We studied the exclusive reaction e p --> e' p' phi using the phi --> K^+ K^- decay mode. The data were collected using a 4.2 GeV incident electron beam and the CLAS detector at Jefferson Lab. Our experiment covers the range in Q^2 from 0.7 to 2.2 GeV^2, and W from 2.0 to 2.6 GeV. Taken together with all previous data, we find a consistent picture of phi production on the proton. Our measurement shows the expected decrease of the t-slope with the vector meson formation time c Delta tau below 2 fm. At = 0.6 fm, we measure b_phi = 2.27 +- 0.42 GeV^-2. The cross section dependence on W as W^{0.2+-0.1} at Q^2 = 1.3 GeV^2 was determined by comparison with phi production at HERA after correcting for threshold effects. This is the same dependence as observed in photoproduction.
Slope of the DSIG/DT distribution in different Q**2 regions.
Cross section as a function of Q**2 and W.
The differential cross section for exclusive PHI electroproduction off the photon, (TP=T-TMIN).
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Total inclusive production cross sections for the SIGMA- beam on the Coppertarget.
Total inclusive production cross sections for the SIGMA- beam on the Carbontarget.
Total inclusive production cross sections per nucleon for the SIGMA- beam, and the exponent in the cross section parametrization of the form A**POWER.
We update the measurement of the top production cross section using the CDF detector at the Fermilab Tevatron. This measurement uses $t\bar{t}$ decays to the final states $e+\nu$+jets and $\mu+\nu$+jets. We search for $b$ quarks from $t$ decays via secondary-vertex identification or the identification of semileptonic decays of the $b$ and cascade $c$ quarks. The background to the $t\bar{t}$ production is determined primarily through a Monte Carlo simulation. However, we calibrate the simulation and evaluate its uncertainty using several independent data samples. For a top mass of 175 $GeV/c^2$, we measure $\sigma_{t\bar{t}}=5.1 \pm 1.5$ pb and $\sigma_{t\bar{t}}=9.2 \pm 4.3$ pb using the secondary vertex and the lepton tagging algorithms, respectively. Finally, we combine these results with those from other $t\bar{t}$ decay channels and obtain $\sigma_{t\bar{t}} = 6.5^{+1.7}_{-1.4}$ pb.
Cross sections from the SVX (secondary vertex), SLT (soft lepton tag), dilepton and all hadronic analyses. See text of article for details. Errors contain both statistics and systematics.
We report on a measurement of the differential cross sections of inclusive$K^{\pm}_{890}$production in$\sigma^-, pi^-$and ne
The production cross sections for K*+- per nucleus and per nucleon for the SIGMA- beam.
The production cross sections for K*+- per nucleus and per nucleon for the PI- beam.
The production cross sections for K*+- per nucleus and per nucleon for the NEUTRON- beam.
The reaction e+e- -> e+e- gamma* gamma* -> e+e- hadrons for quasi-real photons is studied using data from root(s) = 183 GeV up to 202 GeV. Results on the total cross sections sigma(e+e- -> e+e- hadrons) and sigma(+e- gamma* gamma* -> e+e- hadrons) are given for the two-photon centre-of-mass energies 5 GeV < Wgammagamma < 185 GeV. The total cross section of two real photons is described by a Regge parametrisation. We observe a steeper rise with the two-photon centre-of-mass energy as compared to the hadron-hadron and the photon-proton cross sections. The data are also compared to the expectations of different theoretical models.
The measured total cross section for E+ E- --> E+ E- HADRONS. The first DSYS error is the total experimental systematic uncertainty and the second DSYS error is the uncertainty introduced by unfolding the data with PYTHIA and PHOJET corrections seperately.
The total cross section for two photon production of hadrons. The final column gives the data averaged over all energies together with the experimental systematic error (first DSYS) and the difference between the average and the data unfolded with PHOJET (lower sign) and PYTHIA (upper sign) seperately (second DSYS).
The inclusive e^-p single and double differential cross sections for neutral and charged current processes are measured with the H1 detector at HERA, in the range of four-momentum transfer squared Q^2 between 150 and 30000 GeV^2, and Bjorken x between 0.002 and 0.65. The data were taken in 1998 and 1999 with a centre-of-mass energy of 320 GeV and correspond to an integrated luminosity of 16.4 pb^(-1). The data are compared with recent measurements of the inclusive neutral and charged current e^+p cross sections. For Q^2>1000 GeV^2 clear evidence is observed for an asymmetry between e^+p and e^-p neutral current scattering and the generalised structure function xF_3 is extracted for the first time at HERA. A fit to the charged current data is used to extract a value for the W boson propagator mass. The data are found to be in good agreement with Standard Model predictions.
The NC single differential cross section, as a function of X, for Y < 0.9 and Q**2 > 1000 GeV**2. The first DSYS error is the uncorrelated systematic errorand the second is the correlated systematic error.
The NC single differential cross section, as a function of X, for Y < 0.9 and Q**2 > 10000 GeV**2. The first DSYS error is the uncorrelated systematic error and the second is the correlated systematic error.
The CC single differential cross section, as a function of X, for measured for 0.03 < Y < 0.85 and Q**2 > 1000 GeV**2. and corrected by KCOR to Y < 0.9. The first DSYS error is the uncorrelated systematic error and the second is the correlated systematic error.
A precise measurement of the inclusive deep-inelastic e^+p scattering cross section is reported in the kinematic range 1.5<= Q^2 <=150 GeV^2 and 3*10^(-5)<= x <=0.2. The data were recorded with the H1 detector at HERA in 1996 and 1997, and correspond to an integrated luminosity of 20 pb^(-1). The double differential cross section, from which the proton structure function F_2(x,Q^2) and the longitudinal structure function F_L(x,Q^2) are extracted, is measured with typically 1% statistical and 3% systematic uncertainties. The measured partial derivative (dF_2(x,Q^2)/dln Q^2)_x is observed to rise continuously towards small x for fixed Q^2. The cross section data are combined with published H1 measurements at high Q^2 for a next-to-leading order DGLAP QCD analysis.The H1 data determine the gluon momentum distribution in the range 3*10^(-4)<= x <=0.1 to within an experimental accuracy of about 3% for Q^2 =20 GeV^2. A fit of the H1 measurements and the mu p data of the BCDMS collaboration allows the strong coupling constant alpha_s and the gluon distribution to be simultaneously determined. A value of alpha _s(M_Z^2)=0.1150+-0.0017 (exp) +0.0009-0.0005 (model) is obtained in NLO, with an additional theoretical uncertainty of about +-0.005, mainly due to the uncertainty of the renormalisation scale.
The reduced deep inelastic cross section , and F2, with data taken in the dedicated low Q**2 trigger run of 1997. For y < 0.6, F2 is extracted using the quoted values of R, defined from a QCD fit to the H1 cross section data. The firstDSYS error is the uncorrelated systematic error, and the second is the correlat ed systematic error.
The reduced deep inelastic cross section , and F2, with data taken in 1996/97. For y < 0.6, F2 is extracted using the quoted values of R, defined from a QCD fit to the H1 cross section data. The first DSYS error is the uncorrelated systematic error, and the second is the correlated systematic error.
The measured value of the reduced cross section derivative D(SIG(C=REDUCED))/DLN(Y) calculated at fixed Q**2 bins. The data below 13.5 GeV come from the special low Q**2 run in 1997. The larger Q**2 come from the 1996/97 data.
A measurement is presented of dijet and 3-jet cross sections in low-|t| diffractive deep-inelastic scattering interactions of the type ep -> eXY, where the system X is separated by a large rapidity gap from a low-mass baryonic system Y. Data taken with the H1 detector at HERA, corresponding to an integrated luminosity of 18.0 pb^(-1), are used to measure hadron level single and double differential cross sections for 4
Average values, over the specified interval, of the differential hadron level dijet cross section as a function of Q**2.
Average values, over the specified interval, of the differential hadron level dijet cross section as a function of the average transverse momentum of the two jets in the c.m.frame.
Average values, over the specified interval, of the differential hadron level dijet cross section as a function of the average pseudorapidity of the two jets in the lab frame.
We report the first observation of diffractively produced open charm in 800−GeV/c pp collisions of the type pp→pD*X. We measure cross sections of σdiff(D*+)=(0.185±0.044±0.054)μb and σdiff(D*−)=(0.174±0.034±0.029)μb. Our measurements are based on 4.3×109 events recorded by FNAL E690 in the fixed-target run of 1991. We compare our results with previous fixed-target charm experiments.
No description provided.
Open charm production in gamma-gamma collisions is studied with data collected at e+e- centre-of-mass energies from 189 GeV to 202 GeV corresponding to a total integrated luminosity of 410 pb-1. The charm cross section sigma(gamma gamma ---> c c~ X) is measured for the first time as a function of the two-photon centre-of-mass energy in the interval from 5 GeV to 70 GeV and is compared to NLO QCD calculations.
The total cross section for the process E+ E- --> E+ E- CQ CQBAR X.
The total cross section for the process GAMMA GAMMA --> CQ CQBAR X.
Correlation matrix of the data after unfolding.
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