Comput.Phys.Commun.

A description of the Fortran program HECTOR for a variety of semi-analytical calculations of radiative QED, QCD, and electroweak corrections to the double-differential cross sections of NC and CC deep inelastic charged lepton proton (or lepton deuteron) scattering is presented. HECTOR originates from the substantially improved and extended earlier programs HELIOS and TERAD91. It is mainly intended for applications at HERA or LEPxLHC, but may be used also for muon scattering in fixed target experiments. The QED corrections may be calculated in different sets of variables: leptonic, hadronic, mixed, Jaquet-Blondel, double angle etc. Besides the leading logarithmic approximation up to order O(alpha~2), exact order O(alpha) corrections and inclusive soft photon exponentiation are taken into account. The photoproduction region is also covered.

Nucl. Instrum. Meth. A

In this paper we describe a Cherenkov counter of total internal reflection for particle separation in the momentum range where all types of particles radiate Cherenkov light. The Cherenkov counter prototype with the lucite radiator was tested on the secondary beam of the ITEP (Moscow) accelerator. Dependence of the photomultiplier pulse height on the particle entrance angle was clearly observed.

Phys.Lett.B

A measurement of the Δ ++ (1232) inclusive production in hadronic decays of the Z at LEP is presented, based on 1.3 million hadronic events collected by the DELPHI detector in the 1994 LEP running period. The DELPHI ring imaging Cherenkov counters are used for identifying hadrons. The average Δ ++ (1232) multiplicity per hadronic event is 0.079 ± 0.015 which is more than a factor of two below the JETSET, HERWIG and UCLA model predictions. It agrees with a recently proposed universal mass dependence of particle production rates in e + e − annihilations.

AIP Conf.Proc.

A program of exclusive measurements involving spin observables for p↘p→pKY↘ is nearing production phase. A brief description of the apparatus and its present status is given with emphasis on simulations relevant to the extraction of polarization components of Λ and ∑↘0.

Z.Phys.A

A new measurement of $\Delta\sigma_T$ for polarized neutrons transmitted through a polarized proton target at 16.2 MeV has been made. A polarized neutron beam was obtained from the $~{3}\rm{H}(d,\vec n)~{4}\rm{He}$ reaction; proton polarization over 90\% was achieved in a frozen spin target of 20 cm$~3$ volume. The measurement yielded the value $\Delta\sigma_T=(-126\pm21\pm14)$ mb. The result of a simple phase shift analysis for the $~3S_1-~3D_1$ mixing parameter $\epsilon_1$ is presented and compared with the theoretical potential model predictions.

Phys.Lett.B

A sample of 25000 Z 0 → τ + τ − events collected by the DELPHI experiment at LEP in 1991 and 1992 is used to measure the leptonic branching fractions of the τ lepton. The results are B(τ → eν ν ) = (17.51 ± 0.39) % and B(τ → μν ν ) = (17.02 ± 0.31) %. The ratio of the muon and electron couplings to the weak charged current is measured to be g μ g e = 1.000 ± 0.013 , satisfying e-μ universality. The leptonic branching fraction corrected to the value for a massless lepton, assuming e-μ universality, is found to be B(τ → lν ν ) = (17.50 ± 0.25) %.

Nuovo Cim. A

A two-level trigger is to be applied for suppression of the background and for effective selection of events involving short-lived Λ-, Σ- and φ-particles in the experiment DISTO. The first-level trigger is intended for selection of events by their multiplicity. The second-level trigger is applied for track recognition, in searching for a secondary vertex, and for identifying the detected particles.

Z.Phys.C

Within the Constrained Minimal Supersymmetric Standard Model it is possible to predict the low energy gauge couplings and masses of the 3. generation particles from a few parameters at the GUT scale. In addition the MSSM predicts elektroweak symmetry breaking due to large radiative corrections from Yukawa couplings, thus relating the Z~0 boson mass to the top quark mass. From a chi~2 analysis, in which these constraints can be considered simultaneously, one can calculate the probability for each point in the MSGUT parameter space. Our fits include full second order corrections for the gauge and Yukawa couplings, low energy treshold effects, contributions of all (s)particles to the Higgs potential and corrections to m_b from qluinos and higgsinos, which exclude (in our notation) positive values of the mixing parameter in the Higgs potential \mu for the large tan \beta region. Further constraints can be derived from the branching ratio for the radiative (penguin) decay of the b-quark into s \gamma and the lower limit on the lifetime of the universe, which requires the dark matter density due to the Lightest SUpersymmetric Particle (LSP) not to overclose the universe

Nucl. Instrum. Meth. A

An experimental setup has been created to study rare processes with neutron production. The detecting system comprises a scintillation detector in the form of a cup around which thermal neutron detectors ( BF 3 counters) set in paraffin are placed parallel to the common axis in two concentric circles. The detecting system and registering electronics make it possible to obtain time and amplitude information for each registered event.

Annals Phys.

The momentum-space bosonization method of a Nambu and Jona-Lasinio type model with vector and axial-vector mesons is applied to $\pi\pi$ scattering. Unlike the case in earlier published papers, we obtain the $\pi\pi$ scattering amplitude using the linear and nonlinear realizations of chiral symmetry and fully taking into account the momentum dependence of meson vertices. We show the full physical equivalence between these two approaches. The chiral expansion procedure in this model is discussed in detail. Chiral expansions of the quark mass, pion mass and constant $f_\pi$ are obtained. The low-energy $\pi \pi $ phase shifts are compared to the available data. We also study the scalar form factor of the pion.

Nucl. Instrum. Meth. A

A gas-discharge counter with a cathode of semitransparent aluminized mylar film is found to be sensitive to visible light. Time spectrum of counter signals caused by a pulsed light source showed that the sensitivity to light is due to cathode photoeffect. The proposed mechanism for this phenomenon is based on a decrease in the electronic work function of the aluminium cathode by the electric field in conformity with the Schottky-law. Positive ions arising in the gas discharge are deposited on the dielectric oxide film on the aluminium cathode surface. The resulting surface charge produces a strong electric field at the cathode ( E σ ∼ 10 7 V/cm) which decreases the work function and shifts the red boundary of photoeffect on the aluminium from the UV to visible region of the spectrum. The effect of this phenomenon on the operation of gas-discharge detectors and its possible applications are discussed.

Nucl. Instrum. Meth. A

A single electron circulating in a storage ring is a very peculiar object. Synchrotron radiation quantum fluctuation causes stohastic process in the synchrotron oscillation of an electron. The radiation from a undulator permits one to obtain discret moments of longitudional electron motion. Experiments with a single electron on on the VEPP-3 optical klystrons are described.

Z. Phys. C

The results of total cross section measurements for theνμ,\(\bar \nu _\mu\) interactions with isoscalar target in the 3 – 30 GeV energy range have been presented. The data were obtained with the IHEP-JINR Neutrino Detector in the “natural” neutrino beams of the U-70 accelerator. Neutrino fluxes were obtained by averaging the spectra, based on the calculations with the use of the experimental data on secondary particle yields from the target and muon fluxes measurements in 9 gaps of the muon filter, as well as the spectra determined from quasi-elastic events and spectra defined by extrapolating differential distributiondσ/dy in the regiony=0. The significant deviation from the linear dependence forσtot versus neutrino energy is determined in the energy range less than 15 GeV.

Z. Phys. C

A new approach to the analysis of soft and semihard hadron processes is suggested. In the frame of the Quark-Gluon String Model the interaction of valence quarks and diquarks and sea quarks (antiquarks) of colliding hadrons is taken into account. This one is calculated as the exchange by one nonpertubative gluon, i.e., the cut-off parameter in the gluonic propagator is included. This one allows us to analise the inclusive hadron spectra in hadron collisions at transverse momenta up to 3-4 Gev/c.

Nucl.Phys.A

We plan to investigate sub-threshold K + production in proton bombardment of atomic nuclei in order to study the reaction mechanism through a measurement of the double differential cross section and of K + p and K + d coincidences. The status of the theoretical studies is summarized, and the spectrometer to be installed in the COSY ring is briefly described.

Atom. Data Nucl. Data Tabl.

Form factors involving the 1 s , 2 s , 3 s , and 4 s states of hydrogen-like atoms have been calculated in the Born approximation. Coefficients of exact analytic expressions in terms of the momentum transfer are tabulated for all transitions to discrete states with n ′ ⩽ 10 and l ′ ⩽ 3.

J. Phys. G

The one- and two-step mechanisms of the $pd\to ^3H_\Lambda K^+$ reaction in the range of incident proton kinetic energy 1.13-3.0 GeV have been investigated. A remarkable peculiarity of the two-step mechanism which incorporates subprocesses $pp\to d\pi ^+$ and $\pi^+n\to K^+\Lambda $ is the so called velocity matching providing the presence of all intermediate particles nearly to the on-mass-shell. The differential cross section has been calculated using a realistic model for the hypertritium $^3H_\Lambda $ wave function. The maximum value of the cross section is estimated as $\sim $1nb/sr. The contribution of the one-step mechanism with the elementary process $pN\to NK\Lambda $ into the cross section has been found to be two - three orders of magnitude smaller in comparison with the two-step mechanism.

Phys. Lett. B

The ITEP-PNPI collaboration presents the first results of the spin rotation parameter A + measurements in the second resonance region. The experiment was performed at the ITEP accelerator at a positive pion beam momentum 1.43 GeV/c for scattering angles θ cm = 127° and 133°. The setup was based on a polarized proton target and a carbon-plate polarimeter. The obtained data is compared with the predictions of the existing partial-wave analyses.

Nucl.Phys.B Proc.Suppl.

The International Germanium Experiment (IGEX) has six detectors, containing >90 fiducial moles of 76 Ge, operating underground. Data thus far yield T 1/2 2v = (1.1 ± 0.2) × 10 21 y and T 1/2 0v > 4.2 × 10 24 y(90% CL) if interpreted as a null experiment, or T 1/2 0v > 3.3 × 10 24 y(95% CL) in a more conservative case.

Nucl. Phys. B Proc. Suppl.

Since one and a half year, the underwater Cherenkov telescope NT-36 consisting of 36 photomultipliers attached to 3 strings is operated in lake Baikal. The large statistics of collected data allows for comparison with Monte Carlo predictions starting from the level of detector response up to more sophisticated dependences like the angular distribution of muon intensity.

Nucl. Instrum. Meth. A

A movable polarized proton target is planned to be installed in polarized beams of the Synchrophasotron-Nuclotron complex in order to carry out a spin physics experimental program at Dubna. The project is described and the first proposed experiments are discussed.

Nucl.Phys.A

Phys.Lett.B

We obtain a positive effect in the experiment to search for two-neutrino ββ decay of 150 Nd by using the Time Projection Chamber. The half-life T 1 2 (2β2ν ) = [1.88 −0.39 +0.66 (stat.) ± 0.19 (syst.)] × 10 19 yr is defined from the analysis of the data accumulated with samples of 150 Nd (92% enrichment) and nat Nd (the natural isotopic abundance is 5.6%). The effect to the background ratio is equal to 4 1 . The background from radioactive impurities in the sources is estimated experimentally in a special series of measurements.

Nucl. Instrum. Meth. A

A search for double positron decay and electron capture with positron emission in the transition 78 Kr(0 gs + ) → 78 Se(0 gs + ) has been carried out by using a high pressure ionization chamber surrounded by a set of NaI detectors. Coincidences between the emitted positron(s) and the two (four) consequent annihilation gammas have been looked for as signature(s) of the process(es). The ionization chamber of krypton gas (enriched up to 94.08% in the 78 isotope) registers the positron energy, whereas the set of sodium iodide scintillators searches for the annihilation gamma rays. The features and performances of the experimental device are presented and the results obtained for the half-life limits of the processes investigated are reported.

Nucl.Instrum.Meth.A

To investigate double beta decay processes, the NEMO collaboration began a long-range research and development program in 1988. The NEMO 2 detector, which is now running in the Fréjus underground laboratory (L.S.M. Laboratoire Souterrain de Modane), is the second prototype. It consists of a 1 m 2 source foil sandwiched between Geiger cell drift chambers for electron tracking and two plastic scintillator walls for energy and time-of-flight measurements. The technical description of the detector is followed by the study of the various sources of background.