Insights on d μ t sticking from d μ d stripping and μ,3He capture

Data from the recent PSI high statistics experiment on d μ d fusion are used to measure the stripping process in d μ d→ n+μ,³He and test current calculations of the stripping process. The PSI results in μ³He capture are also used to remove a troubling background from this measurement. Combination of these results with the old dμ t sticking analysis slightly raise and improve that result to ω_s= (0.58± 0.04)% and indicate that theory and experiment can meet if theoretical stripping is increased only at the beginning of the track. This conclusion is in accord with the new stripping calculations where excited state stripping is increased significantly. This revised version was published online in August 2006 with corrections to the Cover Date.     

Scattering and bound states in the K − d system

We investigated different properties of the K ^? d system. First, the near-threshold elastic amplitudes of K ^? d scattering were calculated from the three-body Alt-Grassberger-Sandhas equations with the coupled channels using four versions of the -KN-πΣ potentials. The potentials reproduce the very recent SIDDHARTA or older KEK experimental data on kaonic hydrogen, data on K ^? p scattering and have one- or two-pole structure of the Λ(1405) resonance. Second, the 1s-level shifts and widths of kaonic deuterium, corresponding to the results on near-threshold antikaon-deuteron scattering, were calculated. The question of existence of a strong quasi-bound state in the K ^? d system was also investigated.     

Annihilation mechanisms of e+e− and μ+μ− production in relativistic nuclear collisions

We revise the μ⁺μ^? and $q\bar q$ annihilation mechanisms of dilepton production during relativistic nuclear collisions. We focus on the modifications caused by the specific features of in-medium pion and quark states rather than by medium modification of the ρ-meson spectral density. The main ingreditent emerging in our approach is a form-factor of the multi-pion (multi-quark) system. Replacing the usual delta-function the form-factor plays the role of distribution which, in some sense, “connects” the total 4-momenta of the annihilating and outgoing particles. The difference between the c.m.s. velocities attributed to annihilating and outgoing particles is a particular consequence of this replacement and results in the appearance of a new factor in the formula for the lepton pair production rate. We obtained that the form-factor of the multi-pion (multi-quark) system causes broadening of the rate which is most pronounced for small invariant masses, in particular, we obtain a growth of the rate for the invariant masses below two masses of the annihilating particles.     

Zero-field μSR and low-temperature μ+ diffusivity in copper

In this paper I review the history of ⁺ diffusion studies in copper, with particular emphasis on the increased low-temperature diffusivity which has been known for several years now. I survey the theory and practice of the zero-fieldSR method, which has come into increasing favor in the study of muon diffusion and trapping in metals, and discuss its application to the low-temperature copper problem.     

Meson-exchange currents and energetic particle emission from μ− capture

We consider corrections to the impulse approximation calculation of the excitation function generated by muon capture in complex nuclei, in the form of captures on pairs of nucleons induced via meson-exchange currents. Within the Fermi gas model for the nucleus, these multinucleon captures are found to account for 4–8% of the experimental muon capture rates and to produce high excitation energies. The emission of pre-equilibrium protons with energies between 40 and 90 MeV is calculated for several nuclei using the hybrid exciton model. The agreement with experiment on emission spectra and rates is generally good. The emission of neutrons at these energies is also discussed.     

Measurement of the fusion rate in μd3He

Many atomic and molecular processes may occur after a muon has been stopped in a mixture of hydrogen and helium isotopes. In particular, the muonic molecule μd³He can be formed. This molecule either decays or undergoes muon catalyzed fusion. Theory predicts a fusion rate much lower than the decay rate; moreover, the various theoretical predictions differ from each other by several orders of magnitude. With the experiment presented here we intend to measure the effective fusion rate via the detection of the 14.7 MeV fusion proton. A new target and gas mixing system, designed at JINR, were used in a ten-day test run at PSI. The fusion protons and products from other transfer and background reactions were measured with several different detectors (plastic scintillators, BGO, Germanium, neutron, and Silicon detectors). The formation rate of the μd ³He molecule and an upper limit for the effective fusion rate have been measured and are presented here. This revised version was published online in August 2006 with corrections to the Cover Date.     

Anisotropic paramagnetic shift of μ−O in the highT c related materials LaSrCuO and LaCuO

The negative muon (^–) was used as a microscopic probe for the study of the electronic state at the oxygen site in highT _c related LaSrCuO materials. Using good single crystals, two types of signals are obtained corresponding to two different oxygen sites: one highly anisotropic, which shows a large (order of 1%) shift under the magnetic field inc-axis direction, the other less anisotropic and with a smaller amplitude (order of 0.2%). These results of ^–OSR show quit a difference with the result of¹⁷O-NMR, where the paramagnetic shift has axial symmetry along the Cu-O bond direction and a magnitude of the order of 0.2% and 0.05%.     

Pulsed μ− SR measurement of negative muon depolarization in muonic 13C and 14N

Slow depolarization rates of the upper hyperfine (HF) states (F⁺) of μ⁻¹³C and μ⁻¹⁴N were observed by means of the negative muon spin rotation method with a pulsed beam. The result for μ⁻¹³C agrees with the HF transition rates expected by Auger processes, while that for μ⁻¹⁴N is too high, suggesting a HF transition due to the intramolecular excitation effect.     

Higgs boson physics in the s-channel at μ+μ− colliders

Techniques and strategies for discovering and measuring the properties of Higgs bosons via s-channel production at a μ⁺μ⁻ collider, and the associated requirements for the machine and detector, are discussed in detail. The unique feature of s-channel production is that, with good energy resolution, the mass, total width and partial widths of a Higgs boson can be directly measured with remarkable accuracy in most cases. For the expected machine parameters and luminosity the standard model (SM) Higgs boson h_SM, with mass ≲ 2m_W, the light h⁰ of the minimal supersymmetric standard model (MSSM), and the heavier MSSM Higgs bosons (the CP-odd A⁰ and the CP-even H⁰) can all be studied in the s-channel, with the heavier states accessible up to the maximal √s over a large fraction of the MSSM parameter space. In addition, it may be possible to discover the A⁰ and H⁰ by running the collider at full energy and observing excess events in the bremsstrahlung tail at lower energy. The integrated luminosity, beam resolution and machine/detector features required to distinguish between the h_SM and h⁰ are delineated.     

X-ray intensities following the fusions of dμd,dμt and pμd

Muonic X-ray spectra of μ³He and μ⁴He from dμd, pμd, and dμt fusion are analyzed for various target densities. Theoretical values of the intensity ratio μ³He(3→1)/μ³He(2→1) for dμd and pμd fusion at liquid hydrogen density are, respectively, 0.132 and 0.0553. These are in good agreement with the experimental results.     

TheK − d→pλπ− reaction

The (p) mass distribution is calculated for the reactionK ^– dp^– at rest and in flight at 700 MeV/c, for both BDI-1 and NRS-F potentials, with results which do not discriminate strongly between them. The in flight calculations can be brought into satisfactory agreement with experiment after some modification of the¯KNY amplitudes, but the at rest calculations show a strong disagreement with experiment which is not yet resolved, but which may partly reflect the experimental procedures adopted. The discrepancy with the earlier work reported by Dalitz, Hemming and Morris is accounted for, with the conclusion that further physics input may be needed to reach agreement with the data.Presented at the symposium Mesons and Light Nuclei, Liblice, Czechoslovakia, June 1981.     

Defects and transport in SrFe1−xCoxO3−δ

The non-stoichiometry and chemical diffusion coefficient of SrFe_1−xCo_xO_3-δ have been measured by steady state and transient thermogravimetry in the temperature range 750–1200 °C at different oxygen partial pressures. At high oxygen partial pressures, the chemical diffusion coefficient was in the range 1·10⁻⁴ – 7·10⁻⁴ cm²/s. This, combined with high concentration of disordered vacancies make these materials perhaps the fastest solid oxygen ion diffusers known at high temperatures and high oxygen partial pressures. However, due to the high concentration of defects in SrFe_1−xCo_xO_3-δ the compound transforms from a cubic (disordered) perovskite to a brownmillerite type of structure under reduced oxygen partial pressures below approx. 900 °C. Due to this phase transition, the mobility of oxygen vacancies in SrFe_1−xCo_xO_3-δ decreases up to about an order of magnitude at 850 °C. We also observe an ordering effect at 1000 °C, although smaller in size, and this is suggested to be due to short range ordering of four-coordinated polyhedra of Fe. For possible use as oxygen separation membranes, phase stability against sulphur and carbon containing atmospheres is also discussed with respect to the formation of carbonates and sulphates. Paper presented at the 6th Euroconference on Solid State Ionics, Cetraro, Calabria, Italy, Sept. 12–19, 1999.     

Electron Green's function in the planar t − J model

The electron Green's functions G(k, ω) within the t ? J model and in the regime of intermediate doping is studied analytically using equations of motion for projected fermionic operators and the decoupling of the self energy into the single-particle and spin fluctuations. It is shown that the assumption of marginal spin dynamics at T = 0 leads to an anomalous quasiparticle damping. Numerical results show also a pronounced asymmetry between the hole (ω < 0) and the electron (ω > 0) part of the spectral function, whereby hole-like quasiparticles are generally overdamped.     

Redox reaction of μ−O in water determined by the chemical shift

The chemical shift of ^–O in water, ice and in aqueous hydrogen peroxide (H₂O₂) was examined using ^–O resonance. Two distinct signals are obtained in water and ice. Using ⁺ resonance signal as a standard, the observed shiftsg are –7.0×10^–4 (signal A) and –12.1×10^–4 (signal B) respectively. The intensity of the two fractions are almost equivalent in water; however, in ice, the intensity of signal B decreases with increase of signal A. After the addition of hydrogen peroxide to the water signal B disappears, A increases, and the total amplitude is increased.     

Leptonic decays of vector mesons and a possible μ+μ− resonance

The possible existence of a vector leptonic resonance (⁰) in the ^+– system is considered. We discuss the effect such a resonance would have on the g factor of the muon and also on the ratio of the partial widths of the muonic and electronic decay modes (R_V = (V ^+–)/G (V e⁺ e^–)) of the neutral vector mesons ⁰,,,, and. From the experimental values of R and R, the following values are obtained for the mass, coupling constant, and partial decay widths of the resonance: M = 872 ± 60 MeV, f²/4 = 4 ± 2) ·10^–4, ( ^{0 + –}) = 0.12±0.06 MeV, and (^{0 0 +–}) = 0.13±0.06 MeV.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 39–43, May, 1977.     

Measurement of the forward-backward asymmetry of μ+μ− pairs in CMS

The measurement of the forward-backward asymmetry A _FB and the effective weak mixing angle with the Drell-Yan process at the LHC is presented. The samples of 2011 collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 5 fb^?1 and 1.1 fb^?1, were used. The results are consistent with the standard model expectations.     

Quark fragmentation in the θ vacuum

QCD vacuum is a superposition of degenerate states with different topological numbers that are connected by tunneling (the θ vacuum). The tunneling events are due to configurations of gauge fields (e.g., the instantons) that induce local P-odd domains in Minkowski space-time. We study the quark fragmentation in this topologically nontrivial QCD background. We find that even though QCD globally conserves P and CP symmetries, two new kinds of P-odd fragmentation functions emerge. We study their experimental manifestations in dihadron production in e(+)e(-) collisions, and find two interesting dihadron correlations: the cos(?(1)+?(2)) correlation usually referred to as the Collins effect, and a P-odd ～sin(?(10+?(2)) correlation that vanishes in the cross section summed over many events, but survives on the event-by-event basis.     

On μ-mesic-molecular ion dTμ− spectrum

Mesic-molecular systemdT μ ^? in the state with total angular momentumL=0 is considered in a two-channel approximation corresponding to two channels of strong interaction . Coulomb interactionV _dμ +V _Tμ is taken into account by introducing an effective potentialV _μ in the form of the Morse potential. The main result of the research is the following: the eigenvalue with a small real part and a large width exists even at considerable variations of the effective repulsion between the deuteron and tritium at short distances.     

Studying the elemental composition and manganese distribution in Zn1 − x Mn x Te and Zn1 − x Mn x S films using the μ-PIXE and EDAX methods

The methods of proton-induced X-ray emission (μ-PIXE) and energy-dispersive X-ray analysis (EDAX) are used to study the elemental composition and areal distribution of manganese in Zn_{1 ? x} Mn _x Te and Zn_{1 ? x} Mn _x S films. The μ-PIXE technique is implemented using a nuclear scanning microprobe with a proton-beam energy of 1.5 MeV and cross-sectional dimensions of 4 × 4 μm. The semimagnetic solid solution films are obtained under different operating modes of thermal vapor deposition in the quasiclosed volume of a manganese-containing blend.     

The effect of vacuum annealing on the remediation abilities of iron and iron−nickel nanoparticles

Zero-valent iron nanoparticles are effective remediators of uranium from solution. It is postulated that the improved core crystallinity and the migration of impurity phases to the nanoparticle surfaces induced by annealing may improve their corrosion resistance and reactive lifespan. The ability of annealed and non-annealed Fe and FeNi nanoparticles to remediate a U-contaminated effluent from AWE, Aldermaston was investigated. Nanoparticles (of diameter typically between 0 and 100 nm) were introduced to the effluent and allowed to react for 7 days during which the liquid and nanoparticulate solids were periodically sampled. In all the systems, the maximum U-uptake occurred within 1 h of introduction, with variable efficiency. The Fe nanoparticles removed 98% of the total U from solution, resulting in a final U-concentration of <4 μg/L. A rapid release of Fe into solution was recorded early in the reaction period: attributed to limited partial dissolution of the nanoparticles. Annealing the Fe nanoparticles did not affect their efficiency but the dissolution of Fe was significantly reduced and X-ray Photoelectron Spectroscopy indicated slower progressive oxidation. The performance of the FeNi nanoparticles was significantly improved by annealing, with U-uptake increasing from 50 to 94%. Although the dissolution of Ni was completely inhibited by annealing, the Fe dissolution increased compared to that observed for the non-annealed FeNi nanoparticles, in contrast to behaviour exhibited by Fe-annealed nanoparticles. In all the systems, U was reduced to U(IV) and retained on the surfaces of the nanoparticulate solids for up to 48 h; the U-stability was not affected by annealing the Fe or the FeNi nanoparticles before use.