Measurement of inclusive π0 production in hadronic Z 0 decays

An analysis is presented of inclusive π⁰ production in Z ⁰ 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 qq? and bb? events. The number of π⁰’s per hadronic Z ⁰ event is $N(?^0)/Z_{had} ^0=9.2pm 0.2({? stat})pm 1.0 ({? syst})$ and for bb? 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 bb? events to hadronic Z ⁰ 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 → π⁰ X)/B hadron = 2.78 ± 0.15(stat) ± 0.60(syst).     

Properties of K0 and Λ inclusive production in charged-current antineutrino-nucleon interactions

In this paper we discuss inclusive spectra of K⁰'s and Λ's produced in charged in charged-current $\text{ν}{}_{\mathrm{\mu }}\text{N}$ interactions in the Fermilab 15 ft bubble chamber filled with a 64% Ne-H₂ mixture. Data presented in terms of the invariant cross section show, when compared with results from experiments with other incident beams, that the behavior of these distributions is approximately the same. The K⁰ and Λ fragmentation functions are presented and the shape of the K⁰ fragmentation function is found to be consistent with the parametrization of Field and Feynman.The average K⁰ and Λ transverse momentum squared as a function of Q², W², x and z is presented. Comparisons for the K⁰'s produced in the current fragmentation region are in qualitative agreement with QCD predictions. The value of the Λ polarization is measured and a positive normal polarization P_N = 0.34±0.18 is found.     

Absolute branching fraction measurements for D+ and D0 inclusive semileptonic decays

We present measurements of the inclusive branching fractions for the decays D+-->Xe+ nu(e) and D0-->Xe+ nu(e), using 281 pb(-1) of data collected on the psi(3770) resonance with the CLEO-c detector. We find B(D0-->Xe+ nu(e)) = (6.46+/-0.17+/-0.13)% and B(D+-->Xe+ nu(e)) = (16.13+/-0.20+/-0.33)%. Using the known D meson lifetimes, we obtain the ratio Gamma(D+)sl/Gamma(D0)sl = 0.985+/-0.028+/-0.015, confirming isospin invariance at the level of 3%. The positron momentum spectra from D+ and D0 have consistent shapes.     

Geometric scaling in inclusive charm production

We show that the cross section for inclusive charm production exhibits geometric scaling in a large range of photon virtualities. In the DESY ep collider HERA kinematic domain the saturation momentum Q(2)(sat)(x) stays below the hard scale micro(2)(c)=4m(2)(c), implying charm production probing mostly the color transparency regime and unitarization effects being almost negligible. We derive our results considering two saturation models which are able to describe the HERA data for the proton structure function at small values of the Bjorken variable x. A striking feature is the scaling on tau identical with Q(2)/Q(2)(sat)(x) above te saturation limit, corroborating recent theoretical studies.     

Possible odderon effects in inclusive hadron production

We consider the possible contribution of odderon (reggeon with α _Odd(0)∼1 and negative signature) exchange to the differences in the inclusive spectra of particle and antiparticle in the central region. The energies and/or accuracy of the currently available experimental data do not allow for a clear conclusion on the presence of an odderon component, but the upcoming LHC data should finally elucidate the question of the existence of the odderon.     

BKP states in the inclusive gluon production

The inclusive cross-section for gluon production is calculated by the dispersion technique in the NLO in the perturbative QCD with a large number of colours. The found cross-section coincides with the one derived in the dipole picture. No trace of the BKP states is found.     

Λ0 hyperon polarization in inclusive production by 24 GeV protons on platinum

We report a search for Λ⁰ polarization in inclusive production by 24 GeV protons on platinum made on data taken at CERN. These data show Λ⁰ polarization of the same direction and magnitude and with the same p_T dependence as found at 300 GeV at Fermilab.     

Investigation of inclusive production ofK 0 andK * (892)0 mesons inK + A interactions at 11.2 GeV

Inclusive production ofK ⁰ andK ^* (892)⁰ mesons inK ⁺ A-interactions (A=Be, Cu, Pb) at the energy 11.2 GeV has been investigated to study hadronisation of the leading \(\bar s\) -quark; the results are presented. Double differential cross sections d²σ/dx _f dp _t ² were measured in the region of incident particle fragmentation (0.4≦x _f ≦1,p _t ≦0.5 GeV/c). The experimental data obtained were analysed on the basis of the Lund model FRITIOF and a quark-gluon model that takes into account colour screening and hadron formation length effects. The experimental data confirm the picture of hadronisation of the leading \(\bar s\) -quark developed in the latter model.     

Interference effects from inclusive resonance production

If pions produced at high-energy reactions are decay products of narrow resonances, Bose interference effects at small invariant pion-pion masses are model-independently calculable from (inclusive) resonance production cross sections. We find that the π^?π^? correlations due to the analogue of the Hanbury Brown-Twiss effect are narrower than those currently observed, the latter being due to more complicated interferences.     

High-energy hadron production and inclusive reactions

Recent data on multiparticle production at high energies are reviewed. The major topics include exclusive analyses, multiplicity distributions, single-particle inclusive spectra, and correlations. An effort is made to explore the physical significance of these results.     

Spin-spin asymmetries in inclusive muon proton charm production

Spin-spin asymmetries have been calculated in the inclusive process \(\mu ^ + p \to \mu c\bar cX\) with reference to photon gluon events only. The resulting asymmetries are small and relatively insensitive to the exact form of the structure functions used.     

CP asymmetries in (semi-)inclusive B^0 decays

It was recently pointed out that inclusive decays could show mixing-induced CP violation. The totally inclusive asymmetry is expected to be tiny [] because of large cancellations among the asymmetries in the charmless, single charm and double charm final states. Enriching particular final state configurations could significantly increase the CP-asymmetry and observability. Such studies can extract fundamental CKM (Cabibbo-Kobayashi-Maskawa) parameters, and (perhaps) even . A superb vertex detector could see CP violation with flavor-tagged mesons within the CKM model. Because the effects could be significantly larger due to new physics, they should be searched for in existing or soon available data samples. Received: 3 July 1998 / Published online: 22 October 1998