No description available.

Proton radioactivity measurements have been carried out using a new double-sided silicon strip detector. Highly proton rich fusion-evaporation reaction products are velocity and mass separated using the Daresbury recoil separator before being implanted into the strip detector located at the separator's focal plane. The strip detector records the energy and position of charged particles emitted from the implanted residues, allowing the identification of very low cross section decay events with microsecond half-lives. The double-sided silicon strip detector contains 48 strips on each face, orthogonally crossed to provide <i>x,y</i> position information with a strip pitch of ±335 μm. This first use of such a detector has used new high density microelectronics to instrument up to 120 channels of data. A commissioning experiment was carried out using the reaction <SUP>58</SUP>Ni + <SUP>54</SUP>Fe→112Xe<SUP>*</SUP> which successfully tested the performance of the detection system by observing proton emission from <SUP>109</SUP>I. The subsequent production experiment investigated proton radioactivity from nuclei around <SUP>147</SUP>Tm and <SUP>151</SUP>Lu, produced using the reactions <SUP>58</SUP>Ni + <SUP>92</SUP>Mo→150Yb<SUP>*</SUP> and <SUP>58</SUP>Ni + <SUP>96</SUP>Ru→154Hf<SUP>*</SUP>. The first unambiguous identification of the proton emitter <SUP>150</SUP>Lu is reported, with a measured half-life of 30 ± 5 ms. An additional four proton transition half-lives have been re-measured with substantially improved accuracies, and explicit mass assignments are made for the first time for the proton transitions from ^151Lu, ^147mTm and ^109I. In addition a new proton transition has been observed with an energy of 947 ± 5 MeV and a half-life of 5 ± 3 ms, which is tentatively assigned to the decay of an isomeric state in ^147Tm.

No description available.

This thesis establishes the trend of neutron polarization in the D(d,n)3He reaction in the 3 to 5.5 MeV energy region where discrepancies in previous measurements exist. Determinations of the differential polarization at 290 and 460 keV and the analysis of available data below 1 MeV in terms of the T a sin2n 9 expansion gives a reliable parameterization of the reaction characteristics where none was previously available. The dependence of the neutron polarization on energy and angle has thus been established. The use of an experimental approach and apparatus consistent with other measurements at neighbouring energies further enhances the acceptability of this data. An interpretation is performed in the context of various models of the reaction. Further investigations explore the use of the ratio of asymmetries in backward and forward scattering of 3 MeV neutrons by helium as a means of selecting between the various analysing power curves for n- He scattering. The implications of the agreement with the phase shifts of Austin et al are considered and proposals for further studies are made. Important in attaining these objectives were a variety of modifications to detectors and improvements in the modes of data collection which enabled measurements of good statistical accuracy to be obtained under stable accelerator conditions.

No description available.

Measurements of the (γ,<I>p</I>) reaction have been made using target <SUP>12</SUP><I>C, <SUP>14</SUP>N, <SUP>27</SUP>Al </I>and <SUP>209</SUP><I>Bi </I>at the MAX Laboratory, University of Lund. A photon tagging technique was used to produce photons of mean energies 43.7 and 52 MeV for <SUP>209</SUP><I>Bi </I>while the other targets were studied at 73.5 MeV mean photon energy. The proton detection system used comprised of hyperpure germanium and silicon strip detectors. Differential cross sections have been extracted for discrete excitation states in the residual nuclei over an angular range of approximately 60° to 120°. The results show, in general, a trend anticipated on the basis of previous measurements. The Direct Knockout (DKO) calculations tend to reproduce experimental shapes but underestimate the data with the exception of <SUP>209</SUP><I>Bi </I>where difference between the calculations and the data is much less. An estimate of meson-exchange currents (MEC) effects using the Siegert's theorem brings the DKO calculations on average closer to the data. MEC effects, however, are less important for <SUP>209</SUP><I>Bi. </I>

No description available.

This thesis describes the calculation of the form factors for four semileptonic decays. The decays considered are those where a pseudoscalar meson composed of a heavy and a light valence quark decays to a vector meson containing only light valence quarks. The form factors were calculated in nonperturbatively <i>O</i>(a) improved quenched lattice QCD. To estimate discretisation effects the calculation was done at <i>b </i>= 6.0 and <i>b </i>= 6.2, with lattice 16³ x 48 and 24³ x 48 respectively. Results are presented for the following semileptonic decays of charmed mesons: <i>D_s</i> (r) ?, <i>D </i>(r) <i>K^*</i> and <i>D</i> (r) ρ. The <i>b </i>= 6.2 and <i>b </i>= 6.0 results agree within errors. The <i>b </i>= 6.2 results were used to calculate integrated decay rates and form factor ratios at <i>q²</i> = 0. The lattice predictions for integrated decay rates are in reasonable agreement with experiment. In some cases the lattice form factor ratios differ significantly from experiment. The simulation results were extrapolated to obtain <i>B</i> (r) ρ<i> </i>form factors at high <i>q²</i>. The lattice results and |<i>V_ub</i>| = 3.5 x 10^-3 gives the partially integrated decay rate DG(14 GeV² < <i>q²</i> < <i>q²</i>_max) = 8.7^+1.9_-1.2x 10⁷<i>s</i>^-1 (lattice statistical errors). This is in agreement with the experimental results of the CLEO collaboration. The systematic error associated with the heavy quark extrapolation is estimated to be similar to the statistical error.

This thesis is concerned with the study and improvement of methods for generating Monte-Carlo configurations used for providing non-perturbative numerical results from lattice gauge theories such as QCD, the theory of strong interactions between quarks and gluons. At present, lattice calculations require large amounts of CPU time on the largest supercomputers. In spite of this numerical assault, the majority of results generated still contain systematic errors from the use of the quenched approximation. In this approximation, employed to dramatically reduce computational costs, the effects of quantum fluctuations in the vacuum of fermion fields are ignored. Chapter 2 investigates the efficiency of a new approximate technique for dynamical fermion simulations which replaces the fermion action with the action of a large number of flavours of locally interacting auxiliary boson fields. The technique is shown to have problematic behaviour in the approach to the limit in which it exactly reproduces the required lattice gauge theory. The autocorrelation time, a measure of efficiency is shown to rise linearly in the number of boson fields employed. Chapter 3 proposes an improvement to this developing method which removes the bias of the approximation introduced. This avoids the computationally difficult approach to the exact limit of the approximation. Chapter 4 involves the calculation of the mass of the scalar glueball of QCD using large lattice spacings to avoid the high penalty for the approach to the continuum limit with an "improved" lattice action to remove the significant discretisation artifacts present at these spacings.

Rare decays in the neutral kaon sector are very important to understand CP violation mechanisms and the low energy dynamics of the standard model. This thesis describes an analysis of data taken in 1999 by the NA48 experiment. A branching ratio B (K_L (r) <i>e⁺e^-</i> gg) = (6.27 ± 0.26 _Stat ± 0.25 _syst ± 0.31 _BRx 10^-7) and a new upper limit B (K_S (r) p° <i>e</i>⁺<i>e^-</i>) < 1.4 x 10^-7were measured.