104,236 research outputs found
Excited nucleon spectrum from lattice QCD with maximum entropy method
We study excited states of the nucleon in quenched lattice QCD with the
spectral analysis using the maximum entropy method. Our simulations are
performed on three lattice sizes , and
, at to address the finite volume issue. We find a
significant finite volume effect on the mass of the Roper resonance for light
quark masses. After removing this systematic error, its mass becomes
considerably reduced toward the direction to solve the level order puzzle
between the Roper resonance and the negative-parity nucleon
.Comment: Lattice2003(spectrum), 3 pages, 4 figure
Energy Spectra for Fractional Quantum Hall States
Fractional quantum Hall states (FQHS) with the filling factor nu = p/q of q <
21 are examined and their energies are calculated. The classical Coulomb energy
is evaluated among many electrons; that energy is linearly dependent on 1/nu.
The residual binding energies are also evaluated. The electron pair in nearest
Landau-orbitals is more affected via Coulomb transition than an electron pair
in non-nearest orbitals. Each nearest electron pair can transfer to some empty
orbital pair, but it cannot transfer to the other empty orbital pair because of
conservation of momentum. Counting the numbers of the allowed and forbidden
transitions, the binding energies are evaluated for filling factors of 126
fraction numbers. Gathering the classical Coulomb energy and the pair
transition energy, we obtain the spectrum of energy versus nu. This energy
spectrum elucidates the precise confinement of Hall resistance at specific
fractional filling factors.Comment: 5 pages, 3 figure
Spectral Analysis of Excited Nucleons in Lattice QCD with Maximum Entropy Method
We study the mass spectra of excited baryons with the use of the lattice QCD
simulations. We focus our attention on the problem of the level ordering
between the positive-parity excited state N'(1440) (the Roper resonance) and
the negative-parity excited state N^*(1535). Nearly perfect parity projection
is accomplished by combining the quark propagators with periodic and
anti-periodic boundary conditions in the temporal direction. Then we extract
the spectral functions from the lattice data by utilizing the maximum entropy
method. We observe that the masses of the N' and N^* states are close for wide
range of the quark masses (M_pi=0.61-1.22 GeV), which is in contrast to the
phenomenological prediction of the quark models. The role of the Wilson
doublers in the baryonic spectral functions is also studied.Comment: 15 pages, 5 figures included, typos corrected, and references adde
Transition from real to virtual polarized photon structures
We investigate the transition of the polarized photon structure function
when the target photon shifts from on-shell ()
to far off-shell () region. The analysis is performed to the
next-to-leading order in QCD. The first moment of which vanishes
for the real photon, turns to be a negative value when target photon becomes
off-shell. The explicit -dependence of the first moment sum rule as well
as of the structure function as a function of is
studied in the framework of the vector meson dominance model.Comment: 16 pages, 4 eps figure
Spin structure function of the virtual photon
We investigate the spin structure of the virtual photon beyond the leading
order in QCD. The first moment of the virtual photon spin structure function
with QCD effects turns out to be non-vanishing in
contrast to the real photon case. Numerical analysis for virtual as well as
real photon case is presented.Comment: 3 pages, LaTeX, 3 ps figures, uses npb.sty, Contribution to the
Workshop on Deep Inelastic Scattering and QCD (DIS 99), Zeuthen, April 199
Virtual Photon Structure Functions
We discuss the perturbatively calculable virtual photon structure functions.
First we present the framework for analyzing the structure functions of the
virtual photon and derive a first moment of of the virtual photon.
We then investigate the three positivity constraints satisfied by the eight
structure functions of the virtual photon.Comment: 5 pages, LaTeX, 5 eps figures, npb.sty file included Talk given at
RADCOR/Loops and Legs 2002, Kloster Banz, Germany, September 8-13, 2002, to
appear in the Proceeding
Parton Distributions in the Virtual Photon Target and Factorization Scheme Dependence
We investigate parton distributions in the virtual photon target, both
polarized and unpolarized, up to the next-leading order (NLO) in QCD. Parton
distributions can be predicted completely up to NLO, but they are
factorization-scheme-dependent. We analyze parton distributions in several
factorization schemes and discuss their scheme dependence. Particular
attentions are paid to the axial anomaly effect on the first moments of the
polarized quark parton distributions, and also to the large- behaviors of
polarized and unpolarized parton distributions.Comment: 6 pages, LaTeX, 3 ps figures, uses npb.sty, Contribution to the
Zeuthen Workshop on Elementary Particle Theory: Loops and Legs in Quantum
Field Theory, Koenigstein-Weissig, Germany, April 200
Positivity constraints on photon structure functions
We investigate the positivity constraints for the structure functions of both
virtual and real photon. From the Cauchy-Schwarz inequality we derive three
positivity conditions for the general virtual photon case, which reduce, in the
real photon case, to one condition relating the polarized and unpolarized
structure functions.Comment: 10 pages, 1 ps figure, to appear Phys. Lett.
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