Nucl.Phys.A

The NEMO-2 tracking detector located in the Fréjus Underground Laboratory was designed as a prototype of the NEMO-3 detector to study neutrinoless (Oν) and two neutrino (2ν) double-beta decay (ββ) physics. After 10357 h of running with an isotopically enriched selenium source (2.17 mol yr of 82 Se) a ββ2ν decay half-life of T 1 2 = (0.83 ± 0.10( stat ) ± 0.07 ( syst )) × 10 20 yr was measured. Limits with a 90% C.L. on the 82 Se half-lives of 9.5 × 10 21 yr for ββ0ν decay to the ground state, 2.8 × 10 21 yr to the (2 + ) excited state and 2.4 × 10 21 yr for ββ 0 νχ 0 decay with a Majoron ( χ 0 ) were also obtained.

IEEE Trans. Nucl. Sci.

The DISTO collaboration has built a large-acceptance magnetic spectrometer designed to provide broad kinematic coverage of multi-particle final states produced in $pp$ scattering. The spectrometer has been installed in the polarized proton beam of the Saturne accelerator in Saclay to study polarization observables in the $\vec{p} p \to p K^{+} \vec{Y}$ ($Y = \Lambda, \Sigma^{0}$ or $Y^{*}$) reaction and vector meson production ($\phi, \omega$ and $\rho$) in $pp$ collisions. The common signature of such events is the multiplicity of four charged particles in the final state. A flexible 1st level trigger which uses topological information from fast detectors (scintillating fibers and hodoscope) has been built. It is completely software programmable through a menu-driven user interface and allows switching between production and monitor triggers on successive beam spills.

IEEE Trans. Nucl. Sci.

The DISTO collaboration has built a large-acceptance magnetic spectrometer designed to provide broad kinematic coverage of multi-particle final states produced in $pp$ scattering. The spectrometer has been installed in the polarized proton beam of the Saturne accelerator in Saclay to study polarization observables in the $\vec{p} p \to p K^{+} \vec{Y}$ ($Y = \Lambda, \Sigma^{0}$ or $Y^{*}$) reaction and vector meson production ($\phi, \omega$ and $\rho$) in $pp$ collisions. The data acquisition system is based on a VME 68030 CPU running the OS/9 operating system, housed in a single VME crate together with the CAMAC interface, the triple port ECL memories, and four RISC R3000 CPU. The digitization of signals from the detectors is made by PCOS III and FERA front-end electronics. Data of several events belonging to a single Saturne extraction are stored in VME triple-port ECL memories using a hardwired fast sequencer. The buffer, optionally filtered by the RISC R3000 CPU, is recorded on a DLT cassette by DAQ CPU using the on-board SCSI interface during the acceleration cycle. Two UNIX workstations are connected to the VME CPUs through a fast parallel bus and the Local Area Network. They analyze a subset of events for on-line monitoring. The data acquisition system is able to read and record 3500 ev/burst in the present configuration with a dead time of 15%.

Nucl. Instrum. Meth. A

Prototypes of the FERMI system have been used to read out a prototype of the ATLAS hadron calorimeter in a beam test at the CERN SPS. The FERMI read-out system, using a compressor and a sampling ADC, is compared to a standard charge integrating read-out by measuring the energy resolution of the calorimeter separately with the two systems on the same events. Signal processing techniques have been designed to optimize the treatment of FERMI data. The resulting energy resolution is better than the one obtained with the standard read-out.

Yad.Fiz.

Various exact solutions of two-particle eigenvalue problems for nonrelativistic contact four-fermion current-current interaction are obtained. Specifics of Goldstone mode is investigated. The connection between a renormalization procedure and construction of self-adjoint extensions is revealed.

Surveys High Energ.Phys.

On a nonrelativistic contact four-fermion model we have shown that the simple Lambda-cut-off prescription together with definite fine-tuning of the Lambda dependency of "bare"quantities lead to self-adjoint semi-bounded Hamiltonian in one-, two- and three-particle sectors. The fixed self-adjoint extension and exact solutions in two-particle sector completely define three-particle problem. The renormalized Faddeev equations for the bound states with Fredholm properties are obtained and analyzed.

Nucl.Phys.A

We reanalyse the production of $p\bar{p}$ pairs in proton-nucleus and nucleus-nucleus collisions employing novel elementary cross sections for baryon-baryon and pion-baryon production channels based on a boson-exchange model. In contrast to previous transport studies performed in the literature the secondary pion induced channel is found to be most important in both p+A and A+A collisions at subthreshold energies. A detailed comparison with the experimental data available indicates that sizeable attractive $\bar{p}$ potentials in the order of - 100 to - 150 MeV at normal nuclear matter density are needed to reproduce the size and shape of the experimental spectra.

Nucl. Phys. B Proc. Suppl.

We review the present status of the Baikal Underwater Neutrino Experiment and report on neutrino events recorded with the detector stages NT-36 and NT-96.

Prog.Part.Nucl.Phys.

We review the present status of the Baikal Underwater Neutrino Experiment and present results obtained with the various stages of the stepwise increasing detector: NT-36 (1993-95), NT-72 (1995-96) and NT-96 (1996-97). Results cover atmospheric muons, first clear neutrino events, search for neutrinos from WIMP annihilation in the center of the Earth, search for magnetic monopoles, and -- far from astroparticle physics -- limnology.

Nucl. Instrum. Meth. A

The polarization of extracted SATURNE II proton beam as a function of different ion source configurations was studied. Two distinct experiments were necessary for this purpose. In the first one, the LEFT-RIGHT instrumental asymmetry of the beam polarimeter was determined using an unpolarized beam. In the second one this correction factor was applied to asymmetries measured with the beam from the polarized ion source in all polarization states. The measurements were carried out at the proton beam kinetic energy 0.80 GeV, where the pp-elastic scattering analyzing power is near its maximum. The results confirmed that the two so-called “unpolarized states” of the source were polarized to several percent, whereas the absolute values of the beam polarizations in the so-called “polarized states” were equal and opposite. It was observed that the hexapole lens of the ion source produced beam polarization in the absence of any transition. The beam polarization as a function of hexapole current, transition field attenuation, and spin rotation solenoid current was measured. It was also shown how to obtain a strictly unpolarized beam using the polarized source only. The results obtained with the SATURNE II ion source HYPERION may also be relevant to similar sources at other accelerators.

Phys. Rev. C

The 4He p→ 3H pnπ+ reaction channel has been investigated at an incident 4He momentum of 8.6 GeV/c in an exclusive approach. It has been shown that the reaction mainly proceeds via pp→pnπ+ interaction with (pπ+) from Δ++, while triton is a spectator. The anisotropic angular distribution of the nucleons causes the splitting of (3Hn) invariant mass and leads to a natural separation of the interactions occuring either in proton or 4He vertices. Effects such as the shift of peak position in the (pπ+) invariant mass distribution have not been observed.

Phys. Lett. B

We analize semi-inclusive electron-nucleus processes e+A->e'+h+X at moderate Q**2 and energy transfer nu. Our results show that nucleons bound in the nuclear medium are distributed according to a function f_A that reduces to the standard light-cone distribution in the Bjorken limit and exhibits a sizeable Q**2-dependence at lower Q**2, particular Q**2 is order of nu**2.

Teor. Mat. Fiz.

Complicated dynamic systems with several degrees of freedom are investigated with the inverse scattering method using an adiabatic approach based on a consistent statement of two adiabatic problems. An algebraic technique based on the parametric inverse problem in an adiabatic representation is developed for reconstructing two-dimensional (time-dependent and time-independent) potentials and the corresponding solutions. The calculated elements of the exchange interaction matrix determine the system of corresponding gauge equations. The main characteristics of the exchange interaction essentially depend on the statement of the parametric inverse problem. Namely, if the parametric problem is specified on the entire axis, then the constraint matrix elements are regular at degeneration points of two levels. The opposite occurs in the case of the radial parametric problem or the parametric problem specified on the semiaxis. The influence of the parametric spectral characteristics of the fast subsystem on the behavior of the slow subsystem is studied. In particular, it is shown that state transitions of a two-level system vanish for a special choice of the normalization functions.

Phys.Rev.C

Deep inelastic scattering of leptons off nuclear targets is analized within the convolution model taking into account nucleon-nucleon correlations. We show that in the nuclear medium nucleons are distributed according to a function that exhibits a sizeable Q**2-dependence and reduces to the ordinary light-cone distribution in the Bjorken limit. At Q**2 < 50 (GeV/c)**2 and x > 1 this Q**2-dependence turns out to be stronger than the one associated with the nucleon structure function, predicted by pertubative quantum chromodynamics.

AIP Conf. Proc.

A new experimental search for muonium-antimuonium conversion was conducted at the Paul Scherrer Institute, Villigen, Switzerland. The preliminary analysis yielded one event fulfilling all required criteria at an expected background of 1.7(2) events due to accidental coincidences. An upper limit for the conversion probability in 0.1 T magnetic field is extracted as $8 \cdot 10^{-11}$ (90% CL).

Phys.Lett.B

The problem of the $\rho$ meson resonance solution in the extended NJL model is studied. It has been shown previously that the solution for the $\rho$ meson changes smoothly from a bound state to a "virtual state" when the vector channel attraction becomes too weak to support bound state solutions. We have found that together with these solutions a separate resonance branch appears which is not connected smoothly with the bound state solutions. At small values of constituent quark mass, $m\sim 200$ MeV, it corresponds to the physical vector meson resonance solution in the quark-continuum region. The $a_1$ and $\sigma$ resonances are also discussed.

Nucl.Instrum.Meth.A

The NOMAD experiment is a short base-line search for ν μ − ν τ oscillations in the CERN neutrino beam. The ν τ 's are searched for through their charged current interactions followed by the observation of the resulting τ − through its electronic, muonic or hadronic decays. These decays are recognized using kinematical criteria necessitating the use of a light target which enables the reconstruction of individual particles produced in the neutrino interactions. This paper describes the various components of the NOMAD detector: the target and muon drift chambers, the electromagnetic and hadronic calorimeters, the preshower and transition radiation detectors and the veto and trigger scintillation counters. The beam and data acquisition system are also described. The quality of the reconstruction and individual particles is demonstrated through the ability of NOMAD to observe K s 0 's, Λ 0 's and π 0 's. Finally, the observation of τ − through its electronic decay being one of the most promising channels in the search, the identification of electrons in NOMAD is discussed.

Radiat. Eff. Def. Solids

Astropart. Phys.

A first deep underwater detector for muons and neutrinos, NT-200 , is currently under construction in Lake Baikal. Part of the detector, NT-36 , with 36 photomultiplier tubes at three strings, has been installed in 1993. This array allowed for the first time a three-dimensional mapping of Cherenkov light deep underwater. Since then, various arrays have been almost continuously taking data. Presently a 96-PMT array is operating. We describe the NT-200 detector design and present results obtained with NT-36 .

Russ.Phys.J.

Exact solutions of a two-particle eigenvalue problem are obtained for a four-fermion contact interaction. Composite Goldstone modes are found. A relationship, is found between the renormalization procedure and the construction of self-adjoint solutions.

Nucl.Phys.A

The presence of a scalar interaction in nuclear beta-decay was studied by measuring the beta-neutrino correlation coefficient α in the superallowed pure Fermi β-transition 18 Ne(0 + ) → 18 F(0 + , 1040 keV) ( T 1 2 = 1.67 s ). The resulting value, i.e. α = +1.06 ± 0.19 (error quoted at 2σ), corresponds to the limit |C s | 2 + |C′ s | 2 ⩽ 0.29|C v | (95% CL) for the scalar coupling constant.

Hyperfine Interact.

An important decay channel of recently discovered metastable antiprotonic helium atoms is the emission of an electron, i.e., the Auger transition. The rate of this process for a number of states of the 3He\barpe, 4He\barpe and 6He\barpe systems is calculated and a substantial isotopic effect is found. While the reduced mass of heavy particles increases slightly with increasing nucleus mass, the Auger transition rate decreases by about a factor of three. The explanation of this strong amplification is given and the role of this effect in experiments is discussed.

Nucl. Instrum. Meth. A

A cellular automaton for track searching combined with an elastic net for charged particle trajectory fitting is presented. The advantages of the methods are: the simplicity of the algorithms, the fast and stable convergency to real tracks, and a good reconstruction efficiency. The combination of techniques have been used with success for event reconstruction on the data of the NEMO-2 double-beta (ββ) decay experiments.

Nucl. Instrum. Meth. A

In the double beta decay (ββ) experiment NEMO-2, the 214 Bi radioactivity has been measured as background for the ββ processes. The analysis of the 214 Bi contamination has been performed via the signature of 214 Po alpha decay. This method has been applied to data taken with enriched 100 Mo and 116 Cd sources. At the level of NEMO-2's sensitivity, in a 1.0 mole yr study of enriched material, the contamination of the sources can be measured in the range of 2.0 mBq kg −1 . The effects of deposited contamination by 222 Rn are also discussed and estimated at the level of 0.3 mBq per square meter of source foil. Backgrounds for neutrinoless double beta decay (ββ0v) are deduced from these measurements and the consequences for the higher sensitivity ββ experiment NEMO-3 are drawn.

Phys.Rev.C

We discuss semi-inclusive eA→e′hX processes in which the hadron h is emitted backward in the rest frame of the target nucleus. The purpose of our analysis is the comparison of two approaches based on different descriptions of nuclear structure at short interparticle distance. The first one uses nucleonic degrees of freedom and a nuclear spectral function obtained from a microscopic many-body calculation, whereas in the second one the relativistic invariant phase-space volume available to a quark in a nucleus is computed, taking into account nucleon-nucleon correlations. The calculated proton and π-meson spectra are compared to the data taken at SLAC using 14.5 GeV e+ and e− scattering off CO.