Low x deep-inelastic ep scattering data, taken in 1994 at the H1 detector at HERA, are analysed in the Breit frame of reference. The evolution of the peak and width of the current hemisphere fragmentation function is presented as a function of Q and compared with e+e- results at equivalent centre of mass energies. Differences between the average charged multiplicity and the multiplicity of e+e- annihilations at low energies are analysed. Invariant energy spectra are compared with MLLA predictions. Distributions of multiplicity are presented as functions of Bjorken-x and Q^2, and KNO scaling is discussed.
The current hemisphere fragmentation as a function of XP in the Breit frame.
The current hemisphere fragmentation as a function of LN(1/XP) in the Breitframe.
Current hemisphere fragmentation as a function of Q for the XP range 0.02 to 0.05, to show scaling violations.
Using the H1 detector at HERA, charged particle multiplicity distributions in deep inelastic ep scattering have been measured over a large kinematical region. The evolution with $W$ and $Q~2$ of the multiplicity distribution and of the multiplicity moments in pseudorapidity domains of varying size is studied in the current fragmentation region of the hadronic centre-of-mass frame. The results are compared with data from fixed target lepton-nucleon interactions, $e~+e~-$ annihilations and hadron-hadron collisions as well as with expectations from QCD based parton models. Fits to the Negative Binomial and Lognormal distributions are presented.
Fully corrected multiplicity distributions. Note that the value of P0 in the 1 to 5 pseudorapidity region is not measured but taken from the reweighted DJANGO 6.0 Monte Carlo generator.
Fully corrected multiplicity distributions. Note that the value of P0 in the 1 to 5 pseudorapidity region is not measured but taken from the reweighted DJANGO 6.0 Monte Carlo generator.
Fully corrected multiplicity distributions. Note that the value of P0 in the 1 to 5 pseudorapidity region is not measured but taken from the reweighted DJANGO 6.0 Monte Carlo generator.
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.
Rates for gamma + 1 jet.
Rates for gamma + 2 jet.
Rates for gamma + 3 jet.
Deep inelastic scattering (DIS) events, selected from 1993 data taken by the H1 experiment at HERA, are studied in the Breit frame of reference. The fragmentation function of the quark is compared with those of \ee data. It is shown that certain aspects of the quarks emerging from within the proton in \ep interactions are essentially the same as those of quarks pair-created from the vacuum in \ee annihilation. The measured area, peak position and widthof the fragmentation function show that the kinematic evolution variable, equivalent to the \ee squared centre of mass energy, is in the Breit frame the invariant square of the four-momentum transfer. We comment on the extent to which we have evidence for coherence effects in parton showers.
Distribution of the cosine of the Breit frame polar angle for data with the Breit frame energy flow selection. Statistical errors only.
Distribution of the cosine of the Breit frame polar angle for data before the Breit frame energy flow selection. Statistical errors only.
The fragmentation function for the current hemisphere of the Breit frame. Data are Breit frame energy flow selected only. Statistical errors only.
This analysis, based on a sample of 170000 hadronic Z0 decays, provides a measurement of the K ± and p/ p differential cross sections which is compared to string- and cluster fragmentation models. The total multiplicities for K ± and p/ p per hadronic event were found to be: NK = 2.26 ± 0.18 and N p = 1.07 ± 0.14. The positions ξ * of the maxima of the differential cross sections as a function of ξ = ln(1/ x p ) for K ± and p/ p were determined to be 2.63 ± 0.07 and 2.96 ± 0.16 respectively. A comparison of the ξ * values for various identified particles measured at LEP with the prediction of the Modified Leading Logarithm Approximation with Local Parton Hadron Duality model has been performed. The measured ξ * position as a function of the hadron mass, after corrections due to particle decays, is in agreement with the model calculation.
Second systematic error comes from the extrapolation to the full Z range (measured range is 0.018 < Z < 0.5) using the JETSET prediction.
Second systematic error comes from the extrapolation to the full Z range (measured range is 0.031 < Z < 0.11) using the JETSET prediction.
No description provided.
A sample of events enriched in bb̄ quark pairs was selected in the data recorded by the DELPHI experiment at LEP during 1992 and 1993, by the presence of secondary decay vertices from short-lived particles. Using this sample, the average multiplicities of K s 0 , K ± , p(p̄), Λ( Λ ) and of charged particles in bb̄ events have been measured, distinguishing the component from fragmentation and the component coming from the decay of b-hadrons. The measurement of the average charge multiplicity in bb̄ events was used to compute the mean fractional beam energy carried by the primary b-hadron, and the difference in charged particle multiplicity between bb̄ events and light quark (uū, dd̄, ss̄) events.
Event multiplicity in bottom events.
Differential cross section for charged particles in BOTTOM tagged hemispheres.
Differential cross section for charged particles in untagged hemispheres.
An analysis of inclusive production of K0 and the meson resonances K*±(892), ρ0(770),f0(975) andf2(1270) in hadronic decays of the Z0 is presented, based on about 973,000 multihadronic events collected by the DELPHI detector at LEP during 1991 and 1992. Overall multiplicities have been determined as 1.962±0.060 K0 mesons, 0.712±0.067 K*±(892) and 1.21±0.15ρ0(770) per hadronic Z0 decay. The average multiplicities off0(975) for scaled momentum,xp, in the range 0.05≤xp≤0.6 and off2(1270) for 0.05≤xp≤1.0 are 0.098±0.016 and 0.170±0.043 respectively. Thef0(975) and ρ0(770)xp-spectra have similar shapes. Thef2(1270)/ρ0(770) ratio increases withxp. The average multiplicities and the differential cross sections are compared with the JETSET Parton Shower model. The model with default parameters fails to reproduce the experimental K0 momentum spectrum at low momentum, describes the K*±(892) and ρ0(770)xp-spectrum shapes, but significantly overestimates their production rates.
Average multiplicity per hadronic event. Extrapolation to the full X range using the X-shape predicted by JETSET 7.4 PS model.
Average multiplicity per hadronic event. Extrapolation to the full X range using the X-shape predicted by JETSET 7.4 PS model.
Average multiplicity per hadronic event. Extrapolation to the full X range using the X-shape predicted by JETSET 7.4 PS model.
An analysis of the production of the Λ baryon in the hadronic decays of the Z 0 is presented, based on about 993K multihadronic events collected by the DELPHI detector at LEP during 1991 and 1992. The differencial cross section of the Λ and the correlations between Λ and Λ produced in the same event are compared to current models, based both on string fragmentation and on cluster decay. The predictions of the string fragmentation model are found to give satisfactory agreements with the data, clearly better than those of the cluster model.
No description provided.
Combined LAMBDA and LAMBDABAR multiplicity.
Errors contain systematic uncertainties.
A study of inclusive production of the meson resonances ρ 0 , K ∗0 (892), ƒ 0 (975) and ƒ 2 (1270) in hadronic decays of the Z 0 is presented. The measured mean meson multiplicity per hadronic event is 0.83 ± 0.14 for the ρ 0 0.64 ± 0.24 for the K ∗0 (892), 0.10 ± 0.04 for the ƒ 0 (975) in the momentum range p > 0.05 p beam ( x p > 0.05) and 0.11 ± 0.05 for the ƒ 2 (1270) for x p > 0.1 . These values and the corresponding differential cross sections ( 1 σ hadr ) d σ d x p for the vector mesons are in good agreement with the predictions of the JETSET 7.3 PS and HERWIG 5.4 models. The ƒ 2 (1270) production is overestimated by HERWIG but its x p -shape is correctly reproduced. The measured ratios of the production cross sections σ(ƒ 2 (1270)) σ(ρ 0 ) = 0.22 ± 0.08 and σ(ƒ 2 (1270)) σ(ƒ 0 (975)) = 3 −1 +7 for x p > 0.1 are consistent with the results obtained in hadronic reactions.
Average multiplicity per hadronic event. Extrapolation to x = 0 using the x shape predicted by JETSET 7.3 PS.
Average multiplicity per hadronic event. Extrapolation to x = 0 using the x shape predicted by JETSET 7.3 PS.
Average multiplicity per hadronic event. Extrapolation to x = 0 using the x shape predicted by JETSET 7.3 PS.
Forum