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1.
The exotic (μ −, e −) conversion reaction for the 48Ti nucleus is studied in the framework of the quasi-particle random phase approximation (QRPA). For the non-coherent processes the relevant total rate is calculated by summing over partial rates for all the possible intermediate states constructed in the above approximation. For the coherent process the contribution is obtained by using an uncorrelated BCS vacuum. In order to check the validity of closure approximation, which is almost unavoidable in shell-model calculations, we also evaluate the total (μ −, e −) conversion rates by QRPA sum-rules by first explicitly calculating a suitable mean excitation energy of the nucleus. The influence of the ground state correlations to the (μ −, e −) conversion matrix elements is estimated by using a correlated RPA vacuum. The fraction of the transition rate of the coherent process for each of these methods is calculated and the results are compared to those found previously by using shell-model closure approximation. 相似文献
2.
The similarity between the weak interactions of electron and muon is extended to the principle that all e and μ interactions in gauge models are invariant under e ↔ μ exchange. This necessitates the existence of two Higgs doublets φ e and φ μ, and an extended e ↔ μ permutation invariance. After symmetry-breaking, a multiplicatively conserved “permutation parity” π = ± 1 for all particles naturally emerges, with π μ = −π e = 1. The model forbids μ → eγ but predicts e −e − → μ −μ − mediated by π = −1 Higgs bosons at 10 −11 times the rate of typical weak cross sections. 相似文献
3.
The charged current nuclear transition 12C(v e, e −) 12N g.s. has been observed in the KARMEN experiment. The flux average cross section for ve from μ + decay at rest is determined to be σ = [8.1±0.9(stat.)±0.75 (syst.)]×10 −42cm 2. For the first time also the energy dependence of the cross section has been measured for neutrino energies up to 50 MeV. 相似文献
4.
A new type of nuclear spectroscopy to study hadron-nucleus bound states is described. The first successful experiment was to search for deeply bound π − states in heavy nuclei using the 208Pb(d, 3He) reaction at GSI, in which a narrow peak arising from the 2p π − orbital coupled with the neutron-hole states was observed at 135 MeV excitation energy. An improved experiment has just been carried out to separately identify the 1s and 2p π − states. These experiments provide important information on the local potential strength, from which the effective mass of π − is deduced to be 20 MeV. This method will be extended to search for η and ω bound states as well as for K − bound states. The advantage of the bound-state spectroscopy versus invariant mass spectroscopy is emphasized. 相似文献
5.
Coherent Λπ − production on Pb of 600 GeV Σ − hyperons has been studied with the SELEX facility at Fermilab. Using the Primakoff formalism, we set a 90% CL upper limit on the radiative decay width Γ[Σ(1385) −→Σ −γ]<9.5 keV, and estimate the cross section for γΣ −→Λπ − at
GeV to be 56±16 μb. 相似文献
6.
In the light of the recent muon ( gμ−2) result by the E821 experiment at the Brookhaven National Laboratory, we study the event rates of the charged lepton-flavour-violating (LFV) processes in the supersymmetric standard model (SUSY SM) with the heavy right-handed neutrinos (SUSY see-saw model). Since the left-handed sleptons get the LFV masses via the neutrino Yukawa interaction in this model, the event rate of μ→ eγ and the SUSY-SM correction to ( gμ−2)/2 (δ aμSUSY) are strongly correlated. When the left-handed sleptons have a LFV mass between the first and second generations (
) in the mass matrix, it should be suppressed by 10 −3 (10 −9/δ aμSUSY) compared with the diagonal components ( mSUSY2), from the current experimental bound on μ→ eγ. The recent ( gμ−2) result indicates δ aμSUSY10 −9. The future charged LFV experiments could cover
. These experiments will give a significant impact on the flavour models and the SUSY-breaking models. In the SUSY see-saw model
is proportional to square of the tau-neutrino Yukawa-coupling constant. In the typical models where the neutrino-oscillation results are explained and the top-quark and tau-neutrino Yukawa couplings are unified at the GUT scale, a large LFV mass of
is generated, and the large LFV event rates are predicted. We impose a so-called no-scale condition for the SUSY-breaking parameters at the GUT scale, which suppresses the FCNC processes, and derive the conservative lower bound on μ→ eγ. The predicted Br(μ→ eγ) could be covered at the future LFV experiments. 相似文献
7.
Thin films of copper oxide with thickness ranging from 0.05–0.45 μm were deposited on microscope glass slides by successively dipping them for 20 s each in a solution of 1 M NaOH and then in a solution of copper complex. Temperature of the NaOH solution was varied from 50–90°C, while that of the copper solution was maintained at room temperature. X-ray diffraction patterns showed that the films, as prepared, are of cuprite structure with composition Cu 2O. Annealing the films in air at 350°C converts these films to CuO. This conversion is accompanied by a shift in the optical band gap from 2.1 eV (direct) to 1.75 eV (direct). The films show p-type conductivity, 5×10 −4 Ω −1 cm −1 for a film of thickness 0.15 μm. Electrical conductivity of this film increases by a factor of 3 when illuminated with 1 kW m −2 tungsten halogen radiation. Annealing in a nitrogen atmosphere at temperatures up to 400°C does not change the composition of the films. However, the conductivity in the dark as well as the photoconductivity of the film increases by an order of magnitude. The electrical conductivity of the CuO thin films produced by air annealing at 400°C, is high, 7×10 −3 Ω −1 cm −1. These films are also photoconductive. 相似文献
8.
Reversible and irreversible domain wall (DW) motions have been investigated in La 0.7Sr 0.3MnO 3 ceramic samples using frequency-response complex permeability with various amplitudes of AC field. We also examine the effects of temperature in the range from 293 to 368 K and transverse DC magnetic field with a maximum of 4.40×10 5 A/m on the real part of permeability (μ′). Two relaxations corresponding to reversible wall motions and domain rotations occur in low and high frequency regions, respectively. The irreversible DW displacements can be activated as the amplitude larger than the pinning field of 3 A/m, leading to an increase in μ′. The μ′ obeys a Rayleigh law at the temperature below 343 K or under DC field of less than 4.22×10 4 A/m. The Rayleigh constant η increases from 5.45×10 −2 to 1.54×10 −1 (A/m) −1 as the temperature rises from 293 to 343 K, and η decreases from 5.58×10 −2 to 3.67×10 −2 (A/m) −1 with increasing DC field from 1.99×10 3 to 4.22×10 4 A/m. 相似文献
9.
“Rare” annihilation channels for antiprotons stopping on heavy (Ag, Br) nuclei of photoemulsion, have been sought; 4872 stops of antiprotons on photoemulsion nuclei are analysed. Events of formation and decay of the hyperfragment Λ4H, escape of 8He and 8Li nuclei, one-prong stars with the mean range 79.5±5.1 μm of secondary slow “b” particles are found among the annihilation stars at
capture on nuclei (Ag, Br). The lower limits for the production probability of Λ4H and 8He, 8Li nuclei per antiproton stopping in the nuclei (Ag, Br) are WΛ4H2×10−4 and W8He,8Li=(1.3±0.6)×10−3. The branching ratio for the production of one-prong stars with the secondary “b” particles is at least (1.3±0.6)×10−3. Possible mechanisms for a production of these events in annihilation processes are considered. 相似文献
10.
Magninos (neutral spin 1/2 fermions with mass 4–10 GeV and anomalous magnetic moment μ≈10 −2) have been proposed as a solution to both the solar neutrino and dark matter problems. Direct detection of galactic halo magninos is possible via their coherent interaction with heavy nuclei. In this paper we have calculated the relevant non-relativistic cross section. We find a typical counting rate of about 100 events per day per kilogram of either a silicon or germanium detector. The magnetic moment of the magnino was needed in order to solve the solar neutrino problem. When scattering off of heavy nuclei, the charge radius r of the magnino is also relevant. 相似文献
11.
Six rotational bands in the odd-odd nucleus 174Ta have been populated with the 160Gd( 19F,5n) reaction. High-spin states were identified using the NORDBALL array. Both signatures of the doubly decoupled π1/2 − [541] ν1/2 − [521] band and semi-decoupled π1/2 − [541] ν7/2 − [633] band are observed, in addition to the high-K couplings of the π9/2 − [514] ν7/2 + [633], π9/2 − [514] ν5/2 − [512], π7/2 + [404] ν7/2 + [633], and π5/2 + [402] ν5/2 − [512] configurations. The signature splitting of the π1/2 − [541] ν7/2 + [633] band is inverted from the expected splitting, and this is interpreted as being due to a residual proton-neutron interaction. It is shown empirically that this interaction, together with deformation changes, can account for the increased crossing frequency associated with the alignment of i13/2 neutrons in the π1/2 − [541] bands of odd-Z nuclei. 相似文献
12.
A search for the decay μ +→e +e +e −, in which no candidate was found, yields a new upper limit for the branching ratio Rμ→3e<1.6×10 −10 (90% confidence). A total of 16
decays were observed, in agreement both in number and momentum distribution with V - A theory. 相似文献
13.
The lithium intercalation into the layered dichalcogenide 3R-WS 2 has been investigated by electrochemical reduction and by chemical reaction in n-butyl lithium solution. Essential results are (a) a charge transfer of nearly 0.6e −/W in Li xWS 2, (b) a small increase of the c-axis parameter of about 0.6%, and (c) a high mobility of the Li +-ions. The chemical diffusion coefficient of Li +-ions is estimated to be 8 × 10 −9 cm 2 s −1 in the composition range 0 ≤ x ≤ 0.25. The appearance of a structural transformation from 3R-WS 2 to 2H-Li xWS 2 is interpreted on grounds of instabilities in the interlayer structure. 相似文献
14.
The reactions π −p → 2π −π +p, π −p → 2π −π +π op and π −p → 2π −2π +n are analysed at 11 and 16 GeV/ c using longitudinal phase space (LPS) plots. The weighted LPS distributions for π −p → 2π −π +p is dominated by two well separated structures corresponding to single diffraction dissociation of the pion, π −p → (2π −π +)p, and of the proton, π −p → π −(π −π +p). The former is more abundant than the latter, and both are approximately constant with energy. In contrast, processes of type π −p → (2π)(πp) decrease with increasing energy. In the five-body reactions the weighted LPS distribution reveals especially at 16 GeV/c a maximum for single dissociation of the proton into 3πp, namely π−p → π−(π−π+πop); this process is likely to be diffractive. The neutron channel has a corresponding maximum displaced toward a multiperipheral configuration π−p → π−(π−2π+)n. Another strong maximum corresponds to the pion dissociation π−p → (2π−π+πo)p. This is interpreted to be an ω-exchange process because no analogous structure occurs in π−p → (2π−2π+)n. Finally, a broad structure reveals double dissociation of both incident particles; it occurs in the two channels π−p → (2π−π+)(πop) and π−p → (2π−π+)(π+n), being stronger in the latter. Further analysis of this process in terms of isospin exchange suggests that it is partially diffractive. Factorization is also discussed. An appendix gives general aspects of the LPS analysis for the asymptotic study of n-body collisions at very high energy. 相似文献
15.
The olivine crystals from lunar regolith samples taken by the Soviet unmanned spacecrafts Luna-16 and Luna-24 were investigated. Eleven 0.5 –1.0 mm size olivine crystals were mounted in epoxy, polished and then etched in modified WO 4 solution. The Fe-group track densities up to 10 8 tracks.cm −2 (Fe-group) were measured under optical microscope. The tracks of length greater than 30 microns due to Z ≥ 36 cosmic ray nuclei are counted for VVH tracks density for all the crystals. The VVH / VH track densities ratio for these lunar olivine crystals varies from 1.25×10 −4 to 2×10 −3. It corresponds to the averaged depth of these crystals in lunar soil of 2–8 cm during galactic cosmic ray exposure. Lunar crystals are well suited for VVH track studies due to a very high track density. Two crystals were annealed at 430°C for 32 hrs. This procedure eliminates iron group tracks completely and leaves etchable tracks of nuclei with Z 50 even in the olivine crystals with Fe-group tracks up to 1–2×10 8 tracks cm −2. We were able to measure two tracks with the length 195 and 210μm which were produced by Th---U group of Galactic cosmic ray nuclei. 相似文献
16.
The results of the impedance spectroscopy measurements on eutectic samples based on zirconium oxide are presented here. Samples of CaZrO 3---ZrO 2(cubic) and MgO---ZrO 2(cubic) have been grown by a directional solidification procedure such that the different phases appear nearly oriented along the growth direction (lamellae in the system of CaZrO 3-ZrO 2(cubic) and fibers of MgO in a ZrO 2 matrix in the other system). The DC electrical conductivity has been measured by impedance spectroscopy along and across the growth axis. For CaZrO 3---ZrO 2 the coductivity is clearly anisotropic. The following values for σ T have been obtained: the conductivity at 600 °C equals 2.0 × 10 −6 Ω −1 cm −1 perpendicular to the fiber axis and 1.4 × 10 −5 Ω −1 cm −1 parallel to it and with an activation energy of 1.3 eV for σ T. For MgO---ZrO 2(cubic) the isotropic value of the conductivity at 600 °C is 10 −4 Ω −1 cm−1 with activation energy for σ T of 1.5 eV. The anisotropic conductivity in the CaZrO 3---ZrO 2 (cubic) system has been explained by a model of an ordered stacking of oxygen conducting (cubic ZrO 2) and non-conducting (CaZrO 3 or MgO) phases. 相似文献
17.
The βγ circular polarization correlation of the 3 −(β − 621 keV)3 −(γ 1692)2 + cascade in 124Sb, the 4 +(β − 662)4 + (γ 796)2 + (γ 605)0 + in 13Z4Cs and the 6 +(β −529)6 + (γ 937)4 + (γ 885)2 + (γ 658)0 + in 110mAg have been studied by using a Compton effect polarimeter. The measured asymmetry parameters are 0.172±0.004, −0.0702 ±0.0024 and 0.0549±0.0013 respectively. 相似文献
18.
Phosphorescence characteristics of CdWO 4 excited by one-photon ( λ = 308 nm) and two-photon ( λ = 570–590 nm) processes were measured. A Davydov splitting of 120 ± 20 cm −1 was obtained in the phosphorescence spectra, suggesting a diffusion coefficient of about 1.2 × 10 −2 cm 2 s −1, and a diffusion length of about 3.1 × 10 −4 cm for the room temperature measured lifetime of 8μs. The phosphorescence quantum efficiency was less than 2% at low temperatures (only 0.25% at room temperature), indicating that the dominant decay mechanism was radiationless. The radiative lifetime was thus estimated as 1–2 ms. The two-photon phosphorescence excitation is characterized by an absorption cross-section of the order of 10 −49cm 4s. 相似文献
19.
We investigate phenomenological implications of a supersymmetric left-right model based on SU(2) L × SU(2) R × U(1) B–L gauge symmetry testable in the next generation linear colliders. We concentrate in particular on the doubly charged SU(2) R triplet higgsino
, which we find very suitable for experimental search. We estimate its production rate in e +e −, e −e −, e −γ and γγ collisions and consider its subsequent decays. These processes have a clear discovery signature with a very low background from other processes. 相似文献
20.
Data were taken at the energy 2 E = 990 MeV to search for multibody events, with the same large solid angle detector which has been used for the measurement of the , ω andφ production by e +e − annilations. Assuming a π +π −π 0π 0 production by the quasi two-body process e +e − → → ωπ 0 we give the correspondi ng cross section σ(e +e − → π +π −π 0π 0) = (1.1 ± 0.5) 10 −32 cm 2. Since no events with 3 and 4 charged pions have been observed σ(e +e − → π +π −π 0π −) 1.5 × 10 −33 cm 2. 相似文献
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