44977344
The upgraded CDF front end electronics for calorimetry
The front-end electronics used in the calorimetry of the Collision Detector Facility (CDF) detector has been upgraded to meet system requirements for higher expected luminosity. A fast digitizer utilizing a 2- mu s, 16-b analog-to-digital converter (ADC) has been designed and built. Improvements to the front-end trigger circuitry have been implemented, including the production of 900 new front-end modules. Operational experience with the previous system is presented, with discussion of the problems and performance goals.<<ETX>>
120517617
Elastic Photoproduction of omega Mesons from Hydrogen, Deuterium, and Complex Nuclei
We have studied ..omega.. photoproduction using 7.5- to 10.5-GeV tagged photons. Cross sections from hydrogen lie 22% below the bubble chamber results of Ballam et al., but have a similar slope. Density matrices indicate approximate s-channel helicity conservation. The proton--neutron cross-section difference is midway between zero and the value suggested by the ..gamma..p--..gamma..n total-cross-section difference. Fits to the cross sections for D, Be, and Cu and those for Be, C, Al, Cu, and Pb from a previous experiment yield sigma/sub ..omega..N/ = 25.4 +- 2.7 mb and ..gamma../sub ..omega..//sup 2//4..pi.. = 7.6 +- 1.2. (AIP)
118487890
Search for photoproduction of psi (3105)
121484834
Avoidance of counter-example to non-abelian Bloch-Nordsieck conjecture by using coherent state approach
It is shown that the counter-example to the non-abelian Bloch-Nordsieck conjecture in “q + q → γ∗ + soft gluons” to order αs2 is avoided at the cross section level if the initial st prepared according to the coherent state approach for treatment of the infrared region of non-abelian gauge theories.
183079972
Operating Characteristics of Lecroy-2280/2285 ADC System
121999587
Operational performance of a large liquid argon photon calorimeter
Abstract We describe the performance of a large (0.9 × 1.4 m2) liquid argon photon calorimeter in high energy experiments at Fermilab. Resolutions for π0 and electron showers, obtained under data-taking conditions, are compared with electron-beam calibration results. Exceptional spatial and time resolutions have been achieved for isolated showers (σx,y
14270584
Tau decays beyond the standard model
In a recent paper, 8 semileptonic parameters were defined to specify the most general Lorentz-invariant spin correlation functions for 2-body τ decays. These parameters can be used to search for anomalous Γ L , Γ T polarized-partial widths, for non-CKM-type leptonic CP violation, and for leptonic T FS violation. They can also be used to bound the effective-mass scales A for “new physics” arising from additional Lorentz structures, e.g. from lepton compositeness, tau weak magnetism, weak electricity, or second-class currents. It is emphasized that (i) for these tests “different modes have different merits” and that (ii) the parameters can be measured either by using spin-correlation techniques without polarized beams, or with longitudinally polarized beams.
122358666
Production thresholds for quark and for diquark pairs in ee-bar annihilation as tests of charm, then color, excitation
We have pointed out earlier that the decrease at high energies in the ratio of charged-particle energy to total energy in ee-bar annihilation into hadrons and the rise in R in the 4-GeV region suggest first charm, then color, excitation. We present here an analysis of the pair-production thresholds for quarks (responsible for ..mu..e events) and for diquarks (threshold near 4.3 GeV) based on the simple mass spectrum generated by the popular color-octet vector-meson-exchange mechanism, but here in the context of R data and the integrally charged three-quartet model. Our emphasis throughout is a phenomenological one, with special attention to experimental signatures in annihilation and lepton-pair production which can exclude this economical model. For this spectrum we find there must exist a new color-symmetry-violating coupling responsible for the decays of quarks. From the identification of the U particles as quarks, it is suggested that this includes a weak interaction mediated by colored, right-handed quark-neutrino currents coupled to the usual charged currents.
119943713
Non-Abelian structure of Yang-Mills theory and infrared-finite asymptotic states
The idea of Kulish and Faddeev for treating asymptotic dynamics is extended to derive a set of states with which the matrix element of quark scattering from a color-singlet external potential is shown to be free of the leading-order non-Abelian class of infrared divergences to fifth order in g.
124235284
Infrared Properties of Unusual Initial State Interactions
The related roles of gauge invariance and of initial coherent/ degenerate states in the factorization of QCD processes into short-distance and long-distance parts are discussed. For ππ →μ+μ - + X it is shown that although the systematic summation over all possible spectator interactions removes the outside soft-IR divergences in the non- overlapping ladder Glauber diagrams, unphysical inside soft-IR divergences persist. So, the on-shell Glauber region is not a gauge invariant concept which can be physically isolated from radiative corrections which non-trivially involve other diagrammatic regions. It is conjectured that in QCD non-factorization is inconsistent with local gauge invariance.
119907461
Parity determination for the new generation of heavy neutral mesons
We consider how best to experimentally determine the parity quantum number of a new heavy neutral meson, including the possibility of exotic ${J}^{\mathrm{PC}}$. Multiquark and gluon bound states can have exotic ${J}^{\mathrm{PC}}$ quantum numbers forbidden to the nonrelativistic $q\overline{q}$ system. If only the existence of easily identifiable two-body hadronic modes is known, it is not possible to establish the parity so an "exotic" meson, $Jg0$, could be misidentified as a "normal" meson. Direction-linear-polarization coefficients, which would identify the parity, are also found to be small for $e\overline{e}\ensuremath{\rightarrow}{1}^{\ensuremath{-}\ensuremath{-}}\ensuremath{\rightarrow}{1}^{\ifmmode\pm\else\textpm\fi{}+}\ensuremath{\gamma},{0}^{\ifmmode\pm\else\textpm\fi{}+}\ensuremath{\gamma}$ with the high-energy photon externally converting into an $e\overline{e}$ pair. However, important parity tests do exist, independent of the polarization state of the decaying particle, which can be used to settle the confusion. These are listed in Sec. III of this paper.