V. Altini

The ALICE data quality monitoring

ALICE is one of the four experiments installed at the CERN Large Hadron Collider (LHC), especially designed for the study of heavy-ion collisions. The online Data Quality Monitoring (DQM) is an important part of the data acquisition (DAQ) software. It involves the online gathering, the analysis by user-defined algorithms and the visualization of monitored data. This paper presents the final design, as well as the latest and coming features, of the ALICEs specific DQM software called AMORE (Automatic MonitoRing Environment). It describes the challenges we faced during its implementation, including the performances issues, and how we tested and handled them, in particular by using a scalable and robust publish-subscribe architecture.We also review the on-going and increasing adoption of this tool amongst the ALICE collaboration and the measures taken to develop, in synergy with their respective teams, efficient monitoring modules for the sub-detectors. The related packaging and release procedure needed by such a distributed framework is also described. We finally overview the wide range of usages people make of this framework, and we review our own experience, before and during the LHC start-up, when monitoring the data quality on both the sub-detectors and the DAQ side in a real-world and challenging environment.

The ALICE Electronic Logbook

All major experiments need tools that provide a way to keep a record of the events and activities, during both commissioning and operations. In ALICE (A Large Ion Collider Experiment) at CERN, this task is performed by the ALICE Electronic Logbook (eLogbook), a custom-made application developed and maintained by the Data-Acquisition team (DAQ), the group which within the collaboration has the responsibility for Data Acquisition. Started as a statistics repository, the eLogbook has evolved to become not only a fully functional electronic logbook, but also a massive information repository used to store the conditions and statistics of the several online systems. It is currently used by more than 1000 users in 50 different countries and it plays an important role in the daily ALICE collaboration activities. This paper will describe the LAMP (Linux, Apache, MySQL and PHP) based architecture of the eLogbook, the database schema and the relevance of the information stored in the eLogbook to the different ALICE actors, not only for near real time procedures but also for long term analysis. It will also present the web interface, including the different used technologies, the implemented security measures and the current main features. Finally it will present the roadmap for the future, including both technical and functional developments.

Online processing in the ALICE DAQ The detector algorithms

ALICE (A Large Ion Collider Experiment) is the heavy-ion detector designed to study the physics of strongly interacting matter and the quark-gluon plasma at the CERN Large Hadron Collider (LHC). Some specific calibration tasks are performed regularly for each of the 18 ALICE sub-detectors in order to achieve most accurate physics measurements. These procedures involve events analysis in a wide range of experimental conditions, implicating various trigger types, data throughputs, electronics settings, and algorithms, both during short sub-detector standalone runs and long global physics runs. A framework was designed to collect statistics and compute some of the calibration parameters directly online, using resources of the Data Acquisition System (DAQ), and benefiting from its inherent parallel architecture to process events. This system has been used at the experimental area for one year, and includes more than 30 calibration routines in production. This paper describes the framework architecture and the synchronization mechanisms involved at the level of the Experiment Control System (ECS) of ALICE. The software libraries interfacing detector algorithms (DA) to the online data flow, configuration database, experiment logbook, and offline system are reviewed. The test protocols followed to integrate and validate each sub-detector component are also discussed, including the automatic build system and validation procedures used to ensure a smooth deployment. The offline post-processing and archiving of the DA results is covered in a separate paper.

The ALICE online data storage system

The ALICE (A Large Ion Collider Experiment) Data Acquisition (DAQ) system has the unprecedented requirement to ensure a very high volume, sustained data stream between the ALICE Detector and the Permanent Data Storage (PDS) system which is used as main data repository for Event processing and Offline Computing. The key component to accomplish this task is the Transient Data Storage System (TDS), a set of data storage elements with its associated hardware and software components, which supports raw data collection, its conversion into a format suitable for subsequent high-level analysis, the storage of the result using highly parallelized architectures, its access via a cluster file system capable of creating high-speed partitions via its affinity feature, and its transfer to the final destination via dedicated data links. We describe the methods and the components used to validate, test, implement, operate, and monitor the ALICE Online Data Storage system and the way it has been used in the early days of commissioning and operation for the ALICE Detector. We will also introduce the future developments needed from next year, when the ALICE Data Acquisition System will shift its requirements from those associated to the test and commissioning phase to those imposed by long-duration data taking periods alternated by shorter validation and maintenance tasks which will be needed to adequately operate the ALICE Experiment.

Transverse Momentum Distribution and Nuclear Modification Factor of Charged Particles in p plus Pb Collisions at root(NN)-N-s=5.02 TeV

The transverse momentum (p(T)) distribution of primary charged particles is measured in minimum bias (non-single-diffractive) p+Pb collisions at sqrt[s(NN)]=5.02 TeV with the ALICE detector at the LHC. The p(T) spectra measured near central rapidity in the range 0.5<p(T) <20 GeV/c exhibit a weak pseudorapidity dependence. The nuclear modification factor R(pPb) is consistent with unity for p(T) above 2 GeV/c. This measurement indicates that the strong suppression of hadron production at high p(T) observed in Pb+Pb collisions at the LHC is not due to an initial-state effect. The measurement is compared to theoretical calculations.

Development of a simulated trigger generator for the ALICE commissioning

This paper will describe the hardware and the software developed to build a random trigger simulator used to test the detectors of the ALICE experiment. It will also describe the tests performed in our laboratory at CERN on the random trigger generator to confirm its correct behavior and its installation details in one of the counting rooms of ALICE, where it provides the triggers for all the sub-detectors.