We report differential cross sections for the production of D*(2010) produced in 500 GeV/c pi^- nucleon interactions from experiment E791 at Fermilab, as functions of Feynman-x (x_F) and transverse momentum squared (p_T^2). We also report the D* +/- charge asymmetry and spin-density matrix elements as functions of these variables. Investigation of the spin-density matrix elements shows no evidence of polarization. The average values of the spin alignment are \eta= 0.01 +- 0.02 and -0.01 +- 0.02 for leading and non-leading particles, respectively.
Acceptance corrected differential cross sections for D*+- production as a function of XL, Feynman X.
Acceptance corected differential cross sections for D*+- production as a function of PT**2.
Charge production asymmetry as a function of Feynman X.
Characteristics of hadron production in diffractive deep-inelastic positron-proton scattering are studied using data collected in 1994 by the H1 experiment at HERA. The following distributions are measured in the centre-of-mass frame of the photon dissociation system: the hadronic energy flow, the Feynman-x (x_F) variable for charged particles, the squared transverse momentum of charged particles (p_T^{*2}), and the mean p_T^{*2} as a function of x_F. These distributions are compared with results in the gamma^* p centre-of-mass frame from inclusive deep-inelastic scattering in the fixed-target experiment EMC, and also with the predictions of several Monte Carlo calculations. The data are consistent with a picture in which the partonic structure of the diffractive exchange is dominated at low Q^2 by hard gluons.
Energy flow distributions in the gamma*-pomeron CM frame.. Positive etarap corresponds to the direction of the incoming photon.
Energy flow distributions in the gamma*-pomeron CM frame.. Positive etarap corresponds to the direction of the incoming photon.
Energy flow distributions in the gamma*-pomeron CM frame.. Positive etarap corresponds to the direction of the incoming photon.
Measurements are presented of $K~0$ meson and $\Lambda$ baryon production in deep-inelastic positron-proton scattering (DIS) in the kinematic range $10 < Q~2 < 70\,$GeV$~2$ and $10~{-4} < x < 10~{-2}$. The measurements, obtained using the H1 detector at the HERA collider, are discussed in the light of possible mechanisms for increased strangeness production at low Bjorken-$x$. Comparisons of the $x_F$ spectra, where $x_F$ is the fractional longitudinal momentum in the hadronic centre-of-mass frame, with results from electron-positron annihilation are made. The $x_F$ spectra and the $K~0$ ``seagull'' plot are compared with previous DIS results. The mean $K~0$ and $\Lambda$ multiplicities are studied as a function of the centre-of-mass energy $W$ and are observed to be consistent with a logarithmic increase with $W$ when compared with previous measurements. A comparison of the levels of strangeness production in diffractive and non-diffractive DIS is made. An upper limit of $0.9\,$nb, at the $95\%$ confidence level, is placed on the cross-section for QCD instanton induced events.
The XL distribution for K0 particles.
The XL distribution for LAMBDA particles.
Corrected Mean PT**2 for K0 production RE = E+ P --> E+ K0 X.
A measurement of inclusive charged particle distributions in deep inelastic $ep$ scattering for $\gamma~* p$ centre-of-mass energies $75< W < 175$GeV and momentum transfer squared $10< Q~2 < 160$GeV$~2$ from the ZEUS detector at HERA is presented. The differential charged particle rates in the $\gamma~* p$ centre-of-mass system as a function of the scaled longitudinal momentum, $x_F$, and of the transverse momentum, $p_t~*$ and $<\!\!p_t~{*\,2}\!\!>\,\,$ , as a function of $x_F$, $W$ and $Q~2$ are given. Separate distributions are shown for events with (LRG) and without (NRG) a rapidity gap with respect to the proton direction. The data are compared with results from experiments at lower beam energies, with the naive quark parton model and with parton models including perturbative QCD corrections. The comparison shows the importance of the higher order QCD processes. Significant differences of the inclusive charged particle rates between NRG and LRG events at the same $W$ are observed. The value of $<\!\!p_t~{*\,2}\!\!>\,\,$ for LRG events with a hadronic mass $M_X$, which excludes the forward produced baryonic system, is similar to the $<\!\!p_t~{*\,2}\!\!>\,\,$ value observed in fixed target experiments at $W \approx M_X$.
Differential multiplicites for NRG events.. XL is parallel to the virtual photon axis.
Differential multiplicites for NRG events.. PT is relative to the virtual photon axis.
Mean PT**2 for NRG events.. PT is relative to the virtual photon axis.
Experiment WA82 studied charm production by a π − beam of 340 GeV/ c at the CERN Ω′ spectrometer, using a silicon microstrip vertex detector and an impact parameter trigger. Results on the x F distributions of D + and D − mesons are presented and discussed. A clear excess of D − over D + , increasing at high x F , is observed.
No description provided.
No description provided.
A comparison is made between the properties of the final state hadrons produced in 280 GeV μp interactions and ine+e− annihilation. The Lund model of hadroproduction is used as an aid in understanding the differences observed. The hadron distributions from μp ande+e− interactions are consistent with the quark parton model assumption of environmental independence, provided that the differences in heavy quark production and hard QCD effects in the two processes are taken into account. A comparison with aK+p experiment is also made. Values are also determined for the Lund model parameters σq = 0.410 ± 0.002 ± 0.020 GeV and σ′ = 0.29−0.15 −0.13+0.09+0.10 GeV, controlling the transverse momenta in fragmentation and intrinsic transverse momenta of the struck quark respectively.
With respect to the virtual photon axis.
With respect to the sphericity axis.
With respect to the thrust axis.
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