Experimental study study of antiproton-proton annihilation into a pair of charged Pi-Mesons or K-Mesons for incident antiproton mementa in the range from 0.72 GeV/c to 2.62 GeV/c

<p>The cross sections for the two antiproton-proton annihilation-in-flight modes,</p> <p>��p + p ��� ��⁺ + ��^-</p> <p>��p + p ��� k⁺ + k^-</p> <p>were measured for fifteen laboratory antiproton beam momenta ranging from 0.72 to 2.62 GeV/c. No magnets were used to determine the charges in the final state. As a result, the angular distributions were obtained in the form [d��/d�� (��_C.M.) + d��/d�� (�� ��� ��_C.M.)] for 45 ��� ��_C.M. ��� 135��. </p> <p>A hodoscope-counter system was used to discriminate against events with final states having more than two particles and antiproton-proton elastic scattering events. One spark chamber was used to record the track of each of the two charged final particles. A total of about 40,000 pictures were taken. The events were analyzed by measuring the laboratory angle of the track in each chamber. The value of the square of the mass of the final particles was calculated for each event assuming the reaction</p> <p>��p + p ��� a pair of particles with equal masses.</p> <p>About 20,000 events were found to be either annihilation into �� ^��-pair or k ^��-pair events. The two different charged meson pair modes were also distinctly separated.</p> <p>The average differential cross section of ��p + p ��� ��⁺ + ��^- varied from ~ 25 ��b/sr at antiproton beam momentum 0.72 GeV/c (total energy in center-of-mass system, ���s = 2.0 GeV) to ~ 2 ��b/sr at beam momentum 2.62 GeV/c (���s = 2.64 GeV). The most striking feature in the angular distribution was a peak at ��_C.M. = 90�� (cos ��_C.M. = 0) which increased with ���s and reached a maximum at ���s ~ 2.1 GeV (beam momentum ~ 1.1 GeV/c). Then it diminished and seemed to disappear completely at ���s ~ 2.5 GeV (beam momentum ~ 2.13 GeV/c). A valley in the angular distribution occurred at cos ��_C.M. ��� 0.4. The differential cross section then increased as cos ��_C.M. approached 1.</p> <p>The average differential cross section for ��p + p ��� k⁺ + k^- was about one third of that of the ��^��-pair mode throughout the energy range of this experiment. At the lower energies, the angular distribution, unlike that of the ��^��-pair mode, was quite isotropic. However, a peak at ��_C.M. = 90�� seemed to develop at ���s ~ 2.37 GeV (antiproton beam momentum ~ 1.82 GeV/c). No observable change was seen at that energy in the ��^��-pair cross section.</p> <p>The possible connection of these features with the observed meson resonances at 2.2 GeV and 2.38 GeV, and its implications, were discussed. </p>

High energy photoproduction of neutral mesons

<p>Cross sections for the photoproduction of neutral pi, eta, rho and phi mesons on hydrogen have been measured at the Stanford Linear Accelerator Center using a missing mass spectrometer technique. The data cover photon energies between 5.0 and 17.8 GeV and four momentum transfer squared t between -.12 and -1.38 (GeV/c)².</p> <p>Pion differential cross sections at lower energies show a peak at low momentum transfers, a distinctive dip and secondary maximum for t in the region -.4 to -.9 (GeV /c)², and a smooth decrease at higher momentum transfers. As photon energy increases, the dip becomes less pronounced, in contradiction to the expectations of simple Regge theories based on the exchange of omega and B trajectories only.</p> <p>Eta photoproduction was measured only below 10 GeV. The cross section has about the same magnitude as the pion production cross section, but decreases exponentially with t, showing no dip.</p> <p>Rho mesons appear to be diffractively produced. The differential cross section varies approximately as exp(8.5t + 2t²). It falls slowly with energy, decreasing about 35 percent from 6 GeV to 17.8 GeV. A simple quark model relation appears to describe the data well.</p> <p>Phi meson cross sections are also consistent with diffraction production. The differential cross section varies approximately as exp(4t). The cross section tends to decrease slightly with photon energy.</p>

Isotope shift measurements using k x-rays in Sn, Sm, and W

<p>Electronic K��l x-ray isotope shifts have been measured for Sn 116-124, Sm 148-154, W 182-184, W 184-186, and W 182-186 using a curved crystal Cauchois spectrometer. The analysis of the measurements has included the electrostatic volume effect, screening by the transition electron as well as the non-transition electrons, normal and specific mass shifts, dynamical nuclear qudrupole polarization, and a radiative correction effect of the electron magnetic moment in the nuclear charge radii are obtained. Where other experimental data are available, the agreement with the present measurements is satisfactory. Comparisons with several nuclear model predictions yield only partial agreement. </p>

Photoproduction of ETA mesons from hydrogen at photon energies between 0.8 and 1.45 GeV

<p>We measured the differential cross section of the process ��p ��� p�� at the 1.5 GeV Caltech electron synchrotron, at photon energies from 0.8 to 1.45 GeV, at various angles between 45�� and 100�� in the center of mass. A counter-spark chamber array was used to determine the kinematics of all particles in the final state of the partial mode ��p ��� p�� (�� ��� 2��). Analysis of 40,000 pictures yielded 6,000 events above a background which varied with energy from 5% to 30% of foreground. The cross section shows an energy dependence confirming earlier results up to 1000 MeV, but with improved statistics; it then remains roughly constant (at 50�� C.M.), to 1.45 GeV. The data show a small angular variation, within the limited range covered, at energies between 1000 and 1100 MeV.</p>

Thermodynamic and kinetic behavior of an argon plasma jet. Decomposition of nitric oxide between 1300 - 1750 degrees K in an argon plasma

<p>In the first part of the study, an RF coupled, atmospheric pressure, laminar plasma jet of argon was investigated for thermodynamic equilibrium and some rate processes. </p> <p>Improved values of transition probabilities for 17 lines of argon I were developed from known values for 7 lines. The effect of inhomogeneity of the source was pointed out.</p> <p>The temperatures, T, and the electron densities, n_e , were determined spectroscopically from the population densities of the higher excited states assuming the Saha-Boltzmann relationship to be valid for these states. The axial velocities, v_z, were measured by tracing the paths of particles of boron nitride using a three-dimentional mapping technique. The above quantities varied in the following ranges: 10¹² �� n_e �� 10¹⁵ particles/cm³, 3500 �� T �� 11000 ��K, and 200 �� v_z �� 1200 cm/sec.</p> <p>The absence of excitation equilibrium for the lower excitation population including the ground state under certain conditions of T and n_e was established and the departure from equilibrium was examined quantitatively. The ground state was shown to be highly underpopulated for the decaying plasma.</p> <p>Rates of recombination between electrons and ions were obtained by solving the steady-state equation of continuity for electrons. The observed rates were consistent with a dissociative-molecular ion mechanism with a steady-state assumption for the molecular ions. </p> <p>In the second part of the study, decomposition of NO was studied in the plasma at lower temperatures. The mole fractions of NO denoted by x_NO were determined gas-chromatographically and varied between 0.0012 �� x_NO �� 0.0055. The temperatures were measured pyrometrically and varied between 1300 �� T �� 1750��K. The observed rates of decomposition were orders of magnitude greater than those obtained by the previous workers under purely thermal reaction conditions. The overall activation energy was about 9 kcal/g mol which was considerably lower than the value under thermal conditions. The effect of excess nitrogen was to reduce the rate of decomposition of NO and to increase the order of the reaction with respect to NO from 1.33 to 1.85. The observed rates were consistent with a chain mechanism in which atomic nitrogen and oxygen act as chain carriers. The increased rates of decomposition and the reduced activation energy in the presence of the plasma could be explained on the basis of the observed large amount of atomic nitrogen which was probably formed as the result of reactions between excited atoms and ions of argon and the molecular nitrogen.</p>

Relativistic quark models and the current algebra

<p>In this thesis we are concerned with finding representations of the algebra of SU(3) vector and axial-vector charge densities at infinite momentum (the "current algebra") to describe the mesons, idealizing the real continua of multiparticle states as a series of discrete resonances of zero width. Such representations would describe the masses and quantum numbers of the mesons, the shapes of their Regge trajectories, their electromagnetic and weak form factors, and (approximately, through the PCAC hypothesis) pion emission or absorption amplitudes.</p> <p>We assume that the mesons have internal degrees of freedom equivalent to being made of two quarks (one an antiquark) and look for models in which the mass is SU(3)-independent and the current is a sum of contributions from the individual quarks. Requiring that the current algebra, as well as conditions of relativistic invariance, be satisfied turns out to be very restrictive, and, in fact, no model has been found which satisfies all requirements and gives a reasonable mass spectrum. We show that using more general mass and current operators but keeping the same internal degrees of freedom will not make the problem any more solvable. In particular, in order for any two-quark solution to exist it must be possible to solve the "factorized SU(2) problem," in which the currents are isospin currents and are carried by only one of the component quarks (as in the K meson and its excited states).</p> <p>In the free-quark model the currents at infinite momentum are found using a manifestly covariant formalism and are shown to satisfy the current algebra, but the mass spectrum is unrealistic. We then consider a pair of quarks bound by a potential, finding the current as a power series in 1/m where m is the quark mass. Here it is found impossible to satisfy the algebra and relativistic invariance with the type of potential tried, because the current contributions from the two quarks do not commute with each other to order 1/m³. However, it may be possible to solve the factorized SU(2) problem with this model.</p> <p>The factorized problem can be solved exactly in the case where all mesons have the same mass, using a covariant formulation in terms of an internal Lorentz group. For a more realistic, nondegenerate mass there is difficulty in covariantly solving even the factorized problem; one model is described which almost works but appears to require particles of spacelike 4-momentum, which seem unphysical.</p> <p>Although the search for a completely satisfactory model has been unsuccessful, the techniques used here might eventually reveal a working model. There is also a possibility of satisfying a weaker form of the current algebra with existing models.</p>

An investigation of the reaction negative K��p ��� K������� at P_(lab) = 2 Gev/c

<p>The reaction K^-p���K^-��⁺n has been studied for incident kaon momenta of 2.0 GeV/c. A sample of 19,881 events was obtained by a measurement of film taken as part of the K-63 experiment in the Berkeley 72 inch bubble chamber. </p> <p>Based upon our analysis, we have reached four conclusions. (1) The magnitude of the extrapolated K�� cross section differs by a factor of 2 from the P-wave unitarity prediction and the K⁺n results; this is probably due to absorptive effects. (2) Fits to the moments yield precise values for the K�� S-wave which agree with other recent statistically accurate experiments. (3) An anomalous peak is present in our backward K^-p���(��+n) K^- u-distribution. (4) We find a non-linear enhancement due to interference similiar to the one found by Bland et al. (Bland 1966).</p>

Inelastic K+p reactions at incident momenta from 1.37 GeV/c to 2.17 GeV/c

<p>A number of recent experiments have suggested the possibility of a highly inelastic resonance in K⁺p scattering. To study the inelastic K⁺p reactions, a 400 K exposure has been taken at the L.R.L. 25 inch bubble chamber. The data are spread over seven K⁺ momenta between 1.37 and 2.17 GeV/c.</p> <p>Cross-sections have been measured for the reaction K⁺p ��� pK����+ which is dominated by the quasi-two body channels K��� and K*N. Both these channels are strongly peripheral, as at other momenta. The decay of the ��� is in good agreement with the predictions of the rho-photon analogy of Stodolsky and Sakurai. The data on the K*p channel show evidence of both pseudo scalar and vector exchange.</p> <p>Cross-sections for the final state pK⁺��+��- shows a strong contribution from the quasi-two body channel K*���. This reaction is also very peripheral even at threshold. The decay angular distributions indicate the reaction is dominated as at higher momenta by a pion exchange mechanism. The data are also in good agreement with the quark model predictions of Bialas and Zalewski for the K* and ��� decay.</p>

CP and the three pion decay of the K��

<p>The time distribution of the decays of an initially pure K�� beam into ��+��-���� has been analyzed to determine the complex parameter W (also known as ��^+-�� and (x + iy)). The K�� beam was produced in a brass target by the interactions of a 2.85 GeV/c ��- beam which was generated on an internal target in the Lawrence Radiation Laboratory (LRL) Bevatron. The counters and hodoscopes in the apparatus selected for events with a neutral (K��) produced in the brass target, two charged secondaries passing through a magnet spectrometer and a ��-ray shower in a shower hodoscope. </p> <p>From the 275K apparatus triggers, 148 K ��� ��+��-���� events were isolated. The presence of a ��-ray shower in the optical shower chambers and a two-prong vee in the optical spark chambers were devices used to isolate the events. The backgrounds were further reduced by reconstructing the momenta of the two charged secondaries and applying kinematic constraints.</p> <p>The best fit to the final sample of 148 events distributed between .3 and 7.0 K_S lifetimes gives: </p> <p>ReW = -.05 ��.17</p> <p>ImW = +.39 +.35/-.37</p> <p>This result is consistent with both CPT invariance (ReW = 0) and CP invariance (W = 0). Backgrounds are estimated to be less than 10% and systematic effects have also been estimated to be negligible.</p> <p>An analysis of the present data on CP violation in this decay mode and other K�� decay modes has estimated the phase of �� to be 45.3 �� 2.3 degrees. This result is consistent with the super weak theories of CP violation which predicts the phase of �� to be 43��. This estimate is in turn used to predict the phase of ������ to be 48.0 �� 7.9 degrees. This is a substantial improvement on presently available measurements. The largest error in this analysis comes from the present limits on W from the world average of recent experiments. The K ��� ��u�� mode produces the next largest error. Therefore further experimentation in these modes would be useful.</p>