121758406
A large acceptance cylindrical drift chamber detector
Abstract This paper describes a large acceptance cylindrical drift chamber detector designed and built for the study of the np → pp π − reaction at neutron beam energies in the range 500–800 MeV. Details of construction, electronics, testing, and detection efficiencies and resolutions are presented.
121757543
Measurement of single spin asymmetry for direct photon production in pp collisions at 200 GeV/c
The single spin asymmetry for inclusive direct-photon production has been measured using a polarized proton beam of 200 GeV/c with an unpolarized proton target at −0.15 < xf < 0.15 and 2.5 < pt < 3.1 GeV/c at Fermilab. The data on the cross section for pp → γX at 2.5 < pt < 3.8 GeV/c are also provided. The measurement was done using lead-glass calorimeters and photon detectors which surrounded the fiducial area of the calorimeters. Background rejection has been done using these surrounding photon detectors. The cross section obtained is consistent with the results of previous measurements assuming a nuclear dependence of A1.0. The single spin asymmetry, AN, for the direct-photon production is consistent with zero within experimental uncertainty.
121239422
Accurate intensity measurements for proton beams with a 201 MHz structure
A counting system which measures the absolute beam intensity accurately (< 1%) at intermediate energies with a beam microstructure of 201.25 MHz or lower is described in this paper. The number of beam micropulses containing one or more beam particles are counted and time-sequenced coincidences between micropulses correct this number to obtain the actual number of beam particles using formulas based on Poisson statistics. The counting system, both the experimental setup and the correction method, was examined fully with two different beam microstructures. 10 MHz and 201.25 MHz, the two main beam microstructures at LAMPF. Maximum beam intensities, below which the system is accurate within a few tenths of a percent, were determined to be ∼ 0/4 pA and ∼ 0.1 pA average beam currents for the 5 ns and 100 ns beam microstructures, respectively.
13375438
ATLAS Distributed Analysis
The distributed analysis system for the ATLAS experiment is described. Although the system is under construction and the design is still evolving, the major components have been identified. A generic analysis service interface provides the connection between a choice of user environments and a selection of engines capable of carrying out the distributed processing. Other services provide access to catalogs, files and software.
35298179
Analyzing power measurement in inclusive Lambda 0 production with a 200 GeV/c polarized proton beam.
The considerable polarization of hyperons produced at high {ital x}{sub {ital F}} has been known for a long time and has been interpreted with various theoretical models in terms of the constituents` spin. Recently, the analyzing power in inclusive {Lambda}{sup 0} hyperon production has also been measured using the 200 GeV/{ital c} Fermilab polarized proton beam. The covered kinematic range is 0.2{le}{ital x}{sub {ital F}}{le}1.0 and 0.1{le}{ital p}{sub {ital T}}{le}1.5 GeV/{ital c}. The data indicate a negative asymmetry at large {ital x}{sub {ital F}} and moderate {ital p}{sub {ital T}}. These results can further test the current ideas on the underlying mechanisms for hyperon polarization. Copyright {ital 1995} {ital The} {ital American} {ital Physical} {ital Society}.
122179155
Comparison of spin asymmetries and cross sections in π0 production by 200 GeV polarized antiprotons and protons
13372169
Simplified test of universality in lattice QCD.
A simplified test of universality in lattice QCD is performed by analytically evaluating the continuous Euclidean time limits of various lattice fermion determinants, both with and without a Wilson term to lift the fermion doubling on the Euclidean time axis, and comparing them with each other and with the zeta-regularized fermion determinant in the continuous time-lattice space setting. The determinant relations expected from universality considerations are found to be violated by a certain gauge field-dependent factor; i.e., we uncover a "universality anomaly." The physical significance, or lack thereof, of this factor is a delicate question that remains to be settled.
6382264
Theoretical foundation for the index theorem on the lattice with staggered fermions.
A way to identify the would-be zero modes of staggered lattice fermions away from the continuum limit is presented. Our approach also identifies the chiralities of these modes, and their index is seen to be determined by gauge field topology in accordance with the index theorem. The key idea is to consider the spectral flow of a certain Hermitian version of the staggered Dirac operator. The staggered fermion index thus obtained can be used as a new way to assign the topological charge of lattice gauge fields. In a numerical study in U(1) backgrounds in two dimensions it is found to perform as well as the Wilson index while being computationally more efficient. It can also be expressed as the index of an overlap Dirac operator with a new staggered fermion kernel.
14339689
Fermionic topological charge of families of lattice gauge fields
Abstract Topological charge of families of lattice gauge fields is defined fermionically via families index theory for the overlap Dirac operator. Certain obstructions to gauge invariance of the overlap chiral fermion determinant, as well as the lattice analogues of certain obstructions to gauge fixings without the Gribov problem have natural descriptions in this context.
14334225
General bounds on the Wilson-Dirac operator
Lower bounds on the magnitude of the spectrum of the Hermitian Wilson-Dirac operator $H(m)$ have previously been derived for $0lml2$ when the lattice gauge field satisfies a certain smoothness condition. In this paper lower bounds are derived for $2p\ensuremath{-}2lml2p$ for general $p=1,2,\dots{},d$ where d is the spacetime dimension. The bounds can alternatively be viewed as localization bounds on the real spectrum of the usual Wilson-Dirac operator. They are needed for the rigorous evaluation of the classical continuum limit of the axial anomaly and the index of the overlap Dirac operator at general values of m, and provide information on the topological phase structure of overlap fermions. They are also useful for understanding the instanton size dependence of the real spectrum of the Wilson-Dirac operator in an instanton background.
7759198
Accelerated overlap fermions
Numerical evaluation of the overlap Dirac operator is difficult since it contains the sign function $\epsilon(H_w)$ of the Hermitian Wilson-Dirac operator $H_w$ with a negative mass term. The problems are due to $H_w$ having very small eigenvalues on the equilibrium background configurations generated in current day Monte Carlo simulations. Since these are a consequence of the lattice discretisation and do not occur in the continuum version of the operator, we investigate in this paper to what extent the numerical evaluation of the overlap can be accelerated by making the Wilson-Dirac operator more continuum-like. Specifically, we study the effect of including the clover term in the Wilson-Dirac operator and smearing the link variables in the irrelevant terms. In doing so, we have obtained a factor of two speedup by moving from the 
Wilson action to a FLIC (Fat Link Irrelevant Clover) action as the overlap kernel.