HEPData Search

An analysis is presented of inclusive π0 production in Z0 decays measured with the DELPHI detector. At low energies, π0 decays are reconstructed by using pairs of converted photons and combinations of converted photons and photons reconstructed in the barrel electromagnetic calorimeter (HPC). At high energies (up to $x_p={2cdot p≪/{sqrt s}=0.75}$) the excellent granularity of the HPC is exploited to search for two-photon substructures in single showers. The inclusive differential cross section is measured as a function of energy for qq̅ and bb̅ events. The number of π0’s per hadronic Z0 event is $N(≪^0)/Z_{had} ^0=9.2pm 0.2({⤪ stat})pm 1.0 ({⤪ syst})$ and for bb̅ events the number of π0’s is ${⤪ N}(≪^0)/{⤪ b⋏r b}=10.1pm 0.4({⤪ stat})pm 1.1 ({⤪ syst})$. The ratio of the number of π0’s in bb̅ events to hadronic Z0 events is less affected by the systematic errors and is found to be 1.09 ±0.05 ±0.01. The measured π0 cross sections are compared with the predictions of different parton shower models. For hadronic events, the peak position in the $xi_{⤪ p}={⤪ ln}(1/{⤪ x_p})$ distribution is $xi_p^{⋆ar}=3.90_{-0.14}^{+0.24}.$ The average number of π0’s from the decay of primary B hadrons is found to be N(B → π0X)/B hadron = 2.78 ± 0.15(stat) ± 0.60(syst).

4 data tables

Table 1

Differential cross section for all events.

Table 2

Mean PI0 multiplicity extrapolated below 0.011 with JETSET 7.3.

Table 3

Differential cross section for the enriched (b bbar) data set.

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rivet Analysis
Measurement of Delta++ (1232) production in hadronic Z decays

The DELPHI collaboration Abreu, P. ; Adam, W. ; Adye, T. ; et al.

Phys.Lett.B 361 (1995) 207-220, 1995.

Inspire Record 399737 DOI 10.17182/hepdata.48095

A measurement of the Δ ++ (1232) inclusive production in hadronic decays of the Z at LEP is presented, based on 1.3 million hadronic events collected by the DELPHI detector in the 1994 LEP running period. The DELPHI ring imaging Cherenkov counters are used for identifying hadrons. The average Δ ++ (1232) multiplicity per hadronic event is 0.079 ± 0.015 which is more than a factor of two below the JETSET, HERWIG and UCLA model predictions. It agrees with a recently proposed universal mass dependence of particle production rates in e + e − annihilations.

2 data tables

Table 1

Differential DELTA(1232)++ cross section. Errors are combined statistics and systematics.

Table 2

Mean multiplicities. Extrapolation to full x range using a combination of JETSET, HERWIG and UCLA models. The second systematic error comes from the uncertainty in the extrapolation.

Study of prompt photon production in hadronic Z0 decays

The DELPHI collaboration Abreu, P. ; Adam, W. ; Adye, T. ; et al.

Z.Phys.C 69 (1995) 1-14, 1995.

Inspire Record 397391 DOI 10.17182/hepdata.48136

None

3 data tables

Table 1

Rates for gamma + 1 jet.

Table 2

Rates for gamma + 2 jet.

Table 3

Rates for gamma + 3 jet.

rivet Analysis
Inclusive measurements of the K+- and p / anti-p production in hadronic Z0 decays

The DELPHI collaboration Abreu, P. ; Adam, W. ; Adye, T. ; et al.

Nucl.Phys.B 444 (1995) 3-26, 1995.

Inspire Record 394052 DOI 10.17182/hepdata.47973

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.

6 data tables

Table 1

Second systematic error comes from the extrapolation to the full Z range (measured range is 0.018 < Z < 0.5) using the JETSET prediction.

Table 2

Second systematic error comes from the extrapolation to the full Z range (measured range is 0.031 < Z < 0.11) using the JETSET prediction.

Table 3

No description provided.

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rivet Analysis
The Production of neutral kaons in Z0 decays and their Bose-Einstein correlations

The OPAL collaboration Akers, R. ; Alexander, G. ; Allison, John ; et al.

Z.Phys.C 67 (1995) 389-402, 1995.

Inspire Record 393503 DOI 10.17182/hepdata.48008

The production of neutral kaons in e+e− annihilation at centre-of-mass energies in the region of the Z0 mass and their Bose-Einstein correlations are investigated with the OPAL detector at LEP. A total of about 1.26×106 Z0 hadronic decay events are used in the analysis. The production rate of K0 mesons is found to be 1.99±0.01±0.04 per hadronic event, where the first error is statistical and the second systematic. Both the rate and the differential cross section for K0 production are compared to the predictions of Monte Carlo generators. This comparison indicates that the fragmentation is too soft in bothJetset andHerwig. Bose-Einstein correlations in Ks0Ks0 pairs are measured through the quantityQ, the four momentum difference of the pair. A threshold enhancement is observed in Ks0Ks0 pairs originating from a mixed sample of$K^0 \bar K^0$ and K0K0 ($\bar K^0 \bar K^0$) pairs. For the strength of the effect and for the radius of the emitting source we find values of λ=1.14±0.23±0.32 andR0=(0.76±0.10±0.11) fm respectively. The first error is statistical and the second systematic.

3 data tables

Table 1

No description provided.

Table 2

The mean x is computed using the method of Lafferty and Wyatt NIM A355(1995)541.

Table 3

The mean x is computed using the method of Lafferty and Wyatt NIM A355(1995)541.

Inclusive strange vector and tensor meson production in hadronic Z0 decays

The OPAL collaboration Akers, R. ; Alexander, G. ; Allison, John ; et al.

Z.Phys.C 68 (1995) 1-12, 1995.

Inspire Record 393954 DOI 10.17182/hepdata.47993

Measurements have been made in the OPAL experiment at LEP of the inclusive production of strange vector φ(1020) and K*(892)0 mesons, and the tensor meson K2*(1430)0. The overall production rates per hadronic Z0 decay have been determined to be 0.100±0.004stat.±0.007syst. φ(1020) mesons, 0.74±0.03stat.±0.03syst. K*(892)0 mesons and (forxE<0.3) 0.19±0.04stat.±0.06syst. K2*(1430)0 mesons. The measurements for the vector states update previously published results based on lower statistics, while the K2*(1430)0 rate represents the first direct measurement of a strange tensor state in Z0 decay. For the vector states, both the overall production rates and normalised differential cross sections, with respect to the scaled energy variablexE, have been compared to JETSET and HERWIG predictions. The peak positions in the ζ=ln(1/xp) distributions have been measured and compared to measurements of other hadron states.

5 data tables

Table 1

No description provided.

Table 2

No description provided.

Table 3

Extrapolated to full x region.

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rivet Analysis
Strange baryon production in Z hadronic decays

The DELPHI collaboration Abreu, P. ; Adam, W. ; Adye, T. ; et al.

Z.Phys.C 67 (1995) 543-554, 1995.

Inspire Record 394716 DOI 10.17182/hepdata.47953

A study of the production of strange octet and decuplet baryons in hadronic decays of the Z recorded by the DELPHI detector at LEP is presented. This includes the first measurement of the∑± average multiplicity. The total and differential cross sections, the event topology and the baryon-antibaryon correlations are compared with current hadronization models.

7 data tables

Table 1

No description provided.

Table 2

No description provided.

Table 3

No description provided.

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rivet Analysis
Measurement of the production rates of charged hadrons in e+ e- annihilation at the Z0

The OPAL collaboration Akers, R. ; Alexander, G. ; Allison, John ; et al.

Z.Phys.C 63 (1994) 181-196, 1994.

Inspire Record 372772 DOI 10.17182/hepdata.48259

The inclusive production rates of π±,K± andp$\bar p$ inZ0 decays have been measured with the OPAL detector at LEP. Using the energy loss measurement in the jet chamber, the momentum range up to the beam energy (45.6 GeV/c) has been covered. Differential cross sections and total particle yields are given. Comparisons of the inclusive momentum spectra and the total rates with predictions of the JETSET and the HERWIG Monte Carlo model are presented. The total single rates are found to be 17.05±0.43 π±, 2.42±0.13K± and 0.92±0.11p$\bar p$ per hadronic event. Predictions of JETSET for cross sections and total rates agree very well for π±; however, for momenta greater than 4 GeV/c,K± rates are underestimated and$\bar p$ rates are overestimated. Combined with data of other particle species there is evidence that the peak positions in the ξ=ln(1/xp) distributions show a different mass dependence for mesons and baryons. However, both JETSET and HERWIG Monte Carlo predictions agree with the observed data.

4 data tables

Table 1

Normalised momentum distribution for charged pion production.

Table 2

Normalised momentum distribution for charged kaon production.

Table 3

Normalised momentum distribution for proton / antiproton production.

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