1,028 research outputs found
Central Exclusive Scalar Luminosities from the Linked Dipole Chain Model gluon densities
We investigate the implication of uncertainties in the unintegrated gluon
distribution for the predictions for central exclusive production of scalars at
hadron colliders. We use parameterizations of the kT-unintegrated gluon density
obtained from the Linked Dipole Chain model, applying different options for the
treatment of non-leading terms. We find that the luminosity function for
central exclusive production is very sensitive to details of the transverse
momentum distribution of the gluon which, contrary to the kT-integrated
distribution, is not very well constrained experimentally
Large Scale Rapidity Correlations in Heavy Ion Collisions
We discuss particle production mechanisms for heavy ion collisions. We
present an argument demonstrating how the fluctuations of the number of
produced particles in a series of classical emissions can account for KNO
scaling. We predict rapidity correlations in the particle production in the
event by event analysis of heavy ion collisions on the rapidity scales of the
order of one over the strong coupling constant.Comment: REVTeX, 13 pages, 3 figure
A QCD motivated model for soft interactions at high energies
In this paper we develop an approach to soft scattering processes at high
energies,which is based on two mechanisms: Good-Walker mechanism for low mass
diffractionand multi-Pomeron interactions for high mass diffraction. The
pricipal idea, that allows us to specify the theory for Pomeron interactions,
is that the so called soft processes occur at rather short distances
(r^2 \propto 1 /^2 \propto \alpha'_\pom \approx 0.01 GeV^{-2}), where
perturbative QCD is valid. The value of the Pomeron slope \alpha'_\pom was
obtained from the fit to experimental data. Using this theoretical approach we
suggest a model that fits all soft data in the ISR-Tevatron energy range, the
total, elastic, single and double diffractive cross sections, including
dependence of the differential elastic cross section, and the mass dependence
of single diffraction. In this model we calculate the survival probability of
diffractive Higgs production, and obtained a value for this observable, which
is smaller than 1% at the LHC energy range.Comment: 33pp,20 figures in eps file
On the role of longitudinal momenta in high energy hadron-hadron scattering
We demonstrate a new method for the calculation of inelastic scattering
cross-section, which in contrary to the Regge-based methods takes into account
the energy momentum conservation law. By virtue of this method it was shown
that the main contribution to integral expressing inelastic scattering
cross-sections comes not from the multi-Regge domain. In particular this leads
to the fact that accounting of longitudinal momenta contribution to
virtualities is sufficient and results in the new mechanism of cross-section
growth. The necessity of taking into account the large number of interference
contributions is shown and the approximate method for this purpose is
developed. By considering the interference contributions from a single fitting
constant achieved a qualitative agreement of the total and inelastic cross
sections with experimental data.Comment: 38 pages, 19 figures (A misspelled author's name corrected
Charmed particle production in hadron-hadron collision
In the framework of Quark--Gluon--String Model developed recently in ITEP we
calculate spectra of charmed particles , , , ,
in hadron--hadron collisions taking into account the decays of
--wave resonances like , , , , ,
, and . We describe the bulk of the existing data on ,
, and production in and collisions and predict
the yield of charmed particles in and reactions at hyperon
beam energies of and . Because of significant
production of baryon resonances our predictions for unfavored fragmentation
differ from predictions of other models which do not take resonance production
into account.Comment: Latex,19 pages, 12figs. can be received by reques
What is blue growth? The semantics of “Sustainable Development” of marine environments
This Special Issue is intended to help readers gain a better understanding of the various definitions of blue growth, as well as to give a heightened awareness of the constraints of, and possibilities within, the important concept. Increased communication among those working together on these topics is of utmost importance, especially considering the diversity of the backgrounds of those who have a role to play in blue growth and sustainable development. Scientists, policy makers, business people, and the larger society need to become more precise and transparent in their language and meanings in order to effectively work together, and hopefully one day succeed in our joint goal to secure blue growth
Noncolliding Squared Bessel Processes
We consider a particle system of the squared Bessel processes with index conditioned never to collide with each other, in which if
the origin is assumed to be reflecting. When the number of particles is finite,
we prove for any fixed initial configuration that this noncolliding diffusion
process is determinantal in the sense that any multitime correlation function
is given by a determinant with a continuous kernel called the correlation
kernel. When the number of particles is infinite, we give sufficient conditions
for initial configurations so that the system is well defined. There the
process with an infinite number of particles is determinantal and the
correlation kernel is expressed using an entire function represented by the
Weierstrass canonical product, whose zeros on the positive part of the real
axis are given by the particle-positions in the initial configuration. From the
class of infinite-particle initial configurations satisfying our conditions, we
report one example in detail, which is a fixed configuration such that every
point of the square of positive zero of the Bessel function is
occupied by one particle. The process starting from this initial configuration
shows a relaxation phenomenon converging to the stationary process, which is
determinantal with the extended Bessel kernel, in the long-term limit.Comment: v3: LaTeX2e, 26 pages, no figure, corrections made for publication in
J. Stat. Phy
Disks, Tori, and Cocoons: Emission and Absorption Diagnostics of AGN Environments
One of the most important problems in the study of active galaxies is
understanding the detailed geometry, physics, and evolution of the central
engines and their environments. The leading models involve an accretion disk
and torus structure around a central dense object, thought to be a supermassive
black hole. Gas found in the environment of AGN is associated with different
structures: molecular accretion disks, larger scale atomic tori, ionized and
neutral "cocoons" in which the nuclear regions can be embedded. All of them can
be studied at radio wavelengths by various means. Here, we summarize the work
that has been done to date in the radio band to characterize these structures.
Much has been learned about the central few parsecs of AGN in the last few
decades with contemporary instruments but the picture remains incomplete. In
order to be able to define a more accurate model of this region, significant
advances in sensitivity, spectral and angular resolution, and bandpass
stability are required. The necessary advances will only be provided by the
Square Kilometer Array and we discuss the possibilities that these dramatic
improvements will open for the study of the gas in the central region of AGN.Comment: To appear in "Science with the Square Kilometer Array," eds. C.
Carilli and S. Rawlings, New Astronomy Reviews (Elsevier: Amsterdam); 17
pages, 7 figures (four of them in separate gif/tif files) The full paper with
high resolution images can be downloaded from
http://www.astron.nl/~morganti/Papers/AGNenvironment.ps.g
Survival probability for high mass diffraction
Based on the calculation of survival probabilities, we discuss the problem of
extracting the value of , the triple Pomeron 'bare' coupling constant,
by comparing the large rapidity gap single high mass diffraction data in
proton-proton scattering and photo and DIS production. For p-p
scattering the calculation in a three amplitude rescattering eikonal model,
predicts the survival probability to be an order of magnitude smaller than for
the two amplitude case. The survival probabilities calculation for photo and
DIS production is made in a dedicated model. In this process we show
that, even though its survival probability is considerably larger than in p-p
scattering, its value is below unity and cannot be neglected in the data
analysis. We argue that, regardless of the uncertainties in the suggested
procedure, its outcome is important both with regards to a realistic estimate
of , and the survival probabilities relevant to LHC experiments.Comment: 17 pages, 8 pictures and one tabl
Nuclear shadowing in Glauber-Gribov theory with Q2-evolution
We consider deep inelastic scattering off nuclei in the Regge limit within
the Glauber-Gribov model. Using unitarized parton distribution functions for
the proton, we find sizeable shadowing effects on the nuclear total and
longitudinal structure functions, and , in the low-x limit.
Extending a fan-diagram analysis for the large-mass region of coherent
diffraction off nuclei to high Q2, we also find significant shadowing effects
in this kinematical regime. Finally, we discuss shortcomings of our approach
and possible extensions of the model to other kinematical regimes.Comment: 16 pages, 9 figure
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