assumed, it is found that the quarks within the pomeron do not saturate the momentum sum rule.
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A leading order determination of the gluon density in the proton has been performed in the fractional momentum range $1.9 \cdot 10~{-3} < x_{g/p} < 0.18$ by measuring multi-jet events from boson-gluon fusion in deep-inelastic scattering with the H1 detector at the electron-proton collider HERA. This direct determination of the gluon density was performed in a kinematic region previously not accessible. The data show a considerable increase of the gluon density with decreasing fractional momenta of the gluons.
FG is gluon structure function. XPARTON here means the X of the gluon. For the experimental definitions of the XPARTON see paper.
We present a QCD analysis of the proton structure function $F_2$ measured by the H1 experiment at HERA, combined with data from previous fixed target experiments. The gluon density is extracted from the scaling violations of $F_2$ in the range $2\cdot 10~{-4}
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The inclusive cross sections times leptonic branching ratios for W and Z boson production in PbarP collisions at Sqrt(s)=1.8 TeV were measured using the D0 detector at the Fermilab Tevatron collider: Sigma_W*B(W->e, nu) = 2.36 +/- 0.07 +/- 0.13 nb, Sigma_W*B(W->mu,nu) = 2.09 +/- 0.23 +/- 0.11 nb, Sigma_Z*B(Z-> e, e) = 0.218 +/- 0.011 +/- 0.012 nb, Sigma_Z*B(Z->mu,mu) = 0.178 +/- 0.030 +/- 0.009 nb. The first error is the combined statistical and systematic uncertainty, and the second reflects the uncertainty in the luminosity. For the combined electron and muon analyses we find: [Sigma_W*B(W->l,nu)]/[Sigma_Z*B(Z->l,l)] = 10.90 +/- 0.49. Assuming Standard Model couplings, this result is used to determine the width of the W boson: Gamma(W) = 2.044 +/- 0.093 GeV.
The second DSYS error is due to luminosity.
Earlier measurements at LEP of isolated hard photons in hadronic Z decays, attributed to radiation from primary quark pairs, have been extended in the ALEPH experiment to include hard photon productioninside hadron jets. Events are selected where all particles combine democratically to form hadron jets, one of which contains a photon with a fractional energyz≥0.7. After statistical subtraction of non-prompt photons, the quark-to-photon fragmentation function,D(z), is extracted directly from the measured 2-jet rate. By taking into account the perturbative contributions toD(z) obtained from anO(ααs) QCD calculation, the unknown non-perturbative component ofD(z) is then determined at highz. Provided due account is taken of hadronization effects nearz=1, a good description of the other event topologies is then found.
2-jet events. Variable Z has been defined as E(gamma)/(E(gamma)+E(had)), where E(gamma) is the energy of the hard photon in 'photon-jet', E(had) is the energy of the rest hadrons in jet. Ycut is jet resolution parameter (see paper).
2-jet events. Variable Z has been defined as E(gamma)/(E(gamma)+E(had)), where E(gamma) is the energy of the hard photon in 'photon-jet', E(had) is the energy of the rest hadrons in jet. Ycut is jet resolution parameter (see paper).
2-jet events. Variable Z has been defined as E(gamma)/(E(gamma)+E(had)), where E(gamma) is the energy of the hard photon in 'photon-jet', E(had) is the energy of the rest hadrons in jet. Ycut is jet resolution parameter (see paper).
A study of scaling violations in fragmentation functions performed by the ALEPH collaboration at LEP is presented. Data samples enriched in uds, c, b and gluon jets, respectively, together with measurements of the longitudinal and transverse inclusive cross sections are used to extract the fragmentation function for the gluon and for each flavour. The measurements are compared to data from experiments at energies between 22 GeV and 91 GeV and scaling violations consistent with QCD predictions are observed. From this, a measurement of the strong coupling constant α s ( Mz ) = 0.126 ±0.009 is obtained.
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We present a new measurement of the spin-dependent structure function g 1 d of the deuteron in deep inelastic scattering of 190 GeV polarised muons on polarised deuterons, in the kinematic range 0.003 < x < 0.7 and 1 GeV 2 < Q 2 < 60 GeV 2 . This structure function is found to be negative at small x . The first moment Γ 1 d =∫ 0 1 g 1 d d x evaluated at Q 0 2 = 10 GeV 2 is 0.034 ± 0.009 (stat.) ± 0.006 (syst.). This value is below the Ellis-Jaffe sum rule prediction by three standard deviations. Using our earlier determination of Γ 1 p , we obtain Γ 1 p − Γ 1 n = 0.199 ± 0.038 which agrees with the Bjorken sum rule.
Results on the virtual photon deuteron asymmetry.
Results on the spin structure function of the deuteron.
Results on the spin structure function of the neutron.
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Low x domain.
Charged particle multiplicity distributions have been measured with the ALEPH detector in restricted rapidity intervals |Y| ≤0.5, 1.0, 1.5, 2.0 along the thrust axis and also without restriction on rapidity. The distribution for the full range can be parametrized by a log-normal distribution. For smaller windows one finds a more complicated structure, which is understood to arise from perturbative effects. The negative-binomial distribution fails to describe the data both with and without the restriction on rapidity. The JETSET model is found to describe all aspects of the data while the width predicted by HERWIG is in significant disagreement.
Unfolded charged particle multiplicity distribution given the probability to have an hadronic Z0 decay with MULT charged particles.
Unfolded multiplicity distributions for restricted rapidity bin <= 0.5 along the thrust axis.
Unfolded multiplicity distributions for restricted rapidity bin <= 1.0 along the thrust axis.
We analyze a sample of W + jet events collected with the Collider Detector at Fermilab (CDF) in ppbar collisions at sqrt(s) = 1.8 TeV to study ttbar production. We employ a simple kinematical variable "H", defined as the scalar sum of the transverse energies of the lepton, neutrino and jets. For events with a W boson and four or more jets, the shape of the "H" distribution deviates by 3.8 standard deviations from that expected from known backgrounds to ttbar production. However this distribution agrees well with a linear combination of background and ttbar events, the agreement being best for a top mass of 180 GeV/c^2.
A result of the study of the W + >= 4JETS data sample used in PRL 74, 2626, based on 67 pb-1 of integrated luminosity.. Different fit results due to two choices of the Q2 scale in VECBOS program (see paper).
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