856 research outputs found
POWER UP: A Persuasive Writing Strategy for Secondary Students with Emotional and Behavioral Disorders
In the area of written expression, students with emotional and behavioral disorders (EBD) typically perform one to two grades below their same age, non-disabled peers. Unfortunately, there is a lack of research on writing interventions to improve these outcomes. The purpose of this study was to examine the effect of a persuasive writing strategy called POWER UP to improve the quality of persuasive essays for secondary students with EBD. The results suggest that a mnemonic strategy based on the Self-Regulated Strategy Development Model (SRSD) can improve the quality of persuasive writing essays for secondary students with EBD
Single spin asymmetries in DIS
We consider possible mechanisms for single spin asymmetries in inclusive Deep
Inelastic Scattering (DIS) processes with unpolarized leptons and transversely
polarized nucleons. Tests for the effects of non-zero \bfk_\perp, for the
properties of spin dependent quark fragmentations and for quark helicity
conservation are suggested.Comment: 5 pages, LaTeX, no figures. Revised version, to be published in Phys.
Rev. D. Some equations and statements added to clarify text and notation
Axial anomaly: the modern status
The modern status of the problem of axial anomaly in QED and QCD is reviewed.
Two methods of the derivation of the axial anomaly are presented: 1) by
splitting of coordinates in the expression for the axial current and 2) by
calculation of triangle diagrams, where the anomaly arises from the surface
terms in momentum space. It is demonstrated, that the equivalent formulation of
the anomaly can be given, as a sum rule for the structure function in
dispersion representation of three point function of AVV interaction. It is
argued, that such integral representation of the anomaly has some advantages in
the case of description of the anomaly by contribution of hadronic states in
QCD. The validity of the t'Hooft consistency condition is discussed. Few
examples of the physical application of the axial anomaly are given.Comment: 17 pages, 3 figures, to be published in International Journal of
Modern Physics A, few minor correction were done, two references were adde
Models for the Polarized Parton Distributions of the Nucleon
Polarized deep inelastic scattering (DIS) data are analyzed in leading and
next-to-leading order of QCD within the common `standard' scenario of polarized
parton distributions with a flavor-symmetric light sea (antiquark) distribution
, and a completely SU(3) broken `valence' scenario with
totally flavor-asymmetric light sea densities
. The latter flavor-broken
light sea distributions are modelled with the help of a Pauli-blocking ansatz
at the low radiative/dynamical input scales of
(0.40) GeV which complies with predictions of the chiral quark-soliton
model and expectations based on the statistical parton model as well as with
the corresponding, well established, flavor-broken unpolarized sea
(). Present semi-inclusive DIS data cannot yet uniquely
discriminate between those two flavor-symmetric and flavor-broken polarized
light sea scenarios.Comment: 39 pages, LaTe
Hard exclusive electroproduction of decuplet baryons in the large N_c limit
The cross sections and transverse spin asymmetries in the hard exclusive
electroproduction of decuplet baryons are calculated in the large N_c limit and
found to be comparable to that of octet baryons. Large N_c selection rules for
the production amplitudes are derived, leading to new sensitive tests of the
spin aspects of the QCD chiral dynamics both in the nonstrange and strange
sectors. Importance of such studies for the reliable extraction of the pion
form factor from pion electroproduction is explained.Comment: 4 pages, 3 figure
Nuclear Antishadowing in Neutrino Deep Inelastic Scattering
The shadowing and antishadowing of nuclear structure functions in the
Gribov-Glauber picture is due respectively to the destructive and constructive
interference of amplitudes arising from the multiple-scattering of quarks in
the nucleus. The effective quark-nucleon scattering amplitude includes Pomeron
and Odderon contributions from multi-gluon exchange as well as Reggeon
quark-exchange contributions. We show that the coherence of these
multiscattering nuclear processes leads to shadowing and antishadowing of the
electromagnetic nuclear structure functions in agreement with measurements.
This picture leads to substantially different antishadowing for charged and
neutral current reactions, thus affecting the extraction of the weak-mixing
angle . We find that part of the anomalous NuTeV result for
could be due to the nonuniversality of nuclear antishadowing for
charged and neutral currents. Detailed measurements of the nuclear dependence
of individual quark structure functions are thus needed to establish the
distinctive phenomenology of shadowing and antishadowing and to make the NuTeV
results definitive.Comment: 38 pages, 15 figure
Scheme Independence of
We work with two general factorization schemes in order to explore the
consequences of imposing scheme independence on . We see that
although the light quark sector is indifferent to the choice of a particular
scheme, the extension of the calculations to the heavy quark sector indicates
that a scheme like the is preferable.Comment: 11 pages, 2 figures. To appear in the Brief Reports of Phys. Rev.
Gauge Is More Than Mathematical Redundancy
Physical systems may couple to other systems through variables that are not gauge invariant. When we split a gauge system into two subsystems, the gauge-invariant variables of the two subsystems have less information than the gauge-invariant variables of the original system; the missing information regards degrees of freedom that express relations between the subsystems. All this shows that gauge invariance is a formalization of the relational nature of physical degrees of freedom. The recent developments on boundary variables and boundary charges are clarified by this observation
Polarized Parton Distribution Functions in the Nucleon
Polarized parton distribution functions are determined by using world data
from the longitudinally polarized deep inelastic scattering experiments. A new
parametrization of the parton distribution functions is adopted by taking into
account the positivity and the counting rule. From the fit to the asymmetry
data A_1, the polarized distribution functions of u and d valence quarks, sea
quarks, and gluon are obtained. The results indicate that the quark spin
content is \Delta\Sigma=0.20 and 0.05 in the leading order (LO) and the
next-to-leading-order (NLO) MS-bar scheme, respectively. However, if x
dependence of the sea-quark distribution is fixed at small x by "perturbative
QCD" and Regge theory, it becomes \Delta \Sigma=0.24 ~ 0.28 in the NLO. The
small-x behavior cannot be uniquely determined by the existing data, which
indicates the importance of future experiments. From our analysis, we propose
one set of LO distributions and two sets of NLO ones as the
longitudinally-polarized parton distribution functions.Comment: 51 pages, REVTeX, aps.sty, aps12.sty, epsfig.sty, prabib.sty,
revtex.sty, revtex.cls, 17 eps figures. Submitted for publication. Email:
[email protected]
Single spin asymmetries in QCD
Measurements of single transverse spin asymmetries in high energy inclusive
processes have always shown unexpected and challenging results. Several cases
are considered and discussed within a QCD approach which couples perturbative
dynamics to new non perturbative partonic information; the aim is that of
developing a consistent phenomenological description of these unusual single
spin phenomena, based on a generalized QCD factorization scheme.Comment: 14 pages, lectures delivered at School on "Symmetries and Spin",
Praha-SPIN-2001, Prague, July 15 - July 28, 200
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