5,225 research outputs found
Accessing directly the strange quark content of the proton at HERA
We investigate a double-spin asymmetry for the semi-inclusive
hyperon production in the longitudinally deep inelastic lepton-proton
scattering, the sign of which can provide us with important information about
the strange quark helicity distribution in the proton.On the basis of the
interpretation of the longitudinal deep inelastic lepton-nucleon scattering
data as a negative strange quark polarization in the proton and the preliminary
results on the measurement of the longitudinal polarization at the
resonance in electron-positron annihilation,we predict a minus sign for the
suggested observable. The experimental condition required for our suggestion is
met by the HERA facilities, so the asymmetry considered can be measured by the
HERMES experiments at HERA in the near future.Comment: 10 pages, Revtex, completely rephrased, references adde
Q^2-Dependence of the Proton's G_1 Structure Function Sum Rule
We study the variation of the first moment of the nucleon's
spin-dependent structure function . As the moment is
determined by the low energy theorem for Compton scattering. In the
deep-inelastic region the moment is calculated using twist expansion to order
. Based on these limits, we construct a formula which smoothly
interpolates between the two regions.Comment: (revised), 8 pages in REVTEX, 1 figure, MIT-CTP-223
Constraining Right-Handed Scale Through Kaon Mixing in SUSY Left-Right Model
We study flavor-changing neutral current and CP violations in the minimal
supersymmetric left-right model. We calculate the beyond-standard-model
contributions to the neutral kaon mixing and , and find
possible to have a numerical cancelation between the contributions from the
right-handed gauge boson and supersymmetric box diagram. With the cancelation,
the right-handed -boson mass scale can be lowered to about 2 TeV, well
within the search limit of LHC.Comment: 12 pages, new figures adde
Subtle but significant effects of CO<inf>2</inf> acidified seawater on embryos of the intertidal snail, Littorina obtusata
Our understanding of the effects of ocean acidification on whole organism function is growing, but most current information is for adult stages of development. Here, we show the effects of reduced pH seawater (pH 7.6) on aspects of the development, physiology and behaviour of encapsulated embryos of the marine intertidal gastropod Littorina obtusata. We found reduced viability and increased development times under reduced pH conditions, and the embryos had significantly altered behaviours and physiologies. In acidified seawater, embryos spent more time stationary, had slower rotation rates, spent less time crawling, but increased their movement periodicity compared with those maintained under control conditions. Larval and adult heart rates were significantly lower in acidified seawater, and hatchling snails had an altered shell morphology (lateral length and spiral shell length) compared to control snails. Our findings show that ocean acidification may have multiple, subtle effects during the early development of marine animals that may have implications for their survival beyond those predicted using later life stages. © Inter-Research 2009
Quark Orbital-Angular-Momentum Distribution in the Nucleon
We introduce gauge-invariant quark and gluon angular momentum distributions
after making a generalization of the angular momentum density operators. From
the quark angular momentum distribution, we define the gauge-invariant and
leading-twist quark {\it orbital} angular momentum distribution . The
latter can be extracted from data on the polarized and unpolarized quark
distributions and the off-forward distribution in the forward limit. We
comment upon the evolution equations obeyed by this as well as other orbital
distributions considered in the literature.Comment: 8 pages, latex, no figures, minor corrections mad
Gauge Link Structure in Quark-Quark Correlators in hard processes
Distribution functions in hard processes can be described by quark-quark
correlators, nonlocal matrix elements of quark fields. Color gauge invariance
requires inclusion of appropriate gauge links in these correlators. For
transverse momentum dependent distribution functions, in particular important
for describing T-odd effects in hard processes, we find that new link
structures containing loops can appear in abelian and non-abelian theories. In
transverse moments, e.g. measured in azimuthal asymmetries, these loops may
enhance the contribution of gluonic poles. Some explicit results for the link
structure are given in high-energy leptoproduction and hadron-hadron
scattering.Comment: 9 pages, 9 figure
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
Inclusive Photoproduction of Polarized Quarkonium
We analyse inclusive photoproduction of polarized quarkonium in the
framework of QCD. To separate nonperturbative and perturbative parts in the
density matrix of the produced quarkonium we use a method , which is equivalent
to the diagramatic expansion widely used in analysing deeply inelastic
scatterings. A systematic expansion in a small velocity , with which a heavy
quark moves inside the quarkonium in its rest frame, is performed for the
nonperturbative parts, and they are expressed as matrix elements in
nonrelativistic QCD. At the leading order of there are four matrix elements
representing nonperturbative physics. The perturbative parts are calculated at
the leading order of coupling constants. Some numerical results, especially,
numerical results for HERA are given.Comment: 19 pages+7 Figures as one compressed and encoded postcript fil
Universality of the Collins-Soper-Sterman nonperturbative function in gauge boson production
We revise the model for the Collins-Soper-Sterman resummed form factor
to improve description of the leading-power contribution at nearly
nonperturbative impact parameters. This revision leads to excellent agreement
of the transverse momentum resummation with the data in a global analysis of
Drell-Yan lepton pair and Z boson production. The nonperturbative contributions
are found to follow universal quasi-linear dependence on the logarithm of the
heavy boson invariant mass, which closely agrees with an estimate from the
infrared renormalon analysis.Comment: published version; 14 pages, 4 figures, additional discussio
An application of transverse-momentum-dependent evolution equations in QCD
The properties and behaviour of the solutions of the recently obtained
-dependent evolution equations are investigated. When used to reproduce
transverse momentum spectra of hadrons in Semi-Inclusive DIS, an encouraging
agreement with data is found. The present analysis also supports at the
phenomenological level the factorization properties of the Semi-Inclusive DIS
cross-sections in terms of -dependent distributions. Further improvements
and possible developments of the proposed evolution equations are envisaged.Comment: 6 pages, page format correcte
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