7,455 research outputs found
Diffraction for non-believers
Diffractive reactions involving a hard scale can be understood in terms of
quarks and gluons. These reactions have become a valuable tool for
investigating the low-x structure of the proton and the behavior of QCD in the
high-density regime, and they may provide a clean environment to study or even
discover the Higgs boson at the LHC. In this paper we give a brief introduction
to the description of diffraction in QCD. We focus on key features studied in
ep collisions at HERA and outline challenges for understanding diffractive
interactions at the LHC.Comment: 23 pages, 26 figures. Contributed to the Proceedings of the Workshop
on HERA and the LHC, DESY and CERN, 2004-200
Nuclear modification difference between u_v and d_v distributions and its relation to NuTeV sin^2 theta_W anomaly
We investigate a possible nuclear correction to the NuTeV measurement of the
weak-mixing angle sin^2 theta_W. In particular, a nuclear modification
difference between u_v and d_v distributions contributes to the NuTeV
measurement with the iron target. First, the modification differenceis
determined by a chi^2 analysis so as to reproduce nuclear data on the structure
function F_2 and Drell-Yan processes. Then, taking the NuTeV kinematics into
account, we calculate a contribution to the sin^2 theta_W determination. In
addition, its uncertainty is estimated by the Hessian method. Although the
uncertainty becomes comparable to the NuTeV deviation, the effect is not large
enough to explain the whole NuTeV sin^2 theta_W anomaly at this stage. However,
it is difficult to determine such a nuclear modification difference, so that we
need further investigations on the difference and its effect on the NuTeV
anomaly.Comment: 6 pages,3 figure
A Spectrometer to Study Elastic and Diffractive Physics at LHC
The possibility to study elastic and diffractive physics in pp collisions at
LHC is investigated. For this purpose we have considered detectors close to the
beam in conjunction with the magnetic elements of the accelerator to provide a
high precision spectrometer for very forward final state protons. The
geometrical acceptance is given and momentum resolution is calculated for
different spatial resolution detectors.Comment: 26 pages, 13 figures, Latex, submitted in International Journal of
Modern Physics
Effect due to charge symmetry violation on the Paschos-Wolfenstein relation
The modification of the Paschos-Wolfenstein relation is investigated when the
charge symmetry violations of valence and sea quark distributions in the
nucleon are taken into account. We also study qualitatively the impact of
charge symmetry violation (CSV) effect on the extraction of
from deep inelastic neutrino- and antineutrino-nuclei
scattering within the light-cone meson-baryon fluctuation model. We find that
the effect of CSV is too small to give a sizable contribution to the NuTeV
result with various choices of mass difference inputs, which is consistence
with the prediction that the strange-antistrange asymmetry can account for
largely the NuTeV deviation in this model. It is noticeable that the effect of
CSV might contribute to the NuTeV deviation when the larger difference between
the internal momentum scales, of the proton and of
the neutron, is considered.Comment: 15 Latex pages, no figure, final version to appear in PR
Relating high-energy lepton-hadron, proton-nucleus and nucleus-nucleus collisions through geometric scaling
A characteristic feature of small-x lepton-proton data from HERA is geometric
scaling -- the fact that over a wide range of x and Q^2 all data can be
described by a single variable , with all x-dependence
encoded in the so-called saturation momentum . Here, we observe
that the same scaling ansatz accounts for nuclear photoabsorption cross
sections and favors the nuclear dependence , . We then make the empirical finding
that the same A-dependence accounts for the centrality evolution of the
multiplicities measured in Au+Au collisions at RHIC. It also allows to
parametrize the high-p_t particle suppression in d+Au collisions at forward
rapidities. If these geometric scaling properties have a common dynamical
origin, then this A-dependence of should emerge as a consequence
of the underlying dynamical model.Comment: 4 pages, 3 postscript figure
Nuclear parton distributions at next to leading order
We perform a next to leading order QCD global analysis of nuclear deep
inelastic scattering and Drell-Yan data using the convolution approach to
parameterize nuclear parton densities. We find both a significant improvement
in the agreement with data compared to previous extractions, and substantial
differences in the scale dependence of nuclear effects compared to leading
order analyses.Comment: 9 pages, 10 figure
Wavelet Based Fractal Analysis of Airborne Pollen
The most abundant biological particles in the atmosphere are pollen grains
and spores. Self protection of pollen allergy is possible through the
information of future pollen contents in the air. In spite of the importance of
airborne pol len concentration forecasting, it has not been possible to predict
the pollen concentrations with great accuracy, and about 25% of the daily
pollen forecasts have resulted in failures. Previous analysis of the dynamic
characteristics of atmospheric pollen time series indicate that the system can
be described by a low dimensional chaotic map. We apply the wavelet transform
to study the multifractal characteristics of an a irborne pollen time series.
We find the persistence behaviour associated to low pollen concentration values
and to the most rare events of highest pollen co ncentration values. The
information and the correlation dimensions correspond to a chaotic system
showing loss of information with time evolution.Comment: 11 pages, 7 figure
Twist Three Distribution f_\perp(x,k^\perp) in Light-front Hamiltonian Approach
We calculate the twist three distribution f_\perp(x,k^\perp) contributing to
Cahn effect in unpolarized semi-inclusive deep inelastic scattering. We use
light-front Hamiltonian technique and take the state to be a dressed quark at
one loop in perturbation theory. The 'genuine twist three' contribution comes
from the quark-gluon interaction part in the operator and is explicitly
calculated. f_\perp(x,k^\perp) is compared with f_1(x,k^\perp).Comment: Two figures added, one author added, some parts rewritten for
clarificatio
DIPSI: a Monte Carlo generator for elastic vector meson production in charged lepton-proton scattering
We present a Monte Carlo generator for exclusive vector meson production in
charged lepton-proton interactions, l+p --> l+p+V, based on a QCD leading
logarithm model calculation according to which the cross section for this
process is proportional to the square of the gluon momentum density in the
proton. The generator can be used for both fixed target and collider
kinematics. Each event is assigned a weight equal to its cross section, so that
the independent variables can be generated according to convenient
distributions, not necessarily identical to the physics ones.Comment: 24 pages, 7 figures, Latex, to be published in Computer Physics
Communication
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