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The GdMn2O5 multiferroic (a ceramic sample and a sample consisting of a large array of randomly oriented single crystals with linear dimensions 2–3 mm) has been studied by the μSR method within the temperature range 10–300 K. Three anomalies in the temperature behavior of the parameters of the muon polarization relaxation function, namely, close to the phase transition driven by the onset of long-range magnetic order in the manganese ion subsystem (T N1 = 40–41 K), near the lock-in transition initiated by an abrupt change of the wave vector of magnetic order (T L = 35 K), and close to the Gd3+ ion ordering temperature (T N2 = 15 K), have been found. An analysis of the time spectra of muon spin precession in the internal magnetic field of the samples has revealed two positions of preferable muon localization sites in samples, which differ in precession frequencies and the character of their behavior with temperature. The lower-frequency precession driven by Mn4+ ions, ferromagnetic Mn4+-Mn4+ + muonium complexes, and Gd3+ions is observed throughout the temperature region T < T N1 and is practically independent of temperature. At temperatures T < T L = 35 K, a higher-frequency precession associated with Mn3+ ions appears also. It is characterized by a temperature dependence ∼(T/T N1)β with the index β = 0.39, which is typical of Heisenberg-type 3D magnets. For T < T N1, a deficiency of the rest total asymmetry is observed. This phenomenon can probably be assigned to formation of muonium, which suggests that charge transfer processes play an important role in formation of long-range magnetic order.

The ratios of the cross sections for ϕ-meson production induced by 2.83-GeV protons on Cu, Ag, and Au nuclei to the respective cross section for C nuclei were measured at the ANKE-COSY facility in the momentum range of 0.6–1.6 GeV/c and the angular range of 0°–8°. The product ϕ mesons were identified by their decay ϕ → K+K−. The procedure used to separate kaon pairs was described in detail, and all sources of the background and their contribution to the resulting error in the values found for the above cross-section ratios were analyzed. The A dependence of the cross section for ϕ-meson production was shown to obey the A0.56±0.03 law. The total width of the ϕ meson at a normal nuclear density was extracted from a comparison of the measured cross-section ratios with the results of calculations based on two theoretical models. The resulting width value exceeds substantially both the vacuum width and the width expected in the absence of the nuclear-matter effect on the properties of the ϕ meson.

The magnetic properties of the EuMn2O5 multiferroic (samples consisting of single crystals and ceramic samples) have been investigated by the muon-spin-relaxation (μSR) method in the temperature range of 10–300 K. Below the magnetic ordering temperature TN = 40 K, the loss of the polarization of muons and the effect of the external magnetic field have been observed. Both phenomena can be explained by an additional channel of the depolarization of muons owing to the appearance of muons in a medium with a low electron density due to the charge separation process (the redistribution of the electron density in the phase transition process). The “memory” phenomenon has been revealed in a sample in the external magnetic field; the memory relaxation time depends on the size of the structure units of the samples (single crystals or ceramic grains).

The energy spectrum of a neutron beam produced in a thin-wall liquid-deuterium target by a proton beam of energy 1 GeV was measured in a hydrogen bubble chamber by detecting events of the reaction np → ppπ−.

The cross sections for the p p → p p K + K − reaction were measured at three beam energies 2.65, 2.70, and 2.83 GeV at the COSY-ANKE facility. The shape of the K + K − spectrum at low invariant masses largely reflects the importance of K K ¯ final state interactions. It is shown that these data can be understood in terms of an elastic K + K − rescattering plus a contribution coming from the production of a K 0 K ¯ 0 pair followed by a charge-exchange rescattering. Though the data are not yet sufficient to establish the size of the cusp at the K 0 K ¯ 0 threshold, the low mass behaviour suggests that isospin-zero production is dominant.

A ferrofluid based on Fe3O4 nanoparticles dispersed in heavy water D2O is studied using the μSR method. The experiment has been carried out at temperatures 26–300 K. It is found that the diamagnetic (muon) fraction is formed in the ferrofluid in about the same amount as in D2O, but the muon-spin relaxation rate in the ferrofluid is much higher than in D2O. A significant shift of the muon-spin precession frequency in the ferrofluid is observed. It is shown that the shift of the muon precession frequency as a function of the external magnetic field is described by the Langevin function typical of paramagnetic magnetization. The mean magnetic field in the medium due to magnetic-nanoparticle polarization in an external field is experimentally determined. The nanoparticle sizes are estimated.

The magnetic characteristics of homogeneous copper—manganese alloys Cu1 − xMnx are studied by the muon spin relaxation technique for the first time. It is revealed that the specific magnetic phase, which is most likely characterized by a fast spin dynamics and the absence of long-range order, is formed in alloys with concentrations 0.2 < x < 0.7 in the temperature range 10–330 K. The complete magnetic phase diagram is constructed.

Inclusive K + production in proton–proton collisions has been measured at a beam energy of 2.16 GeV using the COSY-ANKE magnetic spectrometer. The resulting spectrum, as well as those corresponding to K + p and K + π + correlated pairs, can all be well described using consistent values of the total cross sections for the p p → K + p Λ , p p → K + p Σ 0 , and p p → K + n Σ + reactions. While the resulting values for Λ and Σ 0 production are in good agreement with world data, our value for the total Σ + production cross section, σ ( p p → K + n Σ + ) = ( 2.5 ± 0.6 stat ± 0.4 syst ) μb at an excess energy of e = 129 MeV , could only be reconciled with other recently published data if there were a highly unusual near threshold behaviour.

The Pd1−xFex)0.95Mn0.05 alloy with random competing interaction was studied by measuring the muon spin relaxation in an external transverse magnetic field and in a zero magnetic field. Using the measured temperature dependence of the dynamic relaxation rate λ and the characteristics of the distribution of local static fields, the phase states of the sample under study are refined. In particular, it is shown that the ferromagnetic and spin-glass states coexist simultaneously in the sample below 25 K. Combined studies of the sample using the μSR and neutron depolarization methods made it possible to determine the size of magnetic inhomogeneities to be 2–6 μm in the temperature range 5–40 K.

The magnetic properties of multiferroics HoMnO3 and YMnO3 have been investigated using the muon (μSR) method. Analysis of the dependence of the dynamical relaxation rate λ and characteristics of the distribution of local static fields makes it possible to more precisely determine the phase states of the samples under investigation.

New data on ϕ -meson production in pp collisions have been obtained at the ANKE facility of COSY-Julich. These data will provide the energy dependence of the total cross section down to an excess energy of 19 MeV above threshold. In combination with the existing SPES-III and COSY-TOF results on ω -meson production the ϕ / ω production ratio at this low excess energy will be extracted. As an exciting new aspect an enhancement in the invariant ϕp mass spectrum is observed at a mass around 1.965 GeV / c 2 .

The reaction pp->pK+Y has been studied with the ANKE spectrometer at COSY-Juelich in order to investigate heavy hyperon production. The missing mass spectra MM(pK+) have been analyzed and compared with Monte Carlo simulations. Indications for a hyperon resonance Y0*(1480) have been found., Baryons2004 Proceedings, 4 pages, 6 figures

The present paper is devoted to studying the multiferroics HoMnO3, YMnO3, EuMn2O5, and GdMn2O5 by means of the µSR-method. Determination of the dynamic relaxation parameter 7n and the distribution of the local magnetic fields results in a clear phase diagram.

The magnetic properties of quenched Cu1−xMnx alloys with x>0.15 were studied by μSR at PNPI. In the samples with x=0.17, 0.45 and 0.80 as well as in the single crystal Cu0.63Mn0.37 magnetic transition temperatures were measured and found to be in good agreement with the published magnetic phase diagram. But in the samples with x=0.25, 0.30 and 0.35 the formation of a magnetic state was observed at essentially higher temperatures (180–200 K) than those defined from the diagram. The second transition from this state into the spin glass phase was observed at 110–120 K in the samples with x=0.25 and 0.35. The analysis of obtained data allows to assume that the interaction of magnetic clusters produces a specific magnetic phase near the percolation threshold.

The new spectrometer ANKE has been put into operation at the accelerator COSY of the Forschungszentrum Julich. An initial scientific goal is to study K+-production in pA collisions at subthreshold energies below the free NN-threshold of T = 1.58 GeV. First measurements of double differential cross sections in p12C collisions at emission angles around 0° have been performed at T = 1.0, 1.2 and 2.0 GeV. The challenge is to identify the kaons in a huge background of pions and protons, since the signal to background ratio decreases to about 10−6 at T = 1.0 GeV. For background suppression detectors and a trigger system based on energy-loss and time-of-flight measurements have been developed. In the analysis the decay of kaons (τ = 12.4 ns) stopped in the detection system into μ+ and π+ is exploited as well as the track information from the wire chambers.

The floating wire (FW) technique was applied to determine particle trajectories in three dipoles which form the magnetic spectrometer ANKE installed in the accelerator ring COSY Juelich. Methodical improvements of the well-known FW technique result in extended applicability and high accuracy. The FW measurements compare well with field map based trajectory calculation using the GEANT code.

The lifetime of a negative muon in the 1S state in the isotopes 84Kr and 136Xe was measured. The values obtained, τ(84Kr)=139.2±2.9 ns and τ(136Xe)=111.0±4.6 ns, correspond to total nuclear capture rates Λc(84Kr)=6.75±0.15 μs−1 and Λ c(136Xe)=8.6±0.4 μs−1. Theoretical calculations of the rate of nuclear capture of a negative muon are performed for the Kr isotopes. The experimental results are compared with the theoretical calculations.

It was shown that in the frustrated ferromagnet belonging to the group of structurally ordered Fe_x Mn1-x Pt3 alloys the temperature of the transition from the ferromagnetic state to the asperomagnetic state followed a Gabay–Toulouse line.

The magnetic state properties have been studied in YBa2Cu3O6+x with (0.06

It was shown that in the Heisenberg frustrated antiferromagnetic FexNi80−xCr20 alloys with the concentrations (x) near critical point the following succession of transitions is observed under cooling: paramagnet — collinear antiferromagnet- non-collinear antiferromagnet (antiasperomagnet) — reentrant spin glass. For the frustrated ferromagnetic (FexMn1−x)Pt3 alloys the existence of slow relaxation processes was shown which are the result of dynamic crossover from the ferromagnetic state to an asperomagnetic one.

The giant mobility of the magnetic flux in FrFC and ZFC conditions have been studied in textured sample Bi2Sr2CaCu2O2-δ byμSR. The comparison of results obtained in both cases showed that it is difficult to explain this phenomenon by only thermally activated flux creep and the melting of vortex lattice must be considered. The magnetic field dependence of the melting temperature was obtained for H

Inclusive differential cross sections of 4,6,8 He, 6,7,8 Li formation in p 9 Be interactions at T p = 1 GeV have been measured. Enhancement of the 8 He yield is observed in the spectator momentum range ( P c ), which is evidence for the process of virtual Δ ++ -isobar knock-out from 9 Be. The ratio of the spectroscopic factors of (Δ ++ 8 He) and (p 8 Li) configurations in 9 Be is estimated to be (6±3) × 10 −4 .

The effect of acoustic oscillations of the α-quartz crystalline lattice on the behaviour of muonium polarization has been studied experimentally. It is shown that when the frequency of the standing ultrasound wave coincides with one of the muonium quadrupole interaction frequencies a specific broadening of the muonium line occurs; that is a muonium acoustic resonance is observed. The possibilities of using this effect for investigating properties of solids by the μSR method are discussed.

Magnetic measurements, neutron diffraction and the μSR method were used to investigate the reentrant temperature transitions in the Heisenberg frustrated antiferromagnetic Fe x Ni 80- x Cr 20 and Fe x Ni 80- x Mn 20 alloys. It was shown that for the alloys whose concentrations are close to the onset of the long-range antiferromagnetic order, the following succession of transitions is observed under cooling: paramagnet - collinear antiferromagnet (antiasperomagnet) - reentrant spin glass. There is no long-range antiferromagnetic order in the reentrant spin glass phase but the antiasperomagnetic correlations with finite correlation length are present.

Measurements of the pd{yields}p{sub sp}dK{sup +}K{sup -} reaction, where p{sub sp} is a spectator proton, have been undertaken at the Cooler Synchrotron COSY-Juelich by detecting a fast deuteron in coincidence with a K{sup +}K{sup -} pair in the ANKE facility. Although the proton beam energy was fixed, the moving target neutron allowed values of the nonresonant quasifree pn{yields}dK{sup +}K{sup -} total cross section to be deduced up to an excess energy {epsilon}{approx_equal}100 MeV. Evidence is found for the effects of K{sup -}d and KK final state interactions. The comparison of these data with those of pp{yields}ppK{sup +}K{sup -} and pp{yields}dK{sup +}K{sup 0} shows that all the total cross sections are very similar in magnitude.

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.

The zero field μSR-method has been used to study the magnetism in the disordered magnetic alloy Fe82−xNixCr18 near the three-critical, pointx=25. The dynamic and static local field distributions are analyzed. The difference between spin-glass states obtained either from the paramagnetic or after the double transition is discussed.

In this work the magnetic and superconducting properties of YBa2Cu3O6+x , ceramic samples are studied with regard to there preparations technology and oxygen content. It is shown that at 0.41≤x≤0.45 the magnetic and superconducting states coexist.

The values of the penetration depths and their temperature dependences were measured for differentc-axis orientations of a textured 2.2.1.2. sample. The remanent magnetic flux was studied. The giant mobility of the trapped vortex structure was found above 40 K.

ANKE is a second generation experimental facility at the internal beam of the accelerator COSY at the Forschungszentrum Julich (Germany). It has recently (May 1998) been installed in the ring, commissioned and immediately after this been exploited for first experiments. Using circulating beams of protons with energies between 1.0 and 2.3 GeV, sub- and near threshold production of K+ mesons in collisions with carbon-strip targets has been investigated. The detection system of ANKE used for the first measurements is capable of detecting positively charged ejectiles in the momentum range between about 100 and 600 MeV/c. In particular, it has been optimized for K+ identification in the presence of an intense background of protons and pions. The final results of the experiments (cross sections and momentum spectra) will be used to obtain more detailed information on the subthreshold production mechanism.

A 0° facility is being developed for the study of meson production in proton‐nucleus collisions and other investigations at intermediate bombarding energies at an internal target position (TP2) of COSY. A set of three laminated magnets will provide a closed orbit bump for the proton beam and deflection as well as momentum analysis for ejectiles with p0/30= p=p0/2 (p0=projectile momentum). this facility will enable the spectroscopy of rare ejectiles like K+ mesons with a momentum resolution of =1%. It also allows studies of ejectiles emitted under 180° like protons from deuteron breakup.

The cross sections of the 12 C (π − , π − n) 11 C and 12 C (π + +, π + n + π 0 p) 11 C reactions and their ratios have been measured at E π = 100, 130, 150, 180, 210, 245 and 295 MeV. The cross-section ratio at 180 MeV is 1.57±0.05.

Differential cross sections for the process pi +d to pp at seven energies in the region Tpi =280-450 MeV and in the angular range theta * approximately=4-90 degrees have been measured on the LNPI synchrocyclotron. The results include 94 new data points. The measurements have been carried out using a ten-channel hodoscope set-up. Statistical errors are between 2.5% and 7.8% depending on the scattering angle and Tpi . The data obtained indicate that there is an essential contribution from the partial wave with orbital angular momentum l=3 over the whole energy range considered. The authors also observe a noticeable contribution from the l=4 partial wave to the differential cross sections of the pi +d to pp reaction from Tpi >or=357 MeV. The total cross sections for the process pi +d to pp are also presented.

Differential cross sections for charge pion production in the pA to pi X reaction have been measured at a proton kinetic energy of 1 GeV with a relative accuracy of 2-5% for the following targets: 1H, 2D, 10B, 11B, 12C, 16O, 24Mg, 25Mg, 26Mg, 27Al, 64Cu, 116Sn, 124Sn, 181Ta, 184W and 208Pb. The measurements were performed with the help of two independent magnetic spectrometers with an angular acceptance of Delta Omega approximately=0.01 sr. The momentum resolution was equal to Delta P/P=1.4% in the range P=200-950 MeV/c at theta =0 degrees and Delta P/P=3% in the range P=75-600 MeV/sc at theta =57.8 degrees . The absolute normalisation of the cross sections was carried out using recent LNPI data on d sigma /d Omega for the pi +d to pp reaction. The contribution of various mechanisms to the inclusive pion spectra is discussed.

Differential cross sections for π+p and π−p elastic scattering have been measured at 12 energies in the region 277–640 MeV. The data were obtained in the angular range θ π ∗ = 40°−176° , with a typical accuracy of 2–5%. The results for 288 MeV and 292.9 MeV are in good agreement with the data of Bussey et al. Using the data obtained, isospin bounds have been calculated for the charge-exchange scattering. It is shown that the charge-exchange cross sections at large angles are grouped near the bottom isospin limit, and at energies larger than 490 MeV they lie beyond the region allowed by isospin invariance. The comparison was carried out with the predictions of different phase-shift analyses. It is shown that the existing phase-shift analyses do not describe all the set of the new data. A new energy-independent phase-shift analysis has been carried out at 12 energies in the region 240–700 MeV.

The Δ − −Δ ++ isobar mass difference has been measured in a deuterium bubble chamber from the reactions π − p→ π + π − n and π + n→ π − π + p at incident momentum 555 MeV/ c . The value obtained for Δ − − Δ ++ is 5.9 ± 3.1 MeV. The error is a factor of two smaller than that from the previous experiment.