15,011 research outputs found
Gluon density in nuclei
In this talk we present our detail study ( theory and numbers) [1] on the
shadowing corrections to the gluon structure functions for nuclei. Starting
from rather contraversial information on the nucleon structure function which
is originated by the recent HERA data, we develop the Glauber approach for the
gluon density in a nucleus based on Mueller formula [2] and estimate the value
of the shadowing corrections in this case. Than we calculate the first
corrections to the Glauber approach and show that these corrections are big.
Based on this practical observation we suggest the new evolution equation which
takes into account the shadowing corrections and solve it. We hope to convince
you that the new evolution equation gives a good theoretical tool to treat the
shadowing corrections for the gluons density in a nucleus and, therefore, it is
able to provide the theoretically reliable initial conditions for the time
evolution of the nucleus - nucleus cascade.Comment: Talk at RHIC'96, 43 pages, 23 figure
Gluon structure function for deeply inelastic scattering with nucleus in QCD
In this talk we present the first calculation of the gluon structure function
for nucleus in QCD. We discuss the Glauber formula for the gluon structure
function and the violation of this simple approach that we anticipate in QCD.
(Talk given by E. Levin at QCD and nuclear target session at the Workshop on
Deep Inelastic Scattering and QCD, Paris, April 1995).Comment: 10 pages(latex file),4 fig (eps.files
Scaling violation and shadowing corrections at HERA
We study the value of shadowing corrections (SC) in HERA kinematic region in
Glauber - Mueller approach. Since the Glauber - Mueller approach was proven in
perturbative QCD in the double logarithmic approximation (DLA), we develop the
DLA approach for deep inelastic structure function which takes into account the
SC. Our estimates show small SC for in HERA kinematic region while they
turn out to be sizable for the gluon structure function. We compare our
estimates with those for gluon distribution in leading order (LO) and next to
leading order (NLO) in the DGLAP evolution equations.Comment: 9pp,6 figures in eps file
Inclusive hadron and photon production at LHC in dipole momentum space
Using a momentum space model for the dipole scattering amplitude we present
an analysis of the saturation effects at LHC energies, describing the data on
proton-proton and proton-lead collisions. The model is based on the asymptotic
solutions of the Balitsky-Kovchegov equation, being ideal in the saturation
domain where the target wave function has a high occupation number. We also
make predictions for the nuclear modification ratios on charged hadron and
prompt photon production in the forward region, where the high parton density
effects are important.Comment: New section added and typos corrected. To be published in PR
Unitarity Corrections to the Proton Structure Functions through the Dipole Picture
We study the dipole picture for the description of the deep inelastic
scattering, focusing on the structure functions which are driven directly by
the gluon distribution. One performs estimates using the effective dipole cross
section given by the Glauber-Mueller approach in QCD, which encodes the
corrections due to the unitarity effects associated with the saturation
phenomenon. We also address issues about frame invariance of the calculations
when analysing the observables.Comment: 16 pages, 8 figures. Version to be published in Phys. Rev.
Aspects of the Unitarized Soft Multipomeron Approach in DIS and Diffraction
We study in detail the main features of the unitarized Regge model (CFKS),
recently proposed to describe the small- domain. It takes into account a
two-component description with two types of unitarized contributions: one is
the multiple pomeron exchange contribution, interacting with the large dipole
configurations, and the other one consists of a unitarized dipole cross
section, describing the interaction with the small size dipoles. We analyze the
ratio between soft and hard pieces as a function of the virtuality, and also
compare the resulting dipole cross section to that from the saturation model.
Diffraction dissociation is also considered, showing the scaling violations in
diffractive DIS and estimating the corresponding logarithmic slope.Comment: 14 pages, 5 postscript figures. Version to be published in Eur. Phys.
J.
Dynamics of the peel front and the nature of acoustic emission during peeling of an adhesive tape
We investigate the peel front dynamics and acoustic emission of an adhesive
tape within the context of a recent model by including an additional
dissipative energy that mimics bursts of acoustic signals. We find that the
nature of the peeling front can vary from smooth to stuck-peeled configuration
depending on the values of dissipation coefficient, inertia of the roller, mass
of the tape. Interestingly, we find that the distribution of AE bursts shows a
power law statistics with two scaling regimes with increasing pull velocity as
observed in experiments. In this regimes, the stuck-peeled configuration is
similar to the `edge of peeling' reminiscent of a system driven to a critical
state.Comment: Accepted for publication in Phys. Rev. Let
Implementing Session Centered Calculi
Recently, specific attention has been devoted to the development of service oriented process calculi. Besides the foundational aspects, it is also interesting to have prototype implementations for them in order to assess usability and to minimize the gap between theory and practice. Typically, these implementations are done in Java taking advantage of its mechanisms supporting network applications. However, most of the recurrent features of service oriented applications are re-implemented from scratch. In this paper we show how to implement a service oriented calculus, CaSPiS (Calculus of Services with Pipelines and Sessions) using the Java framework IMC, where recurrent mechanisms for network applications are already provided. By using the session oriented and pattern matching communication mechanisms provided by IMC, it is relatively simple to implement in Java all CaSPiS abstractions and thus to easily write the implementation in Java of a CaSPiS process
Momentum space saturation model for deep inelastic scattering and single inclusive hadron production
We show how the AGBS model, originally developed for deep inelastic
scattering applied to HERA data on the proton structure function, can also
describe the RHIC data on single inclusive hadron yield for and
collisions through a new simultaneous fit. The single inclusive hadron
production is modeled through the color glass condensate, which uses the
quark(and gluon)--condensate amplitudes in momentum space. The AGBS model is
also a momentum space model based on the asymptotic solutions of the BK
equation, although a different definition of the Fourier transform is used.
This aspect is overcome and a description entirely in transverse momentum of
both processes arises for the first time. The small difference between the
simultaneous fit and the one for HERA data alone suggests that the AGBS model
describes very well both kind of processes and thus emerges as a good tool to
investigate the inclusive hadron production data. We use this model for
predictions at LHC energies, which agree very well with available experimental
data.Comment: 10 pages, 7 figure
Projectile- And Target-charge Dependent Effects In Ionizing Collisions Of H ⁺ And He 2+ With He, Ne And Ar Atoms
The spectra of electrons emitted in collisions between H + and He 2+ projectiles and He, Ne and Ar targets at energies of 50 and 100 keV amu -1 have been studied. The data are in qualitative agreement with results of Irby el al., but are in disagreement with measurements of Bernardi et al. It is shown that the observed electron spectra have a dependence on both target-ion and projectile effective charge that can be understood qualitatively in terms of \u27saddle-point\u27 ionization. Several issues relevant to saddle-point ionization are discussed. © 1990 IOP Publishing Ltd
- …