J. Phys. A

On the basis of Maslov's complex germ method for the Dirac operator in external electromagnetic and torsion fields the quasi-classical spectral series corresponding within the limit h(cross) to 0 to the electron motion along closed stable orbits has been constructed. The quasi-classical energy spectrum is found from the condition of quantization of these orbits, and the quasi-classical asymptotics corresponding to the latter form a complete set of localized quantum state. The method is illustrated in all details by the electron motion in the axial fields as an example.

Phys.Lett.B

A search for lepton flavour violation through the decays Z 0 → eμ , eτ and μτ was made with the DELPHI detector at LEP, using a sample corresponding to an integrated luminosity of 11.2 pb −1 . The number of candidates was consistent with the estimated background. The upper limit on the branching ratio (at 95% confidence level) for Z 0 → eμ was 3.2 × 10 −5 , for Z 0 → eτ was 10.8 × 10 −5 and for Z 0 → μτ was 13.5 × 10 −5 .

Phys.Lett.B

Data from a proton beam-dump experiment at the 70 GeV Serpukhov accelerator were analysed to search for heavy neutrino decays ν H → e + e − ν e at the IHEP-JINR Neutrino Detector. No signal over background was found. The upper limits on the elements if a mixing matrix | U eH | 2 in the mass range 5< m νH <493 MeV and | U eH || U μH | in the mass range 3< m νH <388 MeV. were established at 90% CL.

Phys. Rev. D

We consider deep inelastic (quasi)elastic lepton-nucleon scattering and investigate the possibilities of eliminating or suppressing theoretical uncertainties induced by the nucleon structure in measuring the standard model parameters or in searching for new physics. On the basis of rather general assumptions about nucleon structure we have obtained new relations between cross sections and neutral current parameters which are weakly dependent on the nucleon structure. We also investigate the dependence of the QCD Λ parameter extracted from the data on the unknown large-scale nucleon structure and propose a modification of the conventional QCD predictions in which the dependence on this uncertainty factor is suppressed.

Z.Phys.C

A study ofB meson decays intoDlX final states is presented. In these events, neutral and chargedD mesons originate predominantly fromB+ andB0 decays,

Phys.Lett.B

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.

Phys. Lett. B

A classifier based on a feed-forward neural network has been used for separating a sample of about 123 500 selected hadronic decays of the Z 0 , collected by DELPHI during 1991, into three classes according to the flavour of the original quark pair: u u +d d +s s (unresolved), c c and b b . The classification has been used to compute the partial widths of the Z 0 into b and c quark pairs. This gave Γ c c /Γ h = 0.151 ± 0.008 ( stat. ) ± 0.041 ( syst. ) , Γ b b /Γ h = 0.232±0.005 ( stat. )±0.017 ( syst. ) .

AIP Conf.Proc.

A large deep underwater detector for muons and neutrinos in lake Baikal is currently under construction. We present results on the operation of prototype modules, deployed for long term tests at the future detector site in lake Baikal in April 1992.

Nucl. Phys. B

An analysis of the fluctuations in the phase space distribution of hadrons produced in the decay of 78829 Z 0 has been carried out, using the method of factorial moments. The high statistics collected by the DELPHI experiment at LEP during 1990 allowed studies of the event sample both globally and in intervals of p t and multiplicity, and for different jet topologies and for single jets. A large contribution to the factorial moments of the one-demensional data on rapidity with respect to the event axis comes from hard gluons. Details of factorial moments in two and three dimensions are presented. Influences of resonance decays have been studied by Monte Carlo simulation: one-dimensional factorial moments at low p t , and two-, three-dimensional analyses are affected. Parton shower models describe the data reasonably well.

Nucl. Instrum. Meth. A

A prototype parallel-plate electromagnetic calorimeter, using high pressure gas as active medium, has been tested in an electron beam at Fermilab. Data were taken in the pressure range of 20 to 100 atm, and with incident beam energies ranging from 16 to 125 GeV. Results on the calorimeter response as a function of electric field, gas pressure, and beam energy are presented for pure argon gas and for several argon-methane mixtures. The calorimeter proved easy to operate, and fast signals were obtained with the argon-methane gas.

Phys.Lett.B

Phys. Atom. Nucl.

The 2m hydrogen bubble chamber was exposed to a separated beam of α-particles from the ITEP synchrotron. The momentum of the 4 He-nuclei beam averaged over the bubble-chamber fiducial volume was equal to 2.7 GeV/ c (the kinetic energy of the initial protons in the nuclear rest frame was T p = 220 MeV). The total and topological cross sections were measured as well as the cross section of separate 4 He-p interaction channels and the differential cross sections d σ d t of the elastic 4 He-p scattering. The experimental results have been compared with the data of the previous experiments and with the theoretical predictions based on the Glauber-Sitenko multiple-scattering theory.

Phys.Lett.B

Bose-Einstein correlation between pairs of like-sign charged particles produced in e + e − annihilations near the Z 0 peak have been studied using data taken with the DELPHI detector at LEP. An enhancement is found in the production of pairs of identical pions of similar moments, with respect to a reference sample. Under the hypothesis that the pions are emitted by a spherically symmetrical source with gaussian density, the data indicate a radius of the source of r = 0.62±0.04(stat.)±0.20(syst.) fm. The large systematic uncertainty reflects the sensitivity of r to the choice of the reference sample.

Z.Phys.C

The spectra of prompt electrons and muons from the semi-leptonic decays of heavy hadrons produced inZ0 decays have been used to measure the coupling of theZ0 tob quarks weighted by theB hadrons mean semi-leptonic branching fraction, giving a value:\(BR_{sl}^b *{{\Gamma _{b\bar b} } \mathord{\left/ {\vphantom {{\Gamma _{b\bar b} } {\Gamma _H }}} \right. \kern-\nulldelimiterspace} {\Gamma _H }} = 0.0221 \pm 0.0015\). The data has also been used to measure the value of the fragmentation parameter, defined in the context of the LUND PS Model, version 7.2, giving:\(\varepsilon (b) = \left( {8\begin{array}{*{20}c}{ + 5}\\{ - 3}\\ \end{array}\pm 2} \right)10^{ - 3} \). The corresponding value of the mean fraction of the beam energy taken by aB hadron in the fragmentation of ab quark is:\(\overline {X_E^b }= 0.69\begin{array}{*{20}c}{ + 0.02}\\{ - 0.03}\\ \end{array}\pm 0.01\). If the values of\(\Gamma _{b\bar b} \) andΓH are taken from the Standard Model, the following value is obtained for the mean semi-leptonic braching fraction ofB hadrons: BRslb=(10.1±0.7)%. Taking the value of\({{\Gamma _{b\bar b} } \mathord{\left/ {\vphantom {{\Gamma _{b\bar b} } {\Gamma _{\rm H} }}} \right. \kern-\nulldelimiterspace} {\Gamma _{\rm H} }}\) from an independent analysis of DELPHI data based on the use of the boosted sphericity product, a value: BRslb=(10.1±1.3)% is obtained.

Z.Phys.C

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.

Z.Phys.C

From the analysis of a data sample corresponding to an integrated luminosity of 4.63 pb−1 taken during the 1990 run of LEP at centre of mass energies between 88.2 GeV an 94.2 GeV, the tau decays\(\tau ^ -\to e^ -\bar v_e v_\tau,\tau ^ -\to \mu ^ -\bar v_\muv_\tau,\tau ^ -\to \pi ^ -(K^ -)v_\tau,\tau ^ -\to \rho {}^ - v_\tau\) and their charge conjugates have been studied. The following branching ratios have been measured;\(BR(\tau ^ -\to e^ -\bar v_e v_\tau) = 18.6 \pm 0.8(stat.) \pm 0.6(sys.)\% ,\),\(BR\left( {\tau ^ -\to \mu ^ -\bar v_\muv_\tau} \right) = 17.4 \pm 0.7 \pm 0.6\% ,\), Br(τ− → π− (K−)vτ)=11.9±0.7±0.7%, BR (τ− → ρ− vτ)= 22.4±0.8±1.3%, in good agreement with world averages. The measured electronic and muonic branching ratios lead to a measurement of the strong coupling constant, αs (mτ) = 0.26−0.12+0.09. Extrapolating the αs value frommτ tomZ yields αs (mZ) = 0.109−0.028+0.012.

10.2172/7121463

This report discusses the following topics on the Soleoidal Detector Collaboration: Summary and overview of the detector; physics and detector requirements; central tracking system; superconducting magnet; calorimetry; muon system; electronics; online computing; offline computing; safety; experimental facilities; installation; test and calibration beam plan; and cost and schedule summary.

Z. Phys. C

Inclusive production ofK0 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/dxfdpt2 were measured in the region of incident particle fragmentation (0.4≦xf≦1,pt≦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.

Nucl. Phys. B Proc. Suppl.

The rationale for pursuing beauty physics at the SSC in a fixed target configuration is described. The increased beauty production cross section at the SSC, combined with high interaction rate capability of the proposed detector, results in 10 10–11 produced BB events per year. The long decay length of the B hadrons (≌10 cm) allows direct observation of B decays in the high resolution silicon microstrip vertex detector. To optimize the operation of the proposed beauty spectrometer and the SSC, parasitic extraction of attendant or artificially generated large amplitude protons using crystal channeling is proposed and explored. The large sample of fully reconstructed B events allows detailed studies various CP violating decays with requisite statistics to confront the standard model. The CP physics potentials of the proposed experiment is evaluated and compared with alternative approaches, such as asymmetric e + e − B Factories and specialized hadron colliders.

Nucl.Instrum.Meth.A

Energy deposition as a function of entrance angles and coordinates for 5 GeV e + is studied experimentally in 10×10×35 cm 3 blocks of the lead-glass shower hodoscope detector (SHD); the radiation length is X 0 = 2.5 cm. A method for the reconstruction of electromagnetic shower coordinates ( σ ⋍ 11 mm ) and energies ( σ E /E ⋍ 6% ) is developed for the positron entrance angles 0°–30°.

Phys.Lett.B

The use of low-density hydrogen targets is demonstrated experimentally to be a new way of selecting protonium ( p p atom) annihilations with initial angular momentum L = 1. The mean value and the width of the time distributions which occur between protonium formation and annihilation have been measured at room temperature at 8.2, 4.1, 2.1 mbar. They are (110±10; 45±5), (145±15; 82±9) and (210±25;125±9) ns, respectively.

Phys. Lett. B

The production of prompt and ordinary ( ν ) e was investigated in a proton beam dump experiment at the 70 GeV Serpukhov accelerator measuring their interactions in the IHEP-JINR neutrino detector. An upper limit of σ charm <2.4 μ b/nucleon at 90% CL was obtained near the production threshold.

Phys.Lett.B

Data from a 70 GeV proton-iron beam-dump experiment and the theoretical predictions of light Higgs production from the decays π ± →e ± V (∼) e H, K ± →e ± V (∼) e H, K ± →π ± H, K 0 L →π 0 H, η′→η′H were used to establish limits on the mass of a scalar Higgs boson in the context of the standard model. The mass range 1< m H <72 MeV/ c 2 was excluded at 95% CL.

Nucl.Phys.A

The inclusive cross sections of backward proton production in π − ( K − , p ) -Be, Al, Cu, Pb interactions at 40 GeV/ c are presented. Protons have been detected in the angular range 150°–165° and kinetic energy region 0.1–0.3 GeV. The invariant cross-section ratios for various beam particles are independent of the values of kinetic energy and of the nuclear target type: 〈ƒ K − /ƒ π − 〉= 0.87 ± 0.03 stat ± 0.03 syst , 〈ƒ p /ƒ π − 〉 = 1.82 ± 0.10 stat ± 0.05 syst . The A -dependence of the cross-section slope parameter for A ⩾27 is less than ∼2%.

Phys. Lett. B

From a sample of about 120 000 hadronic Z 0 decays, using a technique based on a separation of the different event categories in the boosted sphericity product, the fraction of b b decays has been measured to be 0.219 ± 0.014 (stat)± 0.019 (syst). Using the DELPHI determination of the hadronic Z 0 width, this corresponds to a partial width τ b b = 378 ± 42 MeV (in good agreement with the standard model prediction of ∼-380 MeV). Combining this measurement with the determinations based on events with high p t leptons gives an estimate for the branching ratio of b into leptons at LEP of (11.2 ± 1.2)%, consistent with previous determinations.