Dynamic configuration of the CMS Data Acquisition cluster

The CMS Data Acquisition cluster, which runs around 10000 applications, is configured dynamically at run time. XML configuration documents determine what applications are executed on each node and over what networks these applications communicate. Through this mechanism the DAQ System may be adapted to the required performance, partitioned in order to perform (test-) runs in parallel, or re-structured in case of hardware faults. This paper presents the CMS DAQ Configurator tool, which is used to generate comprehensive configurations of the CMS DAQ system based on a high-level description given by the user. Using a database of configuration templates and a database containing a detailed model of hardware modules, data and control links, nodes and the network topology, the tool automatically determines which applications are needed, on which nodes they should run, and over which networks the event traffic will flow. The tool computes application parameters and generates the XML configuration documents as well as the configuration of the run-control system. The performance of the tool and operational experience during CMS commissioning and the first LHC runs are discussed

A search for excited electrons with the Compact Muon Solenoid detector

A search for excited electrons using the CMS detector at the LHC with 36 pb$^{-1}$ of proton-proton collision data recorded at $\sqrt{s}$ = 7 TeV is presented. The search is performed for associated production of an electron and an excited electron followed by the decay of the excited electron to an electron and a photon for a final state of $e e \gamma$. No excess of events above the standard model expectation is observed. Interpreting the results in the context of production via novel four-fermion contact interactions and the subsequent decay via electroweak processes, upper limits on the production cross section are set. The exclusion region in the compositeness scale, $\Lambda$, and excited electron mass, $M_{e^*}$ , parameter space is extended beyond previously established limits. For $\Lambda$ = 2 TeV, excited electron masses below 760 GeV/c$^2$ are excluded at the 95% confidence level. The cross sections for masses between 200 and 1500 GeV/c$^2$ are limited to be less than 0.21 - 0.16 pb

Infrastructures and Monitoring of the on-line CMS computing centre

This paper describes in detail the infrastructure and installation of the CMS on-line computing centre (CMSOLC) and its associated monitoring system. In summer 2007, 640 PCs acting as detector Readout Units for the CMS Data Acquisition System (DAQ) were deployed along with ~150 servers for DAQ general services. Since summer 2008, ~900 PCs acting as DAQ Event Builder Units/Filter Units have been added and today, the CMSOLC has an on-line processing capability sufficient for a Level 1 trigger accept rate of 50 kHz. To ensure that these ~1700 PCs are running efficiently, a multi-level monitoring system has been put in place. This system is also described in this paper

Transverse momentum and pseudorapidity distributions of charged hadrons in pp collisions at (s)\sqrt(s) = 0.9 and 2.36 TeV

Measurements of inclusive charged-hadron transverse-momentum and pseudorapidity distributions are presented for proton-proton collisions at sqrt(s) = 0.9 and 2.36 TeV. The data were collected with the CMS detector during the LHC commissioning in December 2009. For non-single-diffractive interactions, the average charged-hadron transverse momentum is measured to be 0.46 +/- 0.01 (stat.) +/- 0.01 (syst.) GeV/c at 0.9 TeV and 0.50 +/- 0.01 (stat.) +/- 0.01 (syst.) GeV/c at 2.36 TeV, for pseudorapidities between -2.4 and +2.4. At these energies, the measured pseudorapidity densities in the central region, dN(charged)/d(eta) for |eta| < 0.5, are 3.48 +/- 0.02 (stat.) +/- 0.13 (syst.) and 4.47 +/- 0.04 (stat.) +/- 0.16 (syst.), respectively. The results at 0.9 TeV are in agreement with previous measurements and confirm the expectation of near equal hadron production in p-pbar and pp collisions. The results at 2.36 TeV represent the highest-energy measurements at a particle collider to date