Installing, Running and Maintaining Large Linux Clusters at CERN

Having built up Linux clusters to more than 1000 nodes over the past five years, we already have practical experience confronting some of the LHC scale computing challenges: scalability, automation, hardware diversity, security, and rolling OS upgrades. This paper describes the tools and processes we have implemented, working in close collaboration with the EDG project [1], especially with the WP4 subtask, to improve the manageability of our clusters, in particular in the areas of system installation, configuration, and monitoring. In addition to the purely technical issues, providing shared interactive and batch services which can adapt to meet the diverse and changing requirements of our users is a significant challenge. We describe the developments and tuning that we have introduced on our LSF based systems to maximise both responsiveness to users and overall system utilisation. Finally, this paper will describe the problems we are facing in enlarging our heterogeneous Linux clusters, the progress we have made in dealing with the current issues and the steps we are taking to gridify the clustersComment: 5 pages, Proceedings for the CHEP 2003 conference, La Jolla, California, March 24 - 28, 200

Autonomic Management of Large Clusters and Their Integration into the Grid

We present a framework for the co-ordinated, autonomic management of multiple clusters in a compute center and their integration into a Grid environment. Site autonomy and the automation of administrative tasks are prime aspects in this framework. The system behavior is continuously monitored in a steering cycle and appropriate actions are taken to resolve any problems. All presented components have been implemented in the course of the EU project DataGrid: The Lemon monitoring components, the FT fault-tolerance mechanism, the quattor system for software installation and configuration, the RMS job and resource management system, and the Gridification scheme that integrates clusters into the Grid

A Pilot Study of Abnormal Growth in Autism Spectrum Disorders and Other Childhood Psychiatric Disorders

The aims of the current study were to examine whether early growth abnormalities are (a) comparable in autism spectrum disorders (ASD) and other childhood psychiatric disorders, and (b) specific to the brain or generalized to the whole body. Head circumference, height, and weight were measured during the first 19 months of life in 129 children with ASD and 59 children with non-ASD psychiatric disorders. Both groups showed comparable abnormal patterns of growth compared to population norms, especially regarding height and head circumference in relation to height. Thus abnormal growth appears to be related to psychiatric disorders in general and is mainly expressed as an accelerated growth of height not matched by an increase in weight or head circumference

Study of Tau-pair Production in Photon-Photon Collisions at LEP and Limits on the Anomalous Electromagnetic Moments of the Tau Lepton

Tau-pair production in the process e+e- -> e+e-tau+tau- was studied using data collected by the DELPHI experiment at LEP2 during the years 1997 - 2000. The corresponding integrated luminosity is 650 pb^{-1}. The values of the cross-section obtained are found to be in agreement with QED predictions. Limits on the anomalous magnetic and electric dipole moments of the tau lepton are deduced.Comment: 20 pages, 9 figures, Accepted by Eur. Phys. J.

CP asymmetry in B→ϕKSB \to \phi K_S in a general two-Higgs-doublet model with fourth-generation quarks

We discuss the time-dependent CP asymmetry of decay $B \to \phi K_S$ in an extension of the Standard Model with both two Higgs doublets and additional fourth-generation quarks. We show that although the Standard Model with two-Higgs-doublet and the Standard model with fourth generation quarks alone are not likely to largely change the effective $\sin 2 \beta$ from the decay of $B \to \phi K_S$, the model with both additional Higgs doublet and fourth-generation quarks can easily account for the possible large negative value of $\sin 2 \beta$ without conflicting with other experimental constraints. In this model, additional large CP violating effects may arise from the flavor changing Yukawa interactions between neutral Higgs bosons and the heavy fourth generation down type quark, which can modify the QCD penguin contributions. With the constraints obtained from $b \to s \bar{s} s$ processes such as $B \to X_s \gamma$ and $\Delta m_{B_s^0}$, this model can lead to the effective $\sin 2 \beta$ to be as large as $- 0.4$ in the CP asymmetry of $B \to \phi K_S$.Comment: 13 pages, 5 figures, references added, to appear in Eur.Phys.J.

Energy dependence of Cronin momentum in saturation model for p+Ap+A and A+AA+A collisions

We calculate $\sqrt{s}$ dependence of Cronin momentum for $p+A$ and $A+A$ collisions in saturation model. We show that this dependence is consistent with expectation from formula which was obtained using simple dimentional consideration. This can be used to test validity of saturation model (and distinguish among its variants) and measure $x$ dependence of saturation momentum from experimental data.Comment: LaTeX2e, 12 pages, 8 figure

A Precise Measurement of the Tau Lifetime

The tau lepton lifetime has been measured with the e+e- -> tau+tau- events collected by the DELPHI detector at LEP in the years 1991-1995. Three different methods have been exploited, using both one-prong and three-prong tau decay channels. Two measurements have been made using events in which both taus decay to a single charged particle. Combining these measurements gave tau_tau (1 prong) = 291.8 +/- 2.3 (stat) +/- 1.5 (sys) fs. A third measurement using taus which decayed to three charged particles yielded tau_tau (3 prong) = 288.6 +/- 2.4 (stat) +/- 1.3 (sys) fs. These were combined with previous DELPHI results to measure the tau lifetime, using the full LEP1 data sample, to be tau_tau = 290.9 +/- 1.4 (stat) +/- 1.0 (sys) fs.Comment: 27 pages, 7 figure

Search for composite and exotic fermions at LEP 2

A search for unstable heavy fermions with the DELPHI detector at LEP is reported. Sequential and non-canonical leptons, as well as excited leptons and quarks, are considered. The data analysed correspond to an integrated luminosity of about 48 pb^{-1} at an e^+e^- centre-of-mass energy of 183 GeV and about 20 pb^{-1} equally shared between the centre-of-mass energies of 172 GeV and 161 GeV. The search for pair-produced new leptons establishes 95% confidence level mass limits in the region between 70 GeV/c^2 and 90 GeV/c^2, depending on the channel. The search for singly produced excited leptons and quarks establishes upper limits on the ratio of the coupling of the excited fermio

Search for lightest neutralino and stau pair production in light gravitino scenarios with stau NLSP

Promptly decaying lightest neutralinos and long-lived staus are searched for in the context of light gravitino scenarios. It is assumed that the stau is the next to lightest supersymmetric particle (NLSP) and that the lightest neutralino is the next to NLSP (NNLSP). Data collected with the Delphi detector at centre-of-mass energies from 161 to 183 \GeV are analysed. No evidence of the production of these particles is found. Hence, lower mass limits for both kinds of particles are set at 95% C.L.. The mass of gaugino-like neutralinos is found to be greater than 71.5 GeV/c^2. In the search for long-lived stau, masses less than 70.0 to 77.5 \GeVcc are excluded for gravitino masses from 10 to 150 \eVcc . Combining this search with the searches for stable heavy leptons and Minimal Supersymmetric Standard Model staus a lower limit of 68.5 \GeVcc may be set for the stau mas

Predictive value of subclinical autistic traits at age 14–15 months for behavioural and cognitive problems at age 3–5 years

It is unclear whether subclinical autistic traits at very young age are transient or stable, and have clinical relevance. This study investigated the relationship between early subclinical autistic traits and the occurrence of later developmental and behavioural problems as well as problems in cognitive and language functioning. Parents of infants aged 14–15 months from the general population completed the Early Screening of Autistic Traits Questionnaire (ESAT). Three groups of children with high, moderate, and low ESAT-scores (total n = 103) were selected. Follow-up assessments included the CBCL 1½–5 at age 3 years, and the SCQ, the ADI-R, the ADOS-G, a non-verbal intelligence test, and language tests for comprehension and production at age 4–5 years. None of the children met criteria for autism spectrum disorder at follow-up. Children with high ESAT-scores at 14–15 months showed significantly more internalizing and externalizing problems at age 3 years and scored significantly lower on language tests at age 4–5 years than children with moderate or low ESAT-scores. Further, significantly more children with high ESAT-scores (14/26, 53.8%) than with moderate and low ESAT-scores (5/36, 13.9% and 1/41, 2.4%, respectively) were in the high-risk/clinical range on one or more outcome domains (autistic symptoms, behavioural problems, cognitive and language abilities). Subclinical autistic traits at 14–15 months predict later behavioural problems and delays in cognitive and language functioning rather than later ASD-diagnoses. The theoretical implications of the findings lie in the pivotal role of early social and communication skills for the development of self-regulation of emotions and impulses. The practical implications bear on the early recognition of children at risk for behavioural problems and for language and cognitive problems