158 research outputs found
On the Q^2 Dependence of Measured Polarized Structure Funtions
We analyse the available data on the polarized asymmetries for proton,
neutron and deuteron targets. We use a homogeneous and updated set of
unpolarized structure functions to derive from , and we accurately
correct for the scaling violations in order to obtain with the
same for all values. The contribution to the evolution of a
possible large gluon polarized density is also considered. The implications for
the Ellis-Jaffe and for the Bjorken sum rules are discussed.Comment: 11 pages (LaTex) + 4 figures (topdrawer, included at the end) CERN-TH
7023/9
The strange-sea quark spin distribution in the nucleon from inclusive and semi-inclusive deep-inelastic scattering
We propose new method which allows determination of the strange-sea quark
spin distribution in the nucleon through measurement of various inclusive and
semi-inclusive polarized deep inelastic electron- or muon-proton reactions. It
is shown, that using combinations of inclusive data and semi-inclusive data
containing neutral pions in the final state, it is possible to extract the
strange-sea quark spin distribution. Similar result can be obtained for charged
pions and some other hadrons also
Jet Production in Polarized Lepton-Hadron Scattering
We calculate exact analytical expressions for \oas 3-jet and \oasz \\ 4-jet
cross sections in polarized deep inelastic lepton nucleon scattering.
Introducing an invariant jet definition scheme, we present differential
distributions of 3- and 4-jet cross sections in the basic kinematical variables
and as well as total jet cross sections and show their dependence on
the chosen spin-dependent (polarized) parton distributions. Noticebly
differences in the predictions are found for the two extreme choices, i.e. a
large negative sea-quark density or a large positive gluon density. Therefore,
it may be possible to discriminate between different parametrizations of
polarized parton densities, and hence between the different physical pictures
of the proton spin underlying these parametrizations.Comment: 35 pages, LaTeX, 9 ps figures available upon request, MAD/PH/827, KA
TTP94-
QCD Sum Rule Calculation of Twist-4 Corrections to Bjorken and Ellis-Jaffe Sum Rules
We calculate the twist-4 corrections to the integral of in the
framework of QCD sum rules using an interpolating nucleon field which contains
explicitly a gluonic degree of freedom. This information can be used together
with previous calculations of the twist-3 contribution to the second moment of
to estimate the higher-twist corrections to the Ellis-Jaffe and
Bjorken sum rules. We get and
. Numerically our results roughly agree
with those obtained by Balitsky, Braun and Kolesnichenko based on a sum rule
for a simpler current. Our calculations are far more stable as tested within
the sum rule approach but are more sensitive to less well known condensates.Comment: 18pp., 1 figure (uuencoded eps-file), Late
Interpolating the Nucleon's Spin-Dependent Sum Rules at High and Low Energies
I discuss a few interpolating sum rules for spin structure functions of the
nucleon. Using the concept of duality, I argue that the sum rule,
including the elastic contribution, is useful for learning higher twist matrix
elements of the nucleon.Comment: 9 pages in Plain TeX, MIT CTP #220
Transverse Momentum in Semi-Inclusive Polarized Deep Inelastic Scattering and the Spin-Flavor Structure of the Proton
The non-valence spin-flavor structure of the nucleon extracted from
semi-inclusive measurements of polarized deep inelastic scattering depends
strongly on the transverse momentum of the detected hadrons which are used to
determine the individual polarized sea distributions. This physics may explain
the recent HERMES observation of a positively polarized strange sea through
semi-inclusive scattering, in contrast to the negative strange sea polarization
deduced from inclusive polarized deep inelastic scattering.Comment: 4 pages, revtex style, 2 figure
Scale Dependence of Polarized DIS Asymmetries
We compare the dependence of the polarized deep inelastic scattering
proton asymmetry, driven by the leading order Altarelli Parisi evolution
equations, to those arising from fixed order and
approximations. It is shown that the evolution effects associated with gluons,
which are not properly taken into account by the leading order approximation,
cannot be neglected in the analysis of the most recent experimental data.Comment: Latex file, (9 figures in postcript available from
[email protected]
Extracting the Proton ubar content from pp->Direct Photon plus Jet Cross Sections
An analysis procedure is proposed to measure the antiquark distributions in
the proton over the region 0.01 < x < 0.1. The procedure involves the
measurement of high p_t asymmetric direct photon and jet final states in pp
interactions. This measurement can be made at the RHIC collider running in pp
mode at an energy of sqrt(s)=500 GeV/c. This analysis identifies a region of
phase space where the contribution from quark-antiquark annihilation
uncharacteristically approaches the magnitude of the contribution from the
leading process, quark-gluon Compton scattering. The forward-backward angular
asymmetry in the parton center of mass is sensitive to the antiquark content of
the proton and the ubar parton density function can be extracted.Comment: 21 pages, 7 figure
Analytic Approaches to the Evolution of Polarised Parton Distributions at Small
The evolution of polarised parton distributions at small is
studied. Various analytic approximations are critically discussed. We compare
the full evolution with that obtained from the leading-pole approximation to
the splitting functions, and show that the validity of this approximation
depends critically on the behaviour of the starting distributions. A
new analytic solution which is valid at small is obtained, and its domain
of applicability is discussed.Comment: 14 pages, LATeX, 4 figures availabe as .uu-fil
The (alpha_s)^3 approximation of Quantum Chromodynamics to the Ellis-Jaffe sum rule
We present the analytical calculation in perturbative Quantum Chromodynamics
of the (alpha_s)^3 contribution to the Ellis-Jaffe sum rule for the structure
function g1 of polarized deep inelastic lepton-nucleon scattering.Comment: 11 pages, Late
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