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 $\pi^- N \to \mu^+ \mu^- X$ 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 $\rho$-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

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.

Valence-quark distributions in the pion

We calculate the pion's valence-quark momentum-fraction probability distribution using a Dyson-Schwinger equation model. Valence-quarks with an active mass of 0.30 GeV carry 71% of the pion's momentum at a resolving scale q_0=0.54 GeV = 1/(0.37 fm). The shape of the calculated distribution is characteristic of a strongly bound system and, evolved from q_0 to q=2 GeV, it yields first, second and third moments in agreement with lattice and phenomenological estimates, and valence-quarks carrying 49% of the pion's momentum. However, pointwise there is a discrepancy between our calculated distribution and that hitherto inferred from parametrisations of extant pion-nucleon Drell-Yan data.Comment: 8 pages, 3 figures, REVTEX, aps.sty, epsfig.sty, minor corrections, version to appear in PR

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

Production of deuterium, tritium, and 3^3He in central Pb+Pb collisions at 20A, 30A, 40A, 80A, and 158A GeV at the CERN SPS

Production of $d$, $t$, and $^3$He nuclei in central Pb+Pb interactions was studied at five collision energies ($\sqrt{s_{NN}}=$ 6.3, 7.6, 8.8, 12.3, and 17.3 GeV) with the NA49 detector at the CERN SPS. Transverse momentum spectra, rapidity distributions, and particle ratios were measured. Yields are compared to predictions of statistical models. Phase-space distributions of light nuclei are discussed and compared to those of protons in the context of a coalescence approach. The coalescence parameters $B_2$ and $B_3$, as well as coalescence radii for $d$ and $^3$He were determined as a function of transverse mass at all energies.Comment: 22 pages, 29 figures, 8 tables, for submission to Phys. Rev.