34092114
Spin asymmetry in muon-proton deep inelastic scattering on a transversely-polarized target
Abstract We measured the spin asymmetry in the scattering of 100 GeV longitudinally-polarized muons on transversely polarized protons. The asymmetry was found to be compatible with zero in the kinematic range 0.006 x Q 2 2 . From this result we derive the upper limits for the virtual photon-proton asymmetry A 2 , and for the spin structure function g 2 . For x 2 is significantly smaller than its positivity limit √R .
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.
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.
13590622
A muon identification and combined reconstruction procedure for the ATLAS detector at the LHC at CERN
Muon identification (MUID) and high-momentum measurement accuracy is crucial to fully exploit the physics potential that will be accessible with the ATLAS experiment at the LHC. The muon energy of physics interest ranges in a large interval from few GeV, where the b-physics studies dominate the physics program, up to the highest values that could indicate the presence of new physics. The muon detection system of the ATLAS detector is characterized by two high-precision tracking systems, namely the inner detector (ID) and the muon spectrometer, (MS) plus a thick calorimeter that ensures a safe hadron absorption filtering with high-purity muons with energy above 3 GeV. In order to combine the muon tracks reconstructed in the ID and the MS, a MUID object-oriented software package has been developed. The purpose of the MUID procedure is to associate tracks found in the MS with the corresponding ID track and calorimeter information in order to identify muons at their production vertex with optimum parameter resolution. The performance of these two combined systems has been evaluated with Monte Carlo studies using single muons of fixed-transverse momentum and with full physics events.
122179155
Comparison of spin asymmetries and cross sections in π0 production by 200 GeV polarized antiprotons and protons
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.
30520304
Improving the locality of the overlap Dirac operator via approximate solutions of the Ginsparg-Wilson relation
Abstract We determine a free field hypercubic lattice Dirac operator which is optimally close to satisfying the Ginsparg-Wilson relation. Inserting this operator into the overlap formula, we show that the analytic locality bound on the resulting overlap Dirac operator is substantially stronger than in the standard case. The improvement generally persists in gauge backgrounds when the plaquette variables are all close to unity.
14889278
Axial Anomaly and Topological Charge in Lattice Gauge Theory with Overlap Dirac Operator
Abstract An explicit, detailed evaluation of the classical continuum limit of the axial anomaly and index density of the overlap Dirac operator is carried out in the infinite volume setting and in a certain finite volume setting where the continuum limit involves an infinite volume limit. Our approach is based on a novel power series expansion of the overlap Dirac operator. The correct continuum expression is reproduced when the parameter m 0 is in the physical region 0 m 0
54580751
A Doubled Discretization of Abelian Chern-Simons Theory
A new discretization of a doubled, i.e., BF, version of the pure Abelian Chern-Simons theory is presented. It reproduces the continuum expressions for the topological quantities of interest in the theory, namely, the partition function and correlation function of Wilson loops. Similarities with free spinor field theory are discussed, which are of interest in connection with lattice fermion doubling. {copyright} {ital 1997} {ital The American Physical Society}
14185169
Gauge fixing, families index theory, and topological features of the space of lattice gauge fields
Abstract The families index theory for the overlap lattice Dirac operator is applied to derive topological features of the space of SU(N) lattice gauge fields on the 4-torus: the topological sectors, specified by the fermionic topological charge, are shown to contain noncontractible even-dimensional spheres when N⩾3, and noncontractible circles in the N=2 case. We describe how certain obstructions to the existence of gauge fixings without the Gribov problem in the continuum setting correspond on the lattice to obstructions to the contractibility of these spheres and circles. We also point out a canonical connection on the space of lattice gauge fields with monopole-like singularities associated with the spheres.
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.