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1.
β-γ(CP) correlation measurements have been carried out on the
sequence in the decay of the ground state of 49Ca to the (presumed) anti-analogue state at 3.105 MeV excitation in 49Sc. An asymmetry parameter of A = −0.132 ± 0.017 was obtained, making any spin-parity assignment other than
very unlikely for the 3.105 MeV state. The deduced Fermi matrix element for the decay is | Mv| = |1.4 ± 9.7| × 10−3, which leads to an isospin impurity (
) corresponding to the mixing of the analogue state (at 11.6 MeV) and the 3.105 MeV state of || 2 1.6 × 10 −5. This leads in turn to an effective Coulomb matrix element of | Hc| = |3.9 ± 27.4| keV, a low value compared to the value of 100 keV obtained from a theoretical estimate based on simple shell-model wave functions for the
single-particle states involved. 相似文献
2.
The time-dependence of the decay rate of initially pure K 0 into the final state (π +π −π 0) has been studied in search for the decay k S0→π +π −π 0. No evidence is found in a sample of 384 observed events. The ratio of the CP -violating K S0 amplitude and the K L0 amplitude is η +−0 = (0.13 −0.20+0.17) + i(0.17 −0.26+0.27); the ratio of the CP-conserving K S0 amplitude and the K L0 amplitude is < 0.4. The energy dependence of the K 0→π +π −π 0 matrix element is found to be a+−0 = −0.31 ± 0.03. 相似文献
3.
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
4.
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
5.
The theoretical mechanisms for the decays ψ′ → ψπ 0 and ψ′ → ψη, which violate SU 2 and SU 3, respectively discussed. It is argued that symmetry breaking in the decay amplitudes may be as important as π 0 −η −η′ mixing. The π 0 −η mechanism ψ′ → ψν → ψπ 0 leads to Γ(ψ′ → ψπ 0) = (3.3±1.0) × 10 −3 Γ(ψ′ → ψν), but this number may be enhanced by a factor as large as 12 by π 0−η′ mixing and isospin violation in the decay amplitude. The related decays ψ → ηγ and ψ → η′γ are also discussed. 相似文献
6.
The lifetimes of the Cd+ 5 2P3/2 and 5 2P1/2 states have been measured by the Hanle effect. The Cd + ions are produced in a d.c. discharge in cadmium vapor, with helium as buffer gas. The results are: τ(5 2P3/2) = (2.60±0.20) ×10 −9sec, and τ(5 2P1/2) = (3.05 ± 0.13) × 10 −9sec. We measured also the cross sections for the destruction of the orientation in the 52P1/2Cd+ state (<5Å2), of the orientation (18±10Å2) and of the alignment (46±10Å2) in the 52P3/2 state due to collisions with the helium atoms. 相似文献
7.
The betaspectra of 12B and 12N have been measured with a NaI crystal as spectrometer. Assuming a shape correction factor 1 + aW + bW2 and b− = 1.106 × 10 −4 MeV −2, b+ = −1.397 × 10 −4 MeV −2, the spectra yield a− = (+0.91 ± 0.11) × 10 −2 MeV −1 and a+ = (−0.07 ± 0.09) × 10 −2 MeV −. the a− − a+ = (+0.98 ± 0.09) × 10 −2 MeV −1 is in agreement with the weak magnetism prediction. 相似文献
8.
We study the ρ 0 and φ decays into π +π −γ, π 0π 0γ and φ into π 0ηγ using a chiral unitary approach to deal with the final state interaction of the MM system. The final state interaction modifies only moderately the large momenta tail of the photon spectrum of the ρ 0→π +π −γ decay. In the case of φ decay the contribution to π +π −γ and π 0π 0γ decay proceeds via kaonic loops and gives a distribution of ππ invariant masses in which the f0(980) resonance shows up with a very distinct peak. The spectrum found for φ→π 0π 0γ decay agrees with the recent experimental results obtained at Novosibirsk. The branching ratio for φ→π 0ηγ, dominated by the a0(980), is also in agreement with recent Novosibirsk results. 相似文献
9.
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
10.
The g-factor of the 3/2 − state at 153 keV in 49V was measured with the 48Ti(p, γ) 49V reaction and the differential spin-precession method. The g value and the remeasured mean life are g = 1.58 ± 0.08 and τ = 28.7 ± 0.5 ns. The result is compared with some theoretical predictions. 相似文献
11.
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
12.
Angular distribution of the reaction 12C( d,τ) 11B leading to the 3/2 − ground state and the 4.44 MeV excited (5/2 − state 11B have measured at Ed = 80 MeV up to about 70° and 40°, respectively. The inclusion of second-order processes in the framework of CCBA calculations gives a good reproduction of the 3/2 − as well as of the DWBA forbidden 3/2 − angular distribution. The strong dependence of the cross section on the sign of the deformation supports a positive β 2 value for 11B. 相似文献
13.
Cluster decay of 242Cm with emission of 34Si-particles was measured using track-recording phosphate glass detectors. The corresponding partial half-life is (1.4±0.3)×10 23 s. The branching ratio relative to decay is 1.0×10 −16 and relative to spontaneous fission 1.6×10 −9. 相似文献
14.
The circular polarization of the 482 keV γ-radiation of 181Ta and the 343 keV γ-radiation of 175Lu was measured with a Compton polarimeter. Spurious effects arising from higher order contributions of quantum electrodynamics to the Compton scattering cross section were discovered. The results for the polarization are P = − (4.1±1.3)10 −6 for 181Ta and P = − (1.5±6.0)10 −6 for 175Lu. These values are corrected for instrument asymmetries, bremsstrahlung and intensity of other lines. 相似文献
15.
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
16.
Measurements have been made of the β-γ circular-polarization correlation paramter A for the 273 keV β-branch in the decay of 59Fe. It has recently been established that each of the principal β-branches of 59Fe involves Δ J=0 and thus has a possible non-zero Fermi matrix element MF which can be determined from the ƒ t value and A. Previous β-γ (_CP) measurements on this nucleide have all employed the usual γ-ray scattering technique. This method is suitable for the 475 keV β-branch but does not produce an accurate measurement of the lower energy branch because of energy discrimination difficulties. A transmission polarimeter with γ-discrimination has been used in the present work to obtain clean data on the 273 keV β-1.29 MeV γ-cascade. Calibration with 60Co (1.33 MeV) and 28Al (1.79 MeV) yielded A = −0.154±0.023. This gives for the isospin impurity coefficient and the effective Coulomb matrix element of the 1.29 MeV state (1.1±1.4) × 10 −3 and 9±11 keV, respectively. 相似文献
17.
Lifetimes of excited 0 + states in 166Er have been measured with the (n,n′γ) reaction. The first and second excited 0 + states have no significant collective enhancements of their decays, and their properties are suggestive of pair-type excitations rather than those of a β vibration or phonon excitation built on the γ vibration. The third excited 0 + state at 1934 keV has an enhanced decay to the ground state band with B( E2; 0 4+ → 2 gsb+) = 8.8 ± 0.9 W.u., consistent with that expected for a β vibration. 相似文献
18.
The 14C(t, p) 16C reaction locates five new states in 16C, at excitation energies of 3120 ± 15, 3983 ± 10, 4136 ± 10 and 6109 ± 15 keV, in addition to the g.s. and 1.76 MeV states. The 3.02 and 3.98 MeV states appear to be the second 0 + and 2 + 2p-2h states, respectively. The 4.14 MeV state has Jπ = 4 + and the 6.11 MeV state has Jπ = 2 +, 3 −, or 4 +. 相似文献
19.
In-beam γ-ray transitions in 181Hg, the lightest odd-A Hg isotope known thus far, have been identified from fragment mass-γ and γ-γ coincidence measurements. Five prolate deformed rotational bands were placed in the level scheme. A decoupled band built on the strongly prolate deformed 1/2 −[521] ground state was observed up to 29/2 −. A 5/2 −[512] configuration is suggested for a pair of strongly coupled bands displaying no signature splitting. The other two bands are also signature partner bands. They are populated with the largest intensity and exhibit splitting. They have been associated with the mixed neutron i 13/2 orbitals and are proposed to decay to an i 13/2 isomeric state associated with an oblate state. 相似文献
20.
The π 0 spectrum in the KL0 → 3π decay was measured using a wire chambers magnetic spectrometer. In the usual approximation, the matrix element can be expressed as: M2 ≈ 1 + 2 a0( MK/ Mπ2)(2 Tπ0− Tπ0max) + a1( MK2/ Mπ4)(2 Tπ0− Tπ0max) 2. We obtained a0 = −0.282 ± 0.011 and a1 consistent with zero. 相似文献
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