Mobility of muons in Cu below 2 K

We have performed transverse fieldSR experiments on several different samples of copper in the temperature range below 2 K, including isotope separated Cu and impurity doped polycrystalline Cu.We do not observe any strong effect of the isotope composition of the sample. A⁶³Cu and a natural Cu sample of identical purity both yield 0.16s^–1 for the low-temperature plateau, while an increased linewidth in the⁶⁵Cu case may be related to the strong effects of Fe impurities.Careful transverse field measurements on large single crystals at 0.08 K reveal non-Gaussian lineshapes in accordance with the picture of diffusing muons at this temperature. This allows us to reject several of the existing models for muon behaviour in copper below 2 K.     

Competition between neutron-proton rescattering and deuteron break-up in (d, np) reactions

Existing final-state interaction (FSI) theories predict observable rescattering effects in low-energy nuclear reactions with three or more particles in the final state. Obvious yields which could be attributed to this effect have only been reported in (d, np) reactions. However,n-p rescattering might be confused with the neutron-proton FSI following deuteron break-up since both contribute strongest at low relative neutron-proton energies. We have re-examined the (d, np) reactions on¹²C and⁴⁰Ca in a kinematically complete experiment making special effort to try to distinguish between rescattering and then-p FSI. Data have been taken within and outside the reaction plane at different bombarding energies. Attempts to simultaneously fit the detailed shapes of the proton spectra and the azimuthal angularn-p correlations with theoretical predictions in a consistent way were unsuccessful forboth reaction mechanisms. Improvements in the fits at particular energy and angle combinations were always at the expense of the agreement at other angles or energies. Therefore it must be concluded from our analysis that on the basis of calculations available at present the contributions fromn-p rescattering and deuteron break-up cannot be distinguished in a conclusive manner in the (d, np) experiments performed to date.     

16, 18O induced transfer reactions on122, 120Sn

The reactions¹²⁰Sn+72 MeV¹⁸O and¹²²Sn+74 MeV¹⁶O were investigated with time of-flightE-E-telescopes. Data are presented for all quasi-elastic reaction channels. The two neutron stripping and pickup reactions (¹⁸O,¹⁶O), (¹⁸O,²⁰O) and (¹⁶O,¹⁸O) are analyzed in detail. It is shown that these heavy ion induced two neutron transfer reactions proceed with essentially the same type of selectivity as the corresponding light ion induced reactions. The differential cross sections for transfer reactions leaving the^{120, 122}Sn nuclei in their 2⁺ first excited states are shown to be influenced by interference effects due to additional inelastic excitations.     

Four-wave mixing reflectivity of silicon at 1.06 μm: Influence of free-carrier absorption

The phase-conjugate reflectivity obtainable by degenerate four-wave mixing in silicon at a 1.06 m is calculated including free-carrier absorption. A maximum reflectivity of more than 100% is possible. The dependence of the reflectivity on the signal and pump energy densities up to 70 mJ/cm² is measured and found to agree with theory. The wave-front-correction property of DFWM is demonstrated with a lens in the signal beam.     

Total cross section for hadron production bye + e − annihilation between 9.4 and 9.5 GeV

The total cross section fore ⁺ e ^? annihilation into hadrons for center of mass energies from 9.4 to 9.5 GeV has been measured with the nonmagnetic DESY-Heidelberg detector at DORIS. A value ofR=σ_had/σ_µµ=3.8±0.7 for the continuum region around the Υ (9.46) resonance has been determined. The ratioΓ _ee Γ _had/Γ _tot of electronic, hadronic and total widths has been reevaluated to be (1.00±0.23) keV for the Υ resonance and (0.37±0.16) keV for the Υ′. In addition, a search for directly produced pohotons from Υ decays of the type Υ→γ+gluon+gluon has been performed. The Υ decay into muon pairs has also been searched for.