30,145 research outputs found
Interference and the lossless lossy beam splitter
By directing the input light into a particular mode it is possible to obtain
as output all of the input light for a beam splitter that is 50% absorbing.
This effect is also responsible for nonlinear quantum interference when two
photons are incident on the beam splitter.Comment: 10 pages, 2 figures, to appear in J. Mod. Op
Uncertainties of predictions from parton distribution functions II: the Hessian method
We develop a general method to quantify the uncertainties of parton
distribution functions and their physical predictions, with emphasis on
incorporating all relevant experimental constraints. The method uses the
Hessian formalism to study an effective chi-squared function that quantifies
the fit between theory and experiment. Key ingredients are a recently developed
iterative procedure to calculate the Hessian matrix in the difficult global
analysis environment, and the use of parameters defined as components along
appropriately normalized eigenvectors. The result is a set of 2d Eigenvector
Basis parton distributions (where d=16 is the number of parton parameters) from
which the uncertainty on any physical quantity due to the uncertainty in parton
distributions can be calculated. We illustrate the method by applying it to
calculate uncertainties of gluon and quark distribution functions, W boson
rapidity distributions, and the correlation between W and Z production cross
sections.Comment: 30 pages, Latex. Reference added. Normalization of Hessian matrix
changed to HEP standar
Lorentz Symmetry and the Internal Structure of the Nucleon
To investigate the internal structure of the nucleon, it is useful to
introduce quantities that do not transform properly under Lorentz symmetry,
such as the four-momentum of the quarks in the nucleon, the amount of the
nucleon spin contributed by quark spin, etc. In this paper, we discuss to what
extent these quantities do provide Lorentz-invariant descriptions of the
nucleon structure.Comment: 6 pages, no figur
Multivariate Fitting and the Error Matrix in Global Analysis of Data
When a large body of data from diverse experiments is analyzed using a
theoretical model with many parameters, the standard error matrix method and
the general tools for evaluating errors may become inadequate. We present an
iterative method that significantly improves the reliability of the error
matrix calculation. To obtain even better estimates of the uncertainties on
predictions of physical observables, we also present a Lagrange multiplier
method that explores the entire parameter space and avoids the linear
approximations assumed in conventional error propagation calculations. These
methods are illustrated by an example from the global analysis of parton
distribution functions.Comment: 13 pages, 5 figures, Latex; minor clarifications, fortran program
made available; Normalization of Hessian matrix changed to HEP standar
Solving the Darwin problem in the first post-Newtonian approximation of general relativity
We analytically calculate the equilibrium sequence of the corotating binary
stars of incompressible fluid in the first post-Newtonian(PN) approximation of
general relativity. By calculating the total energy and total angular momentum
of the system as a function of the orbital separation, we investigate the
innermost stable circular orbit for corotating binary(we call it ISCCO). It is
found that by the first PN effect, the orbital separation of the binary at the
ISCCO becomes small with increase of the compactness of each star, and as a
result, the orbital angular velocity at the ISCCO increases. These behaviors
agree with previous numerical works.Comment: 33 pages, revtex, 4 figures(eps), accepted for publication in Phys.
Rev.
Analyzing powers in inclusive pion production at high energy and the nucleon spin structure
Analyzing powers in inclusive pion production in high energy transversely
polarized proton-proton collisions are studied theoretically in the framework
of the quark recombination model. Calculations by assuming the SU(6)
spin-flavor symmetry for the nucleon structure disagree with the experiments.
We solve this difficulty by taking into account the %We overcome this
difficulty by taking into account the realistic spin distribution functions of
the nucleon, which differs from the SU(6) expectation at large , %but
coincides with a perturbative QCD constraint on the ratio of the unpolarized
valence distributions, as . We also discuss the kaon spin
asymmetry and find in the polarized proton-proton
collisions at large .Comment: 13 pages, 4 figures, late
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