Configuration mixing and total muon capture rates

We modify the Primakoff closure approximation to get independence on the mean neutrino energy and energy weighted sum rules are used for the corrective terms. A near model - independent discussion is then possible, and the total rates are shown to be a very sensitive tool to investigate configuration mixing of the target. Wild discrepancies with experiment would arise if the limit of pure jj or LS couplings are used for ¹²C, whereas the Cohen-Kurath wave function gives a very good result.     

SU (4) × SU (4) symmetry breaking and its implications for SU (3) × SU (3) breaking

We investigate models where the SU (4) × SU (4) symmetry breaking Hamiltonian, $\text{H}$_SB, belongs to the (15, 15) and $\text{(10,}\text{10}\text{) + (}\text{10}\text{, 10)}$ representations, and show how they are equivalent to models of SU (3) × SU (3) breaking where $\text{H}$_SB belongs to a mixture of different representations. The results for the ππ scattering lengths in the (15, 15) model are outside the experimental limits, but the $\text{(10,}\text{10}\text{) + (}\text{10}\text{, 10)}$ model yields solutions with a wide range of values for the scattering lengths within the experimental bounds.     

Giant magnetic dipole analog excitations by the allowed muon capture in 1p-shell nuclei

The distributions of the allowed muon capture strengths in 1p-shell nuclei are shown to exhibit a tendency to concentrate in a few low-lying daughter states. These strong excitations are analogs of the giant magnetic dipole transitions, predicted by Kurath, and observed in inelastic electron scattering. Similar excitations are expected in 1S radiative pion capture and low-energy charged pion photoproduction processes.     

On total muon capture rates and the average neutrino energy

A method of avoiding the uncertainty associated with the average neutrino energy v in the usual closure approach to muon capture rates is discussed. Instead of neglecting the kinematic dependence on each particular channel, the partial capture rate is approximated by a first-order expansion around v. After the sum over the final states is performed, the result is quite independent of the specific value of v. Application to ³He, ⁶Li and closed-shell nuclei is given, as an effective test of the nuclear models used.     

Radiative muon capture in medium-heavy nuclei

Radiative muon capture in nuclei is thoroughly investigated in view of its sensitivity to the pseudoscalar coupling constant g_P. In the photon energy domain of interest (k ? 60 MeV) the effective one-body hamiltonian in use is shown essentially to hold true, with minor corrections due to the muon propagator in the nuclear field and to the two-step process. The closure approximation is avoided by appropriately integrating the response function calculated in the Fermi gas model, in the energy-momentum transfer plane.Theoretical predictions in medium-heavy nuclei of the high-energy photon spectrum, of photon polarization, and of muon-spin photon angular correlation are given for various values of the pseudoscalar coupling constant.     

Ordinary and radiative muon capture in complex nuclei

The total rates of ordinary and radiative muon capture in natural zirconium and molybdenum are calculated within the quasiparticle random phase approximation. The total ordinary-muon-capture rates calculated with the unquenched weak axial-vector coupling are consistent with the experimental data and weakly depend on the weak pseudoscalar coupling. The calculated radiative-muon-capture rates have a clear dependence on the pseudoscalar coupling, but highly overestimate the experimental data. The text was submitted by the authors in English.     

Nuclear structure effects in the allowed muon capture in 14N

Influences of nuclear structure on the allowed muon capture processes in ¹⁴N are studied. The first 2⁺ (T=1) state in ¹⁴C is found to be strongly excited, followed by a moderate excitation of 1⁺ state and a weak excitation of the ground state of ¹⁴C. The ground state transition exhibits interesting effects of its dominance by $\text{[σ × Y}{}^2\text{(}\text{r}\text{?}\text{)]}{}^1$ operator. The (2s?1d)² nuclear excitations may be responsible for the reallocation of the allowed strength to 2⁺(T=1) states.     

Neutron emission following muon capture in heavy nuclei

The energy distribution of neutrons following muon capture in heavy nuclei is investigated. It is shown that the experimental high energy tail (E > 10 MeV) of the neutron distribution can be explained by a direct emission process.     

A microscopic theory of muon capture in nuclei

The muon capture rates are calculated for a series of nuclei, using the Hartree-Fock randomphase approximation, and compared with experiment. The recoil term, the binding energy of the muon and finite size effects are calculated in detail. In a schematic model, the validity of the assumption M²_V = M²_A = M²_P is studied, and found to hold reasonably well even for nuclei as heavy as ²⁰⁸Pb.     

Chiral SU(4) × SU(4) breaking: masses and decay constants of charmed hadrons

The (4, 4*) ⊕ (4*, 4) model of broken chiral SU (4) × SU (4) symmetry has been used to calculate the third-order coupling constants involving charmed and ordinary pseudoscalar mesons. These coupling constants are exploited to derive some interesting new relations among the masses and decay constants of these charmed particles. Using the known masses and decay constants as inputs, we exploit these relations to predict:F _D = −1·41F _π ,F _F = −1·13F _π ,F _D/F_F = 1·25,m(D _s) = 1·43 GeV,m(F _s) = 1·39 GeV andm(K _s) = 1·02 GeV.     

K-forbidden allowed $ \beta$ transitions in heavy nuclei

The role of the band quantum number K in influencing the character of allowed transitions in heavy deformed nuclei is examined. The conditions for the occurrence of K -forbidden decays in this region are explored. Specific cases of “allowed” decays proceeding via K = 2 to K = 6 channels are presented to illustrate the phenomenon. The listed K = 2 transitions, which by themselves contribute over 10% of all the presently known allowed transitions for A 228 nuclei, are seen to have an average , which is clearly outside the normal range for allowed transitions. It is concluded that, wherever the -connected states can be confidently labelled using the quantum numbers, the K -forbiddenness is in general as significant as that involving the other two (spin and parity) quantum numbers.     

Experimental results on radiative muon capture in complex nuclei

Experimental results for the radiative muon capture branching ratio in several nuclei and the photon-muon spin asymmetry in⁴⁰Ca are reported. For the measurements a two arm Nalspectrometer was used. Apart from²⁶O and⁴⁰Ca, where we confirm previous results of our group, new data on¹²C,²⁶Fe,¹⁶⁵Ho and²⁰⁹Bi are presented. No available theoretical models explain all the data consistently. The preliminary results for the asymmetry measurements, obtained using a stroboscopic method are in agreement with previous measurements and with theoretical calculations.Presented at the symposium Mesons and Light Nuclei, Bechyn, Czechoslovakia, May 27–June 1, 1985.     

Emission of neutrons following muon capture in heavy nuclei

The energy and multiplicity distribution of neutrons following muon capture in heavy nuclei is investigated. High energy neutrons (E > 10 MeV) are shown to be emitted directly by the fundamental capture process.     

The vanishing cabibbo angle and muon capture rates

Recent papers have discussed the possibility that a spontaneously broken symmetry is restored at high magnetic fields. We note possible evidence in favour of this idea.     

Flavor mixing within SU(6) × SU(6) breaking

We have investigated flavor mixing within the six-quark model using chiral symmetry breaking. We have derived the mixing angles in terms of the quark mass ratios similarly to discrete symmetry considerations.     

Linear baryons and SU(3) breaking

The recently proposed mechanism of dynamical SU(3) symmetry breaking in linear baryons is applied to the α-γ sector after taking into account two types of α and γ trajectories. The observed splitting pattern of leading strange baryon trajectories is qualitatively explained. The implications of the scheme for ground state baryons are discussed.     

Inclusive radiative muon capture in nuclei: A status report

The problems connected to the use of the effective Hamiltonian and to the nuclear excitation spectrum for inclusive radiative muon capture in nuclei are reviewed. Results are presented for⁴⁰Ca.Presented at the symposium Mesons and Light Nuclei, Liblice, Czechoslovakia, June 1981.     

SU(4) flavor symmetry breaking in D-meson couplings to light hadrons

The European Physical Journal A - This work presents a simple method to determine the significant partial wave contributions to experimentally determined observables in pseudoscalar meson...     

Chiral SU4 × SU4 symmetry breaking and the Cabibbo angle

The structure of chiral SU₄ × SU₄ symmetry breaking, in the limit of exact chiral SU₂ × SU₂ symmetry, is related to the Cabibbo angle, thus leading to a satisfactory determination of the Cabibbo angle in terms of the kaon and D-meson masses and decay constants.