122601142
SVX', the new CDF silicon vertex detector
Abstract The Collider Detector at Fermilab (CDF) radiation hardened silicon vertex detector (SVX') is described. The new detector has several improvements over its predecessor such as better signal to noise and higher efficiency. It is expected to have a radiation tolerance in excess of 1 Mrad. It has been taking data for several months and some preliminary results are shown.
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
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)
183079972
Operating Characteristics of Lecroy-2280/2285 ADC System
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>>
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.
202114504
Presence and Absence of Scaling Violations in Inclusive Leptoproduction
In the standard model, the heavy--quark-parton scaling variable is used to study the effects of the color-octet piece of the integrally-charged--quark-parton electromagnetic current which would violate scaling in deep-inelastic leptoproduction. With spin-1/2 partons it is found that sigma/sub L//sigma/sub T/ would deviate significantly from zero since (sigma/sub L//sigma/sub T/)/sub muN/ approx. = 4m/sub c//sup ts2/f/sub v/(z)/ 5Q/sup 2/f/sub v/(x), where f/sub v/(z) + u/sub v/(z) + d/sub v/(z), m/sub c//sup ts2/ = effective mass-squared of quark-parton in color-excited hadron, and z approx. = x + m/sub c//sup ts2//2MEy. Such scaling violations must occur in the ..mu.. data at currently available energies if the step of 2 units of R (beyond charm) in the 4-GeV region in the SPEAR data for ee-bar annihilation is due to a color threshold for the production of color-octet qq-bar mesons, qqq baryons, and/or quark-antiquark pairs. Consistency is shown between the scaling violations in the electroproduction data in the x < or = 0.2 region and the energy independence in the data of the CDHS collaboration for charged-current neutrino distributions for average y and for sigma/sup nu-bar/sigma/sup ..nu../. Exclusive final states responsible for electroproduction scaling violations in the x < or = 0.2 region would containmore » the tau-particle-antiparticle pairs (i.e., integrally charged quarks) and/or high-momentum photons (few GeV) from radiative decay modes of color-octet hadrons.« less
120421012
The psion family: Relativistic charmonium
The authors have reported earlier that the spectrum of the psion family suggests a treatment based on an O(4) harmonic-oscillator family with O(4) quantum number M = 0 (equally spaced, mass-squared linear Regge trajectories). This results in the new J/subP//subC/ quantum numbers: 0$sup ++$ for 2.8 GeV/ c$sup 2$; 2$sup ++$, 1$sup -+$, 0$sup ++$ for the 3.4-GeV/c$sup 2$ mass region. All radiative decays are related through a single O(4) coupling S/sub mu//sub nu/ F/sub mu//sub nu/, where S/sub mu//sub nu/ is the internal-space angular-momentum operator. The details of the calculations of radiative transition widths and of the $gamma$$gamma$ angular correlation functions are given. Experimental signatures are discussed and compared with the nonrelativistic charmonium scheme; among others J $Yields$ O (2.8) + $gamma$ and psi ' $Yields$ O (2.8) + $gamma$ are small, being forbidden in the strict O(4) limit. O (2.8) is expected to be narrow like all other psions below the 4.0-GeV/c$sup 2$ region. chi$sub 0$(3.41) and chi$sub 1$(3.49) total widths are expected to be around 630 keV and 185 keV respectively. The missing decays of psi ' could be due to psi ' $Yields$ O + $omega$ ( approx. 32%). (AIP)
118047130
Absence of strangeness-changing, neutral current effects from the symmetric quark model
121474561
Color models of hadrons
Abstract The evidence for a three-valued “color” degree of freedom in hadron physics is reviewed. The structure of color model is discussed. Consequences of color models for elementary particle physics are discussed, including saturation properties of hadronic states, π o → 2 ψ and related decays, leptoproduction, and lepton pair annihilation. Signatures are given which distinguish theories with isolated colored particles from those in which color is permanently bound.
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.