Three-body break-up in the d + d → d + p + n reaction

Neutron-charged-particle and charged-particle-charged-particle coincidence spectra from the d + d → d + p + n reaction were measured for θ₁ = −θ₂ = 20° at bombarding energies 6–13 MeV. Deuteron-neutron and deuteron-proton spectra for θ₁ = −θ₂ are dominated by a broad peak associated with deuteron-nucleon quasi-free scattering. The measured data were interpreted using the quasi-free scattering model. The constructed model describes the general behavior of the coincidence spectra rather well, although the calculated spectral shapes are broader than the measured ones. The limitations of the simple quasi-free scattering model are shown also by the fact that the model predicts an order of magnitude too high cross section and that the normalization constant to the measured peak cross section is energy dependent.     

Pole approximation in the quasi-free t + p scattering and the t(p,d)d reaction via the t + d interaction

The t(p,p)t and t(p,d)d channels have been investigated in an indirect way through the ²H(t,tp)n and ²H(t,dd)n three-body reactions performed at E _t = 35.5?MeV in quasi-free kinematics. The agreement with direct data supports the pole approximation at energies above the Coulomb barrier.     

Search for the Theta+ pentaquark in the reaction gammad --> pK-K+n

A search for the Theta+ in the reaction gammad --> pK-K+n was completed using the CLAS detector at Jefferson Lab. A study of the same reaction, published earlier, reported the observation of a narrow Theta+ resonance. The present experiment, with more than 30 times the integrated luminosity of our earlier measurement, does not show any evidence for a narrow pentaquark resonance. The angle-integrated upper limit on Theta+ production in the mass range of 1.52-1.56 GeV/c2 for the gammad --> pK-Theta+ reaction is 0.3 nb (95% C.L.). This upper limit depends on assumptions made for the mass and angular distribution of Theta+ production. Using Lambda(1520) production as an empirical measure of rescattering in the deuteron, the cross section upper limit for the elementary gamman --> K-Theta+ reaction is estimated to be a factor of 10 higher, i.e., approximately 3 nb (95% C.L.).     

Induced long-range dipole-field-enhanced antihydrogen formation in the p + Ps(n = 2) --> e(-) + H(n < or = 2) reaction

We report high-precision calculations that correctly include the rearrangement channels by solving the modified Faddeev equations for energies between the Ps(n = 2) and H(n = 3) thresholds, which involve six and eight open channels. We find that 99% of the antihydrogen is formed in H(n = 2). Just above the Ps(n = 2) threshold the S, P, and D partial waves contribute nearly 1400pi(a(2)0) near the maximum. We find evidence that the induced long-range dipole potential is responsible for such a large H formation cross section. The possibility of utilizing this resonance to synthesize low-energy H is discussed.     

A comment on the interpretation of anomalous enhancements n the reaction p + d → d + missing mass

Difficulties in interpreting the reaction p + d → d + missing mass are discussed. Treating this reaction as a quasi-two-nucleon process, absolute calculations are presented using the OPE model. Comparison is made with other recent calculations.     

The n-n S-wave scattering length from the neutron spectra of the reaction π− +d → 2n+γ

We present a measurement of the neutron-neutron S-wave scattering length, a_nn, from an analysis of the neutron energy and angular spectra for the reaction d(π^?, γ)2n. This reaction provides the unique advantage that while all three final-state particles are experimentally detectable, only the neutrons are strongly interacting. The data are analyzed using the treatment of this reaction given by Bander, taking the effects of experimental resolution into account with Monte Carlo techniques. Two independent analyses of 4200 events yield a_nn = ?16.7 ±1.3 fm assuming r_nn = 2.65 fm. This value is in good agreement with calculations of a_nn which assume charge symmetry of the nuclear components of p-p and n-n interactions.     

The break-up reactionp+d→p+p+n

The three-particle reactionp+d→p+p+n has been investigated at a deuteron bombarding energy of 52.0 MeV. Single counter experiments as well as coincidence measurements have been carried out. The laboratory angular distribution of the break-up reaction and the total break-up cross-section have been determined by means of the single counter experiments. The angular distribution for final-state interacting neutron-proton pairs was obtained by means of coincidence measurements. The coincidence experiments provide a strong evidence for very different shapes of the angular distributions for neutron-proton singlet and triplet final-state interaction.     

Effects due to Coulomb interaction in the sequential decay reaction2H(α,p α)n

Discrepancies between experimental values for the resonance energy and width of⁵He(g.s.) as reported by various authors may be due to the Coulomb interaction in the final channel. Calculations based on a semi-classical model are in good agreement with a recent experiment.     

Gamma polarisation in the n + p → γ + d reaction due to weak parity violating effects

We study the effect of parity violating weak interactions on the polarisation of the photon in the thermal neutron capture np → γd. The effect of various strong potentials is analysed in detail in the non-relativistic calculation. It is shown that, due to the short range of the weak interactions, the high momenta tail of the deuteron wave functions plays an important role. The effects of relativistic corrections are then considered. They are shown to be important for a precise quantitative calculation, but unable to explain the present disagreement between theory and experiment.     

The tensor polarization of 5Li (32−) in the reaction α + d → α + p + n

At the Hamburger Isochronous Cyclotron the formation of the particle unstable ground state of ${}^5\text{Li(}\text{3}\text{2}{}^{\mathrm{?}}$ has been investigated in the reaction α + d → α + p + n at E_α = 28.3 MeV. The neutrons were detected in two liquid scintillation counters, while a large Si (Li) detector was used to observe the α-particles. In a first analysis, the tensor polarization parameters of the five-nucleon system ⁵Li are determined from the experimental data. The results are in quite good agreement with theoretical predictions of Hackenbroich et al.     

Cross sections for the n+d breakup reaction

The n+d breakup cross section has been measured between 8 and 22 MeV by integrating the energy distributions of breakup protons and recoil deuterons observed in a deuterated scintillator. The results obtained deviate from the trend suggested by recent measurements of the cross section for proton-induced breakup and favour predictions based on a local N-N potential having a hard core in the singlet state.     

Bremsstrahlung of soft photons in the reaction p + p → π+ + d + γ

The limit theorem of Low is used to construct the amplitude of the soft bremsstrahlung accompanying the reaction p + p ⁺ + d. The obtained amplitude is expressed in terms of the amplitudes of the nonradiative process.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 29–32, December, 1970.     

The influence of the neutron-neutron off-energy-shell interaction on the differential μ−d capture rates

The effects of the neutron-neutron off-energy-shell interaction in muon capture by deuteron give ríse to uncertainties in the total and differential capture rates. It is shown that the uncertainties in the differential spectra can be reduced by accurate measurements of the total rates. Valuable information ona _n can therefore be expected from aμ ^? d kinematically complete experiment.     

The reaction n + p → d + γ and the isospin structure of the strangeness: Conserving nonleptonic weak Hamiltonian

The circular polarization P_γ and angular asymmetry α of the photons emitted in the reaction n + p → d + γ are computed in a covariant formalism within the framework of a composite-particle theory of the deuteron. The most important magnetic and electric dipole transition amplitudes in this radiative capture process are determined through a low-energy theorem. It is found that some of the proposed models for the strangeness-conserving nonleptonic weak Hamiltonian give variations on the ratio $\text{α}\text{P}{}_{\mathrm{\gamma }}$ of one or two orders of magnitude.     

Study of parity-violating effects in the neutron capture n + p → d + γ

The polarization and asymmetry of γ-rays emitted in the capture of thermal neutrons have been calculated for several strong and weak nucleon-nucleon potentials. The wave functions used in this calculation for the initial and final states, which contain a parity admixture, have been determined by solving the Schrödinger equation.     

On a quasi-elastic mechanism of the reaction d(p, 2p)n

The problem on validity of quasi-elastic mechanism of the reaction d(p, 2p)n in the range of low energies (20–50 MeV) is studied. While estimating the effect of multiple scattering it is shown that the condition of quasi-elasticity holds sufficiently well in all the considered cases under the assumption on peripheral collision of counted particles (the cutoff method). The dependence of the cutoff radius R₀ on the energy of incident particles E₀ is discussed.