We report on a measurement of the differential and total cross sections of inclusive production of Xi resonances in Sigma - nucleus collisions at 345 GeV/c.
Feynman X distribution for producton XI(1530)0 on copper and carbon. The quoted errors are statistical.
PT**2 distribution for XI(1530) producton on copper and carbon. The uoted errors are statistical.
Feynman X distribution (times BR) per nucleon for XI(1820) and XI(1950) production. The quoted errors are statistical.
We measure the neutral D total forward cross section and the differential cross sections as function of Feynman-x ($x_F$) and transverse momentum squared for 500 GeV/c $\pi^-$-nucleon interactions. The results are obtained from 88990+-460 reconstructed neutral D mesons from Fermilab experiment E791 using the decay channels $D\to K^-\pi^+$ and $D\to K^-\pi^+\pi^-\pi^+$ (and charge conjugates). We extract fit parameters from the differential cross sections and provide the first direct measurement of the turnover point in the $x_F$ distribution, 0.0131+-0.0038. We measure an absolute $D^0 + \bar{D^0}$ ($x_F > 0$) cross section of 15.4+1.8-2.3 microbarns/nucleon (assuming a linear A dependence). The differential and total forward cross sections are compared to theoretical predictions and to results of previous experiments.
The neutral D total forward cross section summed over all XL (the 0.8 TO 1.0 XL bin is assumed to be half of the 0.6 TO 0.8 but with the same error).
The Feynman X differential cross section integrated over all PT**2.
The PT differential cross section integrated over the full forward XL direction.
The electroproduction of J/psi and psi(2S) mesons is studied in elastic, quasi-elastic and inclusive reactions for four momentum transfers 2 < Q^2 < 80 GeV^2 and photon-proton centre of mass energies 25 < W < 180 GeV. The data were taken with the H1 detector at the electron proton collider HERA in the years 1995 to 1997. The total virtual photon-proton cross section for elastic J/psi production is measured as a function of Q^2 and W. The dependence of the production rates on the square of the momentum transfer from the proton (t) is extracted. Decay angular distributions are analysed and the ratio of the longitudinal and transverse cross sections is derived. The ratio of the cross sections for quasi-elastic psi(2S) and J/psi meson production is measured as a function of Q^2. The results are discussed in terms of theoretical models based upon perturbative QCD. Differential cross sections for inclusive and inelastic production of J/psi mesons are determined and predictions within two theoretical frameworks are compared with the data, the non-relativistic QCD factorization approach including colour octet and colour singlet contributions, and the model of Soft Colour Interactions.
Cross section for elastic J/PSI photoproduction in W bins.
Cross section for elastic J/PSI photoproduction in W bins.
Cross section for elastic J/PSI photoproduction in W bins.
Photoproduction data collected with the H1 detector at HERA in 1994 are used to study the cross-sections for inclusive charged particle production and the structure of the photon. The differential cross-sections dsigma/dpT2, for |eta| < 1 in the HERA laboratory frame, and dsigma/deta for pT > 2 GeV/c and pT > 3 GeV/c have been measured. Model calculations of these cross-sections, based on perturbative QCD, indicate that the results are sensitive to the parton densities of the photon as well as to higher order effects, which are phenomenologically treated by multiple interactions. This sensitivity is exploited to determine the leading order x_gamma distribution of partons in the photon using a new method based on high pT charged particles. The gluon content of the photon is extracted and found to rise with decreasing x_gamma.
Inclusive gamma-p cross section for charged particles in the photoproduction data.
The measured differential pseudorapidity distribution for inclusive chargedparticle production.
A thrust analysis of Large-Rapidity-Gap events in deep-inelastic ep collisions is presented, using data taken with the H1 detector at HERA in 1994. The average thrust of the final states X, which emerge from the dissociation of virtual photons in the range 10 < Q2 < 100 GeV2, grows with hadronic mass M_X and implies a dominant 2-jet topology. Thrust is found to decrease with growing Pt, the thrust jet momentum transverse to the photon-proton collision axis. Distributions of Pt2 are consistent with being independent of MX. They show a strong alignment of the thrust axis with the photon-proton collision axis, and have a large high-Pt tail. The correlation of thrust with MX is similar to that in e+e- annihilation at sqrt(see)=MX, but with lower values of thrust in the ep data. The data cannot be described by interpreting the dissociated system X as a qqbar state but inclusion of a substantial fraction of qqbarg parton configurations leads naturally to the observed properties. The soft colour exchange interaction model does not describe the data.
PT distribution of the photon-originated jet relative to the to the GAMMA* P collision axis in the jet center-of-mass frame, divided by the total GAMMA* P cross section for the respective M_x bin. Jet momentum defined as vector sum of momenta in the positive(negative) thrust hemisphere (thrust jet momentum).
PT distribution of the photon-originated jet relative to the to the GAMMA* P collision axis in the jet center-of-mass frame, divided by the total GAMMA* P cross section for the respective M_x bin. Jet momentum defined as vector sum of momenta in the positive(negative) thrust hemisphere (thrust jet momentum).
PT distribution of the photon-originated jet relative to the to the GAMMA* P collision axis in the jet center-of-mass frame, divided by the total GAMMA* P cross section for the respective M_x bin. Jet momentum defined as vector sum of momenta in the positive(negative) thrust hemisphere (thrust jet momentum).
This paper presents measurements of the production of Ds- mesons relative to Ds+ mesons as functions of x_F and square of p_t for a sample of 2445 Ds decays to phi pi. The Ds mesons were produced in Fermilab experiment E791 with 500 GeV/c pi- mesons incident on one platinum and four carbon foil targets. The acceptance-corrected integrated asymmetry in the x_F range -0.1 to 0.5 for Ds+- mesons is 0.032 +- 0.022 +- 0.022, consistent with no net asymmetry. The results, as functions of x_F and square of p_t, are compared to predictions and to the large production asymmetry observed for D+- mesons in the same experiment. These comparisons support the hypothesis that production asymmetries come from the fragmentation process and not from the charm quark production itself.
No description provided.
No description provided.
No description provided.
We present a measurement of the inelastic, non diffractive J/$\psi$ photoproduction cross section in the reaction $e^{+} p \to e^{+} {J}/\psi X$ with the ZEUS detector at HERA. The J/$\psi$ was identified using both the $\mu^{+}\mu^{-}$ and $e^{+}e^{-}$ decay channels and events were selected within the range $0.4<z<0.9$ ($0.5<z<0.9$) for the muon (electron) decay mode, where $z$ is the fraction of the photon energy carried by the J/$\psi$ in the proton rest frame. The cross section, the $p^2_T$ and the $z$ distributions, after having subtracted the contributions from resolved photon and diffractive proton dissociative processes, are given for the photon-proton centre of mass energy range $50<W<180$ GeV; $p^2_T$ is the square of the J/$\psi$ transverse momentum with respect to the incoming proton beam direction. In the kinematic range $0.4 < z < 0.9$ and $p^2_T > 1$ GeV$^2$, NLO calculations of the photon-gluon fusion process based on the colour-singlet model are in good agreement with the data. The predictions of a specific leading order colour-octet model, as formulated to describe the CDF data on J/$\psi$ hadroproduction, are not consistent with the data.
Cross section for the MU+ MU- decay channel.
Cross section for the MU+ MU- decay channel.
Cross section for the MU+ MU- decay channel.
We present the xF and pT differential cross sections of J/ψ and ψ′, respectively, in the ranges −0.05<xF<0.25 and pT<3.5 GeV/c. The data samples are constituted by about 12 000 J/ψ and 200 ψ′ produced in proton-silicon interactions at 800 GeV/c and decaying into opposite sign muons. The xF and pT distributions are compared with recent results from experiments E789 at the same energy and to leading order QCD predictions using the MRS D0 parametrization for the parton structure function. The measured shapes of the differential cross sections, except for the dσ/dxF at small xF, agree very well with the prediction, even though their value is quite a bit larger than the prediction. We also present the cosθ differential cross section of the J/ψ which indicates unpolarized production in contrast with color octet models predictions.
Additional systematic error given above.
Additional systematic error given above.
Additional systematic error given above.
This paper presents measurements of D^{*\pm} production in deep inelastic scattering from collisions between 27.5 GeV positrons and 820 GeV protons. The data have been taken with the ZEUS detector at HERA. The decay channel $D^{*+}\to (D^0 \to K^- \pi^+) \pi^+ $ (+ c.c.) has been used in the study. The $e^+p$ cross section for inclusive D^{*\pm} production with $5<Q^2<100 GeV^2$ and $y<0.7$ is 5.3 \pms 1.0 \pms 0.8 nb in the kinematic region {$1.3<p_T(D^{*\pm})<9.0$ GeV and $| \eta(D^{*\pm}) |<1.5$}. Differential cross sections as functions of p_T(D^{*\pm}), $\eta(D^{*\pm}), W$ and $Q^2$ are compared with next-to-leading order QCD calculations based on the photon-gluon fusion production mechanism. After an extrapolation of the cross section to the full kinematic region in p_T(D^{*\pm}) and $\eta$(D^{*\pm}), the charm contribution $F_2^{c\bar{c}}(x,Q^2)$ to the proton structure function is determined for Bjorken $x$ between 2 $\cdot$ 10$^{-4}$ and 5 $\cdot$ 10$^{-3}$.
No description provided.
Integrated charm cross sections in two Q**2 regions.
Distribution of the fractional momentum of the D* in the gamma*-p system.
Inclusive $K^0$ and $\Lambda$ photoproduction has been investigated at HERA with the H1 detector at an average photon-proton center of mass energy of 200 GeV in the transverse momentum range 0.5 <p_t <5 GeV. The production rates as a function of $p_t$ and center of mass rapidity are compared to those obtained in deep inelastic scattering at $\av{Q^2}=23 GeV^2$. A similar comparison is made of the rapidity spectra of charged particles. The rate of strangeness photoproduction is compared with $p\bar p$ measurements. The observations are also compared with next-to-leading order QCD calculations and the predictions of a Monte Carlo model.
Additional systematic uncertainty given above.
Additional systematic uncertainty given above.
Additional systematic uncertainty given above.
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