摘要:

The inclusive production of D*+is measured by DELPHI in photon‐photon collisions at LEP‐II energies. The measured cross sections are compatible with the QCD calculations having the contributions from the resolved processes sensitive to the gluon density in photon. The total cross section of the charm quark production in two‐photon collisions at LEP‐II energies is estimated. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1482541

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

InclusiveJ/&psgr; production in photon‐photon collisions has been observed by the DELPHI collaboration at LEP II beam energies. A clean signal from the reaction &ggr;&ggr; →J/&psgr; +Xis seen. Number of observed events,N(J/&psgr; → &mgr;+&mgr;−) = 36 ± 7 for the integrated luminosity 617 pb−1, yielding a cross section of &sgr;(J/&psgr; → &mgr;+&mgr;−) = 25.2 ± 10.2 pb. Based on a study of the event shapes of different types of &ggr;&ggr; processes in the PYTHIA program, we conclude that (74±22)&percent; of the observedJ/&psgr; events are due to the ‘resolved’ photons, the dominant contribution of which is evidently a single color‐octet gluon within the photon. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1482542

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

The production rates ofP‐wave mesons and promptly produced vector mesons for light and heavy flavours are analyzed using results of the LEP experiments. It is shown that the mass dependence of production rates for the bottom B*,B1*andB2*, charm D*+,D10andD2*0, strange charmDs*+andDs10, and light‐flavour &rgr;0andf2(1275), K*0(892) and&Kgr;2*0(1430), &fgr; andf′2(1525)mesons is very very similar. This allows to relate the relative production rates for mesons with different flavours and, surprisingly, their masses. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1482543

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

The ratios of the production rates K*0(892)/K, &fgr;/K, &rgr;0/&pgr;, &ohgr;/&pgr;, &Dgr;++(1232)/p, &Sgr;*+(1385)/&Lgr;, &Ygr;−/&Lgr; and theirxp‐dependence obtained from results of the LEP and SLD experiments in Z0hadronic decays are analyzed. The corresponding ratios for the promptly produced mesons are estimated atxp→ 1. A comparison of the LEP results with those from the Mirabelle and BEBC bubble chamber K+p experiments at 32 and 70 GeV/cshows striking similarity in fragmentation of thes¯valence quark of the incident K+and strange quarks produced in Z0decays. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1482544

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

A new phenomenological approach is suggested for determining the strangeness content of light‐flavour isoscalars. This approach is based on phenomenological laws of hadron production related to the spin, isospin, strangeness content and mass of the particles. From the total production rates per hadronic Z decay of all light‐flavour hadrons, measured so far at LEP, the values of the nonstrange‐strange mixing angles are found to be |&Jgr;P| = 42.3°±3.5°, |&Jgr;V| = 10°±8°, |&Jgr;T| = 16°±11° and |&Jgr;S| = 13°±9°. Our results on the &eegr;−&eegr;′, &ohgr;−&fgr; andf2−f′2isoscalar mixing are consistent with the present experimental evidence. The strangeness content obtained for thef0(980) scalar/isoscalar is not consistent with the values supported by recent model studies and is discussed further in the framework of our approach and theK‐matrix analysis. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1482545

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

VectorAyand tensorAyyanalyzing powers of the inelastic scattering of deuterons with the momenta of 4.5 GeV/c on9Beand 9 GeV/c on1Hand12Cat an angle of ∼80 mr in the vicinity of the excitation of baryonic resonances with masses between 1200 and 2200 MeV/c2have been measured. The values of parameterAysuggest that the role of the spin‐dependent part of theNN→NN*elementary processes is significant. The newAyydata are in good agreement with the previous data at 4.5, 5.5 and 9 GeV/c, obtained at a zero angle, in an overlapping region oft. The results of the experiments are compared with the calculations within the PWIA and &ohgr;‐meson exchange model. The data obtained show that polarization observables of (d,d′) reaction in the vicinity of the excitation of baryonic resonances may be used to study their properties. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1482546

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

The decay rate ofKL→ &pgr;0&ggr;&ggr;has been measured with the NA48 detector at the CERN SPS. The branching ratio is determined to be (1.36 ± 0.03(stat)± 0.03(syst)± 0.03(norm)) × 10−6and the vector coupling constantaV= −0.46 ± 0.03(stat)± 0.03(syst)± 0.02(theo). Using data collected during a special high intensity run at the end of 1999, the following preliminary branching fractions of the weak radiative decays &Ygr;0:Br(&Ygr;0→ &Sgr;0&ggr;) = (3.7 ± 0.5) × 10−3andBr(&Ygr;0→ &Lgr;&ggr;) = (1.9 ± 0.1 ± 0.2) × 10−3have been obtained. Future prospects aiming to study rareKS, &Ygr;0decays and direct CP violation with charged kaon beams are also presented. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1482547

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

The ALEPH experiment, in the year 2000 recorded an excess of Higgs signal‐like events of ∼ 3&sgr; over the background‐only hypothesis, for a Higgs mass of ∼ 115 GeV. This note presents the first results after the final data taking, which were published in November 2000. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1482548

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

Coherent &pgr;+&pgr;−&pgr;−production in the interactions of a beam of 600GeV &pgr;−mesons with C, Cu and Pb nuclei has been studied with the SELEX facility (Experiment E781 at Fermilab). Thea2(1320) meson signal has been detected in the Coulomb (lowq2) region. The Primakoff formalism used to extract radiative decay width of this meson yields &Ggr; = 284 ± 25 ± 25 keV, which is the most precise measurement to date. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1482549

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

An exhaustive study of radiative transitions in mesons is performed in a non relativistic quark model. Three different types of mesons wave functions are tested. The effect of some usual approximations is commented. Overall agreement with experimental data is obtained. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1482550

出版商:AIP    

年代:1902

数据来源: AIP