787 research outputs found
Experimental and Theoretical Results for Weak Charge Current Backward Proton Production
In this paper, we do three things in the study of deuteron break-up by high
energy neutrino beams. (1) We present previously unpublished data on neutrino
induced backward protons from deuteron targets; (2) we calculate the
contributions from both the two-nucleon (2N) and six-quark (6q) deuteron
components, which depend upon the overall normalization of the part that is 6q;
and (3) we suggest other signatures for distinguishing the 2N and 6q clusters.
We conclude that the 6q cluster easily explains the shape of the high momentum
backward proton spectrum, and its size is nicely explained if the amount of 6q
is one or a few percent by normalization of the deuteron. There is a crossover,
above which the 6q contribution is important or dominant, at 300--400 MeV/c
backward proton momentum.Comment: 8 pages, 5 figure
Leading Chiral Contributions to the Spin Structure of the Proton
The leading chiral contributions to the quark and gluon components of the
proton spin are calculated using heavy-baryon chiral perturbation theory.
Similar calculations are done for the moments of the generalized parton
distributions relevant to the quark and gluon angular momentum densities. These
results provide useful insight about the role of pions in the spin structure of
the nucleon, and can serve as a guidance for extrapolating lattice QCD
calculations at large quark masses to the chiral limit.Comment: 8 pages, 2 figures; a typo in Ref. 7 correcte
Chiral Quark Model with Configuration Mixing
The implications of one gluon exchange generated configuration mixing in the
Chiral Quark Model (QM) with SU(3) and axial U(1) symmetry
breakings are discussed in the context of proton flavor and spin structure as
well as the hyperon -decay parameters. We find that QM
with SU(3) symmetry breaking is able to give a satisfactory unified fit for
spin and quark distribution functions, with the symmetry breaking parameters
, and the mixing angle , both for NMC and the
most recent E866 data. In particular, the agreement with data, in the case of
, F, D, and , is quite striking.Comment: 16 pages, LaTex, Table and Appendix adde
Nuclear Attenuation of high energy two-hadron system in the string model
Nuclear attenuation of the two-hadron system is considered in the string
model. The two-scale model and its improved version with two different choices
of constituent formation time and sets of parameters obtained earlier for the
single hadron attenuation, are used to describe available experimental data for
the -dependence of subleading hadron, whereas satisfactory agreement with
the experimental data has been observed. A model prediction for
-dependence of the nuclear attenuation of the two-hadron system is also
presented.Comment: 8 page
Sea Contributions and Nucleon Structure
We suggest a general formalism to treat a baryon as a composite system of
three quarks and a `sea'. In this formalism, the sea is a cluster which can
consists of gluons and quark-antiquark pairs. The hadron wave function with a
sea component is given. The magnetic moments, related sum rules and axial weak
coupling constants are obtained. The data seems to favor a vector sea rather
than a scalar sea. The quark spin distributions in the nucleon are also
discussed.Comment: 24 page
Right Handed Weak Currents in Sum Rules for Axialvector Constant Renormalization
The recent experimental results on deep inelastic polarized lepton scattering
off proton, deuteron and He together with polari% zed neutron
-decay data are analyzed. It is shown that the problem of Ellis-Jaffe
and Bjorken sum rules deficiency and the neutron paradox could be solved
simultaneously by assuming the small right handed current (RHC) admixture in
the weak interaction Lagrangian. The possible RHC impact on pion-nucleon
-term and Gamow-Teller sum rule for nuclear reactions is
pointed out.Comment: to be published in Phys. Rev. Lett. LaTeX, 8 pages, 21 k
Valence Quark Spin Distribution Functions
The hyperfine interactions of the constituent quark model provide a natural
explanation for many nucleon properties, including the Delta-N splitting, the
charge radius of the neutron, and the observation that the proton's quark
distribution function ratio d(x)/u(x)->0 as x->1. The hyperfine-perturbed quark
model also makes predictions for the nucleon spin-dependent distribution
functions. Precision measurements of the resulting asymmetries A_1^p(x) and
A_1^n(x) in the valence region can test this model and thereby the hypothesis
that the valence quark spin distributions are "normal".Comment: 16 pages, 2 Postscript figure
Nuclear Shadowing in a Parton Recombination Model
Deep inelastic structure functions are investigated in a
rescaling model with parton recombination effects. We find that the model can
explain experimentally measured structure functions reasonably well
in the wide Bjorken range (). In the very small region
(), recombination results are very sensitive to input sea-quark and
gluon distributions.Comment: preprint MKPH-T-93-04, IU/NTC 92-20, 25 pages, TEX file (without
Figs. 1-14)., (address after April 1: Saga U., Japan
Effective Hadron Dynamics: From Meson Masses to the Proton Spin Puzzle
We construct a three flavor chiral Lagrangian of pseudoscalars and vectors
with special emphasis on the symmetry breaking terms. Comparing tree level two
and three point functions with experiment allows us to first, fix the
parameters of the model (including the light quark mass ratios) and second, to
predict and
. The last mentioned quantities come
out reasonably well, in contrast to an ``ordinary" treatment. For this
purpose we need ``second order" symmetry breakers involving the vector fields
analogous to those needed for the chiral perturbation theory program with only
pseudoscalars. An improved description of the system is also
given. We then use the soliton sector of this improved chiral Lagrangian to
investigate some aspects of baryon physics which are especially sensitive to
symmetry breaking. For this purpose a fairly elaborate ``cranking" techinque is
employed in connection with the collective Hamiltonian. In addition to the
``strong" baryon mass spectrum a careful investigation is made of the
non-electromagnetic part of the neutron-proton mass difference. This work is
needed to improve our previous estimates concerning the two component approach
to the ``proton spin" puzzle. We find that both the ``matter" and ``glue"
contributions are small but they do tend to cancel each other.Comment: 33 pages, LaTe
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