Beam-polarization asymmetries for the p(gamma-->, K+)Lambda and p(gamma-->, K+)Sigma(0) reactions for E(gamma)=1.5-2.4 GeV

Beam polarization asymmetries for the p(gamma-->,K+)Lambda and p(gamma-->,K+)Sigma(0) reactions are measured for the first time for E(gamma)=1.5-2.4 GeV and 0.6相似文献   

Low-frequency vibrational modes and temperature dependence of NQR frequencies in 1,2,4,5-tetrabromobenzene

A temperature variation study of the nuclear quadrupole resonance (NQR) frequencies for the two resonance lines in 1,2,4,5-tetrabromobenzene was carried out in the range 77–300 K. The far-infrared spectrum of 1,2,4,5-tetrabromobenzene was recorded and the low-frequency vibrational modes noted. From the nine observed frequencies, the torsional modes contributing to the change in NQR frequencies with temperature are identified by correlating the calculated values of the NQR frequencies at different temperatures with the observed values.     

The reaction γ +d → π+ + π− +p + n between 570 and 850 MeV andΔ ++ Δ − production

The reaction γ+d → π⁺+π^? +p + n has been measured in a kinematically complete way at incident photon energies from 570 to 850 MeV in steps of 40 MeV. From detailed comparison of measured data with results of event simulations, it is concluded that three different mechanisms, the quasi-free, double-delta and phase space productions, contribute to the reaction. Each of the cross sections corresponding to these mechanisms is determined separately.     

Giant resonances in the doubly magic nucleus 48Ca from the (e, e'n) reaction

The 48Ca(e,e(')n) reaction has been investigated for excitation energies 11-25 MeV and momentum transfers 0.22-0.43 fm(-1) at the superconducting Darmstadt electron linear accelerator S-DALINAC. Electric dipole and quadrupole plus monopole strength distributions are extracted from a multipole decomposition of the spectra. Their fragmented structure is described by microscopic calculations allowing for coupling of the basic particle-hole excitations to more complex configurations. Comparison of the excitation spectrum of the residual nucleus 47Ca with statistical model calculations reveals a 39(5)% contribution of direct decay to the damping of the giant dipole resonance.     

Electroexcitation of isovector magnetic dipole and quadrupole transitions in 18O and their relation to radiative pion capture

In a high-resolution ¹⁸O(e, e′) experiment sharp states at E_X=16.38±0.01 MeV (J^π=2^?, ground state analogue of and at E_X=18.86±0.01 MeV (J^π=1⁺) and clustering of strength (possibly with J^π=1^?, 2^?) at E_X≈23.7 MeV have been observed and compared to theoretical predictions. The transition strengths for the narrow states are B(M2) ↑ = 58± 8 μ_K² fm² and B(M1) ↑ = 0.28± 0.04 μ_K², respectively. These results agree qualitatively with the resu lts from the analogous ¹⁸O(π^?, γ)¹⁸N reaction.     

Excitation of 3−1, 5−1 and 7−1 states in Te isotopes A = 120, 122; 124, 126, 128 WITH (p,t) reactions

The reactions ^ATe(p, t)^A?2Te have been studied with even-A targets using 51.9 MeV protons. Three or more strongly excited triton peaks were observed in the spectra of the ^A-2Te nuclei at energies of ≈ 2–3 MeV excitation. Angular distributions are analyzed using DWBA theory. The lowest octupole (3^?₁) states of five Te isotopes are strongly excited. The lowest 3^? state in ¹²⁰Te is established at 2.09 ±0.02 MeV. The systematics of excitation energies and cross sections for the lowest 5^? and 7^? states are interpreted by a quasiparticle model.     

Test of exotic scalar and tensor interactions in K e3 decay using stopped positive kaons

The form factors of the decay K ⁺ → π ⁰ e ⁺ ν _e (K _e3) have been determined from the comparison of the experimental and Monte Carlo Dalitz distributions containing about 10⁵ K _e3 events. The following values of the parameters were obtained: λ ₊=0.0278±0.0017 (stat.)±0.0015 (syst.), |f _S/f ₊(0)|=0.0040±0.0160 (stat.)±0.0067 (syst.), and |f _T/f ₊(0)|=0.019±0.080 (stat.)±0.038 (syst.). Both scalar f _S and tensor f _T form factors are consistent with the Standard Model predictions of zero values.