Production properties ofD 0,D +,D *+ andD s + in 230 GeV/cπ − andK −-Cu interactions

We have studied the hadronic production of charmed mesons in the NA 32 experiment at CERN. A special trigger together with a high resolution vertex detector consisting of charge coupled devices and silicon microstrip detectors allowed the selection of very clean samples of charmed mesons. We have collected 852 fully reconstructed decays: 60D _s ⁺ →K ⁺ K ^?π⁺, 543D°→K ^?π⁺ andK ^?π⁺π^?π⁺ as well as 249D ⁺→K ^?π⁺π⁺ (or charge conjugate). 147 mesons out of our \({{D^0 } \mathord{\left/ {\vphantom {{D^0 } {\bar D^0 }}} \right. \kern-0em} {\bar D^0 }}\) sample were produced via chargedD ^* state. For all charmed mesons we determine the total production cross-section and study thex _F andp _t ² distributions.     

Measurement ofD meson production in 200 GeV π−-Be interactions

We have measured the differential and total cross sections ofD meson production in 200 GeV π^?-beryllium interactions, using a sample of 48 fully reconstructed and nearly background-freeD mesons in the decay channelsK ^?π^±,K ^?π^±π^± andK ^?π^?π^±π^±. A single electron trigger has been used to select events containing a pair of charmed particles. A vertex telescope of 6 silison microstrip detectors allowed the reconstruction of tracks of charged secondaries and the reconstruction of primary and decay vertices with high precision. The ratio of branching fractions for \(\mathop {D^0 }\limits^{( - )} \to K^ \mp \pi ^ \pm \) to \(\mathop {D^0 }\limits^{( - )} \to K^ \mp \pi ^ \mp \pi ^ \pm \pi ^ \pm \) , and an upper limit for \(D^0 - \bar D^0 \) mixing are presented.     

Neutral and charged D1 production in 360 GeV/c π−p interactions

The first data on the production of D¹(2010) are presented as observed in π⁻ -proton interactions at √s = 27 GeV. It is found that D¹(2010) dominates the total charm D-meson production, without a significant non-central component.     

Inclusive production of vector mesons in π+ p interactions at 250 GeV/c

We report on a study of ρ⁰, ρ⁺, ω, \(\bar K^{*0} (892)\) andK ^*0 (892) inclusive production in π⁺ p interactions at 250 GeV/c, for ρ⁺, \(\bar K^{*0} (892)\) for the first time in a π⁺ p experiment. The data are compared withK ⁺ p data in the same experiment, with results of other experiments and with quark-parton models. Interesting differences are found between ρ^+,0 and ω production.     

Pion and kaon production in 70 GeV/c K − p interactions

Results are presented on the total and differential cross sections for the production of π⁺, π^?, γ, \(\bar K^0 \) ,K ⁰,K ⁺, andK ^? in theK ^? p interactions at 70 GeV/c. The energy dependence of the various production processes shows in paticular a strong rise of the γ cross section and an increase of the average transverse momentum of the charged pion in the fragmentation regions.     

Observation of ω1− production in K−p interactions at 11 GeV/c

Clear evidence is presented for the production of an Ω¹⁻ resonance of mass 2253±13 MeV/c² and width 81±38 MeV/c² in K⁻p interactions at 11 GeV/c. The state is observed in the Ξ (1530)K̄ decay mode, and the corresponding inclusive cross section is estimated to be 630±180 nb. Comparisons are made with theoretical predictions and with similar states observed inhyperon beam induced data.     

Light-front analysis of π− mesons produced in MgMg collisions at 4.3A GeV/c

Light-front analysis of π⁻ mesons in MgMg collisions is carried out. The phase space of secondary pions is naturally divided into two parts in one of which the thermal equilibration assumption seems to be in good agreement with the data. Corresponding temperatures are extracted and compared to the results of other experiments. The experimental results have been compared with the predictions of the Quark-Gluon String Model (QGSM) and satisfactory agreement between the experimental data and the model has been found.     

2.22 GeV ηη′ structure observed in 38 GeV / c and 100 GeV / c π−p collisions

A structure has been observed at 2220 MeV in the mass spectrum of ηη′ systems produced by 38GeV/c and 100 GeV/c′ negative pions on protons. The angular distribution of the decay products shows that this structure is presumably a spin J ⩾ 2 meson.     

\bar \Lambda Production inK − p interactions at 32 GeV/c

Antilambda production is studied inK ^? p interactions at 32 GeV/c. Both total and differential cross sections are presented. The inclusive \(\bar \Lambda \) production cross section amounts to 109±7 μb. A remarkable energy dependence is observed, σ( \(\bar \Lambda \) ) increasing by a factor of four between 14.3 and 32 GeV/c. Thep _⊥ ² distribution exhibits an exponential fall-off with a slope of 3.3±0.2 (GeV/c)^?2. Most of the \(\bar \Lambda \) 's are emitted in the forward hemisphere. The invariantx distribution increases between 14.3 and 32 GeV/c. Data are presented for \(\bar \Lambda \) production inK ^- p→Λ \(\bar \Lambda \) +X K ^- p→ \(\bar \Lambda \) K ⁿ +X, andK ^- p→ \(\bar \Lambda \) p+X.     

Production of G(1590) and other mesons decaying into η pairs by 100 GeV/c π− on protons

New data on the scalar G(1590) meson which decays into ηη have been obtained in an experiment at the CERN SPS. η pairs are detected with the electromagnetic calorimeter GAMS both through their decay into 4γ and into 8γ. ϵ(1300), f(1270), f′(1525) as well as the spin-4 h(2030) mesons have also been observed to decay in the same mode. Their branching ratios have been evaluated. The presence of high-mass spin-0 and spin-2 structures is discussed.     

Production of η mesons in e+e− annihilations at √s=29 GeV

Data from e⁺e⁻ annihilations at 29 GeV have been used to measure the production cross section and fragmentation function of η mesons. The signal is observed in the η→γγ decay channel. The fragmentation for p_η>1.5 GeV/c agrees well with the prediction of the Lund model, whereas the prediction of the Webber model lies above the data. The mean multiplicity is measured to be 〈n_η〉=0.58±0.10 η mesons per hadronic event, of which 0.51 represents the direct production of η and η′ mesons in the fragmentation chain.     

Neutral strange particle production in high transverse momentum π− nucleus interactions at ∼40 GeV/c

Measurements ofK _s ⁰ , Λ and \(\bar \Lambda \) production in π^? nucleus (C, Cu, Pb) interactions are presented. The experiment was carried out with the streamer chamber spectrometer RISK using a π^? beam of ～40 GeV/c and a trigger requiring a secondary charged particle with transverse momentum above 1.1 GeV/c. Production cross sections, relative production rates and distributions of Feynmanx and transverse momentum squared as well as correlations between theV ⁰ and the trigger particle are presented. The results are compared and found to be in agreement withK _s ⁰ , Λ and \(\bar \Lambda \) data from untriggered π^? p and π^? C interactions, except for the relative production rate of antilambdas which is about to times larger in high-p _t collisions. Our results can be well interpreted within the dual topological unitarization model.     

Production cross section and electroweak asymmetry of D* and D mesons produced in e+e− annihilations at 29 GeV

The production of D^* and D mesons has been studied in e⁺e⁻ annihilations at √s = 29GeV. The data, corresponding to an integrated luminosity of 300 pb⁻¹, were obtained using the HRS detector at PEP. The cross section is measured to be R (D⁰ + D⁺) = 2.40±0.35 and we determine the electroweak asymmetry to be −9.9 ± 2.7%, which corresponds to an axial vector coupling constant product g^eg^c = 0.26 ± 0.07.     

Study of theK + K − π+ π− system centrally produced in the reactions π+ p→π+(K + K − π+ π−)p andpp→p(K + K − π+ π−)p at 85 GeV/c

The reactions π⁺ p→π⁺(K ⁺ K ^? π⁺ π^? p andpp→p(K ⁺ K ^? π⁺ π^?)p where the (K ⁺ K ^? π⁺ π^?) system is centrally produced have been studied at 85 GeV/c. 48% of the final state proceeds through single or double vector meson resonant production i.e.,K ^*0(890) (37%), ? (4%),ρ ⁰ (7%). Evidence is found for associatedK ^*0 (890) \(\bar K\) ^*o (890) production (6.4±1.1%) with a cross section ten times higher than that found for associated ? ? production in the same experiment.     

Scaling of semi-inclusive spectra of π−mesons frompp interactions

An analysis of experimental data for 6–400 GeV/c shows that a two-parameter dependence of spectra on collision energy \((\sqrt s )\) and the multiplicity of negative particles (n) reduces to a single-parameter dependence on some function of these variables, which can be well approximated by a simple expressions/n.     

The analysis of π− mesons produced in nucleus-nucleus collisions at a momentum of 4.5 GeV/c nucleon in light front variables

The light front analysis of π⁻ mesons in He(Li,C), C-Ne, C-Cu and O-Pb collisions is carried out. The phase space of secondary pions is divided into two parts in one of which the thermal equilibrium assumption seems to be in a good agreement with the data. Corresponding temperatures T are extracted and their dependence on (A _P·A _T)^1/2 is studied. The results are compared with the predictions of the Quark-Gluon String Model (QGSM). The QGSM satisfactorily reproduces the experimental data for light and intermediate-mass nuclei. Received: 29 September 1999     

Angular dependence of Bose-Einstein correlations in interactions of π+ andK + mesons with protons and nuclei at 250 GeV/c

The angular dependence of Bose-Einstein correlations is studied in interactions of ⁺ andK ⁺ mesons with protons and nuclei at 250 GeV/c. The pion source is found to be elongated along the interaction axis in the c.m.s., with the ratioa between transverse and longitudinal dimension equal to 0.55±0.06 for the case of proton, 0.53±0.13 for the case ofAl and 0.33±0.21 for the case ofAu target. For meson-proton interactions, indication for an increase of the elongation is found with increasing event multiplicity, pair momentum and particle transverse momentum.Now at UIA, Wilrijk, Belgium     

Inclusive proton and antiproton production in π± hydrogen and π± nucleus interactions at 30 GeV/c

Data on fast protons and antiprotons produced byπ ^± incident on hydrogen and nuclear targets at 30 GeV/c are presented. The results covering the kinematic range 0.32 F <0.54 andp _T >0.2 GeV/c, complete our previous paper. We give results on inclusive cross-sections as a function ofx _F , ofp _T ² and on cross-section ratios. A search for effects of nuclear matter on the production of protons and antiprotons has yielded no major effects beyond final state absorption.     

Inclusive production ofK s 0 , K s 0 K s 0 andK *±(892) in\bar pp interactions at 3.0, 3.5, 4.0 and 4.5 GeV/c

InclusiveK _s ⁰ andK _s ⁰ K _s ⁰ production in \(\bar pp\) interactions at 3.0, 3.5, 4.0 and 4.5 GeV/c are studied. Cross sections ofK _s ⁰ , K _s ⁰ K _s ⁰ andK ^*±(892) are presented for each incident momentum. The production ofK _s ⁰ andK ^*±(892) through annihilation process is investigated. It is found that the annihilation process is dominant but decreases with incident momentum. The annihilation process is compared withe ⁺ e ^? interactions. Remarkable similarity between them is found in the \({{x_0 = 2E(K_s^0 )} \mathord{\left/ {\vphantom {{x_0 = 2E(K_s^0 )} {\sqrt s }}} \right. \kern-0em} {\sqrt s }}\) distribution. Events with two detectedK _s ⁰ 's are analyzed. The result shows theK _s ⁰ K _s ⁰ pairs are produced in the central region of c.m. system and there is a clearS ^* signal in theK _s ⁰ K _s ⁰ effective mass distribution.     

Inclusive γ and π0 production in\bar PP interactions at 32 GeV/c

The inclusive π⁰ and γ production is studied in a \(\bar PP\) experiment at 32.1 GeV/c performed in the Mirabelle bubble chamber with a sensitivity of ～2.7 events/μb. Total and topological π⁰ cross sections are presented. The π⁰ and γ longitudinal and transverse momentum distributions are obtained and compared with \(\bar PP\) data at 22.4 GeV/c andK ^± P data at 32.1 GeV/c. The inclusive π⁰ distributions are also compared to those obtained for charged pions in the same experiment.