4,062 research outputs found
A Mediated Definite Delegation Model allowing for Certified Grid Job Submission
Grid computing infrastructures need to provide traceability and accounting of
their users" activity and protection against misuse and privilege escalation. A
central aspect of multi-user Grid job environments is the necessary delegation
of privileges in the course of a job submission. With respect to these generic
requirements this document describes an improved handling of multi-user Grid
jobs in the ALICE ("A Large Ion Collider Experiment") Grid Services. A security
analysis of the ALICE Grid job model is presented with derived security
objectives, followed by a discussion of existing approaches of unrestricted
delegation based on X.509 proxy certificates and the Grid middleware gLExec.
Unrestricted delegation has severe security consequences and limitations, most
importantly allowing for identity theft and forgery of delegated assignments.
These limitations are discussed and formulated, both in general and with
respect to an adoption in line with multi-user Grid jobs. Based on the
architecture of the ALICE Grid Services, a new general model of mediated
definite delegation is developed and formulated, allowing a broker to assign
context-sensitive user privileges to agents. The model provides strong
accountability and long- term traceability. A prototype implementation allowing
for certified Grid jobs is presented including a potential interaction with
gLExec. The achieved improvements regarding system security, malicious job
exploitation, identity protection, and accountability are emphasized, followed
by a discussion of non- repudiation in the face of malicious Grid jobs
A Security Monitoring Framework For Virtualization Based HEP Infrastructures
High Energy Physics (HEP) distributed computing infrastructures require
automatic tools to monitor, analyze and react to potential security incidents.
These tools should collect and inspect data such as resource consumption, logs
and sequence of system calls for detecting anomalies that indicate the presence
of a malicious agent. They should also be able to perform automated reactions
to attacks without administrator intervention. We describe a novel framework
that accomplishes these requirements, with a proof of concept implementation
for the ALICE experiment at CERN. We show how we achieve a fully virtualized
environment that improves the security by isolating services and Jobs without a
significant performance impact. We also describe a collected dataset for
Machine Learning based Intrusion Prevention and Detection Systems on Grid
computing. This dataset is composed of resource consumption measurements (such
as CPU, RAM and network traffic), logfiles from operating system services, and
system call data collected from production Jobs running in an ALICE Grid test
site and a big set of malware. This malware was collected from security
research sites. Based on this dataset, we will proceed to develop Machine
Learning algorithms able to detect malicious Jobs.Comment: Proceedings of the 22nd International Conference on Computing in High
Energy and Nuclear Physics, CHEP 2016, 10-14 October 2016, San Francisco.
Submitted to Journal of Physics: Conference Series (JPCS
Statistical model for pionic partons
We present a model for the structure of the pion. Based on ideas of a
recently developed statistical model of the nucleon, we assume the pion to be a
gas of partons. The finite-size corrections (FSC) are incorporated through two
parameters. Using the same two FSC parameters for the proton and pion we
reproduce quantitatively the data on Drell-Yan
production and valence quark distribution of the pion.Comment: revised manuscript, 11 pages, LaTex, including 4 figures, to appear
in Phys. Lett.
Electromagnetic Signals and Backgrounds in Heavy-Ion Collisions:
Aspects of the dilepton spectrum in heavy-ion collisions are discussed, with
special emphasis on using lattice computations to guide the phenomenology of
finite temperature hadronic matter. The background rates for continuum
dileptons expected in forthcoming experiments are summarised. Properly
augmented by data from ongoing measurements at HERA, these rates will serve as
a calibrating background for QGP searches. Recent results on the temperature
dependence of the hadronic spectrum obtained in lattice computations below the
deconfinement transition are summarised. Light vector meson masses are strongly
temperature dependent. Accurate measurements of a resolved -peak in
dimuon spectra in present experiments are thus of fundamental importance.
[file-length=200k characters; instructions for processing given; some Latex
versions give error messages: ignore them completely]Comment: 9 pages (incl figures), preprint HLRZ 53/9
Pion Parton Distributions in a non local Lagrangian
We use phenomenological nonlocal Lagrangians, which lead to non trivial forms
for the quark propagator, to describe the pion. We define a procedure, based on
the Dyson-Schwinger equations, for the calculation of the pion parton
distributions at low Q^2. The obtained parton distributions fulfill all the
wishful properties. Using a convolution approach we incorporate the composite
character of the constituent quarks in the formalism. We evolve, using the
Renormalization Group, the calculated parton distributions to the experimental
scale and compare favorably with the data and draw conclusions.Comment: Latex, 11 pages with 6 figure
Evidence for an exotic S=-2, Q=-2 baryon resonance in proton-proton collisions at the CERN SPS
Results of resonance searches in the Xi - pi -, Xi - pi +, Xi -bar+ pi -, and Xi -bar+ pi + invariant mass spectra in proton-proton collisions at sqrt[s]=17.2 GeV are presented. Evidence is shown for the existence of a narrow Xi - pi - baryon resonance with mass of 1.862±0.002 GeV/c2 and width below the detector resolution of about 0.018 GeV/c2. The significance is estimated to be above 4.2 sigma . This state is a candidate for the hypothetical exotic Xi --3/2 baryon with S=-2, I=3 / 2, and a quark content of (dsdsu-bar). At the same mass, a peak is observed in the Xi - pi + spectrum which is a candidate for the Xi 03/2 member of this isospin quartet with a quark content of (dsusd-bar). The corresponding antibaryon spectra also show enhancements at the same invariant mass
Pion Structure Function in the Nambu and Jona-Lasinio model
The pion structure function is studied in the Nambu and Jona-Lasinio (NJL)
model. We calculate the forward scattering amplitude of a virtual photon from a
pion target in the Bjorken limit, and obtain valence quark distributions of the
pion at the low energy hadronic scale, where the NJL model is supposed to work.
The calculated distribution functions are evolved to the experimental momentum
scale using the Altarelli-Parisi equation. The resulting distributions are in a
reasonable agreement with experiment. We calculate also the kaon structure
function and compare the ratio of kaon to pion valence u-quark distributions
with experiment.Comment: 15 pages with 5 figures as uuencoded postscript files, TMU-NT-930301
(plain LaTeX
Meson Structure in Deep Inelastic Scattering
We study the deep inelastic structure functions of mesons within the Nambu
and Jona-Lasinio model. We calculate the valence quark distributions in ,
, and mesons at the low energy model scale, which are evoluted to
the experimental momentum scale in terms of the Altarelli-Parisi equation. The
resulting distribution functions show reasonable agreements with experiment. We
also discuss the semi-inclusive lepton nucleon scattering process with a slow
nucleon in coincidence in the final state, which reveals the off-shell
structure of the pion.Comment: 31 pages with 16 figures as uuencoded postscript files, TMU-NT-940101
(plain LaTeX
Higher twists in the pion structure function
We calculate the QCD moments of the pion structure function using Drell-Yan
data on the quark distributions in the pion and a phenomenological model for
the resonance region. The extracted higher twist corrections are found to be
larger than those for the nucleon, contributing around 50% of the lowest moment
at Q^2=1 GeV^2.Comment: 8 pages, 3 figures, to appear in Phys. Rev.
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