5507561
Rooting issue for a lattice fermion formulation similar to staggered fermions but without taste mixing.
Toinvestigatetheviabilityofthe4th roottrickforthestaggered ferm ion determ inantin asim pler setting,weconsidera two taste(avor)lattice ferm ion form ulation with no tastem ixing butwith exact taste-nonsinglet chiralsym m etries analogous to the taste-nonsinglet U(1)A sym m etry of staggered ferm ions.M .Creutz’sobjectionsto therooting trick apply justasm uch in thissetting. To counter them we show thatthe form ulation has robustwould-be zero-m odes in topologically nontrivialgauge backgrounds,and that these m anifestthem selves in a viable way in the rooted ferm ion determ inantand also in the disconnected piece ofthe pseudoscalarm eson propagatoras required to solvetheU(1)problem .Also,ourrooted theory isheuristically seen to bein theright universality classforQCD ifthesam eistrueforan unrooted m ixed ferm ion action theory.
14198915
Partition function of a quadratic functional and semiclassical approximation for Witten's three manifold invariant
An extension of the method and results of A. Schwarz for evaluating the partition function of a quadratic functional is presented. This enables the partition functions to be evaluated for a wide class of quadratic functionals of interest in topological quantum field theory, for which no other method has previously been available. In particular it enables the partition functions appearing in the semiclassical approximation for the Witten-invariant to be evaluated in the most general case. The resulting k-dependence is precisely that conjectured by D. Freed and R. Gompf.
5306804
On the continuum limit of fermionic topological charge in lattice gauge theory
It is proved that the fermionic topological charge of SU(N) lattice gauge fields on the four-torus, given in terms of a spectral flow of the Hermitian Wilson–Dirac operator or, equivalently, as the index of the overlap Dirac operator, reduces to the continuum topological charge in the classical continuum limit when the parameter m0 is in the physical region 0
13939487
Eradication of singularities in the next-to-leading order RG evolution for the \Delta S = 1 effective Hamiltonian with 3 quark flavours
We consider the renormalization group evolution for the operators in the $\Delta S=1$ effective Hamiltonian with 3 active quark flavors, which is needed in the numerical analysis of data sets for $\epsilon'/\epsilon$ calculated in lattice QCD. Singularities are present in the original solution of Buras et al. at next-to-leading order. We show how these can be eradicated through a method of analytic continuation to obtain the correct finite solution in this case. Furthermore, we trace the origin of the singularities to a breakdown of the approach of Buras et al. in the 3 flavour case, and show how it can be rectified so that singularitites are absent from the beginning.
85538824
Dimensionally reduced expression for the QCD fermion determinant at finite temperature and chemical potential
A dimensionally reduced expression for the QCD fermion determinant at finite temperature and chemical potential is derived which sheds light on the determinant's dependence on these quantities. This is done via a partial zeta regularisation, formally applying a general formula for the zeta-determinant of a differential operator in one variable with operator-valued coefficients. The resulting expression generalises the known one for the free fermion determinant, obtained via Matsubara frequency summation, to the case of general background gauge field; moreover there is no undetermined overall factor. Rigorous versions of this result are obtained in a continuous time--lattice space setting. The determinant expression reduces to a remarkably simple form in the low temperature limit. A program for how to use this to obtain insight into the QCD phase transition at zero temperature and nonzero density is outlined.
8852930
Index of a family of lattice Dirac operators and its relation to the non-Abelian anomaly on the lattice.
In the continuum, a topological obstruction to the vanishing of the non-Abelian anomaly in 2n dimensions is given by the index of a certain Dirac operator in 2n+2 dimensions, or equivalently, the index of a 2-parameter family of Dirac operators in 2n dimensions. In this paper an analogous result is derived for chiral fermions on the lattice in the overlap formulation. This involves deriving an index theorem for a family of lattice Dirac operators satisfying the Ginsparg-Wilson relation. The index density is proportional to Lüscher's topological field in 2n+2 dimensions.
10735130
DIAL: Distributed Interactive Analysis of Large Datasets
DIAL will enable users to analyze very large, event-based datasets using an application that is natural to the data format. Both the dataset and the processing may be distributed over a farm, a site (collection of farms) or a grid (collection of sites). Here we describe the goals of the project, the current design and implementation, and plans for future development. DIAL is being developed within PPDG to understand the requirements that interactive analysis places on the grid and within ATLAS to enable distributed interactive analysis of event data.
71122772
Scintillating pad detectors
We have been investigating the performance of scintillating pad detectors, individual small tiles of scintillator that are read out with wavelength-shifting fibers and visible light photon counters, for application in high luminosity colliding beam experiments such as the DO Upgrade. Such structures could provide "pixel" type readout over large fiducial volumes for tracking, preshower detection and triggering.
120295653
Quick polarization analyzer (QPAN)
Abstract A high count rate polarimeter for the measurement and monitoring of the polarization of an intermediate energy neutron beam has been developed. The device, QPAN, consists of a double arm telescope with adjustable copper absorbers. The asymmetry of the protons scattered from the liquid hydrogen (LH 2 ) target is calculated from the count differential between two arms, positioned above and below the beam.
121937710
On the relevance of the Dirac equation to the scattering of medium-energy nucleons from nuclei☆
Abstract The differences between relativistic and nonrelativistic descriptions of medium-energy nucleon—nucleus scattering are discussed. Special attention is paid to a recently developed Dirac optical model in which we point out an ambiguity resulting from the use of an incomplete representation for relativistic nucleon—nucleon scattering amplitude. This ambiguity is reflected in contributions from negative-energy states and in the implementation of the impulse approximation. We also review how a nonrelativistic optical potential can be modified to include relativistic projectile kinematics.
26597722
Spin structure of the proton from polarized inclusive deep-inelastic muon-proton scattering
We have measured the spin-dependent structure function g(1)(p) in inclusive deep-inelastic scattering of polarized muons off polarized protons, in the kinematic range 0.003<x<0.7 and I GeV2<Q(2)<60 GeV2. A next-to-leading order QCD analysis is used to evolve the measured g(1)(p)(x,Q(2)) to a fixed Q(0)(2). The first moment of g(1)(p) at Q(0)(2)=10 GeV2 is Gamma=0.136+/-0.013 (stat) +/-0.009 (syst) +/-0.005 (evol). This result is below the prediction of the Ellis-Jaffe sum rule by more than two standard deviations. The singlet axial charge a(0) is found to be 0.28+/-0.16. Ln the Adler-Bardeen factorization scheme, Delta g similar or equal to 2 is required to bring Delta Sigma in agreement with the quark-parton model. A combined analysis of all available proton, deuteron, and He-3 data confirms the Bjorken sum rule.