Phys. Lett. B

A strong increase of the mean transverse momentum 〈 p t 〉 with the number of charged particles n ch is observed in e + e − annihilations into hadrons at LEP energies. The effect resembles correlations observed in hadron-hadron interactions. In e + e − annihilations the 〈 P t 〉 and n ch correlations can be accounted for by gluon radiation.

Phys.Lett.B

The weak mixing angle has been measured from the charge asymmetry of hadronic events with two different approaches using the DELPHI detector at LEP. Both methods are based on a momentum-weighted charge sum to determine the jet charge in both event hemispheres. In a data sample of 247 300 multihadronic Z 0 decays a charge asymmetry of 〈 Q F 〉 − 〈 Q B 〉 = −0.0076±0.0012(stat.)±0.0005(exp. syst.)±0.0014(frag.) and a raw forward-backward asymmetry of A raw FB = −0.0109±0.0020(stat.)±0.0010(exp. syst.)±0.0017(frag.) have been measured. This result corresponds to a value of sin θ eff =0.2345±0.0030(exp.)±0.0027(frag.), sin 2 θ MS =0.2341±0.0030( exp. )±0.0027( frag. ) and to sin 2 θ W =1− m 2 W / m 2 Z =0.2299± 0.0030(exp.)±0.0027(frag.)±0.0028(theor.). The experimental error is the quadratic sum of the statistical and the experimental systematic error and the theoretical error originates from a value of m t =130±40 GeV/ c 2 and a range of m H from 45 GeV/ c 2 to 1000 GeV/ c 2 .

Nucl. Instrum. Meth. A

The structure of traditional data processing systems looks approximately like this: space coordinates of events C i are searched, parameters X j (angles, momenta and so on) are estimated together with their covariance matrix and then kinematical analysis is performed within some hypothesis about the physical event. In the case of the Lagrange multipliers method it means minimization of the functional M=(X−X m ) T S (X−X m )+2ƒα , where X is the parameter vector, X m is its measured value, S −1 the covariance matrix of parameter X, ƒ the vector of constraints, and α the vector of Lagrange multipliers.

Phys.Lett.B

An analysis of the production of strange particles from the decays of the Z 0 boson into multihadronic final states is presented. The analysis is based on about 90 000 selected hadronic Z 0 decays collected by the DELPHI detector at LEP in 1990. K s 0 , K ∗± , Λ( Λ ) and Ξ − ( Ξ + ) have been identified by their characteristic decays. The measured production cross sections are compared with predictions of the Lund Monte Carlo tuned to data at PEP/PETRA energies.

Nucl. Instrum. Meth. A

The problem of minimization of the functional χ 2 = ∑ i, j nf, nf [C i (X)−C m i ]G ij [C j (X)−C m j ]; i, j=1… nf , with the constraints ƒ λ (X)=0; λ=1…nc , is considered. Here: X is the vector of the parameters to be estimated, C i ( X ) = ( C ( X )) i is the vector of functions, C i m are their measured values, and G −1 the covariance matrix.

Theor.Math.Phys.

For the Schrödinger and Dirac equations in an external gauge field with symmetry groupSU(2), we construct to any degree of accuracy in powers ofh1/2,h→0, approximate dynamical states in the form of wave packets—semiclassical trajectory-coherent states. For the quantum expectation values calculated with respect to these semiclassical states we obtain for the operators of the coordinates, momenta, and isospin of the particle Hamiltonian equations of motion that are equivalent (in the relativistic case after transition to the proper time) to Wong's well-known equations for a non-Abelian charge with isospin 1/2.

Phys. Lett. B

We have searched for possible fourth family heavy neutrinos, pair produced in Z 0 decays, in a sample of about 112 000 hadronic Z 0 final states collected with the DELPHI detector. For all mixing matrix elements we exclude a new Dirac neutrino lighter than 44.5 GeV at a 95% confidence level, if the neutrino couples to the electron or muon family, and lighter than 44.0 GeV, if the neutrino couples to the tau family. Depending on the values of the mixing element and to which lepton family the neutrino couples, we obtain mass limits up to 46.2 GeV. For all mixing matrix elements we exclude a new Majorana neutrino lighter than 39.0 GeV, if it couples to the electron or the muon family, and lighter than 38.2 GeV, if it couples to the tau family. Depending on the values of the mixing matrix element and to which lepton family the neutrino couples, we obtain mass limits up to 44.7 GeV. We also exclude stable new Dirac neutrinos lighter than 45.0 GeV and new Majorana neutrinos lighter than 39.5 GeV.

Phys.Lett.B

We have searched for pair produced scalar leptoquarks each decaying to a quark and a charged lepton in a sample of 116 000 hadronic Z 0 events produced at LEP. No candidate was detected and cross section and branching ratio limits are set for the above process at 95% CL. Mass limits are found to be about 42 GeV/ c 2 depending only slightly on the models used and a coupling times branching ratio exclusion line is drawn for a scalar leptoquark with a free coupling. We have also probed the mass region above 45 GeV/ c 2 for a singly produced scalar leptoquark and set limits on the cross section and the coupling λ 2 /4 π up to 60 GeV.

Nucl.Phys.B

The search in DELPHI data for neutral Higgs bosons is described. No candidate for the Standard Model Higgs is seen in Z 0 decays to H 0 ν ν , H 0 μ + μ − or H 0 τ + τ − after selections that proved efficient for finding simulated H 0 . One remaining candidate for Z 0 → H 0 e + e − is consistent with background. Together with our earlier studies, these results restrict the H 0 mass to be above 38 GeV/ c 2 at the 95% confidence level. No signal is found for decays of Minimal Supersymmetric Standard Model neutral Higgs bosons to τ + τ − . Limits are obtained for their decays to produce four jets.

Int.J.Mod.Phys.A

A search has been performed for weakly interacting neutral light scalar and pseudoscalar particles in a proton-iron beam dump experiment via the Bethe-Heitler process. No positive signal was observed. Limits are derived on the masses of these particles in the framework of the Standard Model and its minimal supersymmetric extension (MSSM) comparing the experimental results with expectations for Bethe-Heitler e+e− and μ+μ− pair production. The Higgs particle of the SU2L×U1 Standard Theory is excluded for masses in the range mH<0.9 MeV at 95% CL. Limits on light Higgs particles of the MSSM and Peccei-Quinn like axions are derived.

AIP Conf. Proc.

Information recently obtained by the PS179 (STREAMER) collaboration at LEAR on p̄4He elastic scattering, strangeness production in antiproton annihilation at rest and p̄ annihilation in nuclear photo‐emulsion is presented.

AIP Conf. Proc.

A confirmation of the resonance AX(1565), a precision measurement of the Pontecorvo reaction p̄d→π− p and the first antineutron annihilations are the preliminary results obtained by the OBELIX Spectrometer.

Class. Quant. Grav.

Using Maslov's complex sprout method the complete set of quasiclassical trajectory-coherent quantum states (TCS) for the Klein-Gordon equation in a curved spacetime in the presence of external electromagnetic and background scalar fields up to the order of O(32/) at to 0 was constructed. The approximate solutions Psi v are strongly peaked around the worldline neighbourhood of the charged particles. The method of reducing the initial Klein-Gordon equation to the Schrodinger type equation for which Psi v are exact solutions has been developed. In the quasi-classical trajectory-coherent approximation based on the ' gamma -reconstruction' technique the concept of the local time for a quantum scalar particle in a curved spacetime has been suggested. In general it has been stated that the constructed TCS Psi v permit the standard quantum-mechanical interpretation.

Phys.Lett.B

The q 2 dependence of the vector form factor has been investigated using 3.2 × 10 4 K + → π 0 e + ν decays. The usual linear parametrization. ƒ + (q 2 ) = ƒ(0)(1+λ + q 2 /m π 0 0 ) gives λ + = 0.0284±0.0027. An analysis of the Dalitz plot density distribution for K e3 + decays yields the values for the scalar and tensor couplings ƒ s and ƒ t , and their relative phase angle ø st .

Nucl. Instrum. Meth. A

In this article a simple method for making multiwire chambers is described. The chamber design does not involve any frame structure, which permits the

Phys. Rev. C

The vector analyzing power iT11 of the reaction πd→pp was measured at Tπ=350, 400, and 450 MeV. The results obtained at Tπ=350 MeV are in agreement with earlier measurements of iT11 at 325 MeV. With increasing energies our results show a marked increase in the vector analyzing power up to a value close to its theoretical limit at Tπ=450 MeV (√s =2.40 GeV). In this energy region broad structure has been found in earlier measurements of dσ/dΩ and Ay0.

Nucl.Phys.A

A search for superheavy hydrogen isotopes and multineutrons in the two- and three-body channels of π − absorption at rest on a 9 Be target has been carried out. The 5 H system revealed a broad resonance with E r = 7.4±0.7 MeV and Γ = 8±3 MeV. An indication has been obtained for the resonance in the 3n system with E r = 3±1 MeV. The measured parameters for 4 H are close to the results of previous experiments.

Z. Phys. C

The possibility of the experimental investigation of the radiative tau decay into pion is discussed including background conditions. The decay width is estimated to be Br(τ→vτπγ)=0.15% (at the minimal registered photon energy 50 MeV). The contribution of the structural component is 10% of the total radiation. The main background is produced by photons from the τ→vτπ−π0 decay. We investigate the angular and energy spectra of the decay products and analyse the background conditions. The kinematic region was found where the structural radiation dominates over background.

Nucl. Phys. A

A new technique has been developed for investigation of the spin-neutrino angular correlation in electron capture. The technique is based on measurement of Doppler shifts in the energy of gamma-quanta resulted from the decay of polarized nuclei. This technique was used to investigate the decay of 56 Co nuclei polarized by the magnetic field of the Fe host at the temperature 17 mK. A Doppler shift + 12 ± 1 eV has been obtained for the 2598.5 keV gamma-line. It allows to admit that the magnetic moment of the 56 Co nucleus has a positive sign and to estimate the behaviour of the recoil ion of 56 Fe in the Fe crystal lattice.

J.Phys.G

A status report is given on an experiment started in 1987 at PSI to search for the lepton flavour violating muon to electron conversion process. The motivation for this experiment, the design and performance of the detector (SINDRUM II), and results of a first run are presented. No candidate of the process mu -Ti to e-Ti was found, and, using two independent determinations of the muon stop rate, an upper limit for the branching ratio relative to muon capture Bmu e<4.4.10-12 (90% C.L.) was obtained. This result confirms the current best value for the upper limit found at TRIUMF (4.6.10-12).

Phys.Lett.B

The ( 3 He, t) charge-exchange reaction on carbon nuclei and protons, accompanied by the excitation of Δ isobars in a target, has been studied at beam momenta from 4.40 to 18.3 GeV/ c . The analysis is performed to explain why the Δ-peak in the inclusive A( 3 He, t) and A ( p , n ) measurements is shifted towards lower energy transfers (in comparison with the reactions on free nucleons) but in the exclusive ones it is shifted towards higher transfers. An attempt is undertaken to determine the characteristics of Δ excitation in nuclei by a ( 3 He, t) reaction that is free of the admixture of quasifree Δ production.

Nucl. Instrum. Meth. A

A polarimeter for polarized deuteron beams at the JINR synchrophasotron in the energy range of several GeV per nucleon is described. A left-right-symmetrical detector configuration is used to measure vector and tensor polarizations of deuterons in the forward scattering on a liquid hydrogen target. In this paper we present the results of various measurements to adjust optimum conditions for the working regime of the ion source.

Z. Phys. A

We measured diffractive scattering cross sections of alpha-particles on carbon, aluminium, copper and lead using the beam of the Dubna synchrophasotron at 3.64 GeV/nucleon. The data are compared with model predictions of the Glauber-Sitenko multiple scattering theory. Large discrepancies between experiment and calculations appear at four-momentum transfers above ∼0.25 (GeV/c)2. Various theoretical attempts to improve the description of high-energy alpha-scattering data are discussed.

Nucl. Phys. A

New data are reported on antiproton annihilations at rest with production of Λ and K s 0 , using a streamer chamber with 3 He, 4 He and 20 Ne as gas targets. The data include Λ, K s 0 , ΛK s 0 and K s 0 K S 0 production rates and momentum distributions, π − momentum spectra, mean numbers of charged particles generally and of negatively charged particles separately for different reaction channels. The yields are compared to simple combinatorial calculations based on the extreme assumptions of Λ production via B = 1 or via B = 0 ( K ̄ rescattering) annihilations. Λ and K s 0 momentum spectra are compared to simple model calculations where B = 0 and B = 1 annihilations with and without final-state interactions are considered. A review of existing data on Λ and K s 0 production is presented, showing the dependence on the p ̄ momentum and on the mass number of the target.

Phys. Scripta

A sharp peak at 1150 MeV c−2 in the π−π+π−π+ -system in the final state of 4He-reactions at 0.6 GeV c−1 incident momentum is seen. This system probably has spin-parity = 0+ or 2+, which are possible spin-parity assignments of a glueball.