The production rates and substructure of jets have been studied in charged current deep inelastic e+p scattering for Q**2>200 GeV**2 with the ZEUS detector at HERA using an integrated luminosity of 110.5 pb**-1. Inclusive jet cross sections are presented for jets with transverse energies E_T(jet) > 14 GeV and pseudorapidities in the range -1 < eta(jet) < 2. Dijet cross sections are presented for events with a jet having E_T(jet) > 14 GeV and a second jet having E_T(jet) > 5 GeV. Measurements of the mean subjet multiplicity, <n_sbj>, of the inclusive jet sample are presented. Predictions based on parton-shower Monte Carlo models and next-to-leading-order QCD calculations a re compared to the measurements. The value of alphas(M_Z), determined from <n_sbj> at y_cut=0.01 for jets with 25<E_T(jet)<119 GeV, is alphas(M_Z) = 0.1202 +-0.0052 (stat.) +0.0060-0.0019 (syst.) +0.0065-0.0053 (th.). The mean subjet multiplicity as a function of Q**2 is found to be consistent with that measured in NC DIS.
Inclusive jet cross section DSIG/DQ**2 for jets in the lab. frame. Data from the 1995-1997 sample.
Inclusive jet cross section DSIG/DQ**2 for jets in the lab. frame. Data from the 1999-2000 sample.
Inclusive jet cross section DSIG/DQ**2 for jets in the lab. frame. Data from the combined sample.
The inclusive production of the neutral vector mesons K*0(892) and ϕ(1020), and of the tensor meson ${⤪ K}_{2}^{⇒t 0}(1430)$, in hadronic decays of the Z has been measured by the DELPHI detector at LEP. The average production rates per hadronic Z decay have been determined to be 0.77 ± 0.08 K*0(892), 0.104 ± 0.008 ϕ(1020) and ${⤪ K}_{2}^{⇒t 0}(1430)$. The ratio of the tensor-to-vector meson production yields, $«ngle {⤪ K}_{2}^{⇒t 0}(1430)»ngle$, is smaller than the 〈f2(1270)〉/〈ρ0(770)〉 and $«ngle f_{2}^{⌕ime}(1525)»ngle$ ratios measured by DELPHI. The production rates and differential cross sections are compared with the predictions of JETSET 7.4 tuned to the DELPHI data and of HERWIG 5.8. The K*0(892) and ϕ(1020) data are compatible with model predictions, but a large disagreement is observed for the ${⤪ K}_{2}^{⇒t 0}(1430)$.
SIG in (1/SIG) is the total hadronic cross section. The statistical and systematic errors are combined quadratically.
SIG in (1/SIG) is the total hadronic cross section. The erros are statistical ones. The cross sections SIG(C=A), SIG(C=B), and SIG(C=C) obtained with A) both kaons identified, B) at least one kaon identified, and C) without requiring kaon identification.
SIG in (1/SIG) is the total hadronic cross section. The statistical and systematic erros are combined quadratically. For 0.05<X<0.2 the resulting cross s ection was taken by averaging the results with both identified kaons and with at least one identified kaon, for 0.2<X<1 the results obtained without particle id entification.
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.
The multiplicity distributions of charged particles in full phase space and in restricted rapidity intervals for events with a fixed number of jets measured by the DELPHI detector are presented. The data are well reproduced by the Lund Parton Shower model and can also be well described by fitted negative binomial distributions. The properties of these distributions in terms of the clan model are discussed. In symmetric 3-jet events the candidate gluon jet is found not to be significantly different in average multiplicity than the mean of the other two jets, thus supporting previous results of the HRS and OPAL experiments. Similar results hold for events generated according to the LUND PS and to the HERWIG models, when the jets are defined by the JADE jet finding algorithm. The method seems to be insensitive for measuring the color charge ratio between gluons and quarks.
Corrected charged particle multiplicity for jet resolution parameter YCUT = 0.01.
Corrected charged particle multiplicity for jet resolution parameter YCUT = 0.02.
Corrected charged particle multiplicity for jet resolution parameter YCUT = 0.04.
The multiplicity distributions of charged particles in restricted rapidity intervals inZ0 hadronic decays measured by the DELPHI detector are presented. The data reveal a shoulder structure, best visible for intervals of intermediate size, i.e. for rapidity limits around ±1.5. The whole set of distributions including the shoulder structure is reproduced by the Lund Parton Shower model. The structure is found to be due to important contributions from 3-and 4-jet events with a hard gluon jet. A different model, based on the concept of independently produced groups of particles, “clans”, fluctuating both in number per event and particle content per clan, has also been used to analyse the present data. The results show that for each interval of rapidity the average number of clans per event is approximately the same as at lower energies.
Data for both hemispheres.
Data for both hemispheres.
Data for both hemispheres.
This paper presents an analysis of the multiplicity distributions of charged particles produced inZ0 hadronic decays in the DELPHI detector. It is based on a sample of 25364 events. The average multiplicity is <nch>=20.71±0.04(stat)±0.77(syst) and the dispersionD=6.28±0.03(stat)±0.43(syst). The data are compared with the results at lower energies and with the predictions of phenomenological models. The Lund parton shower model describes the data reasonably well. The multiplicity distributions show approximate KNO-scaling. They also show positive forward-backward correlations that are strongest in the central region of rapidity and for particles of opposite charge.
Charged particle multiplicity distribution for the raw data in full phase space.
Charged particle multiplicity distribution for full phase space. Errors include systematics. A 2 pct correction for excess electrons from photon conversions is not included. The first two points, at N=2 and 4, were not measured but taken from the Lund PS model.
Charged particle multiplicity distribution for single hemisphere. Errors include systematics. A 2 pct correction for excess electrons from photon conversions is not included.
No description provided.
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